Human Anatomy, Physiology, and Health

Hydration means having enough water in your body. Water helps your body work the way it should every day.

Your body needs water to help you stay cool, move, and carry nutrients to all the parts of your body. Nutrients are the healthy things in food that help you grow and have energy.

When you do not drink enough water, your body can get dehydrated. That means your body needs more water. You might feel tired, hot, thirsty, or get a headache.

Why is water important?

• Water helps control body temperature. When you run and play, your body gets warmer. Your body cools down by making sweat. Sweat is mostly water.
• Water helps your joints move. Joints are places where your body bends, like knees, elbows, and fingers. Water helps these parts move smoothly.
• Water helps carry important things through your body. Your blood carries oxygen and nutrients. Water helps your blood do this job.

Water helps you stay cool

Imagine you are playing outside on a warm day. After running, you may feel hot and sweaty. That sweat helps cool your body. If you lose water in sweat, you need to drink water to replace it.

Water helps your body move

Your knees, ankles, and elbows help you walk, jump, and play. Water helps these parts work smoothly. This is one reason drinking water is good for active bodies.

Water helps inside your body

Water is important inside your whole body, even where you cannot see it. It helps move nutrients from food to your cells. Cells are tiny parts that make up your body.

Think of water like a helper that carries useful things where they need to go. It also helps carry waste out of the body.

How can you tell when you need water?

Your body gives you clues. You may:

• feel thirsty
• have a dry mouth
• feel tired
• feel too hot
• have dark yellow pee

If you notice these clues, it may be time to drink some water.

When should you drink water?

• with meals
• after playing or exercising
• when you feel thirsty
• on hot days
• after sweating

Healthy ways to stay hydrated

• Carry a water bottle.
• Drink water during the day, not just at one time.
• Drink water after sports or recess.
• Eat foods with water, like watermelon, oranges, cucumbers, and soup.
• Ask for water when you feel thirsty.

Worked Example 1: After recess

Mila played tag at recess. She comes inside feeling hot and thirsty. What should she do?

Answer: Mila should drink water. She was running and sweating, so her body needs more water to help cool down and feel better.

Worked Example 2: Picking the best drink

Ben can choose between water and a sugary soda after soccer practice. Which drink is better for hydration?

Answer: Water is the better choice for hydration. Water helps replace the water Ben lost while playing.

Worked Example 3: Finding the clue

Lena says, “My mouth feels dry, and I feel thirsty.” What is her body telling her?

Answer: Her body is telling her she needs water. Dry mouth and thirst are signs that it is time to drink.

Worked Example 4: Water in foods

Which snack helps with hydration more: pretzels or watermelon?

Answer: Watermelon helps more with hydration because it has lots of water in it.

Things to remember

1. Your body needs water every day.
2. Water helps cool your body when you sweat.
3. Water helps your joints move smoothly.
4. Water helps carry nutrients through your body.
5. Drinking water is an important way to stay healthy.

Brief Summary

Hydration means having enough water in your body. Water helps keep you cool, helps your body move, and helps carry nutrients where they need to go. Drinking water every day, especially after play and on hot days, helps your body stay healthy and strong.

Skeletal System

Your body needs support, shape, and protection. The skeletal system is the body system made of bones, cartilage, and ligaments. It helps your body stand up, move, and stay safe inside.

You can think of your skeleton like a strong frame inside your body. A house has beams to hold it up. Your body has bones to hold it up.

Even though bones feel hard and strong, they are living parts of your body. They grow with you as you get bigger.

What is in the skeletal system?

• Bones are the hard parts inside your body.
• Cartilage is smooth and bendy. It is softer than bone.
• Ligaments are strong bands that connect bones to other bones.

All of these parts work together to help your body.

What do bones do?

• They give your body shape.
• They give your body support.
• They help you move.
• They protect important body parts.
• They help make blood cells inside some bones.

Bones give shape and support

Without bones, your body would not be able to stand tall. Bones help hold up your head, arms, legs, and body.

Your skull helps shape your head. Your backbone helps keep your body upright. The bones in your legs help you stand and walk.

Bones help you move

Bones do not move all by themselves. They work with muscles. When muscles pull on bones, your body moves.

For example, when you bend your arm, the bones in your arm move at a joint. A joint is a place where two bones meet.

Your knees, elbows, shoulders, and fingers all have joints. Joints help your body bend, twist, and move in many ways.

Cartilage helps at joints

Cartilage is a smooth, bendy tissue. It covers the ends of some bones where they meet at joints.

This helps bones move more smoothly. It also helps keep bones from rubbing too hard against each other.

You also have cartilage in places like your nose and ears. That is why your nose and ears can bend a little.

Ligaments hold bones together

Ligaments are strong bands in your body. They connect one bone to another bone at a joint.

Ligaments help hold joints together, so bones stay in the right place when you move.

Bones protect important organs

Some bones act like shields. They help protect soft, important parts inside your body.

• The skull protects the brain.
• The rib cage protects the heart and lungs.
• The backbone helps protect the spinal cord.

This protection is very important because organs are soft and can be hurt more easily than bones.

Bones make blood cells

Inside some bones is a soft material called marrow. Marrow helps make blood cells.

Blood cells are important because they travel through your body. Your body needs them every day.

You do not need to remember all the kinds of blood cells right now. Just remember this: inside some bones, marrow helps make blood cells.

Important bones to know

• Skull - protects the brain
• Ribs - help protect the heart and lungs
• Backbone - supports the body and protects the spinal cord
• Arm bones - help you lift, reach, and carry
• Leg bones - help you stand, walk, run, and jump

Worked Example 1: Finding a bone's job

Question: What is one job of the skull?

Think: The skull is the hard bone around your head. What important body part is inside your head?

Answer: The skull protects the brain.

Worked Example 2: Bones, cartilage, or ligaments?

Question: Your nose bends a little when you touch it. Is that mostly bone, cartilage, or ligament?

Think: Cartilage is softer and bendy. Bones are hard. Ligaments connect bones to bones.

Answer: It is mostly cartilage.

Worked Example 3: What helps bones move smoothly?

Question: At your knee, what helps bones move more smoothly at the joint?

Think: The ends of some bones are covered by something smooth and bendy.

Answer: Cartilage helps bones move smoothly at the joint.

Worked Example 4: Which part makes blood cells?

Question: A student says, "Blood cells are made inside some bones." What part inside the bone helps do this job?

Think: Inside some bones is a soft material.

Answer: Marrow helps make blood cells.

Let’s review

1. The skeletal system is made of bones, cartilage, and ligaments.
2. Bones give your body shape and support.
3. Bones work with muscles to help you move.
4. Cartilage is smooth and bendy and helps at joints.
5. Ligaments connect bones to other bones.
6. Bones protect organs like the brain, heart, and lungs.
7. Marrow inside some bones helps make blood cells.

Brief Summary

The skeletal system is the body system that gives your body shape, support, movement, and protection. It includes bones, cartilage, and ligaments. Bones also have marrow inside some of them, and marrow helps make blood cells.

The Circulatory System

Your body has a busy job every day. It moves, plays, thinks, and grows. To do all of these things, your body needs a way to carry helpful things to every part.

The circulatory system is the body system that moves blood around your body. Blood carries important things like oxygen and food from digested meals. The heart, blood, and blood vessels all work together.

You can think of the circulatory system like roads in a town. The heart is like a strong pump. The blood vessels are like roads. The blood travels along those roads to bring what the body needs.

What is the heart?

The heart is a strong muscle inside your chest. It squeezes and relaxes again and again. This pumping pushes blood through your body.

When your heart beats, it sends blood out. Then blood travels through blood vessels. Then blood comes back to the heart. This happens all day and all night.

You can often feel your heart working after you run or jump. It may beat faster because your body needs more help moving oxygen and food around.

What is blood?

Blood is a liquid that moves through your body. It carries oxygen you get from breathing. It also carries nutrients, which are tiny bits of food your body uses to grow and have energy.

Blood helps all parts of your body. It goes to your head, arms, legs, fingers, toes, and every place in between.

What are blood vessels?

Blood vessels are tiny tubes in your body. They carry blood from place to place. Some blood vessels carry blood away from the heart, and some carry blood back to the heart.

There are many, many blood vessels in your body. Together, they make a big network. This network helps blood reach all your body parts.

How do the parts work together?

The circulatory system works because all its parts help each other.

• The heart pumps the blood.
• The blood carries oxygen and nutrients.
• The blood vessels give blood a path to travel.

These parts work as a team. If your body were a town, the heart would be the pump station, the blood would be the delivery truck, and the blood vessels would be the roads.

Why does your body need this system?

Every part of your body needs oxygen and nutrients. Your muscles need them to move. Your brain needs them to think. Your skin needs them to grow and heal.

The circulatory system delivers these helpful things all around the body. Without this system, body parts would not get what they need.

What happens when you exercise?

When you run, hop, dance, or play, your body works harder. Your heart may beat faster. That helps move more blood through your body.

This is one way your body takes care of itself. A faster heartbeat during play is a sign that your heart is working to help you.

How can you help keep your circulatory system healthy?

You can make healthy choices to help your heart and blood vessels do their jobs well.

• Be active by running, jumping, walking, or playing.
• Eat healthy foods like fruits and vegetables.
• Drink water.
• Get enough sleep.
• Tell an adult if your body does not feel right.

Worked Examples

Example 1: What does the heart do?

Question: Mia says, “The heart is a pump.” Is she right?

Answer: Yes. The heart is a strong muscle that pumps blood through the body.

Why: The heart squeezes to push blood into blood vessels, and the blood travels where it is needed.

Example 2: What does blood carry?

Question: Ben breathes air and eats lunch. What helpful things can blood carry from these?

Answer: Blood carries oxygen from breathing and nutrients from food.

Why: These help the body grow, move, and have energy.

Example 3: Why does your heart beat faster when you run?

Question: Ava runs on the playground. After running, she feels her heart beating fast. Why?

Answer: Her heart is beating faster to move more blood around her body.

Why: When the body works harder, it needs more oxygen and nutrients delivered.

Example 4: Which part belongs?

Question: Which one is part of the circulatory system: heart, blood vessels, blood, or shoe?

Answer: Heart, blood vessels, and blood are parts of the circulatory system. A shoe is not.

Why: The circulatory system is made of body parts that move blood through the body.

Let’s Remember

1. The heart is a muscle that pumps blood.
2. Blood carries oxygen and nutrients.
3. Blood vessels are tubes that blood travels through.
4. The circulatory system helps all body parts get what they need.
5. Exercise, healthy food, water, and sleep help keep your heart healthy.

Brief Summary

The circulatory system is the body system that moves blood all around the body. The heart pumps, the blood carries oxygen and nutrients, and the blood vessels give blood a path to travel. These parts work together to help your whole body live, move, grow, and play.

Infectious diseases are sicknesses that can spread from one living thing to another. A person can catch them from another person, from an animal, from food or water, or from touching something dirty and then touching their eyes, nose, or mouth.

Very tiny living or almost-living things can cause infectious diseases. These tiny things are called germs. Germs are so small that we cannot see them with just our eyes.

There are different kinds of germs. Some common kinds are bacteria, viruses, fungi, and parasites. They can get into the body, grow or spread, and make a person feel sick.

Let’s learn how these germs can enter the body, what they do inside the body, and how we can help stop them from spreading.

1. Bacteria

Bacteria are tiny living things. Some bacteria are helpful, but some can make people sick. Harmful bacteria can get into the body through dirty hands, spoiled food, cuts in the skin, or dirty water.

Once harmful bacteria get inside the body, they can grow and multiply. That means they make more and more of themselves. When there are many harmful bacteria, the body may not work the way it should, and a person may get a fever, stomachache, sore throat, or other signs of sickness.

2. Viruses

Viruses are even smaller than bacteria. Viruses need to get inside a living body to make more of themselves. They can spread when a sick person coughs, sneezes, or touches things.

A cold or the flu can be caused by viruses. If someone with a virus coughs into the air, tiny wet drops can carry the virus to other people nearby. That is why covering coughs and sneezes is important.

3. Fungi

Fungi are another kind of germ. Some fungi can grow on the skin, especially in warm, wet places. A fungal infection can cause itchy skin, peeling skin, or a rash.

Fungi can spread by sharing things like towels, shoes, or combs. Keeping the body clean and dry can help stop fungi from growing.

4. Parasites

Parasites are tiny living things that live on or inside another living thing. They take what they need from the host. The host is the person or animal they live on or in.

Some parasites can get into the body from dirty water, dirty food, bug bites, or not washing hands. Parasites can cause stomach problems, itching, or other sickness.

How germs get into the body

Germs can enter the body in many ways. They may go in through the mouth, nose, eyes, or a cut in the skin.

• When we eat food with germs on it
• When we drink dirty water
• When we touch a germy surface and then touch our face
• When someone coughs or sneezes near us
• When we do not clean a cut
• When we share hats, towels, or brushes

What happens after germs get inside?

After germs enter the body, they can multiply. Multiply means to increase in number. One germ can become many germs.

As the germs grow or spread, the body may react. A person might feel tired, get a fever, cough, sneeze, have a rash, throw up, or have diarrhea. These are signs that the body is trying to fight the germs.

How infectious diseases spread

Infectious diseases spread when germs move from one host to another host. This is called transmission, which means spreading.

Here are some ways germs can spread:

1. Through the air: Coughing and sneezing can send tiny drops into the air.
2. By touch: Germs can get on hands, toys, desks, doorknobs, and other objects.
3. Through food and water: Dirty food or water can carry germs.
4. From animals or bugs: Some animals and insects can carry germs.
5. By sharing personal items: Sharing cups, towels, combs, or toothbrushes can spread germs.

How the body helps protect us

Our bodies have ways to help protect us. Skin helps keep many germs out. Tears, mucus, and stomach juices also help trap or destroy some germs.

Even though the body works hard to protect us, some germs can still get in. That is why healthy habits are very important.

How to help stop infectious diseases

• Wash hands with soap and water, especially before eating and after using the bathroom.
• Cover coughs and sneezes with a tissue or your elbow.
• Do not share cups, straws, toothbrushes, combs, hats, or towels.
• Clean cuts and keep them covered.
• Eat safe food and drink clean water.
• Keep your body clean and dry.
• Stay home when sick so you do not spread germs to others.
• Tell an adult if you feel very sick or notice a rash, fever, or bad cough.

Worked Example 1: A cough in class

Mia is sick. She coughs into her hands and then touches the table. Later, Ben touches the same table and then rubs his eyes.

Question: How could germs spread in this story?

Answer: The germs may move from Mia’s hands to the table. Then they may move from the table to Ben’s hands. When Ben rubs his eyes, the germs may enter his body.

What should happen instead? Mia should cough into a tissue or her elbow and wash her hands.

Worked Example 2: Sharing a towel

Two children use the same wet towel after gym class. One child has itchy, peeling skin on a foot caused by fungi.

Question: What kind of germ might spread, and how?

Answer: A fungus might spread by the shared towel. Fungi grow well in warm, wet places, so sharing a wet towel can help them move from one person to another.

How can they prevent it? Each child should use their own clean, dry towel.

Worked Example 3: Dirty water

Leo drinks water from a puddle while playing outside. Later, he gets a stomachache.

Question: What may have happened?

Answer: The puddle water may have had germs in it. These could be bacteria or parasites. The germs entered Leo’s mouth and then got inside his body, where they could make him sick.

How can this be prevented? Drink clean water, not water from puddles or other dirty places.

Worked Example 4: A cut on the knee

Sara falls on the playground and gets a cut on her knee. She keeps playing and does not wash it.

Question: Why could this be a problem?

Answer: Germs can enter through a cut in the skin. Harmful bacteria from dirt may get inside and multiply.

What should Sara do? She should tell an adult, clean the cut, and cover it with a bandage.

Important ideas to remember

• Infectious diseases are sicknesses that can spread.
• They are caused by germs such as bacteria, viruses, fungi, and parasites.
• Germs can enter through the mouth, nose, eyes, or cuts in the skin.
• Once inside, germs can multiply and make the body sick.
• Good health habits help stop germs from spreading.

Brief Summary

Infectious diseases are caused by tiny germs that spread from one host to another. Bacteria, viruses, fungi, and parasites can enter the body, grow or spread, and cause sickness. We can help protect ourselves and others by washing hands, covering coughs and sneezes, not sharing personal items, cleaning cuts, and using safe food and water.

Circulatory System

Your body has a busy helper inside it called the circulatory system. Its job is to move blood all around your body.

Blood carries important things your body needs. It brings oxygen and food energy to body parts. It also carries away waste your body does not need.

The main parts of the circulatory system are:

• Heart — the strong muscle that pumps blood
• Blood — the liquid that travels through the body
• Blood vessels — the tiny roads blood travels on

Meet the Heart

Your heart is about the size of your fist. It is a strong muscle in your chest. It works day and night without stopping.

The heart has 4 chambers. A chamber is a space inside the heart that holds blood.

• 2 chambers are on the top
• 2 chambers are on the bottom

We can count them like this:

$$2 + 2 = 4$$

These 4 chambers help the heart move blood in the right direction.

What Does Blood Do?

Blood is very important. It travels to your head, arms, stomach, legs, and feet.

Blood helps by:

• bringing oxygen to body parts
• bringing nutrients from food
• carrying away waste

Your body needs oxygen to work well. When you breathe in, your lungs take in oxygen. Then your blood helps move that oxygen to the rest of your body.

Two Kinds of Blood Trips

Blood takes a trip through the body again and again. On one part of the trip, blood has lots of oxygen. On another part of the trip, blood has less oxygen.

• Oxygen-rich blood has lots of oxygen to deliver.
• Oxygen-poor blood has already dropped off oxygen and goes back to get more.

This is why people sometimes talk about oxygenated blood and deoxygenated blood. For 2nd graders, it is easier to think of them as oxygen-rich and oxygen-poor.

How the Heart and Lungs Work Together

The heart and lungs are a team.

1. Oxygen-poor blood comes back to the heart.
2. The heart sends it to the lungs.
3. In the lungs, the blood picks up oxygen.
4. The oxygen-rich blood returns to the heart.
5. The heart pumps it out to the body.

This trip happens over and over every day.

Blood Vessels: The Roads for Blood

Blood vessels are like roads or tubes that carry blood. There are 3 main kinds to learn.

• Arteries carry blood away from the heart.
• Veins carry blood back to the heart.
• Capillaries are tiny blood vessels where blood reaches body parts.

You can remember it like this:

• Arteries = away
• Veins = back
• Capillaries = tiny connectors

Capillaries are very small. They help oxygen and nutrients move from the blood to the body's cells.

What Happens in the Body?

Imagine blood leaving the heart. First, it travels through arteries. Then it moves into tiny capillaries. There, oxygen is dropped off to the body. After that, the blood travels back through veins to the heart.

Then the heart sends that blood to the lungs to pick up more oxygen. After that, the trip starts again.

Why Is the Heart Called a Pump?

A pump pushes something along. Your heart pushes blood through the blood vessels.

When your heart beats, it squeezes and relaxes. This helps blood move. That is why you may feel your heartbeat after running or jumping.

Worked Example 1

Question: What is the main job of the circulatory system?

Think: The circulatory system moves blood around the body. Blood carries oxygen and nutrients.

Answer: The main job of the circulatory system is to move blood through the body so body parts get what they need.

Worked Example 2

Question: A blood vessel carries blood away from the heart. Is it an artery, vein, or capillary?

Think: Arteries carry blood away from the heart.

Answer: It is an artery.

Worked Example 3

Question: Blood has dropped off oxygen to the body. Where does it go next to get more oxygen?

Think: Oxygen-poor blood goes back to the heart and then to the lungs. In the lungs, it picks up oxygen.

Answer: It goes to the lungs to get more oxygen.

Worked Example 4

Question: The heart has 4 chambers. If there are 2 on top and 2 on bottom, how many are there in all?

Think: Add the top and bottom chambers.

$$2 + 2 = 4$$

Answer: The heart has 4 chambers.

Healthy Habits for Your Heart

You can help keep your heart healthy by making good choices.

• Run, play, and exercise.
• Eat healthy foods.
• Drink water.
• Get enough sleep.

When you are active, your heart may beat faster. That is your heart working hard to move blood to your muscles.

Quick Review

• The circulatory system moves blood through the body.
• The heart is a muscle that pumps blood.
• The heart has 4 chambers.
• Arteries carry blood away from the heart.
• Veins carry blood back to the heart.
• Capillaries are tiny blood vessels.
• Blood carries oxygen and nutrients.
• The lungs help blood get oxygen.

Summary

The circulatory system is the body's delivery system. The heart pumps blood through blood vessels all around the body.

Blood brings oxygen and nutrients to body parts and carries away waste. Arteries carry blood away from the heart, veins bring it back, and capillaries are tiny vessels where blood reaches the body.

The heart and lungs work together so blood can pick up oxygen and deliver it again and again.

The Respiratory System

Your body needs air every minute of every day. The respiratory system is the body system that helps you breathe in oxygen and breathe out carbon dioxide.

Oxygen is a gas your body needs to live and grow. Carbon dioxide is a waste gas your body makes. Your respiratory system brings in the oxygen your body needs and helps remove the carbon dioxide your body does not need.

What happens when you breathe?

When you breathe in, air enters your nose or mouth. Then it travels down a tube called the trachea, or windpipe. After that, the air goes into your lungs.

Inside the lungs, the air moves through smaller and smaller tubes. At the end of these tiny tubes are tiny air sacs called alveoli. Alveoli are very small, but they do a very big job.

The path of air

1. Air enters through the nose or mouth.
2. It moves down the trachea.
3. It goes into the lungs.
4. It reaches the tiny air sacs called alveoli.
5. Oxygen moves into the blood.
6. Carbon dioxide moves from the blood into the alveoli.
7. You breathe out the carbon dioxide.

What do the nose and mouth do?

Your nose and mouth are the openings where air first comes in. Your nose is especially helpful because it can warm, moisten, and help clean the air before it goes deeper into your body.

That is one reason breathing through your nose can be helpful. Your body has smart ways to get the air ready for your lungs.

What is the trachea?

The trachea, or windpipe, is the tube that carries air from your nose or mouth down toward your lungs. It is like a main road that air travels on.

From the trachea, the air branches into smaller tubes that lead into each lung. These tubes are like branches on a tree.

What do the lungs do?

Your lungs are two soft organs in your chest. They fill with air when you breathe in and let air out when you breathe out.

The lungs do not work alone. They work with the tiny alveoli and with your blood to move gases where they need to go.

What are alveoli?

Alveoli are tiny air sacs inside the lungs. There are many, many alveoli in your lungs. Because there are so many of them, they give your body lots of space to move gases in and out.

In the alveoli, oxygen moves from the air into the bloodstream. At the same time, carbon dioxide moves from the blood into the alveoli. Then you breathe that carbon dioxide out.

You can think of alveoli like tiny trading spots. Oxygen goes into the blood, and carbon dioxide comes out of the blood.

Why is the blood important?

The blood carries oxygen from the lungs to the rest of the body. Every part of your body needs oxygen, including your brain, muscles, and heart.

After the body uses the oxygen, carbon dioxide is made. The blood carries that carbon dioxide back to the lungs so you can breathe it out.

Breathing in and breathing out

• Breathe in: oxygen-rich air comes into the body.
• Breathe out: carbon dioxide leaves the body.

This breathing happens again and again all day and all night, even when you are asleep.

Why do we breathe faster when we run?

When you run, jump, or play hard, your body needs more oxygen. Your muscles are working more, so they need extra help from the blood and lungs.

That is why you breathe faster during exercise. Your body is bringing in more oxygen and getting rid of more carbon dioxide.

Keeping the respiratory system healthy

• Get regular exercise.
• Try to breathe clean air.
• Cover your mouth and nose when you cough or sneeze.
• Wash your hands to help stop germs from spreading.
• Do not smoke, and stay away from smoke.

Healthy lungs help your whole body do its best work.

Worked Example 1: Following the path of air

Question: A student takes a deep breath in. Where does the air go first, and where does it go next?

Answer: First, the air goes in through the nose or mouth. Next, it travels down the trachea. Then it goes into the lungs and finally reaches the alveoli.

Why: Air follows a path through the respiratory system before oxygen moves into the blood.

Worked Example 2: What happens in the alveoli?

Question: What job do the alveoli do?

Answer: The alveoli are tiny air sacs where gases are exchanged. Oxygen moves from the air into the blood, and carbon dioxide moves from the blood into the alveoli.

Why: The alveoli are the part of the lungs where the blood picks up oxygen and drops off carbon dioxide.

Worked Example 3: Breathing during exercise

Question: Maya runs across the playground and notices she is breathing faster. Why?

Answer: Maya is breathing faster because her body needs more oxygen while she runs. Her body is also making more carbon dioxide, so she needs to breathe it out faster.

Why: Working muscles need more oxygen, so the respiratory system speeds up.

Worked Example 4: True or false

Question: True or false: The lungs send oxygen straight to the feet without help.

Answer: False.

Why: Oxygen moves from the alveoli into the blood, and then the blood carries it around the body, including to the feet.

Let’s remember the big idea

The respiratory system helps your body take in oxygen and remove carbon dioxide. Air travels through the nose or mouth, down the trachea, into the lungs, and to the alveoli.

In the alveoli, oxygen enters the blood and carbon dioxide leaves the blood. Then the blood carries oxygen to the body, and you breathe out the waste gas.

Quick Review

• The respiratory system helps you breathe.
• Air enters through the nose or mouth.
• Air travels down the trachea to the lungs.
• Alveoli are tiny air sacs in the lungs.
• In the alveoli, oxygen moves into the blood.
• Carbon dioxide moves out of the blood and is breathed out.

Macronutrients and Cellular Fuel

Our bodies need food to live, grow, play, and think. Food gives our body fuel. Fuel is what gives us energy, like gas helps a car go.

Inside our body are tiny parts called cells. Cells are very, very small, but they do big jobs. They help us move, grow, heal, and stay warm. Cells need fuel from food every day.

Different foods do different jobs in our body. Some foods give us quick energy. Some help build and fix our body. Some help keep us warm. Some help our body work the right way.

There are four important food helpers we will learn about today:

• Carbohydrates help give us energy.
• Proteins help build and repair our body.
• Fats help keep us warm and store energy.
• Vitamins and minerals help our body work well.

Let’s learn about each one.

1. Carbohydrates: energy food

Carbohydrates are foods that help give our body energy. We need energy to run, jump, learn, laugh, and play.

When you eat foods like bread, rice, pasta, oats, fruit, or crackers, your body can use them for energy. This energy helps your muscles move and helps your brain think.

You can think of carbohydrates as the body’s go food.

• Bread
• Rice
• Pasta
• Cereal
• Bananas
• Apples

2. Proteins: build and repair food

Proteins help our body grow. They also help fix parts of our body when we get hurt or when our body gets worn out from play and work.

Your muscles, skin, and other body parts need protein to stay strong. If you scrape your knee or your muscles feel tired after playing, protein helps your body repair itself.

You can think of proteins as the body’s grow and fix food.

• Eggs
• Beans
• Chicken
• Fish
• Yogurt
• Nuts or nut butter

3. Fats: warmth and stored energy

Fats help our body in important ways. They help keep us warm. They also store energy for later, kind of like saving food fuel in a little battery.

Our body does not need huge amounts of fat, but it does need some. Fat also helps protect parts inside our body.

You can think of fats as the body’s keep warm and save energy food.

• Avocado
• Cheese
• Nuts
• Seeds
• Peanut butter

4. Vitamins and minerals: helper foods

Vitamins and minerals do not all have the same job, but they are all important helpers. They help our body stay healthy and work the right way.

Some help keep bones strong. Some help us see. Some help our body stay healthy when we are sick. We get vitamins and minerals from many healthy foods, especially fruits and vegetables.

You can think of vitamins and minerals as the body’s helper foods.

• Carrots
• Spinach
• Milk
• Oranges
• Broccoli
• Beans

Why our body needs different kinds of food

No one food does every job. Our body works best when we eat a mix of foods. That way, our cells can get energy, build and repair, stay warm, and work well.

Eating only one kind of food would not give our body everything it needs. A healthy meal often has more than one food group in it.

For example, a meal with rice, beans, and carrots gives the body different helpers:

• Rice gives energy.
• Beans help build and repair.
• Carrots help the body work well.

How food helps the whole body

Your body parts work together. Your stomach helps break down food. Your blood carries the food fuel around your body. Your muscles use the fuel to move. Your brain uses fuel to think and learn.

That means food helps your whole body, from your head to your toes.

Worked Example 1: Find the energy food

Question: Mia wants energy to run at recess. Which food is the best choice: bread, chicken, or cheese?

Step 1: Remember that carbohydrates give energy.

Step 2: Look for the carbohydrate food.

• Bread = carbohydrate
• Chicken = protein
• Cheese = fat and protein

Answer: Bread is the best choice for energy to run.

Worked Example 2: Find the grow-and-fix food

Question: Leo played hard outside. His body needs help building and repairing. Which food helps most: eggs, apples, or rice?

Step 1: Remember that protein helps build and repair.

Step 2: Match the food to the job.

• Eggs = protein
• Apples = mostly carbohydrate and vitamins
• Rice = carbohydrate

Answer: Eggs help most with building and repairing.

Worked Example 3: Choose a balanced plate

Question: Which plate gives the body different kinds of help?

1. Only crackers
2. Rice, beans, and broccoli
3. Only cheese

Step 1: We want foods that do different jobs.

Step 2: Look at each plate.

• Only crackers = mostly energy food
• Rice, beans, and broccoli = energy food, grow-and-fix food, and helper food
• Only cheese = mostly fat and protein

Answer: Rice, beans, and broccoli is the best balanced plate.

Worked Example 4: Count the helper foods

Question: Sam has 4 foods: banana, yogurt, avocado, and carrots. How many different food jobs are there?

Step 1: Match each food to its main job.

• Banana = energy food
• Yogurt = grow-and-fix food
• Avocado = keep warm and save energy food
• Carrots = helper food

Step 2: Count the different jobs.

There are 4 different jobs. We can show it like this: \(1 + 1 + 1 + 1 = 4\).

Answer: Sam has 4 different food jobs in the meal.

Tips for remembering

• Carbohydrates = go
• Proteins = grow and fix
• Fats = warmth and saved energy
• Vitamins and minerals = helpers

Let’s review

Food is fuel for our body’s tiny cells. Carbohydrates help give energy. Proteins help build and repair. Fats help keep us warm and store energy. Vitamins and minerals help the body work well.

When we eat different healthy foods, we help our whole body stay strong, active, and ready to learn.

The Excretory System

Your body is busy all day long. It eats food, drinks water, moves, grows, and makes energy. While your body does these jobs, it also makes waste. Waste is what the body does not need.

The excretory system is the body system that helps remove waste. It also helps keep the right amount of water in the body. This is important because your body needs clean blood and the right balance of water to stay healthy.

One of the most important parts of the excretory system is the kidneys. You have two kidneys. They are bean-shaped organs in your lower back area, inside your body.

The kidneys clean the blood. Blood travels through the kidneys, and the kidneys take out wastes and extra water. Then the body turns that waste into urine.

Urine is liquid waste. Urine is made of water and wastes the body does not need. Making urine is one way your body gets rid of waste and keeps a healthy water balance.

Here are the main jobs of the kidneys:

• Filter waste from the blood
• Remove extra water when the body has too much
• Help keep balance so the body has the right amount of water and chemicals

After the kidneys make urine, the urine moves through two thin tubes called ureters. The ureters carry urine from the kidneys to the bladder.

The bladder is like a storage bag for urine. It holds the urine until it is time to go to the bathroom.

When you go to the bathroom, urine leaves the body through a tube called the urethra. This is the last step in removing liquid waste from the body.

So the path looks like this:

1. Blood goes to the kidneys.
2. The kidneys filter out waste and extra water.
3. Waste becomes urine.
4. Urine travels through the ureters.
5. Urine stays in the bladder.
6. Urine leaves the body through the urethra.

The excretory system does more than just make urine. It helps the body keep a good balance. If you drink a lot of water, your kidneys help remove extra water. If your body needs to save water, your kidneys help keep more of it.

This balance matters because every part of your body needs water to work well. Your blood, muscles, and organs all need the right amount.

The kidneys also help remove toxins. Toxins are harmful substances that the body should get rid of. The kidneys help clean these out of the blood.

Why is the excretory system important?

• It keeps blood cleaner.
• It removes wastes the body does not need.
• It helps control water in the body.
• It helps the body stay healthy and balanced.

How can you help keep your excretory system healthy?

• Drink water each day.
• Use the bathroom when you need to.
• Eat healthy foods.
• Stay active.
• Tell an adult if it hurts when you go to the bathroom or if something feels wrong.

Worked Example 1

Question: What do the kidneys do?

Think: The lesson says the kidneys clean the blood and take out waste and extra water.

Answer: The kidneys filter waste and extra water from the blood and help make urine.

Worked Example 2

Question: Put these body parts in order: bladder, kidneys, urethra, ureters.

Think: First urine is made in the kidneys. Next it travels through the ureters. Then it is stored in the bladder. Last it leaves through the urethra.

Answer: kidneys  ureters  bladder  urethra

Worked Example 3

Question: Maya drinks a lot of water after playing outside. How does her excretory system help her body?

Think: When there is extra water in the body, the kidneys help remove some of it.

Answer: Her kidneys filter the blood and remove extra water. That extra water becomes part of the urine.

Worked Example 4

Question: Which part stores urine before it leaves the body?

Think: The bladder is like a storage bag.

Answer: The bladder stores urine before it leaves the body.

Lets Remember

• The excretory system removes waste from the body.
• The kidneys filter the blood.
• Waste and extra water become urine.
• Urine travels through the ureters to the bladder.
• Urine leaves the body through the urethra.
• This system helps keep the right balance of water in the body.

Brief Summary

The excretory system helps your body get rid of waste and extra water. The kidneys clean the blood and make urine. Urine moves through the ureters, stays in the bladder, and leaves through the urethra. This system helps your body stay clean, balanced, and healthy.

Digestive System means the body parts that help us break down food so our bodies can use it for energy, growth, and staying healthy.

Every time you eat, your body begins a step-by-step job. Food does not stay the same. It gets chewed, mixed, broken into smaller pieces, and moved through your body.

This lesson will teach what happens to food in the mouth, stomach, and intestines. You will learn how these body parts work together like a team.

Why do we need the digestive system?

Your body needs nutrients from food. Nutrients are the helpful parts of food that give your body energy and help you grow.

• Food gives you energy to run, play, and think.
• Food helps your body grow.
• Food helps keep your body healthy.

If food stayed in big pieces, your body could not use it well. The digestive system changes food into tiny parts your body can take in.

The path food takes

Food moves through the body in an order. A simple path is:

1. Mouth
2. Stomach
3. Intestines

Each part has a special job.

1. The mouth: where digestion begins

Digestion starts in the mouth. Your teeth chew food and break it into smaller pieces. This is called mechanical breakdown. That means food is being broken apart by physical action, like chewing.

Your tongue helps move food around in your mouth. It pushes the food while you chew and helps you swallow.

There is also saliva in your mouth. Saliva is the watery liquid called spit. Saliva starts helping break food down even more. This is part of chemical breakdown.

So in the mouth, two things happen:

• Teeth chew food into smaller pieces.
• Saliva starts breaking down the food.

2. Swallowing and moving food

After chewing, you swallow. The food moves down a tube to the stomach. The body is very good at moving food from one place to the next.

You do not have to tell your body what to do. Your body does it automatically.

3. The stomach: mixing and breaking down food

The stomach is like a strong mixing bag. It squishes and stirs the food. This is another kind of mechanical breakdown because the food is being mashed and mixed.

The stomach also uses juices to help break food down. This is chemical breakdown. The food becomes a soft, soupy mixture.

In the stomach, food is:

• mixed
• mashed
• broken down more by juices

4. The intestines: taking in nutrients

After the stomach, food moves into the intestines. The intestines are long tubes inside your body.

The most important job here is absorption. Absorption means the body takes in the tiny helpful parts of food, called nutrients.

The nutrients move from the intestines into the body, where they can be used for energy, growth, and health.

You can think of the intestines like a place where the body collects the good, useful parts of food.

Mechanical and chemical breakdown

The digestive system uses two main ways to break down food:

• Mechanical breakdown: food is broken into smaller pieces by chewing, mashing, and mixing.
• Chemical breakdown: liquids and juices in the body help change food into even smaller parts.

Both kinds are important. They work together so food can become small enough for the body to use.

Digestive system team

The digestive system is a team of body parts working together.

• The mouth chews food and adds saliva.
• The stomach mixes food with strong juices.
• The intestines take in nutrients.

When all the parts do their jobs, your body gets what it needs from food.

Example 1: Eating an apple

You take a bite of an apple. First, your teeth chew it into smaller pieces. Your saliva mixes with the apple pieces.

Then you swallow. The apple goes to your stomach, where it is mixed and broken down more. After that, it moves to the intestines, where the body takes in the nutrients from the apple.

Worked Example 1

Question: What happens first when you eat a cracker?

Step 1: Think about where digestion begins.

Step 2: Digestion begins in the mouth.

Step 3: Teeth chew the cracker, and saliva starts breaking it down.

Answer: First, the cracker is chewed in the mouth.

Worked Example 2

Question: Which body part mixes food with juices: the mouth, the stomach, or the intestines?

Step 1: Remember the job of each part.

• Mouth: chewing and saliva
• Stomach: mixing and strong juices
• Intestines: taking in nutrients

Step 2: The part that mixes food with juices is the stomach.

Answer: The stomach.

Worked Example 3

Question: What is absorption?

Step 1: Think about what happens in the intestines.

Step 2: In the intestines, the body takes in the useful parts of food.

Answer: Absorption is when the body takes in nutrients from food.

Worked Example 4

Question: Put these in order: stomach, mouth, intestines.

Step 1: Ask yourself where food starts.

Step 2: Food starts in the mouth.

Step 3: Next it goes to the stomach.

Step 4: Then it goes to the intestines.

Answer: Mouth  Stomach  Intestines

Helpful reminders

• Digestion starts in the mouth.
• Chewing is a kind of mechanical breakdown.
• Saliva and stomach juices help with chemical breakdown.
• The stomach mixes food.
• The intestines absorb nutrients.

Lets think about it

If you eat a sandwich, your body does not use the sandwich in one big piece. It must be broken down into smaller and smaller parts.

First you chew it in your mouth. Then your stomach mixes it. After that, your intestines take in the nutrients. This is how your body gets energy from your food.

Summary

The digestive system helps your body break down food and use it. Digestion begins in the mouth, where teeth chew food and saliva starts chemical breakdown.

Next, food goes to the stomach, where it is mixed and broken down more. Then it moves to the intestines, where nutrients are absorbed into the body.

The mouth, stomach, and intestines work together to help keep you strong, growing, and healthy.

Excretory System

Your body works hard every day. It moves, grows, eats food, and uses water. While your body does these jobs, it also makes waste. Waste is what your body does not need.

The excretory system is the body system that helps remove waste. It also helps keep the right amount of water in the body. This helps your body stay healthy.

One of the most important parts of the excretory system is the kidneys. You have two kidneys. They are in your back area, below your ribs.

The kidneys clean your blood. Blood travels all around your body. As it travels, it picks up waste. Then the blood goes to the kidneys. The kidneys filter, or clean, the blood by taking out the waste and extra water.

One waste the kidneys remove is called urea. Urea is a waste made when your body breaks down food and uses it for energy and growth. Your body does not need urea, so the kidneys help remove it.

After the kidneys take out waste and extra water, the body makes urine. Urine is the liquid waste your body sends out. Urine is made of water and wastes like urea.

Urine moves through small tubes from the kidneys to the bladder. The bladder is like a storage bag that holds urine until your body is ready to let it out.

When the bladder gets full, your body sends a message that it is time to use the bathroom. Then urine leaves the body through a small tube.

Main Parts of the Excretory System

• Kidneys – filter waste and extra water from the blood
• Ureters – tubes that carry urine from the kidneys to the bladder
• Bladder – holds urine until it leaves the body
• Urethra – the tube urine goes through to leave the body

What the Excretory System Does

1. Blood brings waste to the kidneys.
2. The kidneys filter out waste and extra water.
3. The waste and water become urine.
4. Urine travels to the bladder.
5. Urine leaves the body when you go to the bathroom.

The excretory system is important because too much waste in the body can make us sick. The kidneys help keep the body clean on the inside.

The kidneys also help keep the right amount of water in the body. If there is too much water, the body can get rid of some of it in urine. If the body needs to save water, the kidneys help with that too.

This is one way the body stays in balance. Balance means the body keeps things at healthy levels, like water and waste.

Worked Example 1

Question: What part of the body filters waste from the blood?

Think: The excretory system has kidneys, ureters, a bladder, and a urethra. Which part cleans the blood?

Answer: The kidneys filter waste from the blood.

Worked Example 2

Question: What is urine?

Think: After the kidneys remove waste and extra water, what is made?

Answer: Urine is liquid waste made of water and wastes like urea.

Worked Example 3

Question: Put these in order: bladder, kidneys, urine leaves the body, blood brings waste.

Step 1: First, blood brings waste to the kidneys.

Step 2: Next, the kidneys filter the waste and make urine.

Step 3: Then urine goes to the bladder.

Step 4: Last, urine leaves the body.

Answer: blood brings waste  kidneys  bladder  urine leaves the body

Worked Example 4

Question: Why is the excretory system important?

Think: What would happen if waste stayed in the body?

Answer: The excretory system is important because it removes waste and extra water. This helps keep the body healthy and in balance.

Helpful Things to Remember

• Your body makes waste every day.
• The kidneys clean the blood.
• Urea is a waste the kidneys remove.
• Urine is the liquid waste the body sends out.
• The bladder stores urine until it leaves the body.

Brief Summary

The excretory system helps the body get rid of waste. The kidneys filter waste and extra water from the blood. This makes urine, which travels to the bladder and then leaves the body. The excretory system helps keep the body clean, healthy, and in balance.

Neurology of Stress and Mental Health

Have you ever felt your heart beat faster before a test, a game, or speaking in front of the class? That is your body reacting to stress. Stress is the way your body and brain respond when something feels challenging, scary, exciting, or important.

Your brain and body work together all the time. When you feel stress, your brain sends messages through your body very quickly. These messages can help protect you in an emergency, but too much stress for too long can make your body and feelings harder to manage.

In this lesson, you will learn how the brain helps control stress, what adrenaline and cortisol do, how stress affects mental health, and what healthy choices can help you feel calmer and stronger.

1. What is stress?

Stress is your bodys reaction to a challenge or demand. Sometimes stress is short and goes away quickly. For example, you may feel stress before answering a hard question in class. Other times stress lasts longer, like worrying every day about a problem.

Not all stress is bad. A small amount of stress can help you pay attention, move quickly, or prepare for something important. But when stress happens too often or lasts too long, it can affect your body, thoughts, and emotions.

2. How the brain reacts to stress

Your brain is the control center of your body. It helps you think, feel, remember, and respond to danger.

One important part of the brain is the amygdala. The amygdala helps notice danger and strong emotions, like fear. If it thinks something might be a threat, it sends a warning signal.

Another important part is the hypothalamus. This part acts like a messenger. It tells the body to get ready for action.

Your brain can also use the prefrontal cortex. This part helps you think clearly, make good choices, and calm down. When stress is very high, it can be harder for this thinking part to do its job.

3. Adrenaline: the fast helper

When the brain senses danger or stress, the body may release adrenaline. Adrenaline is a chemical that helps your body react quickly.

Adrenaline can cause:

• Faster heartbeat
• Faster breathing
• More energy for muscles
• Wider eyes and stronger focus for a short time

This is often called the fight, flight, or freeze response.

• Fight means getting ready to face the problem.
• Flight means getting ready to run away.
• Freeze means becoming still for a moment.

These responses can help in real danger. But sometimes the body reacts this way even when the danger is not physical, like before a test or during an argument.

4. Cortisol: the longer-lasting stress chemical

Another chemical connected to stress is cortisol. Cortisol helps your body stay alert and ready when stress lasts longer than a few moments.

Cortisol can be helpful in short periods. It helps the body manage energy and stay prepared. But if cortisol stays high for a long time, it can make a person feel tired, worried, or upset.

Too much stress over time may lead to:

• Trouble sleeping
• Headaches or stomachaches
• Feeling cranky or sad
• Trouble focusing
• Feeling overwhelmed

5. How stress affects mental health

Mental health means how we think, feel, and handle life. It is just as important as physical health.

When stress is managed in healthy ways, the brain and body can return to a calm state. But when stress builds up and a person does not get enough rest, support, or coping tools, it can affect mental health.

A person under too much stress may:

• Worry a lot
• Feel nervous or anxious
• Get upset more easily
• Have trouble paying attention
• Feel lonely or discouraged

Everyone feels stress sometimes. That is normal. What matters is learning healthy ways to respond.

6. Signs that the body may be stressed

Stress can show up in the body, thoughts, feelings, and actions.

Body signs:

• Fast heartbeat
• Sweaty hands
• Shaky feeling
• Headache
• Stomachache

Feeling signs:

• Worry
• Fear
• Frustration
• Sadness

Thinking signs:

• Trouble focusing
• Forgetting things
• Thinking the worst will happen

Action signs:

• Arguing more
• Crying more easily
• Avoiding work
• Not wanting to do favorite activities

7. Healthy coping mechanisms

A coping mechanism is a way to handle stress. Healthy coping skills help your brain and body calm down safely.

Here are some healthy ways to cope with stress:

• Deep breathing: Slow breaths can help tell your body that it is safe to relax.
• Talking to a trusted adult: A parent, teacher, school counselor, or other trusted grown-up can help.
• Exercise and movement: Walking, stretching, dancing, or playing outside can lower stress.
• Sleep: Good sleep helps the brain and body recover.
• Healthy food and water: Eating balanced meals and drinking water helps your body work well.
• Quiet time: Reading, drawing, listening to calm music, or sitting quietly can help.
• Positive self-talk: Saying kind things to yourself, like "I can try my best," can help calm worried thoughts.
• Breaking big problems into small steps: Doing one part at a time can make a problem feel easier.

8. A simple breathing tool

One easy way to calm the stress response is to breathe slowly.

1. Breathe in through your nose for 4 counts.
2. Hold for 2 counts.
3. Breathe out slowly for 4 counts.
4. Repeat a few times.

We can show one breath cycle like this:

Inhale + hold + exhale = total time

\(4 + 2 + 4 = 10\)

So one calm breath cycle takes 10 counts.

9. Worked Examples

Example 1: Spot the stress response

Situation: Maya is about to give a class presentation. Her heart is beating fast and her hands feel sweaty.

Question: Which stress chemical is likely helping her body react quickly?

Answer: Adrenaline.

Why: Adrenaline works fast. It can make the heart beat faster and prepare the body for action.

Example 2: Short stress or long stress?

Situation: Eli feels nervous for a few minutes before a spelling test, but feels better after it is over.

Question: Is this short stress or long stress?

Answer: This is short stress.

Why: The stress lasted a short time and then went away. Short stress can sometimes help a person focus.

Example 3: Choosing a healthy coping skill

Situation: Jordan feels overwhelmed because he has homework, chores, and soccer practice.

Question: What is one healthy coping skill Jordan can use?

Answer: Jordan can break the problem into small steps.

Worked solution:

• Step 1: Finish math homework.
• Step 2: Do one chore.
• Step 3: Pack soccer shoes and water bottle.

Why: Small steps make a big job feel more manageable and can lower stress.

Example 4: Using a calming math pattern

Situation: A student does 3 calm breathing cycles. Each cycle takes 10 counts.

Question: How many counts does the student spend breathing calmly?

Work:

$$3 \times 10 = 30$$

Answer: The student spends 30 counts breathing calmly.

Why: Repeating slow breathing gives the brain and body extra time to settle down.

10. Ways to support good mental health every day

Good mental health is built over time. Small healthy habits each day can make a big difference.

• Get enough sleep each night.
• Eat healthy foods from different food groups.
• Move your body every day.
• Spend time with supportive people.
• Take breaks when you feel overwhelmed.
• Share your feelings with someone you trust.
• Do activities that bring you joy, like art, sports, music, or reading.

11. When to ask for help

It is always okay to ask for help. If stress, worry, or sadness lasts a long time or starts making daily life hard, it is important to tell a trusted adult.

You can talk to:

• A parent or caregiver
• A teacher
• A school counselor
• A doctor or nurse

Asking for help is a strong and healthy choice.

Summary

Stress is the bodys response to challenges. The brain helps control this response by sending signals that can release adrenaline for quick action and cortisol for longer stress support.

These chemicals can help in the short term, but too much stress for too long can affect the body and mental health. Healthy coping skills like deep breathing, movement, rest, talking to a trusted adult, and taking problems one step at a time can help the brain and body return to calm.

Germs are tiny living or nonliving things that can make people sick. They are so small that we cannot see them with just our eyes. Some germs can get into our bodies and cause sickness. This idea is called germ theory: germs can spread and make people sick.

Not all tiny things are bad. But some tiny germs, called pathogens, can cause disease. A disease is an illness in the body.

Two common kinds of pathogens are bacteria and viruses.

• Bacteria are tiny living things. Some bacteria are helpful, but some can make us sick.
• Viruses are even tinier. They can get into our bodies and make us sick too.

When pathogens get into the body, they can make parts of the body stop working the way they should. That is why we may get a fever, cough, sore throat, or runny nose.

Our bodies work hard to protect us. The body has ways to fight germs. Skin helps keep germs out. Washing with soap helps remove germs from our hands. Rest, healthy food, and water help our bodies stay strong.

How do germs spread? Germs can move from one place to another in many simple ways.

• By touching dirty hands or objects
• By coughs and sneezes
• By sharing drinks or food
• By not washing hands after using the bathroom

That is why healthy habits are very important. We can help stop germs from spreading.

Healthy habits that help keep germs away:

• Wash hands with soap and water
• Cover coughs and sneezes with a tissue or your elbow
• Do not share cups, straws, or forks
• Keep hands away from your eyes, nose, and mouth
• Tell an adult if you feel sick

Why handwashing matters

If germs are on your hands and you touch your face, germs can get into your body. Soap and water help wash the germs away.

You can think of it like this: dirty hands may have germs, and clean hands have fewer germs. We want fewer germs on our hands.

Worked Example 1: After a sneeze

Lila sneezes into her hands and then wants to eat crackers. What should she do first?

Answer: Lila should wash her hands with soap and water first.

Why? Germs from the sneeze may be on her hands. Washing helps remove those germs before she eats.

Worked Example 2: Sharing at lunch

Ben wants to share his straw with a friend. Is that a good idea?

Answer: No, that is not a good idea.

Why? Germs can spread when people share straws, cups, or forks.

Worked Example 3: Touching a doorknob

Maya touches a doorknob at school. Then she rubs her eyes. Could germs spread this way?

Answer: Yes, germs could spread this way.

Why? Germs can be on objects. If Maya touches her eyes, the germs may get into her body.

Worked Example 4: Choosing the healthiest habit

Which choice helps stop germs the most?

1. Cover a cough with your elbow
2. Cough into the air
3. Share a spoon with a friend

Answer: Choice 1, cover a cough with your elbow.

Why? Covering coughs helps keep germs from spreading to other people.

Let’s remember the big idea: Tiny pathogens like bacteria and viruses can cause sickness. They can spread from person to person or from surfaces to people. Good health habits help protect our bodies and others around us.

Summary

• Germs are tiny things that can make us sick.
• Pathogens are germs that cause disease.
• Bacteria and viruses are two kinds of pathogens.
• Germs can spread by touch, coughs, sneezes, and shared items.
• Handwashing and covering coughs help stop germs from spreading.

Preventative Health and Hygiene means taking care of your body before you get sick or hurt. Good health habits can help stop germs, tooth decay, skin damage, and some illnesses. These habits include washing hands, brushing teeth, keeping your surroundings clean, and using sunscreen to protect your skin from the sun.

Your body has many systems that work together to keep you healthy. Your skin protects the outside of your body. Your mouth and teeth help you eat and speak. Your immune system helps fight germs. Preventative health habits support all of these systems.

Scientists and doctors study how diseases spread and how to stop them. When people use health habits like handwashing, cleaning surfaces, and using sunscreen, they are using interventions. An intervention is an action taken to improve health or prevent harm.

Why Preventative Health Matters

It is usually easier to prevent a problem than to fix it later. For example, brushing your teeth every day helps stop cavities before they start. Washing your hands helps stop germs before they get into your body. Wearing sunscreen helps protect your skin before the sun can damage it.

Preventative habits help at home, at school, and in the community. When many people follow healthy habits, fewer people get sick. This is one reason schools remind students to wash hands, cover coughs, and keep classrooms clean.

1. Hand Hygiene

Hand hygiene means keeping your hands clean to remove dirt and germs. Germs are tiny living things, like bacteria and viruses, that can make people sick. Germs can get on your hands when you touch doorknobs, desks, pets, food, or your face.

Handwashing is one of the best ways to prevent the spread of disease. Soap helps lift dirt, oils, and germs off your skin. Water rinses them away.

When should you wash your hands?

• Before eating or touching food
• After using the bathroom
• After coughing, sneezing, or blowing your nose
• After touching garbage
• After playing outside
• After touching animals
• When your hands look or feel dirty

How to wash your hands the right way:

1. Wet your hands with clean running water.
2. Put soap on your hands.
3. Rub your hands together for at least 20 seconds.
4. Scrub the fronts, backs, between fingers, and under nails.
5. Rinse well.
6. Dry with a clean towel or air dry.

A good way to measure time is to sing a short song that lasts about 20 seconds. The number 20 is important here because washing too quickly may leave germs behind.

If soap and water are not available, adults may use hand sanitizer. But when hands are very dirty or greasy, soap and water work best.

2. Dental Care

Your teeth are covered by a hard outer layer called enamel. Enamel helps protect teeth, but it can be damaged. Tiny bits of food left on teeth can mix with bacteria in your mouth to form plaque, a sticky layer that can lead to cavities.

A cavity is a hole in a tooth caused by decay. Decay happens when bacteria feed on sugars from food and drinks. These bacteria produce acids that can wear away enamel.

Healthy dental habits include:

• Brushing teeth twice a day
• Using toothpaste with fluoride if recommended
• Flossing once a day to clean between teeth
• Visiting the dentist regularly
• Drinking water
• Eating fewer sugary snacks and drinks

Brushing removes plaque from the front, back, and chewing surfaces of teeth. Flossing removes food and plaque from places a toothbrush may not reach. Together, these habits lower the chance of cavities and gum problems.

Dental care is an example of prevention because it helps stop problems before they become painful or serious.

3. Sanitation and Clean Surroundings

Sanitation means keeping places clean and safely managing waste, water, and food to protect health. Good sanitation helps reduce the spread of germs in homes, schools, and neighborhoods.

Examples of sanitation include cleaning bathrooms, throwing trash away properly, keeping drinking water clean, washing fruits and vegetables, and disinfecting surfaces that many people touch.

If a table is sticky with food, germs may grow there more easily. If trash piles up, it can attract insects or rodents. Keeping areas clean lowers these risks.

Important sanitation habits:

• Use tissues or your elbow to cover coughs and sneezes.
• Throw used tissues in the trash.
• Clean desks, counters, and shared tools.
• Keep bathrooms clean.
• Do not share water bottles, toothbrushes, or utensils when sick.
• Store food safely.

Sanitation helps whole groups of people. If one student washes hands, that helps one person. If a whole class washes hands and keeps desks clean, that helps many people stay healthier.

4. Sunscreen and UV Protection

The sun gives us light and warmth, but it also gives off ultraviolet (UV) rays. UV rays are invisible rays that can damage skin. Too much sun can cause sunburn, early skin damage, and increase the risk of skin disease later in life.

Your skin is your body's outer covering and an important protective organ. Sunscreen helps protect the skin by blocking or absorbing some UV rays.

How to protect your skin:

• Use sunscreen with a good SPF number, such as SPF 30 or higher
• Put sunscreen on before going outside
• Reapply it as directed, especially after swimming or sweating
• Wear a hat and sunglasses
• Wear clothing that covers your skin
• Look for shade when the sun is strongest

SPF stands for Sun Protection Factor. A higher SPF means more protection than a lower SPF when used correctly. For example, SPF 30 protects better than SPF 15.

Sunscreen is preventative care because it helps stop damage before it happens. Even on cloudy days, some UV rays can still reach your skin.

How These Health Actions Work Together

These habits may seem different, but they all have the same goal: protecting the body. Handwashing protects you from many germs. Dental care protects your teeth and gums. Sanitation protects groups of people by keeping environments cleaner. Sunscreen protects your skin from sun damage.

When scientists look at which interventions work well, they ask questions like:

• Does handwashing lower the spread of illness?
• Does brushing and flossing lower the number of cavities?
• Does cleaning surfaces reduce germs in shared spaces?
• Does sunscreen lower the chance of sunburn?

If the answer is yes, then the intervention is effective, which means it works well.

Worked Example 1: Choosing the Best Hand Hygiene Habit

Question: Maya comes in from recess and is about to eat lunch. What is the best preventative health action?

Think: Her hands may have picked up dirt and germs from playground equipment.

Answer: Maya should wash her hands with soap and water before eating.

Why: This helps remove germs so they do not get into her mouth with her food.

Worked Example 2: Preventing Cavities

Question: Jordan brushes his teeth in the morning but often skips brushing at night and eats lots of sticky candy. Is this a good prevention plan?

Think: Brushing only once a day leaves more time for plaque to build up. Sugary candy gives bacteria fuel to make acids.

Answer: No, this is not a strong prevention plan.

Better plan:

• Brush twice a day
• Floss daily
• Eat fewer sugary snacks
• Visit the dentist regularly

Why: These actions help protect enamel and lower the chance of cavities.

Worked Example 3: Sanitation in a Classroom

Question: A class shares scissors, pencils, and tablets. Several students have colds. What are two good sanitation actions the class can take?

Think: Shared items can carry germs from one person to another.

Answer:

• Clean shared tools and surfaces regularly
• Wash hands after coughing, sneezing, or using shared items before eating

Why: These actions help reduce the spread of germs around the classroom.

Worked Example 4: UV Protection Decision

Question: Elena will be at the beach for 3 hours. She puts on sunscreen once before going outside, then swims for a long time. What should she do to stay protected?

Think: Water and sweating can reduce how well sunscreen works over time.

Answer: Elena should reapply sunscreen as directed, especially after swimming, and also use shade, a hat, or protective clothing.

Why: One layer of sunscreen may not protect her for the whole time at the beach.

Quick Compare: Which Intervention Fits?

• Dirty hands before lunch → Handwashing
• Food stuck between teeth → Flossing
• Germs on shared desks → Cleaning and disinfecting surfaces
• Bright sunny day outside → Sunscreen and shade

Healthy Daily Checklist

• Wash hands at important times
• Brush teeth in the morning and at night
• Floss each day
• Keep your room, desk, and shared spaces clean
• Cover coughs and sneezes
• Use sunscreen before spending time outdoors
• Drink water and choose healthy foods often

Summary

Preventative health and hygiene are habits that help stop illness, injury, and damage before they begin. Hand hygiene reduces the spread of germs. Dental care helps prevent cavities and gum problems. Sanitation keeps shared spaces safer and cleaner. Sunscreen protects skin from harmful UV rays.

These actions are effective because they lower risk. When you practice them every day, you help protect your own body and the health of the people around you.

The Immune System and Clean Hands

Your body is amazing. It has special ways to help keep you healthy every day.

Sometimes tiny germs can get into our bodies. Germs are so small that we cannot see them with our eyes. Some germs can make us sick.

Your body has a helper team called the immune system. The immune system helps find germs and fight them off.

One important part of this helper team is white blood cells. White blood cells move through your body and help stop germs that do not belong there.

What does the immune system do?

• It looks for germs that should not be in your body.
• It helps fight those germs.
• It helps your body heal and get better.

You can think of white blood cells like tiny body guards. When germs get in, white blood cells help protect you.

What are hygiene interventions?

Hygiene interventions are healthy actions we do to help stop germs from spreading. That means we do things that keep our bodies and spaces clean.

These healthy actions work with your immune system. Your body fights germs, and you can help your body by washing, covering coughs, and keeping clean.

Ways to help stop germs

• Wash hands with soap and water.
• Cover coughs and sneezes with your elbow or a tissue.
• Do not touch your eyes, nose, or mouth with dirty hands.
• Keep cuts clean and covered.
• Throw away used tissues.

Why is handwashing so important?

Your hands touch many things, like toys, tables, doorknobs, and books. Germs can get on your hands. Then germs can move from your hands to your face or to other people.

Washing hands with soap and water helps remove germs from your skin.

Some germs have a soft outside coat made of fat. This coat is called a lipid envelope. Soap can break apart that soft coat. When the coat breaks, the germ cannot work the same way.

Soap also helps lift dirt and germs off your hands so the water can rinse them away.

How to wash hands

1. Wet your hands with water.
2. Put on soap.
3. Rub your hands together well.
4. Rub the fronts, backs, between fingers, and under nails.
5. Rinse with water.
6. Dry your hands.

It helps to scrub long enough to do a short song. Clean hands help stop germs from spreading.

When should you wash your hands?

• Before eating.
• After using the bathroom.
• After coughing, sneezing, or blowing your nose.
• After playing outside.
• After touching something dirty.

Worked Example 1

Question: Mia comes inside after playing outside. Her hands are dirty. What should she do before eating?

Answer: Mia should wash her hands with soap and water.

Why: Dirt and germs may be on her hands. Washing helps remove the germs before she eats.

Worked Example 2

Question: Jay sneezes into a tissue. What should he do next?

Answer: He should throw the tissue away and wash his hands.

Why: Sneezes can spread germs. Throwing away the tissue and washing hands helps keep germs from moving to other places.

Worked Example 3

Question: Which one helps your body fight germs best?

• A. Never washing hands
• B. Washing hands with soap and water

Answer: B. Washing hands with soap and water.

Why: Your immune system fights germs inside your body, and clean hands help stop many germs before they get inside.

Worked Example 4

Question: Sam has white blood cells in his body. What do they do?

Answer: They help fight germs.

Why: White blood cells are part of the immune system, the body’s helper team that protects you.

Let’s remember

• Germs are tiny and can make us sick.
• The immune system helps protect the body.
• White blood cells help fight germs.
• Soap and water help remove germs from hands.
• Clean habits help your body stay healthy.

Brief Summary

Your body has an immune system that helps protect you from germs. White blood cells are an important part of that system because they help fight germs.

You can help your body by practicing good hygiene. Washing your hands with soap and water, covering coughs and sneezes, and keeping things clean are simple ways to stop germs from spreading.

Human Ontogeny and Lifespan Development means how people grow and change through life.

Every human starts very small, grows bigger, learns new things, and changes over time. This is called the human life cycle.

In this lesson, we will learn that people go through different life stages. At each stage, bodies and brains can do new things.

Introduction

You were not always the size you are now. Once, you were a baby. Now you are a child. One day, you will be a grown-up. Later, you will be old. These are all parts of living and growing.

People change in many ways as they grow:

• They get bigger.
• They get stronger.
• They learn to talk, read, think, and solve problems.
• They learn to care for themselves and others.

Main Teaching Points

1. Life begins with a baby.

A baby is very young. Babies need lots of care from adults. Babies cannot walk or feed themselves at first.

Babies grow quickly. They learn to:

• lift their heads,
• roll over,
• sit,
• crawl,
• stand,
• and walk.

Babies also begin to make sounds, smile, and learn faces and voices. Their brains are growing as they learn about the world.

2. Children keep growing and learning.

After babyhood comes childhood. You are in childhood now.

Children can do more and more things as they grow. They may:

• run and jump,
• talk in longer sentences,
• draw and write,
• make friends,
• ask questions,
• and learn at school.

Children still need healthy food, sleep, exercise, and loving care. These help the body and brain grow well.

3. Teenagers are growing toward adulthood.

When children get much older, they become teenagers. Teenagers are not little kids anymore, but they are not adults yet.

Teenagers grow taller and stronger. They learn more about the world and often do more things on their own. They still need healthy habits and support from family and other caring adults.

4. Adults are fully grown.

Adults are fully grown people. Adults may work, take care of families, help children, and make many choices each day.

Adults still need to take care of their bodies and brains. Eating healthy foods, moving their bodies, sleeping, and seeing a doctor when needed help adults stay healthy.

5. Older adults have lived many years.

When adults get much older, they become older adults. Older adults have learned many things over their lives.

Some older adults may move more slowly. Some may need extra help. But they can still share stories, skills, love, and wisdom with others.

6. All life stages matter.

Each stage of life is important. Babies, children, teenagers, adults, and older adults all have needs and all deserve care and respect.

People do many things at different ages, but everyone grows in their own way. Some children learn to do things a little earlier or a little later than others. That is often okay.

7. The body and brain grow together.

As people grow, their bodies change and their brains change too.

The body helps people move, play, and do work. The brain helps people think, remember, learn, and feel.

These work together. For example:

• A baby’s body grows strong enough to stand.
• A child’s brain learns the steps for reading.
• A teenager learns new ideas and skills.
• An adult uses body and brain together every day.

8. Healthy habits help at every age.

No matter the life stage, healthy habits are important. Healthy habits help people grow, feel good, and stay well.

• Eat healthy foods.
• Drink water.
• Get enough sleep.
• Move and play.
• Wash hands and keep clean.
• Talk about feelings.
• Visit a doctor when needed.

Life Stages in Order

1. Baby
2. Child
3. Teenager
4. Adult
5. Older adult

We can show the order with numbers:

First is \(1\) baby, then \(2\) child, then \(3\) teenager, then \(4\) adult, then \(5\) older adult.

Worked Examples

Example 1: What comes next?

Sam was once a baby. Now Sam is 6 years old and goes to school. What life stage is Sam in now?

Step 1: Think about what children do. Children go to school, learn, play, and grow.

Step 2: Match Sam to the life stage.

Answer: Sam is a child.

Example 2: Put the stages in order.

Here are the stages mixed up: adult, baby, older adult, child.

Step 1: Start with the youngest stage.

Step 2: Go in order as a person grows.

Answer: baby, child, adult, older adult.

Example 3: Which change fits the stage?

Lina is learning to crawl and say simple sounds. Which stage fits Lina best?

Step 1: Think about who crawls and is just starting to talk.

Step 2: Babies do these things.

Answer: Lina is a baby.

Example 4: Healthy habits for all ages

Ben says, “Only kids need sleep.” Is Ben correct?

Step 1: Think about the lesson. Do babies, children, teenagers, adults, and older adults all need healthy habits?

Step 2: Yes. Sleep helps the body and brain at every age.

Answer: Ben is not correct. Everyone needs sleep.

Examples From Real Life

• A baby drinks milk and needs help.
• A child learns to read and ride a bike.
• A teenager learns new school subjects and takes on more responsibility.
• An adult may work and care for others.
• An older adult may tell stories and teach younger people.

Things to Remember

• People grow and change over time.
• The life cycle has stages.
• Bodies and brains both grow.
• Healthy habits matter at every age.
• Everyone deserves care and respect.

Brief Summary

Human ontogeny and lifespan development means the way people grow from baby to child, then to teenager, adult, and older adult.

At each stage, people’s bodies and brains can do new things. Healthy habits like good food, sleep, movement, and care help people grow and stay healthy throughout life.

Reproductive Health and Development is the study of how the human body grows, changes, and stays healthy as people get older. One important time of change is called puberty. Puberty is a normal stage of development when a child’s body begins to mature into an adult body.

This lesson explains the basic body changes during puberty, the role of hormones, the reproductive cycle, and healthy habits that help people care for their bodies. These changes are natural, happen at different times for different people, and are a normal part of life.

Everyone develops at their own pace. Some people begin puberty earlier, and some begin later. That is normal. The most important thing is to understand the changes and know how to stay healthy.

What is puberty?

Puberty is the time when the body begins to change from a child’s body into a more grown-up body. During this time, the brain sends signals to the body to start making special chemical messengers called hormones.

Hormones are chemicals made by the body that help control growth and changes. They act like messages that travel through the body and tell different parts what to do.

During puberty, hormones help cause changes such as:

• Growing taller
• Body shape changes
• Growth of body hair
• Oilier skin and sometimes pimples
• Stronger emotions or mood changes

Common changes during puberty

Some changes happen in many bodies, no matter whether a person is a boy or a girl. These may include:

• A growth spurt, when the body gets taller quickly
• Hair growing under the arms and in the pubic area
• Skin becoming oilier
• Sweating more and body odor becoming stronger
• Emotions feeling stronger or changing more quickly

Other changes are more common in female bodies. These may include:

• Breasts begin to develop
• Hips may become wider
• The menstrual cycle begins

Some changes are more common in male bodies. These may include:

• Shoulders may become broader
• The voice may get deeper
• Facial hair may begin to grow

Why do these changes happen?

The brain and glands in the body work together during puberty. A gland is a body part that makes and releases hormones. These hormones help the reproductive system begin to mature.

The reproductive system is the body system that allows humans to create offspring when they are adults. In 5th grade, it is important to understand that this system develops slowly over time and is guided by hormones and body growth.

Basic parts of the reproductive system

Female reproductive organs include the ovaries, uterus, and vagina. The ovaries store egg cells. The uterus is the place in the body where a baby can grow during pregnancy.

Male reproductive organs include the testes and penis. The testes make sperm cells. Sperm cells and egg cells are reproductive cells.

These body parts are private and should be treated with respect and care. Learning their correct names is part of understanding health and science.

The menstrual cycle

One important part of reproductive development in female bodies is the menstrual cycle. This is a monthly cycle that usually begins during puberty.

About once each month, an ovary releases an egg cell. At the same time, the lining of the uterus becomes thicker to prepare in case pregnancy happens later. If the egg is not used for pregnancy, the body does not need that extra lining.

Then the body sheds the lining of the uterus. This leaves the body through the vagina and is called a period or menstruation. A period is a normal and healthy body process.

Menstrual cycles are often counted in days. A common example is about 28 days, but cycles can be shorter or longer. During puberty, periods may not be regular at first. That is often normal because the body is still adjusting.

We can think of one example cycle like this:

$$1\ \text{cycle} \approx 28\ \text{days}$$

This number is only an example. Every body is different.

Male reproductive development

During puberty, male bodies begin to make sperm cells. The testes also make hormones that help with body changes such as a deeper voice, increased muscle growth, and facial hair.

Just as in female development, these changes do not all happen at once. They take place over several years.

Emotional and social changes

Puberty is not only about body changes. Feelings and thoughts can change too. A person may feel excited, confused, proud, shy, or worried. All of these feelings can be normal.

It is important to talk with trusted adults, family members, school nurses, counselors, or teachers when questions come up. Learning from trusted sources helps people understand what is happening in a safe and healthy way.

Reproductive health

Reproductive health means taking care of the parts of the body involved in growth, puberty, and reproduction. It also means learning healthy habits and understanding body safety.

Healthy habits during puberty include:

• Bathing or showering regularly
• Using deodorant if needed
• Washing the face gently to help with oily skin
• Wearing clean clothes and underwear
• Eating healthy foods
• Getting enough sleep
• Being physically active

Nutrition and growth

During puberty, the body is growing quickly, so good nutrition is very important. Healthy foods help build bones, muscles, skin, and blood.

Helpful foods include:

• Fruits and vegetables
• Whole grains
• Protein foods such as beans, eggs, fish, chicken, or nuts if allowed
• Dairy foods or other calcium-rich foods for strong bones
• Water to stay hydrated

Hygiene and care during menstruation

People who have periods need clean menstrual products, such as pads, and may also use other products when they are older and have learned how. Changing products regularly helps keep the body clean and comfortable.

It is also important to wash hands before and after changing menstrual products.

Body safety and respect

Every person has the right to body privacy and respect. Private body parts should not be touched by others except for health or safety reasons, such as help from a parent, guardian, or doctor when needed.

If something makes a person feel unsafe, confused, or uncomfortable, they should tell a trusted adult right away.

Worked Example 1: Identifying a change during puberty

Question: Mia notices that she is growing taller quickly and has stronger body odor after gym class. Are these normal changes during puberty?

Answer: Yes. A growth spurt and stronger body odor are both common changes during puberty.

Why: Hormones cause the body to grow and sweat more. This is a normal part of development.

Worked Example 2: Understanding the menstrual cycle

Question: A student asks, “What happens during a period?”

Answer: During a period, the body sheds the extra lining of the uterus because pregnancy did not happen.

Why: The uterus had prepared by making a thicker lining. When that lining is not needed, it leaves the body through the vagina. This is a normal monthly process.

Worked Example 3: Comparing body changes

Question: Which change can happen in many bodies during puberty: deeper voice, wider hips, underarm hair, or breast development?

Answer: Underarm hair.

Why: Underarm hair is a change that happens in many bodies during puberty. The other changes are more common in either male or female bodies.

Worked Example 4: Counting a simple cycle

Question: If one menstrual cycle is about 28 days, about how many days are two cycles?

Step 1: Write the multiplication.

$$2 \times 28 = 56$$

Answer: Two cycles are about 56 days.

Why: If one cycle is about 28 days, then two cycles are twice that amount.

Important ideas to remember

• Puberty is a normal stage of growth and development.
• Hormones are chemical messengers that help cause body changes.
• Everyone goes through puberty at their own pace.
• The reproductive system matures during puberty.
• The menstrual cycle is a normal process in female bodies.
• Healthy habits, hygiene, nutrition, sleep, and exercise help the body stay well.
• Trusted adults can help answer questions and support healthy development.

Brief Summary

Reproductive health and development include the body changes that happen during puberty and the healthy habits that support those changes. Hormones help the body grow and mature, including changes in the reproductive system. These changes are normal, happen at different times for different people, and are easier to understand when we learn accurate science and practice healthy care.

Hydration and Cellular Function

Our bodies need water every day. Water is one of the most important things inside the human body. In fact, most of your body is made of water.

Water helps your body do many jobs. It helps you stay cool, move nutrients, and keep your body working the way it should. When we talk about hydration, we mean having enough water in the body.

Your body is made of many tiny parts called cells. Cells are the building blocks of your body. They make up your skin, muscles, blood, and even your brain. Every cell needs water to do its job.

Introduction: Why Water Matters

Think about a plant. When it gets enough water, it stands tall and looks healthy. When it does not get enough water, it droops. People are not plants, but our bodies also need water to stay healthy and strong.

Water is found all through your body. It is in your blood, inside your cells, and around your organs. Because water is in so many places, it helps many body systems work together.

Main Teaching Point 1: Water makes up a lot of the body

A large part of the human body is water. You can think of your body as carrying water almost everywhere inside it. Water is not just something you drink. It becomes part of you and helps your body work.

Water is in:

• your blood
• your muscles
• your brain
• your skin
• your cells

Since water is in so much of the body, not having enough water can make your whole body feel tired or weak.

Main Teaching Point 2: Water helps cells do their jobs

Cells are tiny, but they do big work. They help you grow, move, think, and heal. For cells to work well, they need water.

Water helps cells by:

• bringing in nutrients from food
• helping carry away waste
• helping cells keep their shape
• helping body reactions happen

You can imagine water as a helper that carries things where they need to go. It helps useful things move into cells and helps waste move out.

Main Teaching Point 3: Water is a “universal solvent”

A solvent is something that can dissolve other things. Water is called a universal solvent because it can dissolve many kinds of materials.

This is important for your body. Nutrients from food can mix with water. Then your blood can carry those nutrients to cells around your body.

For example, when you eat fruit or vegetables, your body breaks the food down into small parts. Water helps move those small parts through the body so cells can use them.

Main Teaching Point 4: Water helps control body temperature

Your body needs to stay at a safe temperature. If you get too hot, your body uses water to help cool down.

One way your body cools itself is by making sweat. Sweat is mostly water. When sweat leaves your skin, it helps your body lose heat and cool off.

This is why drinking water is extra important when:

• you play outside
• you exercise
• the weather is hot
• you are sick

Main Teaching Point 5: Water helps with chemical reactions in the body

Your body is always busy. It breaks down food, builds new cells, and makes energy. These jobs happen through tiny body reactions.

Water helps many of these reactions happen. Even though we cannot see them, they are happening all the time inside us. Without enough water, these important jobs become harder for the body to do.

Main Teaching Point 6: What happens when you are dehydrated?

Dehydration means the body does not have enough water. When this happens, cells and body systems cannot work as well as they should.

Signs of dehydration can include:

• feeling thirsty
• a dry mouth
• feeling tired
• getting a headache
• darker yellow urine
• feeling dizzy

If a person is very dehydrated, they may need help from an adult or a doctor. It is important to drink water during the day so the body can stay healthy.

Main Teaching Point 7: How to stay hydrated

Staying hydrated means giving your body water often. You do not need to wait until you feel very thirsty.

Good ways to stay hydrated include:

• drinking water with meals
• bringing a water bottle to school or sports
• drinking water after playing
• eating foods with water, like watermelon, oranges, and cucumbers
• resting and drinking more water when it is hot

Water is usually the best drink for hydration. Sugary drinks may taste good, but plain water is great for helping the body do its jobs.

Worked Example 1: Why does a runner need water?

Question: Mia runs around the playground for a long time on a warm day. Why should she drink water after playing?

Step 1: When Mia runs, her body gets warmer.

Step 2: Her body makes sweat to help cool her down.

Step 3: Sweat uses water from her body.

Answer: Mia should drink water to replace the water she lost in sweat and help her body stay cool and healthy.

Worked Example 2: How does water help cells?

Question: Ben eats an apple. How does water help the nutrients from the apple get to his cells?

Step 1: Ben’s body breaks the apple into small nutrient pieces.

Step 2: Water helps those nutrients dissolve and mix.

Step 3: Blood carries the nutrients through the body.

Step 4: The nutrients reach the cells, where they can be used.

Answer: Water helps move nutrients from food to the cells so the cells can do their jobs.

Worked Example 3: Is this hydration or dehydration?

Question: Ava played soccer. After the game, she has a dry mouth and feels very tired. Is she showing signs of hydration or dehydration?

Step 1: A dry mouth is a sign that the body may need water.

Step 2: Feeling very tired can also happen when the body does not have enough water.

Answer: Ava is showing signs of dehydration. She should rest and drink water, and tell an adult how she feels.

Worked Example 4: Counting cups of water

Question: Leo drank 2 cups of water in the morning and 3 more cups later. How many cups did he drink in all?

We add the cups together:

$$2 + 3 = 5$$

Answer: Leo drank 5 cups of water in all.

This example shows that drinking water during different parts of the day can help you stay hydrated.

Real-Life Examples

• When you wake up thirsty, your body may need water after sleeping.
• When you sweat during recess, your body is using water to cool down.
• When you drink water with lunch, you help your body move nutrients.
• When you are sick, drinking water can help your body keep working well.

Quick Check for Understanding

1. What are cells?
   Cells are tiny building blocks that make up the body.
2. Why do cells need water?
   Cells need water to bring in nutrients, carry away waste, and help them work.
3. How does water help when you get hot?
   Water helps the body make sweat, which cools you down.
4. What does dehydration mean?
   It means the body does not have enough water.

Brief Summary

Water makes up much of the human body, and every cell needs it. Water helps move nutrients, carry away waste, support body reactions, and control temperature.

When you do not get enough water, you can become dehydrated and feel tired, thirsty, or unwell. Drinking water during the day helps your cells and your whole body stay healthy and strong.