METAS ADVENTIST SCHOOL

SUBJECT: SCIENCE

CLASS : V

BY

MARTHA KISHORE

CHAPTER 1

THE CIRCULATORY SYSTEM

INTRODUCTION If you prick your finger or scrape your knee, you'll see some droplets of blood form. Just by

eye, these droplets may seem to be made of uniform red liquid. However, if you were to look

under a microscope, you would see that your blood is actually a mixture of liquid and cells.

And if you could zoom in even further, you would see that there are also many

macromolecules (such as proteins) and ions (such as sodium) floating in the liquid. All of

these components are important to the roles blood plays in the body.

THE CIRCULATORY SYSTEM

The system which helps in transporting nutrients and other substances from one part of the body to

the other part of the body is known as circulatory system.

THE blood

What is blood?

Blood, by definition, is a fluid that moves through the vessels of a circulatory system. In

humans, it includes plasma (the liquid portion), blood cells (which come in both red and

white varieties), and cell fragments called platelets.

Plasma is the main component of blood and consists mostly of water, with proteins,

ions, nutrients, and wastes mixed in.

Red blood cells or Erythrocytes are responsible for carrying oxygen and carbon

dioxide.

Platelets are responsible for blood clotting.

White blood cells are part of the immune system and function in immune response.

https://www.youtube.com/watch?v=VSVYgivfs9c

People have one of these eight different blood types:

1. A negative

2. A positive

3. B negative

4. B positive

5. O negative

6. O positive

7. AB negative

8. AB positive

Blood Components

In humans, blood is an opaque red fluid, freely flowing but denser and more viscous

than water. The characteristic colour is imparted by hemoglobin, a unique iron-

containing protein.

Red blood cells have an average life span of 120 days. Because red blood cells cannot

synthesize protein, reparative processes are not possible.

BLOOD VESSELS

Blood vessels may be tiny but they cover a lot of ground.

The smallest blood vessels measure only five micrometers. To give you some perspective, a

strand of human hair measures about 17 micrometers.

But if you took all the blood vessels out of an average child and laid them out in one line, the

line would stretch over 96,560 Kilometers. An adult’s would be closer to 1,60,934

Kilometers long.

There are three kinds of blood vessels: arteries, veins, and capillaries. Each of these plays a

very specific role in the circulation process.

1. Arteries carry oxygenated blood away from the heart. They’re tough on the outside

but they contain a smooth interior layer of epithelial cells that allows blood to flow

easily. Arteries also contain a strong, muscular middle layer that helps pump blood

through the body.

2. Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs.

The capillaries then deliver the waste-rich blood to the veins for transport back to the

lungs and heart.

3. Veins carry the blood back to the heart. They’re similar to arteries but not as strong

or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one

direction. (Arteries don’t require valves because pressure from the heart is so strong

that blood is only able to flow in one direction.) Valves also help blood travel back to

the heart against the force of gravity.

https://www.youtube.com/watch?v=AlSQEs694qY

Functions of blood Blood has three main functions in the human body i.e Transport of substances from one part

of the body to the other like respiratory gases, waste products, enzymes, etc, protection

against diseases and regulation of body temperature.

Blood regulates body temperature.

It carries oxygen from lungs to different parts of the body.

It carries carbon dioxide from the body cells to the lungs for breathing out.

It carries digested food from the small intestine to all parts of the body.

It carries hormones from the endocrine glands to different organs of the body.

It carries waste product urea from the liver to the kidneys for excretion.

Defends against infection.

On average, a healthy man has about 5 litres of blood in the body, while a woman has

about 500 ml less than man. So, total blood is about 60-80 ml/kg of body weight.

https://www.youtube.com/watch?v=CWFyxn0qDEU

THE HEART

Human heart is really a muscle. It's located a little to the left of the middle of your chest, and

it's about the size of your fist. There are lots of muscles all over your body — in your arms, in

your legs, in your back, even in your behind.

But the heart muscle is special because of what it does. The heart sends blood around your

body. The blood provides your body with the oxygen and nutrients it needs. It also carries

away waste.

Your heart is sort of like a pump, or two pumps in one. The right side of your heart receives

blood from the body and pumps it to the lungs. The left side of the heart does the exact

opposite: It receives blood from the lungs and pumps it out to the body.

How the Heart Beats

How does the heart beat? Before each beat, your heart fills with blood. Then its muscle

contracts to squirt the blood along. When the heart contracts, it squeezes — try squeezing

your hand into a fist. That's sort of like what your heart does so it can squirt out the blood.

Your heart does this all day and all night, all the time. The heart is one hard worker!

Parts of the Heart

The heart is made up of four different blood-filled areas, and each of these areas is called a

chamber. There are two chambers on each side of the heart. One chamber is on the top and

one chamber is on the bottom. The two chambers on top are called the atria (say: AY-tree-

uh). If you're talking only about one, call it an atrium. The atria are the chambers that fill

with the blood returning to the heart from the body and lungs. The heart has a left atrium and

a right atrium.

The two chambers on the bottom are called the ventricles (say: VEN-trih-kulz). The heart

has a left ventricle and a right ventricle. Their job is to squirt out the blood to the body and

lungs. Running down the middle of the heart is a thick wall of muscle called the septum (say:

SEP-tum). The septum's job is to separate the left side and the right side of the heart.

The atria and ventricles work as a team — the atria fill with blood, then dump it into the

ventricles. The ventricles then squeeze, pumping blood out of the heart. While the ventricles

are squeezing, the atria refill and get ready for the next contraction. So when the blood gets

pumped, how does it know which way to go?

Well, your blood relies on four special valves inside the heart. A valve lets something in and

keeps it there by closing — think of walking through a door. The door shuts behind you and

keeps you from going backward.

Two of the heart valves are the mitral (say: MY-trul) valve and the tricuspid (say: try-KUS-

pid) valve. They let blood flow from the atria to the ventricles. The other two are called

the aortic (say: ay-OR-tik) valve and pulmonary (say: PUL-muh-ner-ee) valve, and they're

in charge of controlling the flow as the blood leaves the heart. These valves all work to keep

the blood flowing forward. They open up to let the blood move ahead, then they close quickly

to keep the blood from flowing backward.

How Blood Circulates

You probably guessed that the blood just doesn't slosh around your body once it leaves the

heart. It moves through many tubes called arteries and veins, which together are called blood

vessels. These blood vessels are attached to the heart. The blood vessels that carry blood

away from the heart are called arteries. The ones that carry blood back to the heart are called

veins.

The movement of the blood through the heart and around the body is called circulation (say:

sur-kyoo-LAY-shun), and your heart is really good at it — it takes less than 60 seconds to

pump blood to every cell in your body.

Your body needs this steady supply of blood to keep it working right. Blood delivers oxygen

to all the body's cells. To stay alive, a person needs healthy, living cells. Without oxygen,

these cells would die. If that oxygen-rich blood doesn't circulate as it should, a person could

die.

The left side of your heart sends that oxygen-rich blood out to the body. The body takes the

oxygen out of the blood and uses it in your body's cells. When the cells use the oxygen, they

make carbon dioxide and other stuff that gets carried away by the blood. It's like the blood

delivers lunch to the cells and then has to pick up the trash!

The returning blood enters the right side of the heart. The right ventricle pumps the blood to

the lungs for a little freshening up. In the lungs, carbon dioxide is removed from the blood

and sent out of the body when we exhale. What's next? An inhale, of course, and a fresh

breath of oxygen that can enter the blood to start the process again. And remember, it all

happens in about a minute!

Double circulation:

The blood has to pass twice through the heart so as to circulate once through the body. This

circulation is known as double circulation.

Listen to the Lub-Dub

When you go for a checkup, your doctor uses a stethoscope to listen carefully to your heart.

A healthy heart makes a lub-dub sound with each beat. This sound comes from the valves

shutting on the blood inside the heart.

The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound

(the dub) happens when the aortic and pulmonary valves close after the blood has been

squeezed out of the heart. Next time you go to the doctor, ask if you can listen to the lub-dub,

too.

Pretty Cool — It's My Pulse!

Even though your heart is inside you, there

is a cool way to know it's working from the

outside. It's your pulse. You can find your

pulse by lightly pressing on the skin

anywhere there's a large artery running just

beneath your skin. Two good places to find

it are on the side of your neck and the inside

of your wrist, just below the thumb.

You'll know that you've found your pulse

when you can feel a small beat under your

skin. Each beat is caused by the contraction

(squeezing) of your heart. If you want to

find out what your heart rate is, use a watch with a second hand and count how many beats

you feel in 1 minute. When you are resting, you will probably feel between 70 and 100 beats

per minute.

When you run around a lot, your body needs a lot more oxygen-filled blood. Your heart

pumps faster to supply the oxygen-filled blood that your body needs. You may even feel your

heart pounding in your chest. Try running in place or jumping rope for a few minutes and

taking your pulse again — now how many beats do you count in 1 minute?

Keep Your Heart Happy

Most kids are born with a healthy heart and it's important to keep yours in good shape. Here

are some things that you can do to help keep your heart happy:

Remember that your heart is a muscle. If you want it to be strong, you need to exercise it.

How do you do it? By being active in a way that gets you huffing and puffing, like jumping

rope, dancing, or playing basketball. Try to be active every day for at least 30 minutes! An

hour would be even better for your heart!

Eat a variety of healthy foods and avoid foods high in unhealthy fats, such as saturated fats

and trans fats (reading food labels can help you figure out if your favorite snacks contain

these unhealthy ingredients).

Try to eat at least five servings of fruits and vegetables each day.

Avoid sugary soft drinks and fruit drinks.

Your heart deserves to be loved for all the work it does. It started pumping blood before you

were born and will continue pumping throughout your whole life.

Summery

https://www.youtube.com/watch?v=2T6J20pu2V4

Work sheet 1

Q.1 Label the following diagram.

Q.2 Choose the correct option.

1. Blood vessels are mainly of:

a. Four types

b. Three types

c. Five types

2. Which body system includes arteries and veins?

a. Excretory system

b. Circulatory system

c. Respiratory system

3. The blood travels through the body in tubes called

a. Blood vessels

b. Muscles

c. Plasma

4. Oxygenated blood is poured into:

a. Left auricle

b. Left ventricle

c. Right auricle

5. Blood that is carrying oxygen to the cells is blood.

a. Deoxygenated

b. Oxygenated

c. Defrosted

Q. 3. Match each term in Column A with its description in Column B. Write the correct

letter in the space provided.

Column A Column B

1. circulation a) carry blood away from the heart

2. heart b) pumps blood

3. arteries c) connect arteries and veins

4. veins d) transport of materials in living things

5. capillaries e) carry blood back to the heart

Q.4 Fill in the blanks with suitable words.

1. The impure blood is collected and poured into .

2. The broad portion of heart is on side.

3. Red blood cells are also known as ’

4. Size of human heart is that of .

5. Jerky wave felt when blood is pumped into arteries .

Q.5 Answer the following questions.

1. Define circulatory system

2. Why arteries have thick walls?

3. What is blood?

.

Worksheet 1 – Answers.

Q.1 Label the following diagram.

Q.2 Choose the correct option.

1. a

2. b

3. a

4. a

5. b

Q. 3. Match each term in Column A with its description in Column B. Write the correct

letter in the space provided.

1. d

2. b

3. a

4. e

5.c

Q.4 Fill in the blanks with suitable words.

1. Right auricle

2. Upward

3. Erythrocytes

4. Human closed fist

5. Pulse

Q.5 Answer the following questions.

1. The system which helps in transporting nutrients and other substances from one part of the body

to the other part of the body is known as circulatory system.

2. The arteries have to distribute blood to all parts of the body hence they have thick muscular

walls.

3. Blood, is a fluid that moves through the vessels of a circulatory system. In humans, it

includes plasma (the liquid portion), blood cells (which come in both red and white varieties),

and cell fragments called platelets

Worksheet-2

Q.1 Look at Figure. It shows arteries and veins within

the human body. Each artery and vein branches out to

tiny capillaries.

Write the correct term in each blank to answer the

questions or complete the sentence.

1. What pumps blood through your body?

2. Blood vessels that carry blood away from the heart

are called .

3. Vessels that carry blood back to the heart are called

.

4. Blood moves from arteries to veins through tiny

blood vessels called .

5. The heart, blood vessels and blood make up the

.

Q.2. Fill in the blanks.

1. Red blood cells have an average life span of days.

2. The structures in the blood that are used to fight disease are called .

3. The substance in the blood that gives it its red color is .

4. The smallest blood vessels are .

5. Blood brings to cells things like and _ .

Q.3. Unscramble the following letters to make meaningful words.

(i) IUARELC

(ii) LUPES

(iii) EREVNTICL

(iv) NAUICRCLOIT

(v) NEVIS

Q.4. TRUE or FALSE – In the space, write a ‘T’ or ‘F’

1. Circulation is the transport of materials in living things.

2. Life stops when circulation stops.

3. Blood is pumped by the brain.

4. Blood circulates through the body only a few times a day.

5. Arteries carry blood away from the heart.

Q.5. Answer the following questions.

1. Define double circulation.

2. Differentiate between Artery and Vein.

3. Give any three functions of blood.

Worksheet – 2 Answers

Q.1. Diagram

1. Heart

2. Arteries

3. Veins

4. Capillaries

5. Circulatory system

Q.2. Fill in the blanks

1. 120

2. White blood cells

3. Hemoglobin

4. Capillaries

5. Nutrients, Oxygen

Q.3. Unscramble the following letters to make meaningful words.

1. AURICLE

2. PULSE 3. VENTRICLE 4. CIRCULATION

5. VEINS

Q.4. TRUE or FALSE – In the space, write a ‘T’ or ‘F’

1. True

2.True

3.False

4. False

5.True

Q.5. Answer the following questions.

1. The blood has to pass twice through the heart so as to circulate once through the body. This

circulation is known as double circulation.

2.

3. Functions of blood.

Blood regulates body temperature.

It carries oxygen from lungs to different parts of the body.

It carries carbon dioxide from the body cells to the lungs for breathing out.

It carries digested food from the small intestine to all parts of the body.

It carries hormones from the endocrine glands to different organs of the body.

It carries waste product urea from the liver to the kidneys for excretion.

Defends against infection.

On average, a healthy man has about 5 litres of blood in the body, while a woman has

about 500 ml less than man. So, total blood is about 60-80 ml/kg of body weight.