Circulatory systemLife science 5

8/08

Every cell in your body needs a steady flow of oxygen and nutrients.

The circulatory system is delivering oxygen and nutrients to your cells every time your heart beats.

The heart is the main organ in the circulatory system. It’s a muscle that never gets tired as it continues topump blood to every partof your bodyevery second of your life.

There are 4 chambers in the human heart.

Right atrium

Left atrium

Right ventricle

Right ventricle

Big hoses called

arteries and

veins carry blood in and out of the heart.

Arteries carry blood from the heart out to all parts of the body. This blood is rich with oxygen which gives it a bright red color.

In drawings like this one, arteries are colored red.

Veins carry blood back to the heart

from all parts of the body. This blood is oxygen-poor and is full of carbon dioxide. This gives it a purple-blue color. In drawings veins are colored blue.

Most drawings of the circulatory system show arteries and veins in red and blue.

Arteries leading away from the heart get smaller and smaller as they branch out through every part of the body.

Arteries get really small until they branch into the smallest vessels called capillaries.

Capillary walls are so thin that oxygen and carbon dioxide can pass right through them in and out of the body’s cells.

Red blood cells in the blood act like little buckets that carry oxygen to and carbon dioxide away from every cell in your body.

There are millions of red blood cells in every drop of blood.

Every drop of blood has to go through a capillary to get back to the heart.

Oxygen rich blood coming from the heart

artery

vein

Oxygen poor blood going back to the heart

Capillaries connecting arteries to veins

Veins leading back to the heart get bigger and bigger as they branch together.

Used blood going back to the heart

veins

The blood returning to the heart is full of poisonous carbon dioxide (CO2).

Next, the blood gets pumped to the lungs where CO2 is exchanged for fresh oxygen.

To the lungs

Lungs are the main organs in the

respiratory system

Lungs are the main organs in the

respiratory system

The lungs pull air into and push air out of your body.

Lungs

Air travels from the nose and mouth to the lungs through a tube called the trachea or windpipe.

(tray kee uh)

The trachea branches into the bronchi to go into each lung.

Bronchi (rhymes with

donkey) is the plural for bronchus

1 bronchus

2 bronchi

The bronchi branch smaller and smaller to take air to millions of tiny sacs called alveoli.(al vee oh lie)

Alveoli is plural for alveolus

1 alveolus

2 alveoli

The blood coming from the heart branches down into capillaries that surround the alveoli.

alveolus

Alveoli walls are so thin that oxygen and CO2 can pass right through them to go in and out of the blood cells in the capillaries.

The red blood cells get rid of the CO2 and fill up with fresh oxygen.

Now the blood is bright red again.

It goes back to the heart to be pumped out to all parts of the body.

Oxygen rich blood from lungs

Oxygen rich blood going out to the lower body

Oxygen rich blood going out to the upper body

Let’s Review:

Let’s Review:

What is the most important organ in the circulatory system?

Let’s Review:

What is the most important organ in the circulatory system?

The heart

Let’s Review:

How many chambers does the heart have?

Let’s Review:

How many chambers does the heart have?

4 chambers1

2

3

4

Let’s Review:

What are the vessels that carry oxygen rich blood from the heart out to the body?

Let’s Review:

What are the vessels that carry oxygen rich blood from the heart out to the body?

arteries

Let’s Review:

What are the vessels that carry oxygen poor blood from the body back to the heart?

Let’s Review:

What are the vessels that carry oxygen poor blood from the body back to the heart?

veins

Let’s Review:

What are the vessels that connect arteries to veins?

Let’s Review:

What are the vessels that connect arteries to veins?

capillaries

Let’s Review:

What important activity happens in the capillaries?

Let’s Review:

What important activity happens in the capillaries?

Cells get oxygen and get rid of CO2

Let’s Review:

Where does blood go after it returns to the heart?

Let’s Review:

Where does blood go after it returns to the heart?

The lungs

Let’s Review:

What happens to blood when it goes through the lungs?

Let’s Review:

What happens to blood when it goes through the lungs?

It gets rid of CO2 and fills up with oxygen

Let’s Review:

What is in blood that acts like buckets to carry oxygen and CO2?

Let’s Review:

What is in blood that acts like buckets to carry oxygen and CO2?

Red blood cells