01 The Human Heart

The human heart is one of the most amazing organs in the human body. It pumps life-giving blood throughout the body. It also works together with blood and blood vessels to make sure the cells get everything they need.

The heart, blood, and blood vessels are all part of the circulatory system. Blood carries oxygen and food to the cells of the body. The blood then returns to the heart.

The heart is located slightly to the left in the middle of the chest. It has two hollow spaces or chambers. The blood goes into the atria, and is then pumped into the ventricles —two lower chambers. From here blood goes to the lungs and to every cell in the body. A valve in each ventricle stops blood from flowing backwards

An artery is a blood vessel that carries blood away from the heart. Arteries are sometimes as thick as a thumb.

Blood is composed of red cells, white cells, and platelets floating in a fluid called plasma. This is a liquid, which can easily pass through small blood cells into cells. It makes up over half of the blood. Plasma carries nutrients (food) from the stomach to be used as fuel for energy. Plasma also helps keep the body warm.

The blood returns to the heart through blood vessels called veins. The walls of a vein are much thinner than the walls of an artery. Two large veins bring the blood back to the heart. One comes from the brain and chest, while the other comes from the lower body.

Word List

organ : part of an organism that has a special, vital function

chamber : a cavity in a plant or in the body of an animal

artery : a muscle-walled tube forming part of the blood circulation system

You Practice

I. Answer the following questions.

1) Where is the heart located?

2) What is the circulatory system?

3) What is blood made from?

4) How are veins different from arteries?

5) Why is plasma important?

II. Word power—Use these words from the reading in sentences of your own.

1) organ________________________________________________

2) hollow_______________________________________________

3) chamber______________________________________________

4) artery________________________________________________

5) plasma_______________________________________________

III. True / False / Not Given—Write T if the sentence is true, F if it is not true, or NG if there is no information about this sentence.

____ 1) Blood always travels at the same speed.

____ 2) Blood is mostly made of platelets.

____ 3) The heart is in the centre of the chest.

____ 4) Valves in the heart prevent blood from flowin upwards.

____ 5) Blood returns to the heart through arteries.