Text C. Evolution of the heart

Beginning with the invertebrates, the lowest members of the animal kingdom, the heart is a simple propulsive muscular tube. In the fish the heart has evolved into a chambered organ with an atrium, or receiving chamber, and a ventricle, a thick-walled pumping chamber. This development was necessary because the vertebrates of which the fish are the lowest class have a more complicated structure and are generally larger than the invertebrates and require more oxygen. With the development of lungs in the higher vertebrates the atrium became divided into two parts by the formation of a dividing wall called septum. Thus, in man and other animals with a four-chambered heart blood from the body cells enters the heart at the right atrium, and from here it passes into the right ventricle from which the blood is pumped through the pulmonary artery towards the lungs. The oxygenated blood is carried back to the heart through the pulmonary veins which empty into the left atrium. From the left atrium the blood passes into the left ventricle which then pumps it into the aorta for the distribution throughout the body.

X. Complete the sentences:

1. An atrium is …

2. A ventricle is a …

3. The septum is …

4. Blood enters the heart …

5. Then it passes...

6. The blood is pumped … towards the lungs.

7. The oxygenated blood is carried back to the heart …

8. They empty …

9. The left ventricle pumps the blood …

XI. Translate the sentences paying attention to the words in the bold type:

1. The atria collect blood returning to the heart.

2. The ventricles are larger than the atria and the left one is more conical.

3. The body uses food and oxygen carried by the blood.

4. This deoxygenated blood collects in the right atrium.

5. The blood returning to the heart has no oxygen.

6. The function of the liver is different from that of the heart.

7. One of the most interesting problems in medicine is that of pathogenesis.

8. Metabolic diseases are those in which certain physiological processes become

disturbed.

9. You are to know physiology as well as anatomy.

10. There are four chambers in the heart: two smaller ones, the arteries, and two

larger ones, the ventricles.