P2

Question 1

The heart

Blood is pumped around the body by the heart.

Answer 1

The heart has four chambers - two atria and two ventricles.

Question 2

Explain how the heart functions

Answer 2

Blood enters the heart through the atria. Blood from two vena cavae enters the right atrium. Blood from the pulmonary veins enters the left atrium. The atria fill, followed by the ventricles. Blood is prevented from flowing back into the atria by heart valves.

Blood leaves the heart in the body’s main artery - the aorta - from the left side, and the pulmonary artery, from the right.

Question 3

What are the two circuits the heart pumps through?

Answer 3

1. the pulmonary circulation

2. the systemic circulation

Question 4

How does the pulmonary circulation work?

Answer 4

1. oxygen diffuses into the blood from the alveoli - the blood becomes oxygenated
2. carbon dioxide diffuses from the blood into the lungs

Question 5

How does the systemic circulation work?

Answer 5

It transports oxygen and nutrients to the body and it transports carbon dioxide and any other waste away from the cells.
The pulmonary circulation is under lower pressure, because:
1. blood is delivered to the lungs only, which are very close to the heart
2. in a healthy person, this lower pressure is optimum for the diffusion of gases