# 70 Structure and function of the heart

The function of the heart is to pump blood around the body. The right side pumps blood to the lungs and the left side pumps blood to the rest of the body. 

Heart's function

• Blood circulation 

1. Blood in the right ventricle (RV) is pump to the lungs 
2. Blood from the lungs flows back into the left atrium (LA) and then into the left ventricle (LV).
3. Blood in the LV is pumped through the body (except for the lungs)
4. Blood returns to the heart where it enters the right atrium (RA). 

• Muscular contraction

The heart is made of a special type of muscle called cardiac muscle which contracts and relaxes regularly, throughout life.

The heart’s muscle is constantly active, so it needs its own blood supply, through the coronary artery, to provide it with oxygen and glucose. 

• Working of the valves 

Valves in the heart prevent blood from being pushed backwards up into the atria when the heart ‘beats’. 

Animation: 

Heart Contraction and Blood Flow

How the heart pumps blood

Try this 

1.On a copy of the diagram of the double circulatory system, labell:

i)            The 4 main blood vessels (4 marks)

ii)           The chambers of the heart (4 marks)

iii)         The 2 valves shown (2 marks)

2.State 2 differences in composition between blood leaving the right ventricle and blood entering the left atrium. (2 marks)

Answers:

1.

2.Blood leaving the right ventricle has more CO₂ and less O₂ than blood entering the left atrium. 


Common misconceptions

Remember that blood passing through the chambers of the heart does not supply the heart muscle with oxygen or glucose. The heart muscles has its own blood supply - via the coronary arteries - to do this.