B3e - the circulatory system

Question 1

Describe the function of plasma(1 + 4 examples)

Answer 1

Carries a number of important substances around the body

• dissolved food substances(e.g.glucose)
• hormones from the glands where they are made to their target cells
• plasma proteins(e.g. antibodies)
• waste substances(e.g.urea)

Question 2

How is the structure of a red blood cell adapted to its function(4)

Answer 2

Small size so they can pass through the smallest blood vessels

Biconcave discs shaped to provide a larger surface area to volume ratio so oxygen can be exchanged quicker

Contain haemoglobin which reacts with oxygen in the lungs to form oxyhaemoglobin, this reaction reverses in body tissues to release the oxygen to the cells(haemoglobin also gives the cell its red colour)

Does not have a nucleus so more haemoglobin can fit so it can carry more oxygen

Question 3

How do the parts of the circulatory system work together to bring about the transport of substances around the body(3)

Answer 3

Arteries transport blood away from the heart to the tissues

Veins transport blood to the heart from the tissues

Capillaries link arteries to veins and allow materials to pass between the blood and the tissues

Question 4

How are the arteries, veins and capillaries adapted to their functions(3)

Answer 4

Arteries have thick muscular and elastic wall to resist the high pressure

Veins have large lumen and valves to prevent the backflow of blood into the heart since the pressure is low

Capillaries have permeable walls so substances can be transferred between the blood and the tissues

Question 5

Describe the functions of different parts of the heart(5)

Answer 5

Left and right atria receives blood from veins

Left and right ventricles pump blood out into arteries

Semilunar, tricuspid and bicuspid valves prevent any backflow of blood

Pulmonary veins and the vena cava carries blood to the heart

Aorta and pulmonary arteries carry blood away from the heart

Question 6

Describe the flow of blood through the heart(2)

Answer 6

Right: vena cava brings deoxygenated blood from the body → right atrium → tricuspid valve → right ventricle → semilunar valve → pulmonary artery which takes the deoxygenated blood to the lungs

Left: pulmonary vein brings oxygenated blood from the lungs → left atrium → bicuspid valve → left ventricle → semilunar valve → aorta which takes oxygenated blood to the body

Question 7

Why does the left ventricle have a thicker muscle wall than the right ventricle

Answer 7

Left ventricle need to pump blood all around the body rather than just to the lungs, which are close by, so it needs to pump it at a higher pressure

Question 8

What are the advantages of the double circulatory

system in mammals

Answer 8

Blood is pumped at a higher pressure so it flows to the tissues at a faster rate

Question 9

What is a double circulatory system

Answer 9

Blood is pumped to the lungs and returns to the heart to be pumped to the body