Mass Transport in Humans

Question 1

Explain how the arteriole can reduce the blood flow into capillaries (2)

Answer 1

1. Muscle contracts
2. Constricts lumen

Question 2

Describe how the heart muscle and heart valves maintain a one way flow of blood from the left atrium to the aorta (6)

Answer 2

1. Atrium has higher pressure than ventricle
2. Atrioventricular valve opens
3. Ventricle has higher pressure than atrium
4. Atrioventricular valve closes
5. Ventricle has higher pressure than aorta
6. Semilunar valve opens
7. Higher pressure in aorta than ventricle
8. Semilunar valve closes
9. Muscle contraction causes increase in pressure

Question 3

Calculation for Cardiac Output?

Answer 3

Cardiac Output = Stroke Volume x Heart Rate

Question 4

What does the vena cava do? (1)

Answer 4

Main vein returning blood to right atrium of heart

Question 5

What does the pulmonary artery do? (1)

Answer 5

Artery taking blood from right ventricle to lungs

Question 6

What does the pulmonary vein do? (1)

Answer 6

Vein returning blood from lungs to left atrium

Question 7

What does the aorta do? (1)

Answer 7

Main artery taking blood from heart to organs

Question 8

Out of the capillary, veins and artery … state in order which blood vessel has the smallest lumen to the largest.

Answer 8

1. Capillary
2. Artery
3. Vein

Question 8

Describe how the movement of the diaphragm leads to air movement into the lungs (4)

Answer 8

1. Diaphragm contracts and flattens
2. Volume of lungs increases
3. Pressure inside lungs is lower than atmospheric pressure
4. Air moves into lungs

Question 8

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. (2)

Answer 8

1. Many alveoli folded provide a large surface area
2. Many capillaries provide a large surface area SO fast diffusion
3. Squamous epithelium SO short diffusion distance
4. Ventilation SO maintains a diffusion / concentration gradient

Question 9

Describe the pathway taken by an oxygen molecule from an alveolus to the blood (2)

Answer 9

1. Across alveolar epithelium
2. Across endothelium of capillary

Question 10

Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6)

Answer 10

ELASTIC TISSUE
1. Elastic tissue stretches when heart contracts
2. Then recoils
3. Evens out pressure and flow
MUSCLE
4. Muscle contracts
5. Reduces diameter of lumen
6. Changes flow and pressure
EPITHELIUM
7. Epithelium is smooth
8. Reduces friction

Question 11

The thickness of the aorta wall changes all the time during each cardiac cycle. Explain why (5)

Answer 11

1. Aorta wall stretches
2. Ventricle contracts
3. Aorta wall recoils;
4. Ventricle relaxes
5. Maintain smooth flow and pressure

Question 12

Describe how tissue fluid is formed and how it is returned to the circulatory system. (6)

Answer 12

FORMATION
1. High hydrostatic pressure
2. Forces water out through fenestrations
3. Large plasma proteins remain in capillary
RETURN
4. Low water potential in capillary
5. Due to plasma proteins
6. Water enters capillary
7. By osmosis
8. Excess water removed via lymph vessels

Question 13

Explain how the highest blood pressure is produced in the left ventricle (1)

Answer 13

strongest contractions

Question 14

Explain the role of the heart in the formation of tissue fluid (2)

Answer 14

1. Contraction of ventricle produces high hydrostatic pressure
2. Forces water out of capillaries

Question 15

Explain four ways in which the structure of the aorta is related to its function (4)

Answer 15

1. Elastic tissue to allow stretch and recoil
2. Muscle to allow vasoconstriction
3. Thick wall withstands pressure
4. Smooth endothelium reduces friction
5. Aortic valve / semi-lunar valve prevents backflow