Mass Transport in Humans

Question 1

Describe the flow of blood through the heart (6 marks)

Answer 1

• Deoxygenated blood enters right atrium via vena cava
• Enters right ventricle via atrio-ventricular valve
• Exits heart and travels to lungs via semi-lunar valve through pulmonary artery where blood is oxygenated.
• Oxygenated blood enters left atrium via pulmonary vein
• Travels to left ventricle via atrio-ventricular valve
• Enters aorta via semi-lunar valve and pumped to rest of the body

Question 2

Define systole

Answer 2

Contraction of cardiac muscle

Question 3

Define diastole

Answer 3

Relaxation of cardiac muscle

Question 4

Why does the right ventricle produce less pressure?

Answer 4

• Thinner cardiac muscle walls than left ventricle
• To prevent damage to capillaries in the lungs and slower blood flow to allow time for gas exchange

Question 5

Cardiac output formula

Answer 5

Stroke Volume x Heart Rate

Question 6

Define Stroke Volume

Answer 6

Volume of blood expelled from left ventricle on one cycle

Question 7

Define Heart Rate

Answer 7

Number of cardiac cycles (beats) per minute

Question 8

What is coronary heart disease (2 common causes)

Answer 8

The interference of the coronary arteries which supply blood to the cardiac muscles. 2 main causes:

• Atherosclerosis (Narrowing/blockage of coronary arteries due to damage to artery walls due to high blood pressure, high cholesterol levels, etc.)
• Thrombosis
  (Plaque may rupture and cause blood clotting over the damaged area, causing further blockage of the artery).

Question 9

Coronary Heart Disease risk factors

Answer 9

Age, Gender, Genetic Factors
High Cholesterol/Lipid Diet, Smoking

Question 10

Define mass flow

Answer 10

The bulk movement of substances due to a pressure difference

Question 11

Why are closed systems more efficient than open systems?

Answer 11

Liquids within tubes are easier to generate and maintain a pressure gradient

Question 12

Cardiac cycle

Answer 12

• Blood vol. in atrium increases, atrium pressure greater than ventricle
• AV valve opens and atrium muscles contract to force remaining blood out
• AV valve closes, inc. pressure in ventricle greater than aorta/PA
• SL Valve opens, blood pumped to body (aorta) or lungs (pulmonary artery)
• Pressure in aorta/PA greatert than ventricle, SL Valve closes.

Question 13

What is atherosclerosis and thrombosis

Answer 13

Atherosclerosis:
- Narrowing/blockage of arteries due to damage to artery wall (high blood pressure, high cholesterol levels)

Thrombosis:
- Plaque rupture + triggers blood clotting over damaged area

Question 14

Five layers of arteries/veins

Answer 14

• Lumen
• Lining layer
• Elastic layer
• Muscle layer
• Tough outer layer

Question 15

Difference between artery and vein

Answer 15

• Artery transports blood away from heart, vein transports blood to heart
• Artery carries oxygenated blood, vein carries deoxygenated blood
• Artery has larger lumen diameter
• Vein has smaller lumen diameter
• Artery pressure is greater than vein
• Vein blood flow is non-pulsar whereas artery flow is pulsar
• Vein has thinner elastic and muscle wall than artery.

Question 16

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

Answer 16

• Higher hydrostatic pressure in capillaries
• Forces fluid out of fenestrations into surrounding tissue fluid
• Large proteins remain in capillary
• Lower water potential in capillary
• (Due to plasma proteins)
• Water from tissue fluid enters capillaries down water potential gradient via osmosis