Mass Transport in Mammals: Circulation and Heart Disease

Question 1

What is the structure of the heart?

Answer 1

1. The heart has four chambers. The right and left atria and the left and right ventricle.
2. The right side side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood around the body.
3. The semi-lunar valves and the atrioventricular valves prevent the backlog of blood.
4. The cords prevent the AV valves from being forced into the atria.

Question 2

What is the passage of the blood around the body and heart?

Answer 2

1. The vena cava takes deoxygenated blood to the right atria.
2. The right atria contracts which pushes the blood into the right ventricle.
3. The pulmonary artery carries deoxygenated blood to the lungs to be oxygenated.
4. The pulmonary vein carries oxygenated blood from the lungs to the left atria.
5. The left atria contracts which pushes the blood into the left ventricle.
6. The aorta carries oxygenated blood from the heart to the rest of the body.
7. The renal artery carries oxygenated blood to the kidneys and the renal vein carries the deoxygenated blood back to the heart.

Question 3

Why are the walls of the ventricles thicker than the wall of the atria?

Answer 3

The muscle needs to be thicker to have stronger contraction. This is because the ventricles pump blood to the lungs and the rest of the body and the atria only pump the blood to the ventricles.

Question 4

Why is the wall of the left ventricle thicker than the wall of the right ventricle?

Answer 4

The muscle needs to be thicker to have stronger contractions. This is because the left ventricle pumps blood all around the body and the right ventricle only pumps blood to the lungs.

Question 5

What is the function of the arteries?

Answer 5

They pump oxygenated blood from the heart to the rest of the body.

Question 6

How does the structure of the arteries help them to carry out their function?

Answer 6

1. Their walls have a thick layer of muscle tissue that helps them withstand high blood pressure. They can also contract and relax to control blood flow.
2. Their walls have a thick layer of elastic tissue which allows them to stretch and recoil. This allows them to maintain a high pressure inside them.
3. Their smooth endothelium helps reduce friction. The folded endothelium also helps to stretch.
4. They have a narrower lumen which helps maintain the high pressure in the arteries.

Question 7

What are arterioles and venules ?

Answer 7

They are smaller vessels that branch off from arteries and veins and go into capillaries.

Question 8

How does the structure of the arterioles help them to carry out their function?

Answer 8

They contain muscle tissue which can contract and relax to control blood flow in certain parts of the body.

Question 9

What is the function of the veins?

Answer 9

They carry deoxygenated from the body to the heart.

Question 10

How does the structure of the veins help them to carry out their function?

Answer 10

1. They have a wider lumen and less muscle and elastic tissue in their walls compared to arteries because the blood pressure is lower.
2. They have valves that prevent the backflow of blood.

Question 11

What is the purpose of capillaries?

Answer 11

Carry blood directly to respiring cells.

Question 12

How does the structure of the capillaries help them to carry out their function?

Answer 12

1. They are one cell thick, which means that the diffusion pathway is shorter.
2. There is a large number of them to increase the surface area for exchange.

Question 13

How do the valves in the heart work?

Answer 13

1. When the pressure in the atria is higher compared to the ventricles, the atrioventricular valves open, and when the pressure in the ventricles is higher compared to the atria they close.
2. When the pressure in the ventricles is higher compared to the arteries, the semi-lunar valves close, and when the pressure in the arteries is higher, they close.

Question 14

What are the different stages of the cardiac cycle?

Answer 14

1. Atrial systole.
2. Ventricular systole.
3. Diastole.

Question 15

What happens during atrial systole?

Answer 15

1. The ventricles relax.
2. The atria contract which causes the volume inside the atria to decrease and the pressure to increase.
3. The pressure inside the atria is higher compared to the ventricles which causes the atrioventricular valves to open.
4. Blood flows into the ventricles, which causes the volume and pressure to rise slightly.

Question 16

What happens during ventricular systole?

Answer 16

1. The atria relax.
2. The ventricles contract. This causes a decrease in volume and an increase in pressure.
3. The pressure inside the ventricles is higher compared to arteries, so the semilunar valves open, and blood flows into the arteries.

Question 17

What happens during diastole?

Answer 17

1. The atria and ventricles relax, which causes an increase in volume and a decrease in pressure.
2. The pressure inside the ventricles is lower compared to the arteries so the semi-lunar valves close.
3. Blood returns to the atria which causes a slight increase in the volume of blood and pressure.
4. The AV valves open which causes the passive flow of blood into the ventricles.

Question 18

What us meant by the term stroke volume?

Answer 18

The volume of blood pumped out of the left ventricle during one cardiac cycle.

Question 19

How do you calculate cardiac output?

Answer 19

Stroke volume ( cm3) x heart rate ( bmp)

Question 20

The formation of tissue fluid.

Question 21

What is the blood compromised of?

Answer 21

It contains small molecules like water and oxygen and also larger molecules like proteins, glucose and red blood cells.

Question 22

What is tissue fluid and what does it consist of?

Answer 22

It is tissue that surrounds cells and exchanges substances with them. It consists of water and other small molecules like oxygen and carbon dioxide.

Question 23

How is tissue fluid formed?

Answer 23

1. At the arteriole end of the capillaries the hydrostatic pressure is higher compared to the tissue fluid.
2. This increases the outward pressure which forces water and other small molecules out of the capillaries and into the tissue fluid.
3. As you go across the capillary bed to the venule end of the capillaries the hydrostatic pressure decreases as more water is forced out of the capillaries.
4. This means that at the venous end of the capillaries, there are fewer water molecules and a higher concentration of plasma proteins. The proteins remain in the plasma as they are too big to pass through the walls of the capillaries.
5. This means that the water potential inside the capillaries is lower compared to the tissue fluid and water moves into the capillaries via osmosis.

Question 24

How is excess tissue fluid returned to the Circulatory system?

Answer 24

The excess tissue fluid drains into the lymphatic system, which transports it back to the Circulatory system.

Question 25

What are coronary heart diseases?

Answer 25

Diseases that involve the heart and the blood vessels.

Question 26

What is an atheroma and how does it form? What effect does it have on the arteries?

Answer 26

It is a build-up of connective tissue, white blood cells and lipids in the blood vessels which over time becomes hard plaque. It blocks the artery lumen, which decreases blood flow and increases blood pressure.

Question 27

What is thrombosis and how does it form? How could it lead to an aneurysm?

Answer 27

The formation of an atheroma weakens the blood vessels. If high-pressure blood flows over the atheroma, it ruptures the endothelium, which causes a ballon-like swelling. If the swelling bursts it leads to an aneurysm.

Question 28

What happens during a myocardial infarction? How can the formation of an atheroma lead to a MI?

Answer 28

A heart attack is caused by a blockage of the coronary arteries. This is because not enough blood will be going to the heart muscle tissue for aerobic respiration. This blockage can be caused by the formation of an atheroma in the coronary arteries.

Question 29

What are the modifiable and non-modifiable risk factors of CHD and MI?

Answer 29

Modifiable: Poor diet, Smoking, Lack of exercise. Non-modifiable: High blood pressure, age, sex, genetic predisposition.

Question 30

How does high blood pressure cause an excess build-up of tissue fluid?

Answer 30

1. The hydrostatic pressure in the alveolar end of the capillaries will be higher, which will increase the outward pressure. 2. This will force more water and other small molecules out of the capillaries. 3. There will be too much tissue fluid forming for the lymphatic system to drain it all in time.