mass transport in humans

Question 1

Describe the function of valves in the heart and veins.

Answer 1

Prevent backflow ensuring unidirectional flow of blood

Question 2

Function of coronary arteries?

Answer 2

carry oxygen and glucose from blood to the heart muscle itself

Question 3

Explain how the heart muscle and valves maintain a one way flow of blood from atrium to artery.

Answer 3

Atrium contracts increasing pressure.
Atrium higher pressure than ventricle = Atrioventricular valves open
blood passes to ventricle down pressure gradient.
Ventricle fills and contracts increasing pressure.
Ventricle higher pressure than atrium = Atrioventricular valve closes
valve prevents backflow.
Ventricle higher pressure than aorta/pulmonary artery = semilunar valve opens
blood passes to aorta down pressure gradient
Aorta/pulmonary artery higher pressure than ventricle = semilunar valve closes
Valve prevents backflow.

Question 4

Name the key arteries, chambers, valves and veins in order describing the pathway a red blood cell takes when going from:

Heart to lungs to heart to kidneys to heart

Answer 4

right atrium-(through atrioventricular valves)-right ventricle-(through semilunar valves)-pulmonary artery - lungs - pulmonary vein - left atrium - (through atrioventricular valves) - left ventricle -( through semilunar valves)- aorta - renal artery - kidney - renal vein - vena cava - right atrium

Question 5

Name the key arteries, chambers, valves and veins in order describing the pathway a red blood cell takes when going from:

Heart to lungs to heart to liver to heart

Answer 5

right atrium-(through atrioventricular valves)-right ventricle-(through semilunar valves)-pulmonary artery - lungs - pulmonary vein - left atrium - (through atrioventricular valves) - left ventricle -( through semilunar valves)- aorta - hepatic artery - liver - hepatic vein - vena cava - right atrium

Question 6

What blood vessel has the lowest pressure?

Answer 6

Vena cava

Question 7

Describe how the structure of a capillary is
related to its function.

Answer 7

endothelium one cell thick so short
diffusion pathway
-narrow lumen so reduces rate of flow
making more time for diffusion
-pores between cells to increase rate of
diffusion.
-branched so large surface area.

Question 8

Explain how the structures of the walls of arteries and arterioles are related to their functions.

Answer 8

Elastic tissue

1. Elastic tissue stretches when ventricle contracts then recoils
   maintaining pressure by smoothing out flow of blood

Muscle

3. Muscle contracts to constrict and decrease diameter of lumen (vasoconstriction)
4. so Changes flow

Endothelium
5. Endothelium is smooth
6. Reduces friction

Question 9

Describe how the structure of an aorta related to it’s function

Answer 9

-elastic tissue to allow stretching and recoiling to smooth out flow of blood
-elastic tissue stretches just after ventricles contract so high pressure
-elastic tissue recoils when ventricles relax so low pressure.
-muscles for contraction
-thick wall withstands pressure stopping bursting.
-smooth endothelium to reduce friction
-semi-lunar valve to prevent backflow.

Question 10

Explain how blood in a vein is returned to the heart

Answer 10

1. Muscles around veins contract pressing on the walls and squeezing blood through valves.
2. Valves prevent backflow to ensure unidirectional flow towards heart
3. Wide lumen so little resistance.
4. Heart contracts to pump blood through arteries into veins to move blood further.
5. Heart during diastole causes less pressure than veins so draws blood from veins into atrium

Question 11

Contrast the structure of a vein and artery

Answer 11

artery has narrow lumen whereas vein has a wider lumen
artery has a thicker wall whereas veins have a thinner wall
artery have more muscle whereas veins have less muscle
artery have more elastic tissue whereas veins have less elastic tissue
artery have no valves ( aorta has semi-lunar valve) whereas veins have valves

Question 12

Explain how tissue fluid is formed and how it may be returned to the circulatory system.

Answer 12

1. high hydrostatic pressure at arterial end of capillary
2. Water (and small molecules) in plasma fluid passes out through fenestrations
3. Plasma proteins remain in capillary
4. This lowers water potential
5. A small volume of water moves back into capillary at venous end down its water potential gradient by osmosis
6. Lymphatic vessels drain excess tissue fluid which returns to blood (by lymphatic vessels joining to subclavian vein -> vena cava)

Question 13

List risk factors for heart disease

Answer 13

Anything that increases blood pressure for a prolonged time can damage endothelial layer -heart disease.
Age
Gender
Genetic predisposition
Increased LDL cholesterol /unhealthy diet (specify something not in question)/ excessive alcohol
Smoking
Overweight
Sedentary (not active) life style
Excessive stress