Mass Transport In Mammals 2 - Human Circulatory System & Blood Vessels

Question 1

What is the closed circulatory system?

Answer 1

Blood is contained in blood vessels

Question 2

What is the double circulatory system?

Answer 2

Blood pumped by the heart twice in full circulation

Question 3

What are the two circuits in the double circulatory system?

Answer 3

Pulmonary = heart - lungs - heart
Systemic = heart - body - heart

Question 4

What is a blood vessel?

Answer 4

Channels through which blood is distributed to body tissues

Question 5

Describe the function of the three blood vessels

Answer 5

Arteries carry blood away from the heart
Capillaries allow exchange of materials between bloods and body tissues
Veins carry blood to into the heart

Arteries - arterioles - capillaries - venules - veins

Question 6

How does the structure of an artery relate to its function?

Answer 6

Have thick walls with layers of collagen, smooth muscle and elastic fibres = can withstand high pressure
Elastic fibres = allow artery walls to expand around blood surging through at high pressure when the heart contracts and recoil when heart relaxes
Narrow lumen = maintains high blood pressure

Question 7

How does the structure of a vein relate to its function?

Answer 7

Thin wall with thinner layers of collage, smooth muscle and elastic fibres = allows blood from the capillary to pass through at a low pressure to the heart
Larger lumen = blood is at a lower pressure
Valves = prevent backflow of blood, helping it return to the heart

Question 8

What is a capillary and what is its structure and function?

Answer 8

A capillary is a type of blood vessel that forms networks called capillary beds ~ these are very important exchange surfaces
- lumen with a small diameter which forces blood to travel slowly allowing more diffusion to take place
- branch between cells so substances can diffuse between blood and cells quickly as there is a short diffusion distance
- wall is one cell thick of endothelial cells reducing diffusion distance for O2 and CO2
- cells in the wall have gaps (pores) which allow blood plasma to leak out and form tissue fluid

Question 9

What is tissue fluid?

Answer 9

Plasma = liquid made of 95% water, water is a good solvent so substances can easily dissolve through plasma ~ contains more proteins than tissue fluid due to size of gaps in walls of capillaries
Blood passes through capillaries and some plasma leaks out through the pores in the cells resulting in TISSUE FLUID

Question 10

Why does exchange between cells and the blood occur via tissue fluid?

Answer 10

Substances can easily dissolve into tissue fluid due to it being mainly composed of water
Eg. CO2 produced in aerobic respiration will leave a cell, dissolve into the tissue fluid surrounding it, and then diffuse into the capillary

Question 11

Describe the formation of tissue fluid in the arteriole end

Answer 11

Outward hydrostatic pressure is higher than the inward osmotic pull = pushes molecules out of the capillary
Proteins remain in the blood creating a water potential so water moves out from capillary into tissue fluid

Question 12

Describe the formation of tissue fluid in the venue end

Answer 12

Less fluid is pushed out as inward osmotic pull is higher than outward hydrostatic pressure that is reduced
Water potential gradient between capillary and the tissue fluid remains the same at arteriole end = water flows back into capillary from tissue fluid
More fluid leaves capillary than returns
High blood pressure (hypertension) pressure at arteriole end is even greater = more fluid punished out and fluid accumulates around the tissues (oedema)