circulatory system

Question 1

why do mammals need a specialised transport system

Answer 1

-because they have a low surface area to volume ratio

Question 2

arteries description

Answer 2

• thick and muscular walls
• have elastic tissue to stretch and recoil as the heart beats helping maintain the high pressure
• the endothelium is folded, allowing the artery to stretch and maintain high pressure

Question 3

arteries path

Answer 3

• carries blood from the heart to the rest of the body

- carries oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs

Question 4

arterioles description

Answer 4

• smaller vessels that were divided from arteries
• blood is directed to the different areas of demand in the body by muscles in the arterioles, which contract to restrict the blood flow or relax to allow full blood flow

Question 5

veins description

Answer 5

• wider lumen
• little elastic or muscle tissue
• veins contain valves to stop backflow

Question 6

veins path

Answer 6

• takes blood back to the heart under low pressure

- veins carry deoxygenated blood except for the pulmonary veins which carry oxygenated blood to the heart from the lungs

Question 7

capillaries

Answer 7

• found very near cells in exchange tissues to reduce diffusion distance
• walls are only one cell thick which shortens diffusion pathway
• always large number of capillaries to increase surface area

Question 8

formation of tissue fluid

Answer 8

1. at the start of the capillary bed, nearest the arteries, the hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid
2. the difference in hydrostatic pressures means an overall outward force forces fluid out of the capillaries and into the spaces around the cells, forming tissue fluid
3. as fluid leaves, the hydrostatic pressure reduces in the capillaries so the hydrostatic pressure is much lower at the venule end of the capillary bed
4. due to the fluid loss and an increasing concentration of plasma proteins, the water potential at the venule end of the capillary bed is lower than the water potential in the tissue fluid
5. some water re-enters the capillaries from the tissue fluid at the venule end by osmosis