The Circulatory System 3B

Question 1

Circulatory system components

Answer 1

Heart and blood vessels

Question 2

Why do multi-cellular organisms need a transport system

Answer 2

They have a low SA:VOL ratio so can’t rely on diffusion

Question 3

Circulatory system root

Answer 3

heart -> blood vessels

Question 4

Double circulatory system root

Answer 4

1. heart -> lungs -> heart
2. heart -> body -> heart

Question 5

Where does the heart get its blood supply from

Answer 5

coronary arteries

Question 6

Artery structure and function

Answer 6

Carry blood from heart to the rest of the body
Thick muscular walls
Elastic tissue to stretch and recoil - helps maintain higher pressure
Folded epithelium allowing artery to stretch
All arteries carry oxygenated blood apart from pulmonary artery
Divide into arterioles

Question 7

Arterioles function

Answer 7

Form a network throughout the body direct blood to specific areas by muscles which contract or relax depending on demand

Question 8

Vein structure and function

Answer 8

Take blood back to heart under low pressure

Wider lumen with very little elastic or muscle tissue

Valves prevent backflow of blood

Blood flow helped by muscles around valves

All veins carry deoxygenated blood apart from pulmonary veins

Question 9

Capillary structure and function

Answer 9

Site of substance exchange
One cell thick - short diffusion pathway
Large network to increase SA called capillary beds

Question 10

What is tissue fluid

Answer 10

fluid that surrounds cells in tissues

Question 11

How is tissue fluid formed

Answer 11

1. Start of capillary bed hydrostatic pressure inside the capillaries is greater than the hydrostatic pressure in the tissue fluid
2. Difference in hydrostatic pressure means an overall outward pressure forces fluid out of the capillary beds 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 is lower than the water potential in the tissue fluid
4. This means that water re-enters the the capillaries from the tissue fluid at the venule end by osmosis

Question 12

Where does excess tissue fluid go

Answer 12

It drains into the lymphatic system