Chapter 8: Transports in Mammals

Question 1

Circulatory system is needed for?

Answer 1

1) Transport of nutrients and oxygen around the body
2) Disposal of waste materials (eg:- carbon dioxide, urea)
3) Transport of hormones
4) Circulate WBC’s and RBC’s in body

Question 2

Closed circulation

Answer 2

-> blood contained in blood vessels
-> always in heart, arteries, veins, or capillaries

Question 3

Double circulation

Answer 3

Blood passes through the heart twice in one complete circuit. ( 1 circuit = 2 circulations)

Question 4

How many circulation are there? Name and define them.

Answer 4

There are two types of circulation. Pulmonary circulation ( circulation through the lungs and heart). Systemic circulation ( circulation through the heart and other parts of the body except the lungs).

Question 5

Explain the blood vessel cycle.

Answer 5

Blood comes into the right atrium from the body, moves into the right ventricle and is pushed into the pulmonary arteries in the lungs. After picking up oxygen, the blood travels back to the heart through the pulmonary veins into the left atrium, to the left ventricle and out of the body’s tissues through the aorta.

Question 6

Order in which blood flows.

Answer 6

Arteries -> Arterioles -> Capillaries -> Venules -> Veins

Question 7

What is the function of arteries?

Answer 7

-> carry blood away from the heart
-> carries oxygenated blood (except pulmonary arteries)

Question 8

What is the function of capillaries?

Answer 8

-> exchange vessels, bring blood close to tissues
-> link arteries and veins

Question 9

What is the function of veins?

Answer 9

-> carry blood towards the heart
-> carries deoxygenated blood (except pulmonary vein)

Question 10

Appearance of arteries , how many layers are there and name them.

Answer 10

• well defined oval shape
• thick wall
• narrow lumen in relation to thickness of wall
• folded endothelium
  -There are three layers of arterial wall
  1) tunica intima/ endothelium
  2) tunica media
  3) tunica externa

Question 11

Difference between the three layers of arteries.

Answer 11

Tunica intima/ endothelium
- squamous epithelial cells = flattened cells
- one cell thick
- smooth surface facing lumen

Tunica media
- thickest
- three components (collagen fibres, elastic fibres and smooth muscle)

Tunica externa
- 2 components : only collagen fibres and elastic fibres

Question 12

Roles of each component. ( collagen fibres, elastic fibres and smooth muscle)

Answer 12

1) collagen fibres:
- withstand high pressure
- prevents rupture of vessels

2) elastic fibres:
- allows vessels to stretch and withstand high pressure
- when blood enters at low pressure, it recoils to give blood a small push to increase blood pressure
- smooths out pulsatile flow
- maintains blood pressure

3) smooth muscle - many layers :
- maintains blood pressure
- contract/relax to change volume of blood delivered
- keep blood moving forwards

Question 13

What happens when muscle relax and when contracts?

Answer 13

when muscle relax:
- arterioles become wide (vasodilation)
- increase blood flow

when muscle contract:
- arterioles become narrow (vasoconstriction)
- reduce blood flow

Question 14

Appearance of veins.

Answer 14

• tunica externa is the thickest in veins
• thin tunica media
• tunica intima is smooth and not crinkly
• blood is transported at low pressures so no need for thick walls
• contain semi-lunar valves (formed from their endothelium)
• large lumen
• irregular shape