3.1.2 TRANSPORT IN ANIMALS

Question 1

Blood vessels

Answer 1

Structure and function of arteries, arteriales, capillaries, venules and veins
Distribution of different tissues within the vessel walls

Question 2

Basic structure

Answer 2

• tough collagen outer layer ( provides structural support to maintain shape of vessel and can resist pressure )
• smooth muscle layer ( can contract and relax to control the flow of blood by changing the size of the lumen )
• elastic layer ( can stretch and recoil to maintain blood pressure contains elastin )
• endothelium ( inner lining of cells. A smooth layer to prevent friction and thin for a short diffusion pathway in the case of caps )
• lumen ( cavity which blood flows through )

Question 3

Structure and function of arteries

Answer 3

Function: to transport blood rapidly at high pressure away from the heart to tissues. Most carry oxygenated blood (except the pulmonary artery)
•Thick muscle layer – control the flow of blood via contracting and relaxing
•Thick elastic layer – to allow stretching under high blood pressure when ventricle contracts and recoils under low blood pressure when ventricle relaxes to withstand and maintain high pressure and to smooth blood flow during pressure surges created by the beating heart
•Smooth endothelium- reduces friction to allow blood to flow easily
•Overall very thick wall- withstands high pressure to prevent bursting
•No valves- blood always at high pressure due to heart pumping and so blood doesn’t naturally flow backwards
•Collagen- thick collagen layer to maintain shape of vessel and prevent it stretching too much. It also helps to withstand high pressure

Question 4

Structure and function of arterioles

Answer 4

Function: to transport blood rapidly at high pressure away from the heart to tissues. Most carry oxygenated blood (except the pulmonary artery)
•Thick muscle layer – control the flow of blood via contracting and relaxing
•Thick elastic layer – to allow stretching under high blood pressure when ventricle contracts and recoils under low blood pressure when ventricle relaxes to withstand and maintain high pressure and to smooth blood flow during pressure surges created by the beating heart
•Smooth endothelium- reduces friction to allow blood to flow easily
•Overall very thick wall- withstands high pressure to prevent bursting
•No valves- blood always at high pressure due to heart pumping and so blood doesn’t naturally flow backwards
•Collagen- thick collagen layer to maintain shape of vessel and prevent it stretching too much. It also helps to withstand high pressure

Question 5

Structure and function of capillaries

Answer 5

•Function: to exchange metabolic substances between blood and body tissues i.e. very slow blood flow, and single file red blood cells
•Overall very thin wall- one cell thick endothelium for short diffusion pathway
•Numerous and branched- large surface area for exchange
•Narrow diameter– can permeate tissues so no cell is far away from capillary- short diffusion pathway. Forces red blood cells to move slowly in single file to allow time for diffusion to take place. Also allows for a greater surface area of red blood cell to be in contact with the capillary wall to help make diffusion more efficient by decreasing the diffusion pathway
•Spaces between endothelial cells– allows white blood cells to leave blood and enter tissue fluid, also allows exchange of some substances
•Total cross-sectional area of capillaries is greater than the arteriole supplying them– this makes the rate of blood flow decrease, giving more time for exchange of substances

Question 6

Structure and function of venules

Answer 6

•Function: to transport blood slowly at low pressure from capillaries to veins
•Very thin muscle layer – as they don’t control the flow of blood via constricting and dilating
•Very thin elastic layer – as blood pressure is low and so veins do not need to stretch and recoil
•Valves- to prevent backflow of blood (when they get compressed when muscles contract) as blood is always at low pressure
•Smooth endothelium- reduces friction to allow blood to flow easily

Question 7

Structure and function of veins

Answer 7

•Function: to transport blood at low pressure from venules to the heart. Most carry deoxygenated blood (except the pulmonary vein)
•Thin muscle layer – as they don’t control the flow of blood via constricting and dilating
•Thin elastic layer – as blood pressure is low and so veins do not need to stretch and recoil
•Overall thin wall- no need to withstand high pressure and so no risk of bursting. Allows compression which aids blood flow
•Do not have a pulse- the surges of blood are lost as the blood passes through the narrow veins
•Valves- to prevent backflow of blood (when they get compressed when muscles contract) as blood is always at low pressure
•Smooth endothelium- reduces friction to allow blood to flow easily
•Collagen- thick collagen layer to maintain shape of vessel as veins carry large volumes of blood

Question 8

Circulatory systems

Answer 8

• Need for transport systems in multicellular animals (size met rate and sa:v)
• dif types of circulatory systems
  (single, double, open and closed in insects and fish as well as mammals)

Question 9

Insects circulatory system (often open)

Answer 9

• invertebrates
• haemolymph (interstitial )found between cells in body) mix of blood and tissue fluid) transports nutrients and nitrogenous waste
• simple pumping organ runs along length of thorax and abdomen
• some can just rely on body movement for pumping haemolymph
• very few vessels to hold haemolymph which come into direct contact with body tissues / cells to allow exchange to take place returning to heart from an open ended vessel
• carries blood at a higher pressure

Question 10

Why is an open system less efficient

Answer 10

Because not as efficient at diffusion bcs steep conc gradient cant be maintained as haemolymph is used and vessels aren’t used