Blood vessels

Question 1

General?

Answer 1

• arteries carry blood away from heart into arterioles
• arterioles r smaller than arteries (bigger than capillaries) & connect to capillaries
• capillaries connect arterioles to veins
• veins carry blood back into heart

Question 2

Features of mass transport systems?

Answer 2

• suitable medium in which to transport substances - usually liquid/water based
• A closed system in tubes/vessels - contains transport medium & forms a network to distribute to all parts of the organism
• A form of mass transport - a mechanism for moving the medium within the vessels (through pressure differences)
• mechanism to maintain mass flow movement in 1D (e.g. valves)
• a means of controlling flow of medium to suit changing needs of diff parts of organism
• mechanism for mass flow of water or gases (e.g. diaphragm + intercostal muscles)

Question 3

Open v Closed circulatory system?

Answer 3

open - heart pumps blood/liquid thru vessels into open cavities - bathes all organs & tissues (e.g. insects)
closed - (larger, more active animals & all vertebrates) blood remains in vessels & is transported to all extremities of body

Question 4

Single v double circulatory system?

Answer 4

• single e.g. fish - blood travels from heart to gills (where it’s oxygenated) then straight to rest of body
• double (higher metabolic rates so - body temps) - blood from heart to lungs then back to heart - then from heart (2nd loop) to rest of body
• returned to heart to boost pressure - blood flow is quicker as pumped around at higher press

Question 5

Arteries v Veins structures related to function: Muscle layer?

Answer 5

A:
- thick
- so - constriction & dilation can occur to control blood volume
V:
- thin
- so it can’t control blood flow

Question 6

Arteries v Veins structures related to function: Elastic layer?

Answer 6

A:
- thicker
- help maintain high blood pressure
- walls can stretch & recoil in response to heart beat (stretches at systole & recoils at diastole)
- helps smooth press surges created by heart beat
V:
- relatively thin
- press much lower (won’t cause them to burst & press too low to create recoil action)

Question 7

Arteries & Veins structures related to function: Wall thickness?

Answer 7

A:
- thicker
- helps prevent vessels bursting due to high press
V:
- thin
- press much lower so - low risk of bursting
- allows them to be flattened easily - aiding flow of blood within

Question 8

Arteries structures related to function: Valves?

Answer 8

A:
- blood under constant high press - due to heart pumping blood into arteries so - tends not to flow backwards
V:
- when body muscles contract - veins r compressed - pressuring blood within - valves ensure ts pressure directs blood in 1D - towards heart

Question 9

Capillaries?

Answer 9

• wall consists of single layer of endothelial cells & basement membrane (on top) & between cells - gaps
• form capillary beds as exchange surfaces aka many branched capillaries
• all hv narrow diameter to slow blood flow
• RBCs only just fit thru & r squashed against walls - maximises diffusion

Question 10

Capillary structures related to function?

Answer 10

1. Walls consists mainly of the lining layer (endothelium) - extremely thin so - short diffusion dis - allows for rapid diffusion of materials between blood & cells
2. Numerous & highly branched - large SA for exchange
3. Spaces between endothelial cells - allows WBCs to escape so can deal w tissue infections
4. Narrow lumen - RBCs squeezed flat against side of capillary - brings even closer to cells to give O2 - reduces diffusion dis
5. Narrow diameter - permeate tissues so - no cell far from a capillary & short diffusion dis

Question 11

Arteriole structures to function?

Answer 11

• muscle layer thicker than in arteries - helps restrict blood flow into capillaries (by constriction of lumen) - tm press could damage capillaries
• elastic layer thinner than in arteries - as press is lower
• wall thickness - thinner as press slightly lower