7.5 Blood Vessels Flashcards
The main types of blood vessel The structure and function of arteries and arterioles The structure and function of capillaries The structure and function of veins and venules
What are the five main types of blood vessels?
- Arteries
- arterioles
- capillaries
- venules
- veins
What do arteries do?
Carry blood away from the heart
What do arterioles do?
Carry blood from arteries to capillaries
What do capillaries do?
Site of diffusion between blood and body tissues
What do venules do?
Carry blood from capillaries to veins
What do veins do?
Return blood to the heart
What are arteries adapted to do?
Collagen - Provides strength to prevent the vessel from bursting and to maintain vessel shape.
Elastic fibres - Contain elastin that lets them stretch and recoil to minimise changes in pressure.
Thick smooth muscle layer - Contracts/relaxes to constrict/dilate the lumen and control blood flow.
What does collagen do in arteries?
Provides strength and maintains vessel shape
What do elastic fibres do in arteries?
Stretch and recoil to minimise pressure changes
What does the thick smooth muscle layer do in arteries?
Contracts/relaxes to control blood flow
How do arterioles differ from arteries?
4 things
- Smaller
- larger lumen
- less elastin
- more smooth muscle
What is vasoconstriction?
- Smooth muscle contracts
- decreasing blood flow
What is vasodilation?
- Smooth muscle relaxes
- increasing blood flow
What are capillaries adapted for?
Lumen is very narrow - This allows red blood cells to be close to body cells.
Walls are thin - Substances can be exchanged across a short distance by diffusion.
Highly branched - This provides a large surface area for diffusion.
Why is the capillary lumen narrow?
Allows red blood cells to be close to body cells
Why are capillary walls thin?
Short diffusion distance
Why are capillaries highly branched?
Large surface area for diffusion
What are veins adapted to do?
Collagen - Provides strength to prevent the vessel from bursting and maintain vessel shape.
Little smooth muscle and elastic fibre - Not much is needed due to low blood pressure, and thinner walls allow veins to be easily compressed, aiding the flow of blood.
Valves - Pocket valves shut to prevent the back flow of blood when veins are squeezed by surrounding skeletal muscle.
Why does collagen do in veins?
Provides strength and maintains vessel shape
Why do veins have little smooth muscle and elastic fibre?
Low blood pressure
What do valves do in veins?
Prevent backflow of blood
What controls pocket valves in veins?
Skeletal muscle
How do venules differ from veins?
Smaller thinner walls less smooth muscle
