What’s the function of the tough fibrous outer layer ?
Resist internal and external pressure changes
What’s the function of the muscle layer ?
Constricts and dilates the vessel to control blood flow
What’s the function of the elastic layer ?
Stretches and recoils to maintain blood pressure
What’s the function of the endothelium ?
Smooth to reduce friction
What layers do capillaries have ?
Endothelium and lumen
4 ways in which artery structure is different to veins and how this helps with its function ?
Thicker muscle than veins - blood at higher pressure so can constrict and dilate to control volume of blood into arterioles
Thicker elastic layer than veins - stretch and recoils allows high pressure to be maintained
Thicker wall - ensures no bursting under high pressure
No valves - blood unlikely to back flow as at constant high pressure
2 ways in which arterioles structure is different to arteries and how it helps with their function ?
Thicker muscle than arteries - allows lumen to constrict to restrict and control blood flow into capillaries
Thinner elastic layer than arteries - more area so at lower pressure, not a much stretch or recoils allows high needed
4 ways in which vein structure is different to arteries and how this helps their function ?
Thinner muscle - blood not at high pressure, carry away from tissues
Thinner elastic - lower pressure, no need to stretch or recoil
Less thick walls - low pressure, allows flattening during skeletal contraction
Valves - low pressure so prevents backflow of blood
4 ways in which capillaries structure aids their function ?
Walls are mostly endothelium - thin so shorter diffusion distance for rapid diffusion
Numerous and highly branched - provides a larger surface area for exchange
Narrow lumen - squeezes RBCs against walls, reducing diff distance
Spaces between endothelial cells - all WBCs to move out and fight infection in tissues and tissue fluid formation
What pressure does the pumping of the heart create?
Hydrostatic pressure
What is tissue fluid formed by ?
The ultrafiltration of blood plasma
Explain how tissue fluid is formed and returned back to the circulatory system
Ventricular systole means hydrostatic pressure is high at arterial end of capillaries
pressure causes small molecules (oxygen, water, ions, AA, glucose) to move out of blood plasma by ultrafiltration
hydrostatic pressure and water potential in the capillary is now lower than the tissue fluid outside
so water is forced back into capillary at venule end by the higher hydrostatic pressure also water leaves tissue fluid and enters blood via osmosis down a water potential gradient
How is excess tissue fluid returned to the circulatory system ?
carried back in the lymphatic system
Drains into blood via 2 ducts into veins close to the heart
In what 2 ways is the contents of the lymphatic system moved ?
Hydrostatic pressure of tissue fluid that left the capillaries