Exchange (BLOOD VESSELS) Flashcards
(16 cards)
The heart is a….
Muscle
Give the 5 blood vessels
Arteries
Arterioles
Capillaries
Venules
Veins
What is the function of the arteries
Carry high pressure oxygenated blood away from the heart (apart from the pulmonary artery)
Give the structure and the function of arteries
Small lumen
Folded endothelium - smooth to reduce friction
Thick elastic tissue - stretches due to high blood pressure. Ventricles contracts then recoils which MAINTAINS smooth blood pressure
Thick muscle layer - Thick to help artery WITHSTAND high blood pressure
Tough outer layer - made of proteins to stop bursting
Does the artery have valves
No as blood is high pressure
Give the structure and function of arterioles
Smooth Muscle walls - thicker than in arteries in order to restrict blood flow into the capillaries:
Lumen can constrict if smooth muscle contracts (vasocontraction)
Lumen can widen if smooth muscle relaxes (vasodilation)
Elastic layer - thinner than in arteries as the blood is at lower pressure
What do capillaries form and what do they provide
Form capillary bed which provides a large total surface area for exchange with surrounding tissues
Also provides a high total cross sectional area
Also slows the movement of blood so provides more time for diffusion of substances
Give the structure and function of capillaries
Thin lining layer (endothelium) - once cell thick which shortens diffusion pathway
Narrow lumen - just big enough for a red blood cell so cells are in close contact with endothelium and blood flow is slow which allows for more difusion time
Pores between endothelial cells - allow water and certain dissolved substances to leak out of blood and form tissue fluid
Give the structure and function of venules
Wider lumen
Thinner muscle layer
Thinner elastic tissue
Give the function of veins
Carry’s low pressure deoxygenated blood back to the heart (apart from pulmonary vein)
Give the structure and function of veins
Thinner muscle and elastic tissue - thinner as blood travels at a lower pressure so ventricles don’t stretch and recoil
Pocket valves - stops the backflow of blood
What does a graph of blood vessels pressure show
Arteries and arterioles have pulsating lines as they have elastic tissue so ventricles stretch an recoil. Capillaries, venules, veins have thinner elastic tissue so dont pulsate
What is tissue fluid
Fluid containing water, oxygen, amino acids, glucose and other nutrients which bathes the cell. Tissue fluid delivers oxygen and nutrients to respiring cells and removing waste products
Note: only called tissue fluid when its outside of the cell. If its inside, its called water and ions)
Describe how tissue fluid is formed and its returned to the circulatory system
1) At the arterial end of the capillary, there is a higher hydrostatic pressure so water + ions are forced out through the pores of the capillary which leaves behind larger proteins remain in the capillary
2) This causes the tissue fluid to have a higher water potential than blood
3)At the venule end, the hydrostatic pressure has decreased due to water loss, but the osmotic pressure remains high due to the retained proteins.
4)Therefore, water re-enters the capillaries from the tissue fluid by osmosis down the water potential gradient.
What happens to the remaining 10% of tissue fluid that does not get reabsorbed into the capillary
Drains into the lymphatic system
Describe the net outflow of water at arterial end of capillary and net inflow in at venous end of capillary.
Arterial end - Net OUTflow is greater than net inflow as hydrostatic pressure is greater than osmotic effect
Venule end - Net INflow is greater than net outflow as osmotic effect is greater than hydrostatic pressure
