blood vessels and blood Flashcards
endothelium
smooth lining of vessels, single layer of squamous epithelial cells, reduces friction.
blood cells not damaged.
tunica media
contain elastic fibres which stretch to accommodate increased blood flow and pressure. they recoil pushing blood onwards along vessel maintaining blood pressure.
tunica externa
contain collagen fibres which resist overstretching of vessel walls
structure of artery
-thick muscular wall and elastic tissue.
-small lumen -this together with elastic recoil maintains blood pressure.
-valves present at junction of heart to aorta and pulmonary artery only.
what moves blood in arteries
heart muscle contracts forcing blood into artery.
-smooth muscle contracts and elastic fibres recoil evening out blood flow.
arteriole
small artery found in organs
-smooth muscle contracts to regulate blood flow. (vasocontriction)
structure of veins
few elastic fibres and thin muscle layer, bp is low.
have a wider lumen to reduce resistance and friction , have valves.
what moves blood in veins
skeletal muscle contracts .
reduced pressure in the chest draws blood back towards the heart when breathing in.
reduced pressure in heart draws blood into heart as heart muscle relaxes.
venules
small veins present in tissues connect capillaries to veins.
why do capillaries have thin , small diameter
increase friction and slows blood flow. many capillaries create a large cross sectional area further reducing blood flow.
this aids exchange of water and small molecules.
also have pores in walls for this.
in which vessel does pressure fall and why
arteriole -due to friction between blood cells and vessel walls and have a large total sa.
ventricle contraction effects pressure in vessels, in which vessel does this not effect
veins. -contraction of skeletal muscle and valves maintain blood flow back to heart.
what is found in plasma
mostly water and distributes heat
-contains dissolved minerals salts and hormones.
-contain waste products and urea.
-organic molecules e.g amino acids
-plasma proteins, antibodies and vitamins.
what are adaptations of a red blood cell
-biconcave shape and large sa:v ratio -rapid rate of diffusion of co2 and 02.
-flexible shape allows cells to squeeze through capillaries.
-no nucleus to hold max volume of oxygen and haemoglobin.
-no organelles for haemoglobin space.
-contain haemoglobin for efficient transport of gases.
a RBC has no organelles what does this suggest about the cell
-no growth and repair/no protein synthesis.
-respiration is anaerobic .
