Blood vessels and their functions Flashcards
what are the four different types of blood vessel?
artery, arterioles, capillaries, vein
what order does blood flow through the different blood vessels?
ARTERIES carry blood from the heart into the ARTERIOLES. ARTERIOLES control the blood flow into the CAPILLARIES. The CAPILLARIES link arterioles to VEINS which carry blood back to the heart.
what are the 5 basic layers from outside inwards of arteries, veins and arterioles?
tough outer layer muscle layer elastic layer thin inner layer lumen
what is the function of the tough outer layer?
to resist pressure changes from inside and outside
what is the function of the muscle layer?
to CONTRACT and control the flow of blood
what is the function of the elastic layer?
maintain BLOOD PRESSURE by stretching and springing back
what is the function of the thin inner layer?
smooth- prevents friction and thin- allow diffusion
what is the lumen?
central cavity of the blood vessel where the blood flows
what is the structure of a capillary?
lumen and lining layer
what is the function of arteries?
to transport blood RAPIDLY under high pressure FROM the heart to the tissues.
how is the structure of arteries adapted to their function?
- the muscle layer is THICK compared to veins. can be constricted + dilated control what’s going through.
- the elastic layer is RELATIVLEY THICK compared to veins. maintain high pressure
- the OVERALL THICKNESS of the wall is large. resist vessel bursting
- there are NO VALVES. blood is under constant pressure- doesn’t tend to flow backwards.
what is the function of arterioles?
carry blood, under lower pressure than arteries, from arteries to capillaries.
how are arterioles adapted to their function?
- muscle layer relatively THICKER than artery. restrict blood flow, controls movement into capillaries.
- elastic layer THINNER than arteries- blood pressure lower
what is the function of veins?
transport blood SLOWLY, under pressure from the tissues to the heart.
how are veins adapted for their function?
- muscle layer relatively thin compared to arteries. can’t control flow of blood.
- elastic layer relatively thin compared to arteries. low pressure of blood won’t cause to burst
- overall thickness of wall is SMALL. pressure too low create risk bursting
- valves throughout- blood doesn’t flow backwards
what is the function of capillaries?
to exchange metabolic materials eg oxygen, glucose, carbon dioxide between the blood and the cells of the body.
why is the flow of blood much slower in the capillaries? What does this allow more time for?
the pressure is very low.
more time to exchange materials
how are capillaries adapted to their function?
- walls only lining layer- short diffusion distance
- numerous + highly branched, large SA for diffusion
- narrow diameter- no cell is far from capillary
- lumen is narrow- red blood cells squeezed flat, even closer to cells
- spaces between the lining and cells- allow WHITE BLOOD CELLS escape to deal with infections in tissues
what is tissue fluid?
watery liquid that contains GLUCOSE, AMINO ACIDS, FATTY ACIDS, SALTS + OXYGEN.
it supplies these substance to tissues
what does tissue fluid receive from tissues?
carbon dioxide and other waste materials
what is tissue fluid formed from?
blood plasma
how is HYDROSTATIC PRESSURE created and what role does it play in tissue fluid?
- blood is pumped along narrower blood vessels (artery, arterioles and capillaries)- creates hydrostatic pressure at arterial end of capillaries.
hydrostatic pressure forces tissue fluid out of the blood plasma
what is the outward hydrostatic pressure opposed by?
- hydrostatic pressure of tissue fluid OUTSIDE capillaries-prevents outward movement of liquid
- lower WATER POTENTIAL of blood due to plasma proteins - pulls water back into blood with capillaries
what is the combined effect of hydrostatic pressure at the end of capillaries, hydrostatic pressure outside capillaries and lower water potential in the blood?
create an overall pressure that pushes tissue fluid OUT of the capillaries. force small molecules out BUT leave cells and proteins inside the blood.
what is ultrafiltration?
filtration capable of removing small molecules under pressure
what happens to tissure fluid after it has exchanged metabolic materials with the cells?
it returns to the circulatory system
how does most tissue fluid return to the blood plasma directly via the capillaries?
- the loss of tissue fluid from capillaries REDUCE hydrostatic pressure in them
- when the blood reaches the venous end of the capillary network it’s hydrostatic pressure is less than the tissue fluid outside
- tissue fluid FORCED back into the capillaries
- in addition osmotic forces resulting from PROTEINS in the blood plasma pull water back into the capillaries
how is the remainder of the tissue fluid carried back to the blood plasma?
by the LYMPHATIC SYSTEM
a system of vessels that begin in the tissues, gradually merge into larger vessels that form a network throughout the body
what is the lymphatic system?
a system of vessels that begin in the tissues, gradually merge into larger vessels that form a network throughout the body
how are the contents of the lymphatic system moved?
- HYDROSTATIC PRESSURE of tissue fluid that left the capillaries
- CONTRACTION OF BLOOD VESSELS squeeze the lymph vessels
