8.2 Blood Vessels Flashcards
Different blood vessels have different proportions of tissues depending on their _____ and the _____ of blood flow through them.
function, rate
What are the different types of tissues found in blood vessels?
endothelium, smooth muscle, collagen, elastic fibres
What is the endothelium layer in blood vessels?
thin membrane lining the inner surface of the vessel
made from endothelial cells
What is the elastic fibre layer in blood vessels?
made from elastin,
can STRETCH + RECOIL in response to pressure changes
What is the collagen layer in blood vessels?
tough outer layer
structural support + limits stretching
What is the smooth muscle layer in blood vessels?
CONTRACTS + RELAXES
which changes the size of lumen + change/direct blood flow
What are the characteristics of arteries?
NARROW LUMEN (maintain fast blood flow),
THICK ELASTIC LAYER (recoil to withstand higher pressure),
SMOOTH ENDOTHELIAL LAYER (less friction for fast blood flow),
VERY THIN COLLAGEN LAYER (less restriction of stretching)
Why do arteries have a NARROW LUMEN?
maintain fast rate of blood flow
Why do arteries have a THICK ELASTIC LAYER?
blood is pumped out of the heart into the arteries at very HIGH PRESSURE
thick elastic fibres allow arteries to WITHSTAND high pressure by allowing them to STRETCH
Why do arteries have a VERY THIN COLLAGEN LAYER?
arteries must be able to recoil greatly using elastic fibres to withstand high blood pressure
thin collagen layer = less restriction of stretching
Why do arteries have a SMOOTH ENDOTHELIAL LAYER?
less friction»_space; faster blood flow
What are the differences between arterioles and arteries?
arterioles have MORE SMOOTH MUSCLE»_space; control blood flow to areas (would be cutting off blood flow to large areas if arteries vasoconstricted)
arterioles have LESS ELASTIC FIBRES»_space; increased total cross-sectional area = lower pressure so less stretch + recoil
What are the characteristics of veins?
THIN ELASTIC LAYER (low pressure, little stretching)
WIDE LUMEN + SMOOTH ENDOTHELIAL LAYER (less friction for fast blood flow)
VALVES (prevent backflow of blood)
Where is the site of gas exchange in mammals?
alveoli
What are the characteristics of capillaries?
1 CELL THICK ENDOTHELIUM (short diffusion distance)
LARGE SURFACE AREA
TOTAL CROSS SECTIONAL AREA > ARTERIOLES (blood flow slows so more time for diffusion)
NARROW LUMEN (red blood cells travel in single file for complete diffusion)
