7.6- BLOOD VESSELS AND THEIR FUNCTIONS Flashcards
What are the 4 different types of blood vessels?
arteries
arterioles
capillaries
veins
What do arteries carry?
blood away from heart + into arterioles
What are arterioles?
smaller arteries that control blood flow from arteries to capillaries
What are capillaries?
tiny vessels that link arterioles to veins
What do veins carry?
blood from capillaries back to heart
What is the basic layered structure of arteries, arterioles + veins from outside inwards? (5)
tough fibrous outer layer muscle layer elastic layer thin inner lining (endothelium) lumen
What does the tough fibrous outer layer of the basic layered structure of arteries, arterioles + veins do?
resists pressure changes from both within + outside
What does the muscular layer of the basic layered structure of arteries, arterioles + veins do?
can contract + so control flow of blood
What does the elastic layer of the basic layered structure of arteries, arterioles + veins help do?
helps maintain blood pressure by stretching + springing back (recoiling)
What does the thin inner lining (endothelium) of the basic layered structure of arteries, arterioles + veins do?
smooth to reduce friction + thin to allow diffusion
What is the lumen of the basic layered structure of arteries, arterioles + veins?
not actually a layer but the central cavity of the blood vessel through which blood flows
What differs between the arteries, arterioles + veins?
relative proportion of each layer
How is the structure of arterioles different from arteries?
arterioles smaller in diameter + having relatively larger muscle layer + lumen
What is the difference in structure of arteries, arterioles + veins related to?
differences in function that each type of vessel performs
What is the function of arteries?
transport blood rapidly under high pressure from heart to tissues
How is the structure of arteries adapted to their function? (4)
muscle layer thick compared to veins
elastic layer relatively thick compared to veins
overall thickness of wall great
no valves
What can smaller arteries do as the muscle later is thick compared to veins?
smaller arteries can be constricted + dilated to control volume of blood passing through them
Why is the elastic layer of arteries relatively thick compared to veins?
as it’s important that blood pressure in arteries kept high if blood is to reach extremities of body
What happens to the elastic walls of the arteries during systole + diastole?
elastic wall stretched at each beat of heart (systole)
then springs back when heart relaxes (diastole)
What does the stretching + recoiling action of the arteries help maintain?
helps maintain high pressure + smooth pressure surges created by beating of heart
What does the overall thickness of the wall of arteries being great resist?
resists vessel bursting under pressure
Which arteries do have valves? - they’re an exception
arteries leaving the heart
Why are there no valves in arteries?
blood under constant high pressure due to heart pumping blood into arteries
so tends not to flow backwards
What do arterioles carry?
blood under lower pressure than arteries, from arteries to capillaries
What do arterioles control?
control flow of blood between arteries + capillaries
What structures of arterioles is related to their function? (2)
muscle layer relatively thicker than in arteries
elastic layer relatively thinner than in arteries
What does the contraction of the muscle layer of arterioles allow?
constriction of lumen of arteriole
What does the contraction of the muscle layer constricting the lumen of arterioles do?
restricts flow of blood + so control its movement into capillaries that supply the tissue with blood
Why is the elastic layer of arterioles relatively thinner than in arteries?
as blood pressure lower
What do the veins do?
transport blood slowly, under low pressure, from capillaries in tissues to heart