Q3: Pressure in blood vessels and heart rate Flashcards
(28 cards)
Different types of blood vessels
4
veins
capillaries
arteries
arterioles
Arteries
Carry blood away from the heart and into arterioles
Arterioles
Smaller arteries that control blood flow from arteries to capillaries
Capillaries
Tiny vessels that link arterioles to veins
Veins
Carry blood from capillaries back to the heart
Five components of same basic layered structure in arteries, arterioles and veins
- tough fibrous outer layer
- muscle layer
- elastic layer
- thin inner lining (endothelium)
- lumen
Tough fibrous outer layer
resists pressure changes from both within and outside
Muscle layer
can contract and so control the flow of blood
Elastic layer
Helps to maintain blood pressure by stretching and springing back (recoiling)
Thin inner lining (endothelium)
Is smooth to reduce friction and thin to allow diffusion
Lumen
Not a layer but the central cavity of the blood vessel through which the blood flows
Pressure in arteries?
high pressure
Why is the elastic layer in arteries relatively thick compared to veins?
important that high blood pressure is maintained so it can reach the extremities of the body,
elastic wall stretches and recoils to maintain high pressure and smooth pressure surges creating by the beating of the heart
Thickness of the overall wall of the artery?
over thick
to resist bursting under high pressure
Why are there no valves in arteries?
blood tends not to flow backwards due to constant high pressure
Arterioles vs arteries pressure of blood
arterioles carry blood under lower pressure
Muscle layer in arterioles compared to arteries?
relatively thicker in arterioles which allows constriction of the lumen of the arteriole, restricts blood flow and so controls its movement into capillaries
Why is the elastic layer relatively thinner in arterioles compared to arteries?
because the blood pressure is lower in arterioles
Veins blood pressure
where do they transport blood from and to?
low pressure
from capillaries in tissues to the heart.
Why is the elastic layer in veins relatively thin?
low pressure blood won’t cause them to burst and pressure is too low to create a recoil action
Why do veins have valves?
pressure is low, so they ensure backflow doesn’t occur
Pocket valves
occur throughout the venous system
Semi-lunar valves
in the aorta and pulmonary artery, prevent backflow of blood into the ventricles when the pressure in these vessels exceeds that in the ventricles
Atrioventricular valves
between the atrium and ventricle on both sides, prevents backflow of blood when ventricular pressure exceeds atrial pressure
