Arteries, veins and capillaries Flashcards
What is the outer layer of blood vessels called?
Tunica externa
What is the middle layer of blood vessels called?
Tunica media
What is the internal layer of blood vessels called?
Tunica interna
What is the tunica externa layer of the arteries?
It has a thick outer layer made of elastin and collagen
What is the tunica media of arteries?
A thick middle layer containing smooth muscle
What is the tunica interna of arteries?
Thin inner layer made of folded layer of endothelial cells
What is the lumen of arteries?
Smaller lumen relative to its diameter
What is the blood in arteries?
Oxygenated blood
What is the pressure in arteries?
Blood pressure interesting is high to reach extremities
What is the movement in arteries?
Fast movement of blood
What is the tunica externa of veins?
Thinner outer layer and thinner layer of elastin and collagen
What is the tunica media of veins?
Thinner middle layer and thinner layer of smooth muscle
What is the tunica interna of veins?
Thin inner layer made of endothelial cells
What is the lumen in veins?
Larger lumen relative to diameter
Are there valves in veins?
Yes
What is the blood in veins?
Deoxygenated blood
What is the blood pressure in veins?
Relatively low blood pressure
What is the movement in veins?
Slower movement of blood
What is the outer layer of capillaries?
No outer layer of elastin or collagen
What is the middle layer of capillaries?
No layer of smooth muscle
What is the inner layer of capillaries?
Single layer of squamous endothelial cells
What is the lumen in capillaries?
Larger lumen relative to diameter but very small
What is the blood in capillaries?
Mix of blood
What do arteries branch into?
Arterioles
What do veins branch into?
Venules
What is the structure in arteries?
Endothelium, collagen, elastic recoil, smooth muscles and elastic fibres
What is the function of endothelium?
Can unfold when artery stretches during a heartbeat to allow changing volumes of blood as heart beats
What is the function of collagen?
It helps artery walls to withstand the pressure of the blood
What is the function of elastic recoil?
It helps maintain high blood pressure when heart relaxes to push blood along
What is the function of smooth muscle?
Narrow or dilate lumen to thermoregulate
How are lumen narrow or dilates?
Constrict or contract artery
How does narrowing or dilating cause thermoregulation?
It limits blood to one area and redirects to a more active area
What is the function of elastic fibres?
It allows artery to stretch and recoil as heart pumps
What is the function of arterioles?
It links arteries and capillaries together
What is the structure of arterioles?
More smooth muscle and less elastin in walls
What is the function of vasodilation and vasoconstriction?
To regulate temperature
What is the structure of veins?
Large lumen, thin layer of elastic tissue, thin layer of smooth muscle, valves and veins can be squeezed flat
What is the function of large lumen?
Ease flow of blood
What is the function of thin layer of elastic tissue?
They don’t need to stretch and recoil
What is the function of thin layer of smooth muscle?
Do not need to constrict blood flow
What is the purpose of valves?
They prevent back flow to help blood flow back to heart
How can veins be squeezed flat?
By skeletal muscle contracting next to them to push blood along
What is the capillary wall?
A single layer of flattened endothelial cells
What are the size of gaps between endothelial cells?
Large, except in CNS where there are tight junctions
What is the structure of capillaries?
Gaps between endothelial cells, very narrow lumen, small size and no valves
What is the function of gaps between endothelial cells?
It allows exchange of materials between the blood and cells via tissue fluid
What is the function of very narrow lumen?
Red blood cells are pressed up against capillary wall, reducing diffusion distance to help them give up oxygen
What is the function of no valves and small size?
Cross sectional area of capillaries is huge with arterioles leading into capillaries slows blood down and blood loses pressure
