Flashcards in 2.5. The Structure and Function of Arteries, Veins and Capillaries Deck (21):
What is the pathway between arteries and veins?
Arteries -> Arterioles -> Capillaries -> Venules -> Veins
What is the central space of a blood vessel called?
What is the thin layer of cells that line the lumen called?
What direction do arteries go in?
Away from the heart.
What are the characteristics of arteries?
Thick muscular walls with elastic fibres, narrow lumen.
Why do arteries have elastic walls?
When the heart contracts a surge of high pressure blood surges into the arteries. The arteries need elastic walls in order to stay in tact after these surges of blood. The fibres also recoil during contractions which keeps the high pressure in the arteries.
What is vasoconstriction?
When the muscle in the middle layer of the arteries contract and narrow the lumen. This decreases blood flow into the capillaries.
What is vasodilation?
When the muscle in the middle layer of the arteries relaxes which widens the lumen and increases blood flow into the capillaries.
What direction do veins go in?
Towards the heart.
What vital thing do veins have in their lumen and why do they need them?
Valves, to prevent the backflow of blood due to the low pressure in them.
What are the characteristics of veins?
Thick outer elastic wall, but a much thinner middle layer of elastic muscle compared to arteries. They contain valves and also have a wider lumen than arteries.
How thick are capillaries?
One cell thick.
How narrow is the lumen of capillaries?
Only wide enough to let one red blood cell pass through.
Why is a very thin wall beneficial for capillaries?
Allows easy exchange of materials between blood and tissue.
What is a network of capillaries known as?
Why do capillaries exude plasma and what does it turn into once exuded?
The high pressure of blood from the arterioles forces the capillaries to exude plasma which turns into tissue fluid.
What is the function of tissue fluid?
It bathes the cells, then exchanges material with the cells and returns to the capillaries by osmosis and diffusion.
Where does excess tissue fluid go?
It gets transferred to the lymphatic system through lymph vessels and turns into lymph.
What are the characteristics of lymph vessels?
Very low pressure, contain valves to prevent backflow, skeletal muscles surround them to help push the lymph through.
What is the function of the lymphatic system?
It returns the excess tissue fluid back to the bloodstream.