2.5 Flashcards
What is the role of arteries?
to carry blood under high pressure away from the heart
What are the features of arteries?
arteries have an outer layer of connective tissue containing elastic fibres and a middle layer containing smooth muscle with more elastic fibres.
What feature of arteries allow them to dilate and constrict?
thick walls of smooth muscle
What is the role of veins?
to carry blood under low pressure back towards the heart
What are features of the veins?
The muscular layer and the layers of elastic fibres in the wall of a vein are thinner than those in an artery.
The lumen of a vein is wider, this reduces resistance to flow of blood to a minimum.
What do veins contain to stop the back flow of blood?
valves
What is vasodilation?
the dilating (widening) of the inner circumference of an arterial lining that occurs when smooth muscle in the arterial wall relaxes
What is vasconstriction?
the constricting (narrowing) of the inner circumference of an arterial lining that occurs when smooth muscle in the arterial wall contracts.
How can vasodilation and vasconstriction control blood flow to different areas of the body?
Vasoconstriction in an area of the body causes that area to cool down, as there is decreased blood flow.
Vasodilation in an area of the body causes that area to warm up, as there is increased blood flow.
What is the role of capillaries?
to exchange nutrients between blood and tissues while connecting arteries and veins together.
What are the features of a capillary?
composed of epithelium and are only one cell thick
How are materials exchanged between the blood, tissue fluid and cells?
Blood travels at high pressure from arteries and enters capillaries. Pressure filtration allows plasma to pass through the cappilary walls into tissue fluid. Materials can then be transported between tissue fluid and tissue cells by passive and active transport.
What is the difference between blood plasma and tissue fluid?
Blood plasma contains plasma proteins whereas tissue fluid does not as these proteins are too large to filter through capillary walls.
What is the role of lymphatic vessels?
to absorb excess tissue fluid
What is plasma?
a watery yelow fluid that contains many dissolved substances such as glucose, amino acids, respiratory gases, plasma protein and useful ions.
