veins, arteries, capillaries

Question 1

what is the structure of veins? what do they do?

Answer 1

• floppy appearance
• carry deoxygenated blood to heart( expect for pulmonary vein)
• have valves to prevent back flow due to low pressure
  structure
• constant pressure so no need for elastic walls.
• outer layer= connective tissue
  middle= little smooth muscle and nearly no elastic
  inner= endothelium

Question 2

what are small veins called? what do they do?

Answer 2

venules= carries blood from cells
join up to make larger veins

Question 3

why do veins have a low pressure?

Answer 3

due to blood losing most of its pressure as if flows through tiny capillaries.

Question 4

what are valves?

Answer 4

ensure that blood can only flow in one direction

Question 5

what is the structure of arteries?
what are they?

Answer 5

carry oxygenated blood away from heart to all cells for CR ( expect pulmonary artery)

• outer layer= connective tissue
• middle= smooth muscle and elastic fibres
  -inner layer= endothelium
• tight appearance
• no valves( expect semilunar valves in heart and pulmonary artery)
• high pressure so must have thick ,smooth muscle layer with elastic fibres

Question 6

what are small arteries called? what do they do?

Answer 6

arterioles= supply blood to capillaries

Question 7

how do arteries work?

Answer 7

• ventricles contract, push blood into arteries.
• wall of arteries stretch to accomodate the extra blood,
• when ventricles relax elastic artery recoils
• recoil keeps the blood moving- maintaining pressure
• muscle in artery does not contract but relax to keep moving blood along

Question 8

what is vasoconstriction?

Answer 8

muscle in artery can contract to reduce blood flow to a certain organ- usually when its cold

Question 9

what is vasodilation?

Answer 9

muscle in artery relaxs to increase blood flow to an organ- usually when its hot

Question 10

what are vasodilators?

Answer 10

substances that cause vasodilation to increase e.g. Co2 from CR

Question 11

what are capillaries?

Answer 11

microscopic blood vessels that form a net work to carry blood to cells in the body
- enable cells to get their requirements from blood and produce their waste products into the blood
- 1 cell thick

Question 12

what are the blood vessels?

Answer 12

arteries, capillaries and veins