3.2.2 blood vessels Flashcards
arteries
vessels that carry blood away from heart
arterioles
small blood vessels that distribute blood from artery to capillaries
capillaries
very small vessels w/ very thin walls
closed circulatory system
blood is held in vessels
open circulatory system
blood is not held in vessels
veins
vessels that carry blood back to heart
venules
small blood vessels that collect blood from capillaries & lead into veins
describe an open circulatory system
blood fluid circulates through body cavity & tissues/cells bathed directly in blood
disadvantages of open circulatory system
- blood pressure is low
- blood flow is slow
- circulation of blood may be affected by body movements/lack of
advantages of closed circulatory system
- higher pressure so blood flows quicker
- rapid delivery of oxygen/nutrients
- rapid removal of carbon dioxide/other waste
- transport is independent from body movements
what is the inner lining of a blood vessels called & describe its role
endothelium
- single layer of cells
- smooth which reduces friction with flowing blood
characteristics of arteries
- carry blood away from heart
- blood at high pressure = wall is thicker
- lumen small = maintain high pressure
- inner wall folded so lumen can expand as blood flow increases
how many layers is the artery wall made of
3
describe the inner layer of the artery wall & it’s role
(tunica intima)
- thin layer of elastic tissue
- stretch/recoil to help maintain blood pressure
describe the middle layer of the artery wall
(tunica media)
- thick layer of smooth muscle
describe the outer layer of the artery wall & it’s role
(tunica adventitia)
- thick layer of collagen & elastic tissue
- strength to withstand high pressure & recoil to maintain pressure
describe arterioles
- small blood vessels
- distribute blood from artery to capillaries
- contain layer of smooth muscle –> contraction restricts diameter
- constriction of walls can be used to divert flow of blood to regions with high demand (vasoconstriction)
describe structure of capillaries
- very thin walls
- allow exchange of materials between blood/tissue fluid
structure:
- lumen very narrow = RBC squeezed against walls as reduces diffusion pathway & increases resistance
- single layer of flattened endothelial cells = reduces diffusion distance for exchange of materials
- walls are leaky = allow blood plasma & dissolved substances to leave blood
describe venules
- collect blood from capillary bed & lead into veins
- walls consists of thin layers of muscle & elastic tissue outside endothelium
- thin outer layer of collagen
describe structure of veins
- carry blood back to heart (low pressure)
structure:
- lumen large = ease flow of blood
- thinner layers of collagen, smooth muscle & elastic tissue as don’t need to stretch/recoil & not actively constricted
- contain valves = prevent backflow of blood
- walls are thin, so vein can be flattened by surrounding skeletal muscles which applies pressure & forces blood to move in direction determined by valves
what impact does the flattening of surrounding skeletal muscles have on veins
applies pressure to blood = forces blood to move along in direction determined by valves
describe an open circulatory system in insects in steps
- muscular pumping organ = long tube lying just under dorsal (upper) surface of body
- blood from body enters heart via pores (ostia)
- heart pumps blood towards by peristalsis
- at forward end of heart (nearest head), blood pours into body cavity
describe an open circulatory system in larger insects in steps (eg. locust)
- have open-ended tubes attached to heart
- direct blood towards active parts of body
structure of arteries
- lumen
- endothelium
- elastic fibres
- smooth muscle
- collagen fibres
structure of veins
- lumen
- endothelium
- elastic fibres
- smooth muscle
- collagen fibres
structure of capillaries
- lumen
- endothelium
