circulatory system structure Flashcards
why do multicellular organsims need a transport system
they have a low surface area to volume ratio and therefore they cannot rely on diffusion for gas exchange
what are the 2 types of circulatory systems and where are they found
open - insects
closed - insects and mammals
what is the difference between a single and double circulatory system
a single has 2 chambers in the heart and so blood passes through the heart once every circuit
a double has 4 chambers and so blood can pass through the heart twice every circuit
what is the role of the thin endothelium layer of cells in all vessels
inner lining of the lumen which reduced friction for a smooth flow of blood
what is the role of the elastic layer of tissue
allows the walls of the vessel to stretch and recoil controlling the flow of blood in the arteries, arterioles and veins
what is the role of the smooth muscle layer
contracts and relaxes to control the flow of blood in the arteries, arterioles and veins
describe the general features of an artery
- carries oxygenated blood away from the heart (except pulmonary artery)
- thick muscular walls
- high pressure
what allows the artery to carry blood at a high pressure
- narrow lumen
- elastic layer
- smooth muscle
describe the general features of a vein
- carry deoxygenated blood to the heart (except the pulmonary vein)
- lower pressure
- thinner layers of smooth muscle and elastic tissue
- valves to prevent back flow
