Circulatory System Structure Flashcards
Why can’t multi cellular organisms rely on diffusion to transport substances around the body?
They have a low surface area to volume ratio and cannot rely on diffusion as the diffusion pathway is too long
what is the structure and function of blood vessels?
arteries branch into arterioles which can contract to restrict blood flow and relax to increase blood flow.These branch into capillaries then deoxygenated blood flows into the venules which join veins and blood is transported back to the heart.
Describe the structure and functions of arteries
-narrow lumen to help maintain high pressure
-thick muscular walls and elastic layer allows stretching and recoiling with ventricular contractions maintaining high blood pressure
-folded endothelium with allows stretching to help maintain high pressure
describe the structure and functions of veins
-wide lumen than arteries as blood is at low pressure
-thinner layers of muscle and elastic tissue
-valves to ensure that blood does not flow backwards
-when veins are compressed this increases pressure and pushes blood along
describe the structure and functions of capillaries
-site of substance exchange with cells
-walls are one cell thick for short diffusion pathway
-fenestrations between endothelial cells allow substances to diffuse out
-large numbers of capillaries increase the surface area for gas exchange
why does blood pressure decrease as you move from arteries to veins?
blood flows from high pressure to low pressure due to pressure along the vessels from the aorta due to it branching into many vessels.
how do arteries even out blood pressure?
the walls of the arteries stretch when blood moves through high pressure then recoils as blood pressure drops which evens out the blood pressure
What does the blood transport?
Gases, products of digestion, metabolic waste, and hormones
