Blood vessels Flashcards
Open circulatory systems
> mainly found in insects
blood is not always held in vessels
tissues directly bathed in blood
How do insects pump blood around the body?
> long muscular tube lies under the dorsal
blood enters the heart through pores called ostia
heart pumps the blood towards the head by peristalsis
blood then pour into the body
Disadvantages of open circuit?
> blood pressure is low so flow is slow
> circulation of blood affected by body movements
Advantages of closed?
> higher pressure so faster flow
rapid delivery of oxygen and nutrients
rapid removal of toxins
transport is independent of body movement
Arteries
> carry blood away from the heart
thick walls to withstand high pressures
lumen small to maintain high pressure
inner wall is folded to allow lumen to expand
Three layers of arteries?
> inner layer - tunica intima - thin layer of elastic tissue which allows wall to stretch and recoil
middle layer tunica media - thick layer of smooth muscle
outer layer - tunica adventina - thick layer of collagen and elastic tissue, providing strength for high pressure
Arterioles
> small blood vessels that distribute blood from artery to capillaries
contain smooth muscle
Capillaries
> narrow lumen to help transfer of oxygen as it reduces diffusion distance
walls contain one layer of endothelial cells to reduce diffusion distance
walls are leaky allowing blood plasma and dissolved substances to leave blood
venules
> small vessels coming from veins
collect blood from capillary bed and lead into veins
consists of thin layers of muscle and elastic tissue and thin layer of collagen
Veins
> carry blood back to heart
lumen is relatively large to allow blood flow
walls have a thin layer of collagen, smooth muscle and elastic tissue
dont stretch or recoil
contain valves to prevent blood flowing in the wrong direction
