circulation Flashcards
exchange of substances
occurs at the cellular level by crossing the plasma membrane
in unicellular organisms exchange occurs directly with the environment via diffusion
diffusion important for short distances
in multicellular organisms direct exchange with the environment isn’t possible and most require specialised transport system
circulatory system components
circulatory fluid, interconnecting vessels and muscular pump
circulatory system function
connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients and dispose of waste products
types of circulatory systems
open and closed
open circulatory system
has circulatory fluid hemolymph which is a mixture of blood and lymph in sinuses and this bathes body cells and organs
arthropods (grass hoppers) and molluscs (clams) have open circulatory systems
closed circulatory system
blood is confined to vessels and is distinct from the interstitial fluid
annelids (earth worms), cephalopods (squids and octopuses) and all vertebrates have closed circulatory systems
closed system organisation
arteries branch into arterioles
networks of capillaries called capillary beds are the sites of chemical exchange between the blood and interstitial fluid
venules converge into veins
single circulation
one atrium and one ventricle
blood leaves the heart and passes through two capillary beds
bony fish, rays and sharks
double circulation
amphibians, reptiles, birds and mammals
amphibians
double circulation with three chambers, two atria, one ventricle
some mixing of blood
reptiles
double circulation three chambers, two atria, one ventricle thats partially divided by an incomplete septum
some mixing of blood
mammals and birds
double circulation with four chambers
cardiac cycle
