ch. 42 Flashcards
how do small molecules move between cells and their surroundings
diffusion
why is diffusion only efficient over small distances
because the time it takes to diffuse is proportional to the square of the distance
how do most animals exchange materials with the environment?
via a fluid-filled circulatory system
cnidarians and circulatory system
- gastrovascular cavities function in both digestion and distribution of substances throughout body
- body wall enclosing gastrovascular cavity is 2 cells thick
flatworms and circulatory
gastrovascular cavity and flat body that minimizes diffusion distances
what does a circulatory system have
- circulatory fluid
- set of interconnecting vessels
- muscular pump (heart)
ex. of phylums/organisms with open circulatory system
- insects
- arthropods
- some molluscs
open circulatory system
hemolymph bathes organs directly
closed circulatory system
blood is confined to vessels and is distinct from interstitial fluid
ex. of phylum/organisms with closed circulatory
- annelids
- cephalopods
- vertebrates
what does hemolymph lack
special cells to help transport oxygen
what is the closed circulatory system called in humans/other vertebrates
cardiovascular system
3 main types of blood vessels
- arteries
- capillaries
- veins
blood flow progression away from heart and back
- arteries
- arterioles
- capillaries
- venules
veins
capillary beds
networks of capillaries that are sites of the chemical exchange between blood and interstitial fluid
how are arteries and veins distinguished?
by direction of blood flow, not O2 content
how many chambers are in vertebrate hearts
2+
single circulation
blood leaving heart passes through 2 capillary beds before returning
ex. of organisms with single circulation
bony fish, rays, sharks
- 2 chambered heart
double circulation
oxygen-poor and oxygen-rich blood are mostly pumped separately from right ad left sides of heart
ex. of organisms with double circulation
amphibians, reptiles, mammals
in reptiles/mammals, where does oxygen-poor blood flow through to pick up oxygen through the lungs?
pulmonary circuit
in amphibians, where does oxygen-poor blood flow through to pick up oxygen through the lungs?
pulmocutaneous circuit
where does oxygen-rich blood deliver oxygen
through the systemic circuit