3. circulatory system Flashcards
1
Q
why are circulatory systems necessary
A
multicellular organisms small SA to volume ratio
need transport system to carry raw materials from exchange organs to cells
2
Q
what does blood transport
A
repiratory gases
digestion
metabolic waste
hormones
3
Q
arteries
3 points
A
- carry blood from heart to rest of body
- walls thick and muscular. elastic tissue to stretch and recoil.
inner lining/endothelium folded allowing artery to stretch. (helps maintain high pressure) - carry oxygenated blood (with exception of pulmonary artery)
4
Q
arterioles
2 points
A
- arteries divide into smaller vessels - arterioles
2. blood directed to areas of demand by muscles inside arterioles
5
Q
veins
5 points
A
- take blood back to heart under low pressure
- wider lumen, very little elastic or muscle tissue
- valves to stop blood flowing backwards
- helped by contraction of surrounding body muscles
- all carry deoxygenated blood with exception of pulmonary vein
6
Q
capillaries
A
- branch from arterioles. smallest.
- near cells in exchange tissues
- walls 1 cell thick = short diffusion pathway
- large number of capillary’s = increased SA
7
Q
networks of capillaries in tissue called
A
capillary beds
8
Q
tissue fluid
A
- start/artery end = hydrostatic pressure inside capillaries greater than in tissue fluid
- difference in pressure = fluid forced out forming tissue fluid
- fluid leaves = pressure reduced in capillaries = pressure lower at venule end
- fluid loss = increasing conc of plasma proteins = water potential at venule end lower than tissue fluid
- water re-enters capilarries by osmosis
9
Q
what is tissue fluid made of
A
small molecules that leave blood plasma e.g. O2, H2O, nutrients.
doesn’t contain RBC or big proteins = too large
10
Q
excess of tissue fluid ?
A
drained into lymphatic system -> back into circulatory system
