The circulatory system
- Created by: jessicawarren
- Created on: 01-05-16 15:59
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- The Circulatory System
- Mass transport system
- 1) Multicellular organisms have small SA:V ratio- need specialised transport systems to carry materials from exchange organs to body cells
- 2) Made up of heart and blood vessels
- 3) Heart pumps blood through blood vessels (veins, arteries, arterioles, capillaries)
- 4) Blood transports respiratory gases, products of digestion, metabolic waste and hormones around the body
- 5) Two circuits- one takes blood from heart to lungs, other takes blood from heart to rest of body
- 6) Heart has own blood supply- left and right coronary arteries
- Tissue fluid
- Fluid that surrounds cells
- Made of small molecules that leave blood plasma e.g oxygen, water, nutrients
- Doesn't contain red blood cells/big proteins- too large to be pushed out of capillary walls
- Cells take in oxygen/ nutrients from tissue fluid, release metabolic waste into it
- Pressure filtration
- 1) At start of capillary bed (nearest arteries) the hydrostatic pressure inside capillaries is greater than in the tissue fluid
- 2) Difference in hydrostatic pressure means overall outward pressure forces fluid out of capillaries into spaces around cells- forms tissue fluid
- 3) As fluid leaves, hydrostatic pressure reduces in capillaries, lower at venule end of capillary bed
- 4) Water potential at venule end lower than that in tissue fluid
- 5) Some water re enters capillaries from tissue fluid at venule end by osmosis
- Mass transport system
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