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Open Circulatory system:
Insects and some other small animal groups
Blood circulates in large open spaces
Single heart pumps blood out into cavities surrounding animal's organs
Substances diffuse between blood and cells
Closed circulatory system:
Blood is enclosed within tubes
Arteries arterioles capillaries venules - veins
Animals with a closed circulatory system have either single or double circulation. Single
circulation is found in for example fish:
The heart pumps deoxygenated blood to the gills
Here gaseous exchange takes place; there is diffusion of carbon dioxide from the
blood into the water that surrounds the gills, and diffusion of oxygen from this
water into the blood.
The blood leaves the gills then flows round the rest of the body before eventually
returning to the heart.
The blood flows through the heart once for each complete circuit of the body.
Birds and mammals have double circulation:
The right ventricle of the heart pumps deoxygenated blood to the lungs where it
The oxygenated blood then returns to the heart to be pumped a second time (by
the left ventricle) out to the rest of the body.
Veins: Wide lumen, thinner walls, less collagen, elastic fibres & smooth muscle, valves
Arteries: Narrow lumen, thicker walls, more collagen, elastic fibres & smooth muscle, no valves
Capillaries: endothelium (single layer of cells)
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1. endothelium becomes
2. Inflammatory response
a. White blood cells leave blood and move into artery wall
b. These cells accumulate chemicals from the blood e.g cholesterol
3. A deposit builds up called an atheroma
a. Calcium salts and fibrous tissue build up resulting in a plaque
4. Artery wall loses some elasticity
5. Artery becomes narrower rise in blood pressure other plaques more likely to form.
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Myocardial infarction: coronary artery becomes completely blocked by blood clot no supply of
Stroke: rapid loss of brain function, due to a disruption in blood supply to brain.…read more