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transport in animals (circulatory systems (single closed - blood flows…
transport in animals
circulatory systems
single closed - blood flows through the heart and is pumped around the body before returning to the heart. blood passes through two sets of capillaries before returning to the heart, in the first it exchanges co2 and o2 and in the second it exchanges substances. as a result of passing through the vessels the blood pressure drops so it slows down
closed - blood is enclosed in vessels and does not come into contact with the cells, the heart pumps the blood around the body under pressure. substances leave the blood via diffusion before returning to the heart.
double closed - involves two separate circulations, blood is pumped from the heart to the lungs to pick up o2 and unload co2 before returning to the heart. blood flows through the heart and is pumped out to travel around the body before returning to the heart. each only passes through one capillary network so it maintains a relatively high pressure
open - very few vessels to contain the blood, it is pumped straight from the heart into the body cavity of the animal, called the haemocoel, it is under low pressure and comes into direct contact with the cells
transport of and co2 in the blood
5% dissolves in plasma
10% binds to Hb forming carbaminohameoglobin
85% is converted to carbonic acid using carbonic anhydrase, the carbonic acid then dissociates into hydrogen carbonate ions and hydrogen ions. The hydrogen ions bind to oxyhaemoglobin to produce oxygen and haemoglobonic acid and the hydrogen carbonate ions leave the cell in exchnage for chloride ions in the chloride shift
blood vessels
capillaries - link arterioles and venules, they have gaps between the endothelium cells for exchange of substances, they have a large surface area and are one cell thick to allow for diffusion
arteries & arterioles - arteries carry oxygenated blood away from the heart under high pressure, they contain elastic fibres which allow them to withstand the high pressure, smooth muscle, and collagen. arterioles connect arteries and capillaries, they have more smooth muscle and less elastin so they can constrict and dilate
veins & venules - carry deoxygenated blood away from the cells towards the heart under low pressure, they have valves to prevent back flow. the walls contain lots of collagen, a large lumen, a smooth lining of endothelium cells. veins run between active muscles so when the muscles contract the blood is pushed towards the heart
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tissue fluid - substances dissolved in plasma can pass through fenestrations in the capillary wall, at the arterial end the plasma proteins have an osmotic effect which creates a high oncotic pressure but there is a higher hydroststic pressure causesd by contraction of the heart so fluid moves out of the capillary. However, at the venous end of the capillary the hydrostatic pressure drops but the oncotic pressure remains the same so water moves back into the capliiary
lymph - tissue fluid that leaves the blood vessels, passes along lymph vessels where lymphocytes are passed from the lymph nodes into the fluid wcich eventually retunrs to the blood. Lympy nodes also intercept bacteria which are ingensted by phagocytes
blood - consists of yellow plasma, erythrocytes, platelets, and leucocytes. Its functions include transport of co2, o2, platelets for clotting, chemical messages, and antibodies
the heart
electrical activity
the atria-ventricular node picks up the signal and passes the wave onto the bundle of his which passes it onto the purkyne fibres in the walls of the ventricles causing them to contract from the bottom up
Sino-atrial node generates a wave of signal which spreads across the walls of the atria causing them to contract, a layer of non-conducting tissue prevents it from spreading to the ventricles
cardiac cycle
ventricular systole - both ventricles contract causing the volume to decrease and the pressure to rise, this pushes the atrioventricular valves shut and makes blood flow into the aorta to the body and into the pulmonary artery to the lungs through the semi-lunar valves
ventricular diastole - the atria and the ventricles relax causing blood to flow into the atria through the pulmonary vein from the lungs and through the vena cava from the body, the semi-lunar velves shut and blood flows passively from the atria into the ventricles through the atrioventricular valves
atrial systole - both atria contract causing a decrease in volume and an increase in preasure making blood flow from the atria into the ventricles through the atrioventricular valves