Transport in animals

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Transport in animals

mutlicellular organisms need transport systems because they have a low SA:V and a high metabolic rate and they mostly active therefore lotsof cells are respiring quickly and diffusion cant supply whats needed and remove waste.

Circulatory systems


blood only passes through the heart once for each circut E.G fish


blood passes through the heart twice fro each circut E.G mammals


blood is enclosed within vessels E.G vertebrates


blood flows freely through the body cavity E.G insects  

Types of blood vessels


carry blood from the heart. thick walls that are muscular and have elastic tissue to streach and recoil as heart beats, to maintain high pressure, the endolhelium is folded which allows the artery to expand. all carry oxygenated blood except pulmonary artery.


arteries branch into these, are smaller arteries, have a layer of smooth muscle but less elastic, muscle allows them to expand or contract controlling the maount of blood to tissues


arterioles branch into these, smallest vessel. substances are diffused between them and cells, walls are only one cell thick (endothelium) and lumen only fits one blood cell, slows down blood flow


capillaries connect to these, have very thin walls with some muscle cells they join to form veins


take blood back to heart under low pressure.wide lumen with very little elastic or muscle tissue. they have valves to prevent back flow. blood flow is helped by the contractions of muscles around them. all carry deoxygenated blood except pulmonary veins.

Tissue fluid

fluid that surrounds cells in tissues, made from substances from plasma. cells take in oxygen and nutrients from the tissue fluid and release waste into it. in a capillary bed substances move into tissue fluid by pressure flitration

pressure flitration-at start of capillary bed, by arteries. the hydrostatic pressure in capillaries is higher than in fluid. this forces fluid out of the capillaries forming tissue fluid. as fluid leaves the pressure reduces and so is lower at the end near to veins. as water leaves capillaries concentration of plasma proteins increases and water potential decreases . this forms oncotic pressure. so at venule end there is a high oncotic pressureand low water potential and so some water re enters.

Lymph vessels

not all the fluid re enters capillaries so the excess fluid is returned to the blood by the lymphatic system. smallest lymph vessels are lymph capillaries. excess fluid passes into lymph vessels (inside called lymph). valve stop lymph going back. lymph gradually moves to main lymph vessels in thorax then it is returned to blood. 

composition of blood, tissue fluid, lymph

RBC- in blood (too big for tissue fluid and lymph)

WBC-in blood and lymph (very few in tissue only enter if infected)

Platelets-in blood (only in tissue fluid if capillaries damaged)

Proteins- in blood (very few in tissue fluid and only antibodies in lymph) 

Water- in all 

Dissolved solutes- in all

The Heart



heart valves

atrioventricular valves (AV…


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