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The Kidney




The role of the kidney is to remove waste products from the blood and produce urine.
Each kidney is supplied with blood from the renal artery and is drained from the renal
vein. Urine passes down the kidney through the ureter to be bladder were it is stored…

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Each nephron starts in the cortex. In the cortex, capillaries form a knot called the
Glomerulus. This is surrounded by the Bowman 's capsule. This leads on to the
proximal convoluted tubule, then the loop of henle. This carries on to the distal
convoluted tubule and then to the collecting…

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Basement membrane ­ is made of collagen fibres and gylcoprotiens which act
as a filter and stop larger molecules getting through, such as proteins, red
blood cells and glucose.

Endothillium ­ has narrow gaps between so that the plasma can get through.

Podocytes ­ have finger like projections called major…

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Glucose
Urea
Inorganic ions

That means that what is left is red blood cells and proteins.




Selective Reabsorption
As blood moves along the nephron substances are removed and reabsorbed back into
the blood. Most reabsorption (around 85%) occurs in the proximal convoluted tubule.
All glucose, amino acids, some salts and…

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3. As the Glucose and amino acid concentration rises within the cell it raises the
concentration this allows them to diffuse back into the tissue fluid, these then
diffuse back into the blood and are carried away.
4. Reabsorption of salts makes the surrounding cells water potential higher than
inside…

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Water Reabsorption
The role of the loop of henle is to create really low water potential in the tissue of the
medulla. This ensures that even more water can be reabsorbed from the fluid in the
collecting duct.

The loop of henle consists of a descending limb that descends into…

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How does this happen?

As the fluid in the tubule travels down the descending limb into the medulla the water
potential becomes lower, more negative. This is because of diffusion of sodium and
chloride ions from surrounding tissues and loss of water through osmosis.

Then as the tubule fluid travels…

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This arrangement is known as hairpin countercurrent multiplier. This is to increase the
efficiency of salt transfer from the ascending limb to the descending limb, this cause a
build-up of salt in surrounding tissue fluid. The removal of ions from the ascending
limb makes the urine very dilute and water…

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Osmoregulation
Osmoregulation is the control of water and salt levels in the body. Water is gained
from food, drink and metabolism but some is lost in urine, faeces and sweat.

The permeability of the walls of the collecting duct can be changed according to the
needs of the body, they…

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