P4: Explain the role of the kidney in the homeostatic control of water balance
P5: Explain dysfunction in relation to water balance and possible treatments
M3: Discuss dysfunction in relation to water balance and possible treatments
D2: Analyse the impact on the human body of dysfunctions in relation to water balance

For P4, I’m going to outline the physiological overview of the kidneys and then I am going to explain the renal system. Also I am going to explain the kidneys in more detail.
The physiological overview involves the kidneys processing blood by eliminating any excess mineral salts, urea and water as this provides homeostasis and it enables the body to work effectively. The nephron (which is part of the kidneys) for …show more content…

However, “water is reabsorbed from the loop of Henle, distal convoluted tubule and the collecting duct” as quoted by (Parson’s, R: p129). For this reason, water arrives in the blood via osmosis for the reason that the water potential of the filtrate is higher than the blood. The remaining filtrate is urine, which takes place along the ureter to the bladder and it is reabsorbed via diffusion.
Furthermore, the loop of Henle consists of two limbs known as the descending limb and the ascending limb. Also the tissue fluid enclosing the loop is hyperosmotic (increased osmotic pressure) because of the sodium ions. As well as this, both limbs help establish a mechanism known as the counter current multiplier mechanism. This therefore aids the reabsorption of water back into the blood.
Nevertheless, there are four key stages that enable this mechanism to work. The first stage involves sodium and chloride ions being actively expelled into the medulla, near the top of the ascending limb. Since this limb is impermeable to water, the water stays inside the tubule and this produces a low water potential in the medulla due to the high concentration of ions. The second stage consists of the water moving out of the descending limb into the medulla via osmosis, given that there is higher water potential in the descending limb than in the medulla. The consequence of this is that the filtrate is more concentrated because the ions cannot diffuse out; plus the descending