Kidney question (1 Viewer)

[abdog]

Explain how the process of filtration and reabsorption in the nephron of a mammalian kidney regulates body fluid concentration. (4 marks)

 

[VivaLaVida21]

The nephron is the regulatory unit in the kidney. The main processes of urine formation including filtration, reabsorption and secretion occur within the nephron.
Filtration occurs in the glomerulus whereby substances areseparated due to size. High blood pressure in the glomerulus forces small molecules to be passed through into the Bowman's Capsule (i.e. Glucose, Amino Acids, Ions, Water, Salts, Urea, etc) leaving large molecules such as protein and red blood cells.
The composition of the glomerular filtrate varies as it flows throughout the nephron whereby the substances that are essential for the body are reabsorbed (such as glucose, amino acids and salts) so they are not lost through the urine. Henceforth, those substances that are not reabsorved are those not useful for the body and even toxic for some (e.g. urea and excess water and salts).

EXTRA : /Water is reabsorbed in the descending limb of the loop of Henle and the collecting duct and salts are reabsorbed in the proximal tubule, the distal tubule and the ascending limb as their reabsorption is regulated by the hormones ADH and aldosterone respectively./

Therefore filtration and reabsorption regulate body fluid composition by getting rid of waste products such as urea and excess salts and reabsorbing those that are useful and essential to the body's functioning through metabolism. eg. glucose into the bloodstream.

 

[Rhinoz8142]

Nephrons is basicially a regulatory unit, which abosrbs and secretes substance in order to maintain homeostasis. This is done by filtration and re absorption and secretion

Filtration is when the blood arrive into the nephrons which gets splits into the spherical network of blood vessels (glomerous) in the Bowman Capsule and creates glomerus filtrate. Blood and Protein stays with in the blood because there are too large, but water gets passed with the dissolved substance (salts,glucose and urea). Then the substance that the body need will require re absorption which occurs in the loop of henle. But the excessive stuff like water,salts get excerted with urea and becomes urine.

Reabsorption
This is when vary amounts of soultes are reabsorbed from the solution which occurs in the loop of henele.

Secretion
It forms urine in the distall and collecting tubule. The liquid present in the tuble which are added with metabolic waste which are brought by active transport to the distall tube..

 

[ipikip]

Explain how the process of filtration and reabsorption in the nephron of a mammalian kidney regulates body fluid concentration. (4 marks)

Easy. Time to show off.

Pressure in the glomerular capillaries generates an ultrafiltrate of blood plasma which passes into the proximal convoluted tubule. Only molecules that are positively charged and small are filtered (i.e., blood cells and larger serum proteins are excluded). As the filtrate moves along the tubules electrolytes and proteins are selectively reabsorbed into the blood or secreted from the blood into the tubule lumen. The bulk of the fluid is reabsorbed in the proximal tubular segments isotonically to plasma. Serum osmolality ('body fluid concentration') is detected by osmorecptors in the hypothalamus, which secrete ADH when osmolality rises. ADH increases the permeability of the distal convoluted tubule and cortical collecting duct to free water. Thus free water is reabsorbed in a negative feedback loop thereby restoring serum osmolality to its set-point (about 280 mOsm/L).

The free water is reabsorbed due to the highly concentrated renal medulla; this is simply a process of diffusion down water's concentration gradient from a less concentrated tubule lumen. The concentrated medulla is generated by the the counter-current multiplier mechanism that occurs at Henle's loop (as well as medullarly urea secretion elsewhere in the nephrons).

Complicated much?