Question

Demonstrate BY DRAWING the Nephon  

1. Be sure to draw the following:
   1. Glomerulus
   2. PCT, Loop of Henle, DCT, Collecting Duct
2. Using arrows, demonstrate filtration, reabsorption, and secretion in your drawing
3. 3. Using arrows show, the active / passive transport of Na, Cl, water, Amino acids, glucose, K, NH₄, Urea, and HCO₃

_{ALSO PLEASE ***Please don't copy and paste a picture from the internet***}

Answer 1

Urine formation involves three main processes namely, glomerular filtration, reabsorption and secretion, that takes place in different parts of the nephron .

The first step in urine formation is the filtration of blood , which is carried out by the glomerulus and is called glomerular filtration. The glomerular capillary blood pressure  causes filtration of blood through 3 layers : the endothelium of glomerular blood vessels , the epithelium of Bowman's capsule and a basement membrane between these two layers . Blood is filtered so finely through these membranes , that almost all the constituents of the plasma except proteins pass onto the lumen of the Bowman's capsule . Therefore, it is considered as a process of Ultrafiltration.

A comparison of the volume of the filtrate formed per day(180 litres per day) with that of the urine released (1.5 litres) , suggest that nearby 99 percent of the filtrate has to be reabsorbed by the renal tubules . This process is called reabsorption. Proximal convoluted tubule(PCT) is lined by simple cuboidal brush border epithelium which increases the surface area for reabsorption. Nearly all the essential nutreints and 70-80 percent of electrolytes and water are reabsorbed by this segment . PCT also helps to maintain the _PH and ionic balance of the body fluids by selective secretion of hydrogen ions , ammonia, and potassium ions into the filtrate and by absorption of HCO₃^- from it.

Henle's Loop: Reabsorption in this segment is minimum. However this region plays a significant role in the maintenance of high osmolarity of medullary interstitial fluid. The descending limb of loop of henle is permeable to water but almost impermeable to electrolytes. This concentrates the filtrate as it moves down. The ascending limb is impermeable to water but allows transport of electrolytes actively or passively. Therefore, as the concentrated filtrate pass upward , it gets diluted due to the passage of electrolytes to the medullary fluid.

Distal convoluted tubule(DCT): Conditional reabsorption of Na⁺ and water takes place in this segment . DCT is also capable of reabsorption of HCO₃^- and selective secretion of hydrogen and potassium ions and NH₃ to maintain the P_H and sodium-potassium balance in blood.

Collecting duct: This long duct extends from the cortex of the kidney to the inner parts of the medulla. Large amounts of water could be reabsorbed from this region to produce a concentrated urine . This segment allows passage of small amounts of urea into the medullary interstitium to keep up the osmolarity . It also plays a role in the maintenance of P_H and ionic balance of blood by the selective secretion of H⁺ and K⁺ ions .