Question

part a- what are the three physiological processes of urine in the kidneys? describe each process.

part b- explain the cellular structures involved in each process.

Answer 1

A)

The three Physiological process of urine in the kidney are :-

Glomerular filtration

• Blood pressure pushes water and solutes from the capillaries into Bowman's capsule through glomerular filtration membrane.
• All particles except blood cells and proteins are passed through the membrane.
• As filtration begins,the urine formation process.

Reabsorption

• The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids,
• Filtered molecules such as glucose, bicarbonate reabsorbed in proximal convoluted tubule.
• As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries.
• Urine concentration is done in loop of Henle.

Secretion

• As the nutrients are reabsorbed in renal tubule, hydrogen ions are passed from capillaries into the renal tubule is called reabsorption.
• The secreted ion combine with filtrate and form the urine.
• And then urine passed through collecting duct and to urinary bladder.

B)

• Glomerulus is  involved in glomerular filtration.It contain a filtration slits called podocytes through which particles are filtered into Bowman's space.
• the volume of liquid filtered per unit time in all glomeruli can be expressed as the glomerular filtration rate (GFR).
• GFR depend on renal blood flow, the filtration pressure, the plasma oncotic pressure, and the size of the filtration area.
• Most of the reabsorption occur in proximal convoluted tubule (PCT), which is lined by simple cuboidal epithelium.
• Almost 100 percent of glucose reabsorbed by secondary active transport with Na+  which occur in PCT.
• 65% of sodium, 50% of urea , almost all vitamins , lactate are reabsorped in PCT.
• Then filtrate pass into Loop of Henle, which contain a descending limb , which is permeable to water ,impermeable to solutes and ascending limb , which is permeable to solutes and impermeable to water.
• Concentration of urine occur here because of counter current pattern of loop of henle and vasa recta, which is capillary which passes near to loop of henle.
• Then urine pass into Distal convoluted tubule,having simple cuboidal cells that are shorter than those of the proximal convoluted tubule (PCT).
• Secretion of potassium ion and some drugs occur here.
• 5% of sodium is actively reabsorped in these area.
• Finally urine passes into collecting duct , where Anti diuretic hormone acts for water reabsorption.
• Conditional sodium reabsorption occur with the help of aldosterone.