Question

In the accompanying diagram of urine formation, identify a, b, c and d.

• A. a- Pressure filtration, b- Re-absorption, c- Secretion, d- Collection of urine
• B. a- Pressure filtration, b- Secretion, c - Re-absorption, d- Collection of urine
• C. a- Collection of urine, b- Secretion, c- Re-absorption, d- Pressure filtration
• D. a- Re-absorption, b- Secretion, c- Pressure filtration, d- Collection of urine
  

Answer 1

Answer: (A)

a- Pressure filtration, b- Re-absorption, c- Secretion, d- Collection of urine

a) Pressure filtration - GLOMERULUS -The hydrostatic pressure in the glomerulus is the driving force that pushes filtered out of the capillaries and into slits in the nephron. Hence pressure filtration.

b) Re-absorption- PROXIMAL CONVOLUTED TUBULE(PCT) - it is lined with Cuboidal epithelium with brush border. It increases the surface area for reabsorption. Almost all essential nutrients and 70-80 % of electrolytes and water are reabsorbed by PCT.

c) Secretion-DISTAL CONVOLUTED TUBULE(DCT)- in distal convoluted tubule selective secretion of hydrogen and potassium ions and NH3 to maintain the pH and sodium-potassium balance in the blood.

d) Collection of urine -COLLECTING DUCT -Collecting ducts are straight tube present in kidney, many of which converge and open into the renal pelvis through medullary pyramids in the calyces. The DCTs(Distal convoluted tubules) of many nephrons open into collecting duct. Hence collecting duct is not a part of the nephron. Hence it collects formed urine from DCT.

So, the correct answer is 'a- Pressure filtration, b- Re-absorption, c- Secretion, d- Collection of urine'.