Question

Explain how kidney nephrons work to excrete nitrogenous wastes and yet retain water, be sure to label and discuss how the following are involved in this process: Bowman’s capsule (glomerulus), salts, loop of Henle, counter current exchange, and capillaries. Then, explain how compounds like alcohol and caffeine are involved in excess urine production.

Answer 1

Answer. Ultra filtration :- In this process filtration of blood is carried out by glomerulus.on an average 1200 - 1300 ml of blood filtered by kidney per minute.this process held due to high process.GHP,BCOP,CHP these process require for ultra filteration.(GHP - glomerular Hydrostatic pressure) ( BCOP - blood colloidal osmotic pressure) ( CHP - capsular hydrostatic pressure).NFP ( net filtration pressure )or NEFP ( net effective filtration presssure) is 10mm of hg (range = 10 - 25 mm of hg) at this pressure ultra filtration is continue.

Glomerular filtrate contains large amount of water,other dissolve substances like glucose,amini acid,vitamins,urea,uric acid ,creatinine,Na+,K+,Cl-,HCO3- etc

Thus, 10mm of hg NFP cause a normal amount of blood plasma to filter from glomerulus into bowman's capsule.

Reabsorption :- In this process reabsorption of selected materials takes place from filtrate into blood.

PCT (proximal convulated tubule) - max. Absorption in this part of nephron ( 70 - 80 %).all essential nutrients, nitrogenous waste like urea.

Loop of Henle - Descending part permeable for water and impermeable for electrolytes. Ascending part permeable for electrolyts and impermeable for water.

DCT ( distal convulatee tubule ) active reabsorption of Na+,Cl- and water.

Collecting duct - water,urea and Cl- reabsorb in this partbof nephron.

Tubular secretion :- it probably play a minor role in the function of human kedney but in lower vertebrates play important role.

Counter current mechanism or mechanism of conc. Of the filtrate :- this process for make urine concentrated ( hypertonic).

The loop of henle and vasa recta play important role to produce concentrated urine.

Juxta medullary type nephron takes part in this process.