Give the location of ultrafiltration and reabsorption in nephron.Enumerate the factors favouring glomerular filtration.
these are the steps of urine formation.
Glomerular Filteration or ultrafiltration- It occurs in glomerulus. The total volume of blood is filtered through the kidney. The filtration forms an ultrafiltrate in the lumen's of the bowman's capsule which contain essentially all constituents of blood except for blood corpuscles and the plasma proteins. Nearly 15-25% of the water and solutes are removed from the plasma that flows through the glomerulus.
Tubular reabsorption- Re-absorption occurs through the epithelial cells of the various segments of the nephrons. The small molecules which are essential for the body must be returned to the interstitial fluid and blood plasma. This selective transport of the substances across the epithelium of the excretory tubule from the ultrafilterate to the interstitial fluid is called reabsorption. The proximal & distal convoluted tubules, Henle's loop and collecting duct contribute to reabsorption. Nearly all sugar, vitamins, organic nutrients and most of water is reabsorbed.
Tubular secretion- Secretion is a selective process involving both active and passive transport. As the filtrate travels through the nephron tubule, tubular cells secrete substances such as H+ , K+ and ammonia into the filtrate. The proximal & distal convoluted tubules are the main sites of tubular secretion and helps in maintenance of ionic and acid-base balance of body fluids.Factors that affect glomerular filtration or its rate are:
1. Change in glomerular filtration membrane permeability.
2. Change in blood flow in renal arteries.
3. Change in glomerular capillary hydrostatic pressure.
4. Change in filtration surface area
5. Change in systemic blood pressure etc