Nephrons

• Nephrons are long tubules surrounded by capillaries, selectively reabsorbing substances
• Filtration:

  • Blood flows into the glomerulus, the smaller efferent diameter causes high hydrostatic pressure
  • Water and small molecules are forced out of the capillary into the renal capsule via basement membrane
• Podocytes provide support for the renal capsule
• Filtrate passes through the proximal convoluted tubule, selective reabsorption of glucose and other ions; same process as epithelial cells
• Loop of Henle maintains a Na+ gradient so water can be reabsorbed in the medulla; ions are lost, lowering the water potential of the surrounding area
• Aquaporins allow water to pass from the filtrate to the interstitial fluid
• Filtrate reaches the distal tubule, more water is reabsorbed into the blood via osmosis using ADH from posterior pituitary gland
• Collecting duct reabsorbs any remaining water needed before it is excreted in the urine