human physiology

  WATER REABSORPTION Amount of filtrate formed = 125 ml/minute or 180 lt/day Amount of filtrate reabsorbed = 124 ml / minute or 178.5 lt/day Amount of fluid excreted in urine = 1.5 lt /day Reabsorption at PCT (65% of filtered fluid)       Mechanism : Pumping of sodium out of tubular epithelial cells by Na + -K + ATPase pump                                           ↓                           Passive diffusion of Na + along with other solutes                              ...

  1.       FILTERING MEMBRANE COMPLEX -           Filtration membrane is otherwise called as filtration barrier or glomerulo-capillary membrane -           It is the membrane through which the fluid from the plasma of glomerular capillaries pass in to the Bowman’s Capsule. Components: 1.       Capillary endothelium:        – Fenestrated (contains pores of 70-90 nm diameter)        – Freely permeable to water, small solutes & small proteins 2.       Basal lamina:       – Union of glomerular capillary basement membrane & Bowman’s capsule             basement membrane       – Consists of glycoproteins & mucopolysaccharides   ...

                                                    Micturition Definition: The periodic complete voluntary emptying of the bladder is called micturition Events involved : -           Micturition is basically a spinal reflex -           Influenced by higher centers a)       Micturition reflex b)       Voluntary control of micturition c)       Role of other muscles in micturition a)       Micturition reflex:    Stimulus: Filling of bladder by 300 to 400 ml of urine    Receptors: Stretch receptors in the detrussor muscl...

  1.       SPECIAL FEATURES OF RENAL CIRCULATION a.       Renal Blood Flow (RBF): The normal blood flow to kidney is about 1200 ml. This forms about 25% of cardiac output. Kidney receives the maximum blood flow next to liver. b.       Portal circulation: An arteriole is interposed between two capillaries. Glomerulus (capillary tuft) – Efferent arteriole – Peritubular capillary c.        High pressure system: The pressure in the glomerular capillaries is 45 mmHg. This is much higher compared to the pressure in the systemic capillaries which is 30 mmHg. This high pressure is the main driving force for glomerular filtration d.       Vasa recta: Longest capillaries in the form of hairpins. It runs parallel to LOH of juxtamedullary nephron. It acts as countercurrent exchanger and maintains the osmotic gradient from the cortex towards the inner medu...