Elucidate the formation of Urine.( Glomerular ultrafiltration, selective reabsorption..)


Ultrafiltration is the first step of urine production in which small molecules filter through Bowman's capsule to the filtrate from the blood.

While selective reabsorption is the second step of urine production in which important molecules reabsorb back to the blood capillaries from the ultrafiltrate.
The details of these two processes are as follows - 
Ultra Filtration- This occurs inside the glomerulus, blood pressure pushes fluid from capillaries into the glomerular capsule through a specialized layer of cells. This layer, the filtration membrane, allows water and small solutes to pass but blocks blood cells and large proteins. Those components remain in the bloodstream. The filtrate (the fluid that has passed through the membrane) flows from the glomerular capsule further into the nephron.
Selective Reabsorbtion-The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.

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