Sem 2 Week 4 Describe how a nephron works. How is this similar to counter currents or hydrostatic skeletons?

Nephron is the basic function unit of a kidney.  Each kidney has about 1 million nephrons, all packed into an area of the kidney called the cortex.

The main function of the nephron is to regulate concentration of water and soluble substances like sodium salts by filtering blood, reabsorbing what is needed and excreting the rest as urine.  It eliminates wastes from the body, which in turn regulates blood volume and blood pressure, regulating blood pH.

The nephron carries out all of the kidney's functions.

Blood enters the kidney from the renal artery and moves into the glomerulus.  This is where filtration occurs.  The filtrate contains water and other toxic substances.  The glomerulus is enclosed by the Bowman's capsule so only water and small molecules can pass through this area.  The filtrate is then collected in the Bowman's capsule for transport through the nephron.

Fluid in the filtrate entering the proximal convoluted tubules is reabsorbed into capillaries.  In the proximal tubule, tubular reabsorption occurs.  Tubular reabsorption is when the cells in the proximal tubule remove water and nutrients from the filtrate and pass them back into the blood.  The filtrate flows from the proximal tubule into the loop of Henle.  The loop of Henle extends from the proximal tubule.  It receives filtrate from the proximal convoluted tubule and exit into the distal convoluted tubule.  The primary role of the loop of Henle is to concentrate the salt in the interstitium (tissue surrounding the loop).  The distal convoluted tubule excrete more sodium and secretes hydrogen and ammonium to regulate pH.  The process of tubular secretion occur in the distal tubule.  During tubular secretion, wastes that were not initially filtered out in the bowman's capsule are removed from the blood in the distal tubule.  Each distal convoluted tubule delivers its filtrate to a system of collecting ducts.  The collecting duct system prepares the urine for transport out of the body.  it is collected in the renal pelvis where it eventually enters the ureter and goes to the bladder.

The capillaries twisted around the nephron join back to the renal vein and become part of the ciculatory system.


http://images.wikia.com/analytical/images/f/fe/Nephron.jpg