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Explain the structure of Nephron.

The nephron is a long tube that runs from the cortex into the medulla and back again to the cortex before joining another tube called the collecting duct. The nephron starts as a small cup-like structure known as the Bowman’s capsule and leads into what is known as the first convoluted tubule (also known as the proximal convoluted tubule). It descends into the medulla as the loop of Henle then back into the cortex to become the distal convoluted tubule. These tubules drain into the collecting duct. Several convoluted tubules drain into each collecting duct, these collecting ducts empty into the renal pelvis. From the renal pelvis the excretory product, urine, drains into the ureter. The ureter from each kidney empties into the bladder, and urine leaves the body via the urethra.
There is a branch of the renal artery, the afferent arteriole, entering the small cup-like space of the Bowman’s capsule as a network of blood capillaries. This network is known as the glomerulus. Emerging from this network,the capillaries re-unite to form a small arteriole, known as the efferent arteriole. As the efferent arteriole continues it twines around the proximal and distal convoluted tubule. The efferent arteriole divides into capillaries at several points along the length of the tubules, absorbing various substances. These capillaries eventually reunite to drain into the renal vein. The efferent arteriole is smaller than the afferent arteriole. This difference in diameter helps to raise the glomerular pressure and aids in ultra filtration.
Broadly the nephron has two main parts – the glomerulus and tubule.
The glomerulus is the first part of the nephron where fluid is filtered from the blood. It has two parts, namely the network of capillaries that transport the blood to the site (glomerular capillaries) and the enlarged head of the nephron which collects the filtered fluid (Bowman’s capsule). This part of the nephron lies in the renal cortex. It is lined by thin epithelial cells which allow for fluid and other substances in the blood to easily pass into the nephron.
The glomerular capillaries have a thin endothelial wall which is closely associated with the visceral epithelium separated by a basement membrane. This is in contact with the parietal epithelium of the Bowman’s capsule. This arrangement allows the capillaries and Bowman’s capsule to be in close contact with only minimal cell layers in the path of the fluid leaving the capillaries and entering the capsule.
Different parts of the nephron are responsible for its various functions. Fluid filtered from the blood enters the Bowman’s capsule then flows into the proximal tubule, down the descending limb of the loop of Henle, then up the ascending lip, into the distal tubule and then the connecting and finally the collecting tubule.
There are three stages to urine formation:
    Glomerular filtration
    Tubular reabsorption
    Tubular secretion
Function of the Nephrons:
    Remove excess water,wastes and other substances from your blood.
    Return substances like sodium, potassium or phosphorus whenever any of these substances run low in your body.Each nephron is composed of two main structures: the glomerulus and renal (kidney) tubule.


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