explain osmo-regulation and glomerular filtration

Asked by nehajb | 7th Sep, 2008, 11:31: AM

Expert Answer:

Glomerular filtration - It is the first step in urine formation, which is carried out by the glomerulus.

Malpighian tubule shows a cup shaped Bowman's capsule and a tuft of blood capillaries called glomerulus fitted into the cavity of the Bowman's capsule. These capillaries connect the 2 branches of renal artery, the afferent arteriole (that brings in blood) and an efferent arteriole (that drains blood away from the glomerulus). The diameter of afferent arteiole is greater than that of the efferent, hence blood flows under great pressure in the glomerulus.

Ultra- filtration occurs in the malpighian body. It is the filtration of blood under pressure. Here, blood is filtered so finely that almost all the constituents of the plasma, except the proteins pass onto the lumen of the Bowman's capsule, hence it is called ultra-filtration. The filtrate formed by ultra filtration is the primary urine.

Osmoregulation is the control of the levels of water and mineral salts in the blood. It is a homeostatic mechanism. 


Four processes are involved in the process of osmoregulation:

  • filtration - fluid portion of blood (plasma) is filtered from a nephron structure known as the glomerulus into Bowman's capsule or glomerular capsule (in the kidney's cortex) and flows down the proximal convoluted tubule to a  the Loop of Henle in the medulla portion of the kidney.
  • reabsorption - most of the viscous glomerular filtrate is returned to blood vessels which surround the convoluted tubules.
  • secretion - the remaining fluid becomes urine, which travels down collecting ducts to the medullary region of the kidney.
  • excretion - the urine is stored in the urinary bladder and exits via the urethra.

The figure of the process of urine formation has already been given. Kindly refer to the list of already answered questions.

Answered by  | 7th Sep, 2008, 01:26: PM

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