Regulatory Functions Of Kidney
The kidney performs regulatory functions by different processes,
viz , filteration ,reabsorption ,tubular secretions and current ex-
change.These processes are carried on at the level of each
nephron.
ULTRA FILTERATION
In the first stage non-selective, ultra filteration(filtration at molec-
ular level) of blood occurs while passing through the glomerulus
of the Malpighian body.Two factors are responsible for this ultra-
filtration.Both the capillary walls of glomerulus and the walls of
Bowman’s capsule are sieve-like in nature, which permit all the
molecules except plasma proteins and blood cells that pass
through them.Blood pressure in glomerulus is high because the
diameter of efferent arteriole is much less than that of afferent
arteriole.Thus a hydrostatic pressure is generated which forces
the smaller molecules of blood from glomerulus into the Bow-
man’s capsule.
REABSORPTION
Active reabsorption of the glomerular filtrate occurs in the proxi-
mal convoluted tubule, so a large amount of filtrate is reabsorbed
and returned to circulation.Here glucose, amino acids, water,
salts are reabsorbed. Reabsorption of water also occurs when the
filtrate from the proximal convoluted tubule passes down into the
descending limb of the loop of henle. It is permeable to water and
sodium but almost impermeable to any solutes.Unlike the de-
scending limb, the ascending limb is permeable water.Here reab-
sorption of sodium and chloride ions takes place through active
transport.Sodium and chloride ions move out of filtrate and enter
into the interstitial fluid where they are taken up by blood.The
fluid that leaves the ascending limb and collected by distal con-
voluted tubule concentration of various salts is adjusted under
the influence of hormones.The filtrate being almost urine now is
passed into the collecting duct where the concentration of water
in the filtrate is finally adjusted.
The kidney performs regulatory functions by different processes,
viz , filteration ,reabsorption ,tubular secretions and current ex-
change.These processes are carried on at the level of each
nephron.
ULTRA FILTERATION
In the first stage non-selective, ultra filteration(filtration at molec-
ular level) of blood occurs while passing through the glomerulus
of the Malpighian body.Two factors are responsible for this ultra-
filtration.Both the capillary walls of glomerulus and the walls of
Bowman’s capsule are sieve-like in nature, which permit all the
molecules except plasma proteins and blood cells that pass
through them.Blood pressure in glomerulus is high because the
diameter of efferent arteriole is much less than that of afferent
arteriole.Thus a hydrostatic pressure is generated which forces
the smaller molecules of blood from glomerulus into the Bow-
man’s capsule.
REABSORPTION
Active reabsorption of the glomerular filtrate occurs in the proxi-
mal convoluted tubule, so a large amount of filtrate is reabsorbed
and returned to circulation.Here glucose, amino acids, water,
salts are reabsorbed. Reabsorption of water also occurs when the
filtrate from the proximal convoluted tubule passes down into the
descending limb of the loop of henle. It is permeable to water and
sodium but almost impermeable to any solutes.Unlike the de-
scending limb, the ascending limb is permeable water.Here reab-
sorption of sodium and chloride ions takes place through active
transport.Sodium and chloride ions move out of filtrate and enter
into the interstitial fluid where they are taken up by blood.The
fluid that leaves the ascending limb and collected by distal con-
voluted tubule concentration of various salts is adjusted under
the influence of hormones.The filtrate being almost urine now is
passed into the collecting duct where the concentration of water
in the filtrate is finally adjusted.
