Answer:
Structure of Nephron: Nephron
is the structural and functional unit of kidney.
(i) It consists of a long coiled tubule differentiated into
proximal tubule, loop of Henle and distal tubule. The latter opens into
the collecting tubule.
(ii) At the proximal end of the nephron lies a double-walled
cup-shaped structure called Bowman's capsule.
(iii) The Bowman's capsule contains a bundle of blood capillaries
which is called glomerulus.
(iv) In the glomerulus, the blood that comes in through
afferent arteriole is drained out through efferent arteriole.
Functions
of Nephron:
(i) Filtration: Filtration of blood takes place in
Bowman's capsule from the capillaries of glomerulus. This takes place under
high pressure. The filtrate passes into the tubular part of the nephron. This
filtrate contains glucose, amino acids, urea, uric acid, salts and major amount
of water.
(ii)
Reabsorption: As the filtrate flows along the tubule, useful substances such
as glucose, amino acids, salts and water are selectively reabsorbed into the
blood by capillaries surrounding the nephron tubule. The amount of water
reabsorbed depends on the need of the body and also on the amount of wastes to
be excreted.
(iii)
Tubular secretion: Certain substances which are harmful and not needed by
the body like ammonia, potassium, creatinine and hydrogen ions are secreted
from the capillary blood into the lumen of distal tubule. This is called
tubular secretion.
The
fluid entering the collecting tubule is called urine. It flows through the ureters
into urinary bladder, where it is stored and discharged from time to time
through urethra.
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