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Now let us know the structure of human excretory system and its fig-2: LS of
functions. Kidney of goat
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Free distribution by T.S. Government 2019-20 77
Kidneys
In Human beings there is a pair of bean shaped, reddish brown structures
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in the abdominal cavity attached to dorsal body wall (fig-3) one on either
side of the back bone they are kidneys. The right kidney is placed slightly
lower than the left kidney. Think why it is so?
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The size of the kidney is 10 cm in length, 5-6 cm in breadth, and 4 cm
in thickness. Each kidney is convex on the outer side and concave on the
inner side. The position of the right kidney is lower than the left kidney
due to the presence of liver above.
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Let us recall the last question in your lab activity. The inner side of
each kidney has a fissure or hilum for the entry of a renal artery
artery, exit of a
renal vein and an ureter.. Renal artery brings oxygenated blood loaded
with waste products and renal vein carries deoxygenated blood. The waste
products generated in various organs of the body are filtered and removed
by the kidneys.
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posterior vena cava dorsal aorta
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adrenal gland renal artery
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left kidney
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renal vein
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left ureter
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opening of ureter
bladder into bladder
urethra
fig-3: Location of kidneys
external opening
fig-4: Excretory system
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Internal structure of the kidney:
Let us observe L.S of the kidney to know more about internal structure.
It shows two distinct regions. Dark coloured outer zone called the cortex
and pale inner zone called medulla. Each kidney is made up of approximately
more than one million (1.3 to 1.8 million) microscopic and thin tubular
functional units called nephrons or uriniferous tubules.
78 X Class Excretion The wastage disposing system
Structure of nephron
Each nephron has basically two parts. 1) Malpighian body and 2) Renal
tubule.
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Malpighian body: It consists of a blind cup shaped broader end of nephron
called Bowman’s capsule and bunch of fine blood capillaries called
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glomerulus. The Bowman’s capsule and glomerulus together called
malpighian capsule or renal capsule. Glomerulus develops from afferent
arteriole. It gives rise to an efferent arteriole.
Think why the diameter of the efferent arteriole is less than that of
afferent arteriole?
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Because of the narrower out let (efferent arteriole) pressure exerts in
the glomerulus.It functions as a filtration unit. Bowmans capsule which