Excretory Products and Their Elimination
| 275
Malpighian tubules: In Insects. Help in the removal of nitrogenous
wastes and osmoregulation.
Antennal or green glands: In Crustaceans (prawn etc.)
Kidneys: In higher animals
HÜMÅÑ ËXÇRËTØRÝ SÝSTËM
It includes kidneys, a pair of ureters, urinary bladder & urethra.
STRÜÇTÜRË ØF KÏDÑËÝ
Reddish brown, bean shaped structures
situated between the levels of last
thoracic & 3rd lumbar vertebra.
Length:
10-12
cm,
Width:
5-7
cm,
Thickness: 2-3 cm. Average weight: 120-
170 gm.
It is enclosed in a tough, 3 layered fibrous
renal capsule.
On the concave side of kidney, there is
a notch (hilum or hilus) through which
blood vessels, nerves, lymphatic ducts
and ureter enter the kidney. (NEET 2013)
Hilum leads to funnel shaped cavity called renal pelvis with projections
called calyces.
A kidney has outer cortex & inner medulla.
Medulla has few conical masses called medullary
pyramids (renal pyramids) projecting into the
calyces.
Cortex extends in between the medullary pyramids
as renal columns (Columns of Bertini).
Each kidney has nearly one million tubular structure
nephrons
Nephrons are the structural & functional units of
kidney.
Each nephron has 2 parts: Glomerulus & Renal tubule.
Glomerulus: A tuft of capillaries formed by afferent arteriole (a fine branch
of renal artery). Blood from glomerulus is carried away by efferent arteriole
Dorsal aorta
Medullary
pyramid
Kidney
Cortex
Medulla
Calyx
Renal
columns
Ureter
Renal
capsule
Renal vein
Renal
artery