Excretion and osmoregulation
in mammals
•
In mammals, both Excretion and osmoregulation are
carried out mainly by the urinary system.
The urinary system consist of the kidneys ,ureters, urinary
bladder, and urethra.
• The urine from the kidneys flows down the ureters to the
bladder where it is stores temporarily before being
expelled via the urethra
•
Structure of the kidney

The kidneys are two bean-shaped organs located on the back of the
abdomen

Kidneys has three main parts:
Cortex: outer part of the kidney
Medulla: inner most part of the kidneys
.
Renal pelvis :area of the center of the
kidneys where urine collects here.
Funnel-shaped
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The nephron

The nephron is the structural and functional unit of the kidney.

Once the renal artery enters the kidney, it divides and subdivides,
ultimately forming small vessels called Afferent arterioles.

Each afferent arterioles subdivides further to form a ball-shaped tuft
of capillaries called the Glomerulus.

The glomerulus capillaries then coalesce to form an efferent
arteriole.

This subdivides further to form a network of capillaries that surround
the renal tubule.

The latter capillaries coalesce once more to form a Venule which
takes deoxygenated blood to the renal vein.

Each glomerulus is partially enclosed by a cup-shaped structure called
The nephron con.

The renal capsule or Bowman's capsule leads to a coiled tube called the renal
tubule.

The glomerulus, Bowman's capsule and renal tubule form what is called nephron

Each kidneys contains about 1.5 million of nephron.

The first part of the renal tubule is a coiled tube called proximal convoluted
tubule ( pct. ) in the cortex

Continuous with the PCT is U-shaped tube called loop of Henle in the medulla

The loop of Henle leads into another coiled tube called distil convoluted tubule
{DCT } In the cortex

The DCT leads to the collecting duct which drains its content ( urine ) into pelvis
which then flows into the bladder via the ureter