Transcript The Urinary System

The Urinary System
Structure & Function
Anatomy of the Urinary system
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2 - Kidneys
2 - Ureters
2 - Renal arteries
2 – Renal veins
1 - Urinary bladder
1 - Urethra
The Kidneys
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Two bean shaped
kidneys 4-6 ozs. each,
found in the
retroperitoneal cavity.
Filter wastes from blood,
and maintain water &
electrolyte balance.
Fist sized
Protected by adipose
tissue and fibrous
connective tissue
Structures of the kidney
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Renal Pelvis: a basin
like are in the central
part of kidney
Renal Cortex: outer
layer of kidney
containing nephrons
Nephrons are the
functional units of the
kidney.
Medulla: Inner layer
containing urine
collecting tubules
Nephrons
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Each nephrons forms
urine by the processes
of filtration, reabsorption
and secretion
Each contains a
glomerulus, which is a
cluster of capillaries,
surrounded by a
membrane called the
Bowman’s capsule
The Ureters
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Ureters- slender tube
carries urine from renal
pelvis/kidneys to
bladder.
15-18 in. long
Urine enters the tube
every 10-30 seconds in
spurts due to peristaltic
activity
Ureteral orifice at
bladder prevents reflux
The Bladder and Urethra
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Bladder- muscle sac that receives and stores
urine.
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Urethra- slender tube carries urine from
bladder outside body.
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Lined with ruggae
Stores 250 cc (about 1 pint) of urine
Female: 1-1.5 in.
Male: 8 in. long (in the male, the urethra conveys
both urine and semen, Neck of the urethra is
surrounded by the prostrate gland)
Urethral meatus – external opening of the
urethra
Main Function of the Urinary System
Remove urea (nitrogenous waste) from
the blood stream so that it does not
accumulate in the body and become
toxic
 Urea: formed in liver from ammonia
(from breakdown of simple proteins,
amino acids, in the body cells)
 Urea carried by the blood stream to the
kidneys for excretion.
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Other functions
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Maintain proper balance of water, salts and acids
 Example: Na and K which are electrolytes needed
for proper functioning of muscle cells.
 Kidneys can adjust what is excreted or held back
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Kidneys also act as an endocrine organ as they
secrete renin, which controls blood pressure
Help with calcium reabsorption in the intestines
Extract insulin and parathyroid hormone from the
blood stream
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How do kidneys produce urine?
Blood from the aorta branches into the
Rt. And Lt. Renal artery
 The arteries branch into arterioles
throughout the renal cortex
 Blood flow is slow and constant
 If the blood flow diminishes the kidneys
would produce renin, which stimulates
contraction of the arterioles, increased
BP and blood flow will be restored!
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Continued…
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In each cortex, blood passes through the glomerulus
and water, salt, sugar and urea are filtered out of the
bloodstream.
 This waste is collected in the Bowman’s Capsule and
transported to the renal tubule.
 In the renal tubule, reabsorption of needed substances
and secretion of waste products is completed.
 It is now urine, 95% water and 5% waste substances .
 The tubules lead to the renal pelvis, which narrows to
the ureter, then the bladder and excreted out of the
urethra!
 Sphincters hold urine until desire to urinate.
Urine
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95% water
5% waste, toxins and
salts
Clear, pale amber
1000cc – 2000cc
excreted every 24 hours
Urochrome is the
pigment that gives urine
its normal yellow color
Facts
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The acid found in urine gives off that typical urine
smell. In diabetics, urine may smell fruity due to the
presence of glucose.
Freshly made urine from the kidney is sterile but when
it leaves the body, it is exposed to bacteria present in
the surrounding skin.
A bacterial invasion leads to a breakdown of the salts
in the urine to give off a foul-smelling odor. If urine
smells offensive the minute urination starts then there
is already an infection in the urinary tract.