Download The Urinary System

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The Urinary System
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Organs of the Urinary System
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Kidneys
Functions of the Kidneys
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Remove metabolic waste
products from the blood
Secrete hormone
erythropoietin, which
stimulates the bone marrow to
produce red blood cells
Secrete hormone renin which
helps regulate blood pressure
Characteristics
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Bean-shaped
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Retroperitoneal position
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Renal sinus – concave
depression
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Hilum – where the renal artery,
vein, and ureter enter
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Renal pelvis – area where
urine is drained from the
kidney
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Calyces – smaller tubes in
which the renal pelvis divides
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Kidneys Cont.
Layers of the Kidney
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Renal cortex – outermost layer
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Renal medulla – middle portion
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Renal pyramids – triangularshaped areas of the medulla
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Renal pyramids – portion of
cortex between the pyramids
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Blood enters the kidneys
through the renal artery and
exits through the renal vein
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Nephrons
Function and Parts
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Waste products are removed
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Each kidney has about 1M
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Renal Corpuscle
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Glomerulus
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Bowman’s capsule
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Blood filtration occurs
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Renal Tubule
 Proximal convoluted tubule
 Attached to Bowman’s
capsule
 Loop of Henle
 Straighter tubule that
curves back toward the
renal corpuscle
 Distal Convoluted tubule
 Several combine to form
collecting ducts
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Collecting ducts – deliver urine
to the renal pelvis, which
empties into the ureters
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afferent arteriole  glomerulus  efferent arteriole  peritubular capillaries  veins of the kidneys
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Glomerular Filtration
 Takes place in the renal corpuscles
(glomerulus)
 Blood that contains wastes is forced into the
glomerulus – glomerular filtrate
 Depends on filtration pressure which is
determined by blood pressure
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Tubular Reabsorption
 Second process
 Glomerular filtrate flows into the proximal
convoluted tubule
 Where nutrients, water and ions are
reabsorbed back into the bloodstream
 Water reabsorption depends on ADH and
aldosterone (hormones)
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Tubular Secretion
 Third process
 Where substances (drugs, hydrogen ions,
waste products) are excreted into the urine
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Urine Composition
 Water (mostly)
 Urea
 Uric Acid
 Trace amounts of amino acids
Urine Formation
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Ureters, Urinary Bladder, Urethra
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Ureters
 Two
 Carry urine from kidney to
bladder
 Peristalsis propels urine
toward the bladder
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Urinary Bladder
 Expandable organ that stores
urine
 Up to 600 mL on average
 Detrusor muscle – contracts to
push urine from the bladder
to the urethra
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Urethra
 Tube that carries urine from
bladder to the outside
 Shorter in females
Micturition
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Process of urination
Bladder distends with urine 
Stimulates stretch receptors in
the bladder  Parasympathetic
nerves stimulate the detrusor
muscle  Sense the need to
urinate  Brain sends impulses
to voluntarily contract the
urethral sphincter to inhibit the
need to urinate  Voluntary
decision to urinate relaxes
sphincter  Contraction of
detrusor muscle and urine is
expelled through the urethra