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Gross Anatomy of Urinary system
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Urinary system
Functions of Urinary System
• Kidneys carry out four functions
– Filter nitrogenous wastes, toxins, ions, etc. from blood to be
excreted as urine.
– Regulate volume and chemical composition of blood (water,
salts, acids, bases).
– Produce regulatory enzymes.
• Renin – regulates BP/ kidney function
• Erythropoietin – stimulates RBC production from marrow.
– Metabolism of Vitamin D to active form.
Urinary System
• Two Kidneys
– Perform all functions except actual excretion.
• Two Ureters
– Convey urine from Kidneys to Urinary Bladder
• Urinary Bladder
– Holds Urine until excretion
• Urethra
– Conveys urine from bladder to outside of body
Renal Connective Tissue
• Renal fascia- anchors the kidneys to
nearby structures. It is dense
connective tissue
• Adipose capsule/Pararenal Fat
Mass of fat tissue that surrounds renal
capsule
Functions
– Keeps kidney in place
– Provide cushion effects
• Renal capsule- Layer of dense
connective tissue that surrounds
kidney and supports the soft internal
tissues.
Position of the Kidneys
• Kidneys are located on
either side of the
vertebral column:
– left kidney lies
superior to right
kidney
– superior surface
capped by adrenal
gland
Location and Position of the Kidneys
• The kidney is positioned between
the 12th thoracic and 3rd lumbar
vertebrae.
• It is retroperitoneal (lies on the
posterior abdominal wall,
posterior to the peritoneum).
• Right kidney is lower than left
kidney due to the shape of the
liver.
• Lateral surface of kidney is convex
while medial is concave.
External Anatomy of Kidney
• Average size – 12cm x 6cm x 3 cm
• Weights 150 grams or 5 oz
• Surrounded by three membranes (deep to superficial)
– Renal capsule – fibrous barrier for kidneys.
– Adipose capsule – fatty tissue designed for protection /
stability.
– Renal fascia – dense fibrous connective tissue that anchors
kidneys/ adrenals to surroundings.
External Anatomy of the Kidney
• Lateral surface- convex
• Medial surface is concave
– Renal Hilum
• Indentation where blood vessels, nerves
and ureters enter and exit the kidneys.
– Renal Sinus
• Internal cavity within kidney.
Internal Anatomy of the Kidney
• Cortex - Superficial region of kidney.
– It is light and granular
• Medulla - Deep central region of the
kidney.
– Deep layer
– It is darker
• Renal pyramids- Cone shaped
structure within the renal medulla.
• Base lies against cortex
• Apex is the papilla
• Renal column- Extensions of cortex
that separate renal pyramids
within the medulla.
Kidney Internal Anatomy
• Renal Pelvis
– Flat funnel-shaped expansion
of ureter
– Major Calices
• Large cup-shaped branches
of renal pelvis
– Minor Calices
• Cup-shaped divisions of
major calices
• Surround papilla of pyramid
Renal Lobe
• Consists of:
– One renal pyramid
– overlying area of
renal cortex
– adjacent tissues of
renal columns
Blood Flow – Arteries
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Renal arteries
Segmental arteries
Lobar arteries
Interlobar arteries
Arcuate arteries
Interlobular arteries
Afferent arterioles
Blood Flow – Veins
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From nephron
Interlobular veins
Arcuate veins
Interlobar veins
Renal vein
Ureters
• Continuation of renal pelvis
• Slender tubes that
transport urine from
kidneys to bladder
• Retroperitoneal/Runs
behind the peritoneum
Urinary Bladder and Urethra
•
•
A collapsible muscular sac
Stores and expels urine
Urinary Bladder
- Full bladder – spherical
•
Expands into the abdominal cavity
- Empty bladder – lies entirely within the pelvis
Prostate gland: Found in In males
- Lies directly inferior to the bladder
- Surrounds the urethra
Urinary Bladder
• Muscular sac that stores
and expels urine
• Location
– Pelvic floor
– Posterior to public
symphysis
– Anterior to
• Rectum in males
• Vagina & uterus in
females
Urinary Bladder and Urethra in Male and Female
• Trigone of the urinary bladder
has three openings;
- Two openings from the
ureters
-One opening to the urethra
Structure of the Urinary Bladder
Male:
Penis
Dual function
Female:
External urethral orifice
Structure of the Urethra
Urethra
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In females
– Length of 3–4 cm
In males – 20 cm in length – three named regions
– Prostatic urethra
• Passes through the prostate gland
– Membranous urethra
• Through the urogenital diaphragm
– Spongy (penile) urethra
• Passes through the length of the penis
Copyright © 2008 Pearson
Education, Inc., publishing as
Benjamin Cummings
Urethral Sphincter
• Internal urethral sphincter
– Involuntary smooth muscle
• External urethral sphincter
– Voluntarily inhibits urination
– Relaxes when one urinates
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