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

capsuleFunctions

– 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 • Renal arteries• Segmental arteries• Lobar arteries• Interlobar arteries• Arcuate arteries• Interlobular arteries • Afferent arterioles

Blood Flow – Veins• 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

Urinary Bladder• A collapsible muscular sac• Stores and expels urine

- 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 BladderMale:

PenisDual functionFemale: External urethral orifice

Structure of the Urethra

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Urethra• 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

Urethral Sphincter• Internal urethral sphincter

– Involuntary smooth muscle• External urethral sphincter

– Voluntarily inhibits urination– Relaxes when one urinates

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