Anatomy and Physiology

Urinary SystemDr Ashwini Kalantri

The Urinary System

Paired kidneys

A ureter for each kidney

Urinary bladder

Urethra

Functions

Filter blood Toxins Metabolic wastes Excess water Excess ions

Nitrogenous wastes from blood Urea Uric acid Creatinine

Regulate the balance of water and electrolytes, acids and bases

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Uriniferous tubule

NephronRenal corpuscle (in cortex)

Glomerulus (tuft of capillaries)Glomerular (Bowman’s) capsule

Tubular sectionProximal convoluted tubuleLoop of HenleDistal convoluted tubule

Collecting duct

Uriniferous tubule

a. Filtration

b. Reabsorption

c. Secretion

Collecting Duct

The most important role is to conserve body fluids

When the body must conserve water, the posterior pituitary gland secretes ADH (antidiuretic hormone)

ADH increases the permeability of the collecting tubules and distal tubules to water so more is reabsorbed

This decreases the total volume of urine

Alcohol inhibits the release of ADH, so less water is reabsorbed producing copious amounts of dilute urine (can cause dehydration)

Ureters

Slender tubes about 25 cm (10”) long leaving each renal pelvis

One for each kidney carrying urine to the bladder

Run medially within posterior bladder wall before opening into interior

This oblique entry helps prevent backflow of urine

Bladder

Collapsible muscular sac

Stores and expels urine

Lies on pelvic floor posterior to pubic symphysis Males: anterior to

rectum Females: just anterior

to the vagina and uterus

Urethra

Smooth muscle with inner mucosa Changes from transitional through stages to

stratified squamous near end Drains urine out of the bladder and body

Male: about 20 cm (8”) long

Female: 3-4 cm (1.5”) long Short length is why females have more urinary

tract infections than males - ascending bacteria from stool contamination

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