Urinary System

Functions Maintains normal concentrations of water and electrolytes in body fluids Regulates pH Regulates volume of body fluids Helps control RBC production Helps control blood pressure

Organs of the Urinary System Kidneys (paired bean shaped organs) Filter blood and form urine Ureters (paired tubes) Transport urine from kidneys Urinary bladder (single sac) Stores urine Urethra (single tube) Transports urine outside body

An introduction to the Urinary System

Internal Structure of the Kidney Renal cortex – forms shell around the medulla. Forms renal columns (between renal pyramids) Renal medulla Made of renal pyramids Renal pelvis Continuous with ureter Calyces (Major & minor) Extensions into the renal pyramids Function – collect urine

The Structure of the Kidney

Nephron Each kidney has about 1 million nephrons Made of a renal tubule & A renal corpuscle Corpuscle = glomerulus(capillaries) Glomerular capsule (surrounds glomerulus) Glomerulus filters plasma to form urine

A Representative Nephron

Urine Composition 95% water Urea (amino acids) Uric acid (nulceic acids) Trace amounts of amino acids electrolytes

Urine Elimination Nephrons Collecting ducts Calyces (minor then major) Renal pelvis Ureter Bladder Urethra

Ureters 3 layers thick Middle layer is smooth muscle Peristalsis propels urine

Bladder Hollow, distensible, muscular organ Stores urine Internal urethral sphincter (smooth muscle) Prevents bladder from emptying Distention of the bladder triggers micturition reflex Micturition = urination (expel urine from bladder) External urethral sphincter Skeletal muscle (conscious control)

Bladder Volumes 150 mL = urge to micturate begins (0.63 cup) 300 mL = urge intensifies (1.26 cups) 600 mL = stimulate pain receptors (2.54 cups) Produce between 0.6 – 2.5 liters/day (2.54 – 10.57 cups)

Urethra Tube from bladder to outside Female = 4 cm / anterior to vaginal opening Functions only in urination Male = from bladder to tip of penis Used for urinary and reproductive purposes

Urine Urine output of 50-60 milliliters per hour is normal The usual amount of urine voided at one time is about 150 ml

Kidney Failure Kidney failure can become life threatening as toxic wastes build up in the blood. If kidneys fail - there are only two options: hemodialysis - blood passes through dialysis machine which cleans it of toxins every two or three days (new dialysis techniques are being developed to clean blood more frequently) transplant - rejection can occur if immune system is not suppressed with cyclosporin (drugs used to suppress immune system)

Disorders/Diseases Anuria- absence of urine formation Cystitis - inflammation of the urinary bladder. Fistula – abnormal connection between the urethra and bladder. Hematuria - presence of blood, specifically red blood cells, in the urine. Polyuria - passage of large volumes of urine Nephrectomy – Removal of kidney Kidney stones – solid concentrations formed in the kidney’s from dissolved urinary materials.