The URInary

System

Organs of the Urinary System

Kidneys

Ureter

Urinary Bladder

Urethra

Kidneys

Bean-shaped organ located between the 12th thoracic

and 3rd lumbar vertebrae in the flank area

Divided into the cortex (outer layer) and medulla

(middle portion)

Concave border has a notch called the hilum where the

renal artery, vein, nerves and lymphatic vessels enter.

The ureter starts at the hilum

Contains the nephrons (functional units of the kidney)

Nephron

Microscopic

1 million in each kidney

Divided into the renal corpuscle (glomerulus &

Bowman’s capsule) and tubule (proximal

convoluted tubule, descending loop of Henle,

ascending loop of Henle, distal convoluted

tubule, collecting duct)

Functions of the Nephron

Removes the wastes products (urea, nitrogen, uric acid & creatinine) of metabolism from the 1.5 million mL of blood that pass through each kidney every day

Maintain fluid balance by regulating the amount of fluid and electrolytes reabsorbed through the tubules into the blood and excreted into the tubules in the urine

Micturition/Production of 1,000-1,500 ml of clear, straw colored, and mildly aromatic urine daily with a gravity of 1.003-1.050 and a pH of 6

Concentrate the urine when the person is dehydrated and dilute the urine when the person is overhydrated

Ureters

Two muscular tubes that carry the urine from

each kidney to the bladder

Urinary Bladder

Muscular sac in the pelvic cavity that stores the

urine

Can hold up to 500 mL of urine when its wall

stretches

Urethra

Musculomembranous tube transporting the

urine from the bladder to the urinary meatus

Has an internal sphincter and an external

sphincter

Urine Formation

Glomerular Filtration : All the small molecules (glucose, amino acids & uric acid) except the blood cells and plasma protein in the blood pass through the pores of the capillaries (glomerulus) into the Bowman’s capsule to form the glomerular filtrate

Tubular Reabsorption : 99% of the water that passed through the pores are reabsorbed through the tubules into the capillaries surrounding the tubules. Useful substances like glucose and salt (NaCl) are also reabsorbed in the proximal convoluted tubule

Tubular Secretion : Medications and other substances

Common Disorders Associated with the Urinary System

Renal Failure : When the kidney ceases

functioning

Cystitis : Inflammation of the bladder. Causes

frequency and dysuria

Glomerulonephritis : Inflammation of the

glomeruli

Kidney Stones : Renal calculi caused by

deposits of mineral salts in the kidney

Polycystic Kidney Disease : Cluster of cysts

developing in the kidneys

Pyelonephritis : Infection of the kidney and

renal pelvis

Urinary Incontinence : Involuntary and

unpredictable flow of urine

The End