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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
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