The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. The urine travels from the kidneys down the ureters into the urinary bladder, where it is stored until emptying through the urethra. The nephrons are the functional units of the kidney that filter the blood and regulate water and electrolyte balance to produce urine and maintain homeostasis. Common disorders of the urinary system include renal failure, cystitis, kidney stones, and urinary incontinence.
2. Organs of the Urinary System
Kidneys
Ureter
Urinary Bladder
Urethra
3. 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)
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9. 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)
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11. 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
21. 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