BIOL 1303 Urinary System Notes

Urinary system:
 Organs
 Kidneys
 Ureters
 Bladder
 Urethra
 Functions
 Filtration of blood plasma
 Reabsorption of essential substances
 Secretion of nonessential substances
 All help to maintain body homeostasis and maintain fluid and electrolyte balance
Kidney external anatomy:
 Pair of reddish organs
 Shaped like kidney beans, size of bar soap in adults
 Found on each side of the vertebral column between peritoneum and back wall of
abdominal cavity at 12th thoracic and 1st - 3rd lumbar vertebrae
 11th and 12th pair of ribs protect superior portion of kidneys
 Right kidney is slightly lower than left, due to liver occupying more space on the right
 Encapsulated in renal capsule
 Smooth, transparent connective tissue sheath
 Maintains shape of kidney
 Protects against trauma
 Adipose capsule surrounds renal capsule
 Cushions kidney (more trauma protection)
 Together with thin layer of dense connective tissue, anchors kidney to posterior
abdominal wall

,Kidney functions:
 Regulation of blood volume
 Return water to blood
 Eliminate water in urine
 Regulation of blood pressure

,  Secrete renin enzyme
 Regulation of blood composition and blood pH
 Regulate blood ion levels
 Regulate blood pH by regulating hydrogen ion (H+) and bicarbonate ion (HCO3-)
concentrations in the blood
 Production of two hormones
 Calcitriol (active form of vitamin D)
 Regulates calcium homeostasis
 Erythropoietin
 Stimulates production of red blood cells
 Excretion of wastes
 Urine takes out metabolic wastes such as ammonia, urea, bilirubin, creatinine,
uric acid
 Urine takes out foreign substances such as drugs and environmental toxins
Kidney internal anatomy:
 Two main regions
 Renal cortex
 Receives majority of blood supply
 Renal medulla
 Contains tubules that collect and concentrate filtrate fluid to become
urine




Kidney internal anatomy:
 Renal pelvis
 Minor calyx