Urinary system

• Kidneys

  • bean-shaped organs, 11 cm long, 6 cm wide, 3 cm thick, weigh 150 grams
  • secretes urine
  • enclosed by renal fascia
• Renal fascia

  • sheath of fibrous connective tissue that encloses the kidney and renal fat
• Fibrous capsule

  • surrounds the kidney
• Cortex

  • reddish brown layer of tissue immediately below the capsule
• Medulla

  • innermost layer, pale conical-shaped striations
  • aka pyramids
• Hilum

  • concave medial border of kidney; renal blood, lymph vessels, ureter, and nerves enter here
• Urine formed within the kidney passes through a renal papilla at the apex of pyramid into a minor calyx
• Minor calyces

  • merge into major calyces
• Major calyces

  • 2 or 3
  • combine to form the renal pelvis
• Renal pelvis

  • funnel-shaped structure that narrows when it leaves the kidney as the ureter
• Nephrons

  • structural and functional units of the kidneys
  • responsible for forming urine
  • 1-2 million
• Renal corpuscle

  • responsible for the initial filtration of blood to form urine
  • composed of glomerulus and glomerular capsule
• Glomerulus

  • network of capillaries that performs the filtration of blood
• Glomerular capsule

  • aka bowman's capsule
  • cup-like structure that surrounds the glomerulus and collects the filtrate
• Filtrate

  • fluid extracted from the blood during initial filtration
• Urine formation:

  1. filtration
  2. reabsorption
  3. secretion
• Renal tubule

  • reabsorption of essential substances from the filtrate
  • secretion of waste products into the filtrate, leading to the formation of urine
• Proximal convoluted tubule

  • first segment of the renal tubule
  • highly convoluted, with brush border of microvilli
  • reabsorption mostly takes place
  • secretion of waste products and maintenance of pH
• Loop of henle

  • u-shaped structure with descending and ascending limbs extending to the renal medulla
  • establishes osmotic gradient for water reabsorption
  • aka medullary loop
• Distal convoluted tubule

  • located in the renal cortex, less convoluted than the PCT
  • fine-tuning of electrolyte and fluid balance
  • regulation by hormones (aldosterone &PTH)
  • secretion of K+ and H+ and reabsorption of Na+ and Ca+
• Collecting ducts

  • unite forming larger ducts that empty into minor calyces
  • site of secretion
  • final concentration of urine through water reabsorption regulated by ADH
  • regulation of acid-base balance and urea recycling
  • Na+ reabsorption and K+ secretion regulated by aldosterone
• Afferent arteriole

  • carries blood into the glomerulus that is to be filtered
• Efferent arteriole

  • carries blood away from the glomerulus after filtration has occurred
• Peritubular capillary

  • occurs when efferent arteriole divides
  • network which wraps around the remainder of the tubule
  • allows exchange between the fluid in the tubule and the bloodstream
• Functions of the kidney:

  • formation of Urine, maintaining water, electrolyte and acid-base balance
  • excretion of waste products
  • production and secretion of erythropoietin
  • production and secretion of renin
• Hormones that influence selective reabsorption:

  • parathyroid hormone
  • antidiuretic hormone
  • aldosterone
  • atrial natriuretic peptide
• Ureters

  • continuous with the funnel-shaped renal pelvis
  • carries urine from the kidney to the urinary bladder
  • consists of fibrous tissue, muscular layer, mucosa
• Urinary bladder

  • hollow muscular organ located in the pelvis
  • stores urine until it is ready to be expelled
  • capacity: more than 600mL
• Detrusor muscle

  • empties the bladder when it contracts
• Intravesical pressure

  • pressure inside the bladder
• Urethra

  • tube that connects the bladder to the external opening of the body
  • shorter in females; longer in males
  • allows urine to be excreted from the body
• Micturition

  • aka voiding
  • act of emptying the bladder
• Functions of the urinary system:

  1. filtration
  2. reabsorption
  3. excretion
  4. regulation of blood pressure and volume
  5. electrolyte balance
  6. acid-base balance
  7. erythropoiesis
• Acute renal failure

  • decrease in glomerular filtration rate (GFR) occurring over hours to weeks that is associated with an accumulation of waste products, including urea and creatinine
• Chronic kidney disease

  • progressive, irreversible deterioration of renal function, usually resulting from long-standing disease
  • sometimes derives from ARF that does not respond to treatment
• Treatment for edema

  • ACE inhibitors (captopril, enalapril, lisinopril)
  • osmotic diuretics (mannitol)
  • loop diuretics (furosemide)
• Treatment for hypertension

  • ACE inhibitors
  • calcium channel blockers (amlodipine, felodipine)
  • beta-adrenergic blockers (propranolol, atenolol)
• Treatment for hypocalcemia

  • vit D (calcitriol)
  • oral calcium salts (calcium carbonate)
• Treatment for anemia

  • epoetin alfa
  • darbopoetin
• Treatment for GI disturbances

  • antiemetics
  • docusate Na