The Urinary System

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The Urinary System

• Functions
• Remove wastes from the blood.
• Form urine.
• Regulate metabolic functions.
• Control the rate of red blood cell production
• Regulate the pH, volume, and composition of body
  fluids.
• Regulate blood pressure.
• Activate Vitamin D.

• Kidney
• 12 cm X 6 cm X 3 cm
• Lie retroperitoneally
• Lateral surface is convex.
• Medial surface is concave.
• Hilumentrance to kidney for blood vessels,
  nerves, and lymphatic tissues.
• Renal sinushollow chamber.
• Renal pelvissuperior end of a ureterlocated in
  the sinus.

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The Kidney

• Renal pelvis branches to form 2-3 major calyces.
• These branch to form 8-14 minor calyces.
• These have projections called renal papillae.

• Renal Medullainner area. Contains renal
  pyramidsBases are pointed toward convex
  surfaceApexes form the renal papillae.
• Renal cortexouter area. Dips into the medulla
  to form the renal columns.
• Covered by the renal capsule.

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Blood Vessels

• Abdominal aorta
• Renal artery
• Interlobar arteries
• Arcuate arteries
• Interlobular arteries
• Afferent arterioles
• Glomerulus
• Efferent arterioles
• Peritubular capillaries
• Interlobular vein

• Arcuate vein
• Interlobar vein
• Renal vein
• 15 to 30 of the cardiac output is directed to
  the kidneys.
• The kidneys account for only 1 of body weight.

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Nephrons

• Functional filtering units of the kidneys.
• Over 1 million per kidney.
• Consist of
• A renal corpuscle
• Glomerulus
• Glomerular capsule
• Renal tubule
• Proximal convolute tubule
• Nephron loop or Loop of Henle
• Descending limb
• Ascending limb

• Distal convoluted tubule
• Collecting duct (in cortex)
• To Renal Medulla
• Minor calyx
• Major calyx
• Renal pelvis
• Ureter
• Urinary Bladder
• Urethra
• Out

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Juxtaglomerular Apparatus

• Located in the area at which the distal
  convoluted tubule passes between the afferent and
  efferent arterioles.
• Consists of the macula densa and the
  juxtaglomerular cells.
• Regulates the secretion of renin
• Renin helps to raise blood pressure and increase
  sodium ion uptake.

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Urine Formation

• Glomerular Filtration
• Substance move from glomerular capillaries into
  the renal tubules.
• Glomerular capillaries are very permeable.
• High hydrostatic pressure in the capillaries.
• Osmotic pressure of the water is higher than that
  of the filtrate.

• Glomerular filtrate may contain
• Water, glucose, amino acids, urea, uric acid,
  creatine, creatinine, and sodium, chlorine,
  potassium, calcium, bicarbonate, phosphate, and
  sulfate ions.
• GFRglomerular filtration rate.
• Effects of vasodilation and vasoconstriction of
  afferent and efferent arterioles.
• 180 Liters of glomerular filtrate are formed per
  day (over 45 gallons)

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Urine Formation

• Tubular Reabsorption
• Transport of substances from the renal tubule to
  the interstitial fluid into the peritubular
  capillaries.
• Much of this happens by diffusion and osmosis,
  while some happens due to active transport.
• Peritubular capillaries have low hydrostatic
  pressure and high osmotic pressure.
• Enhances reabsorption

• Most reabsorption occurs in the proximal
  convoluted tubule.
• Contains microvilli that form a brush border.
• Certain segments of the tubule reabsorb certain
  substances
• Glucoseproximal convoluted tubule by active
  transport
• Waterproximal convoluted tubule by osmosis.
• Role of carrier proteins
• Limited transport capacity
• Renal plasma threshold
• glucosuria

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Urine Formation

• Amino acidsproximal convoluted tubule by active
  transport.
• Proximal convoluted tubulecreatine, lactic,
  citric, uric, and ascorbic acids phosphate,
  sulfate, calcium, potassium, and sodium ions by
  active transport.

• Aldosterone affects sodium reabsorption rates
  which can also affect the reabsorption of water.
• Distal convoluted tubule is normally impermeable
  to water.
• ADH causes it to become more permeable, hence
  more water is reabsorbed.

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Urine Formation

• Tubular Secretion
• Substances move from the plasma of the
  peritubular capillary into the renal tubule.
• Active transport is responsible.
• Substances that are excreted include some
  organic compounds, penicillin, histamine,
  hydrogen ions, potassium ions.

• .6 to 2.5 liters of urine are produced per day.
• Urine may contain
• Ureaa by product of amino acid catabolism
• Uric Acida by product of nucleic acid catabolism
• 95 water
• Creatinine from the metabolism of creatine

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Elimination of Urine

• Ureter
• 25 cm long
• Joins the bladder
• Peristaltic waves move urine through the ureter
• Initiated by urine in the renal pelvis.

• Urinary Bladder
• Contains transitional epithelial cells,
  connective tissues, and smooth muscle tissues.
• Detrusor MuscleForms internal Urethral sphincter

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Elimination of Urine

• Urethra
• In women4 cm long
• External urethral orifice
• In men 19.5 cm long
• External urethral orifice
• Micturition
• Detrusor muscle contracts
• External urethral sphincter relaxesvoluntary.

• Distension of the bladder stimulates the urge to
  urinate.
• Bladder can hold up to 600 milliliters of urine.
  
• The urge to urinate appears when the bladder
  contains approximately 150 milliliters.

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Disorders of the Urinary System

• Glomerulonephritis
• Acutetriggered by a Strep infection
• Chronic
• Glomerular capillaries are blocked by antigen
  antibody complexes.
• Kidneys may fail
• Polycystic Kidney Disease
• Genetic
• Leads to abdominal pain, bloody urine, elevated
  blood pressure

• CystitisInflammation of the bladder. (more
  common in women)
• Ureteritis
• Urethritis
• Kidney StonesForm in renal pelvis. May move
  into a ureter.
• 60 pass spontaneously
• Extracorporeal shock wave lithotripsy

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Urinalysis

• Common Tests
• ammonia
• Bacteria
• pH
• Glucose
• Hemoglobin
• Specific gravity
• Urea
• Uric acid
• creatine

• Alkaptonuriaurine turns black when allowed to
  standgenetic
• Beeturiaurine turns pink after eating beets.
• Urinary excretion of the odoriferous component of
  asparagus
• Blue diaper syndromeDefect in transport of
  tryptophan.