Urinary System 2

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Urinary System 2
2011-03-24 10:36:03
Urinary System

Urinary System
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  1. Autoregulation Feedback
    High GFR, Rapid flow of filtrate in renal tubules, Sensed by macula densa, Paracrine Secretion, Constriction of afferent arteriole, Reduced GFR
  2. Glomerular Blood Pressure: Sympathetic Regulation
    • Sympathetic nervous system and adrenal epinephrine constrict afferent arterioles during exercise and when blood pressure drops.
    • Reduces GFR and urine output
    • Redirects blood to heart, brain, skeletal muscles
    • In extreme athlete, it can lead to hypoxia in the kidneys, and proteinuria and hematuria
  3. Glomerular Blood Pressure: Endocrine Regulation
    • Renin secreted by juxtaglomerular cells when blood pressure drops (systemic or local), renal artery blockage occurs, or the sympathetic nervous system is activated
    • Renin converts angiotensinogen to angiotensin 1
    • Lungs and kidneys convert angiotensin I to angiotensin II (with angiotensin-converting enzyme)
    • Angiotensin affects constriction
  4. Angiotensin II
    • Promotes vasoconstriction throughout the body
    • Except: lowers blood pressure in peritubular capillaries to enhance reabsorption of NaCl and water
    • Stimulates aldosterone and ADH secretion
  5. Tubular Reabsorption in the PCT
    • Proximal convoluted tubule reabsorbs about 65% of glomerular filtrate
    • Reabsorbs almost all glucose, amino acids, electrolytes through special channels and ion pumps
    • Water is reabsorbed through aquaporins
    • As water leaves, it pulls urea and electrolytes with it
    • 40-60% of urea reabsorbed, creatinine remains in filtrate
    • Most reabsorbed water and solutes diffuse into peritubular capillaries
  6. Glycosuria
    • A limited number of solutes can be reabsorbed in tubules
    • Limited number of transport proteins
    • Blood glucose over 220 mg/dl exceeds maximum transport, so glucose appears in urine
  7. Tubular Secretion in the PCT
    • Renal tube extracts chemicals from capillary blood and secretes them into tubular fluid
    • Necessary because filtration doesn't remove everything from blood (and reabsorption adds some things back to blood)
  8. Waste Removal
    • Urea, uric acid, bile acids, ammonia, catecholamines, prostaglandins, some creatinine
    • Clears pollutants, morphine, penicillin, aspirin, other drugs
  9. Acid Base Balance
    Secretion of H+ and bicarbonate regulates pH of body fluids
  10. Reabsorption in the Loop of Henle
    • Loop of Henle generates salt gradient that helps collecting duct concentrate urine and conserve water
    • Thick segment reabsorbs about 25% of the sodium, potassium, and chloride that we in glomerular filtrate
    • Impermeable to water
    • Thin segment reabsorbs about 15% of water that was in glomerular filtrate
  11. Reabsorption in the DCT and Collecting Duct
    • Fluid arriving in distal convoluting tubule still contains 20% of water and 7% of salts from filtrate
    • Amounts of water/salt reabsorbed regulated by hormones
    • Aldosterone, ADH, parathyroid hormone, atrial natriuretic peptide
  12. Effects of Aldosterone On the DCT/CD
    • Aldosterone secreted when blood Na+ concentration falls or blood pressure drops
    • Stimulates reabsorption of NaCl and water
    • Reduces urine volume
  13. Effects of ADH on the DCT/CD
    • ADH secretion during dehydration
    • Stimualtes reabsorption of water
    • Reduces urine volume
  14. Effects of Parathyroid Hormone on the DCT
    • Parathyroid hormone secreted when blood calcium levels are low
    • Acts on thick segment and DCT to increase calcium reabsorption
  15. Effects of Atrial Natriuretic Peptide (ANP) on the DCT
    • Secreted by atrial myocardium when blood pressure is high
    • Dilates afferent arteriole and constricts efferent arteriole to increase GFR
    • Inhibits renin, aldosterone, and ADH secretion
    • Inhibits NaCl reabsorption
  16. Reabsorption and Secretion Review
    • PCT reabsorbs 65% of filtrate and returns it to peritubular capillaries
    • Nephron loop reabsorbs 25% of filtrate
    • DCT reabsorbs NaCl and water
    • Tubule extract (secrete) drugs, wastes from peritubular capillaries into tubular fluid
    • Collecting duct conserves water
  17. Water Conservation
    • Collecting duct (CD) reabsorbs water and concentrates urine up to 4 times
    • Medullary part of CD is more permeable to water than NaCl
    • Medulla fluid is very salty, so water leaves
  18. Countercurrent Multiplier of Loop of Henle
    • Pumping ions out of the thick segment of the loop increases osmolarity of medulla
    • Increased osmolarity of medulla causes lots of water conservation
  19. Countercurrent Exchange
    • Need blood supply to medulla, but don't want blood to carry away salt
    • Vasa recta exchanges salt and water to maintain osmolarity of medulla
  20. Hypotonic Urine
    • Urine has a low concentration of solutes
    • Typically from water diuresis (drinking lots of water)
  21. Hypertonic Urine
    • Urine has high concentration of solutes
    • Dehydration
    • High blood osmolarity causes ADH release, more water is reabsorbed, urine more concentrated
  22. Urinalysis
    • Provides a very good "snapshot" of the physiological state of the body
    • Examination of physical and chemical properties of urine
    • Appearance: clear to deep amber; yellow color due to breakdown of hemoglobin. Cloudiness, pus or blood suggests some kind of infection or trauma
    • Odor: due to breakdown of urea. Abnormal odor can indicate diabetes mellitus, UTI, or other condition
    • Specific gravity: reflects solute concentration
    • Osmolarity: reflects hydration state of body
    • pH: reflects pH regulation in tissues
    • Chemical composition: 95% water, 5% solutes
  23. Urine Volume
    Typically average adult produces 1-2 L/day
  24. Polyuria
    • Excess of 2 L/day
    • Symptom of diabetes
  25. Oliguria
    • Less than 500 ml/day
    • Can result from kidney disease, dehydration, prostate enlargement
  26. Anuria
    • 0-100 ml/day
    • Body can't get rid of waste
  27. Renal Insufficiency and Hemodialysis
    • Kidneys can't maintain homeostasis because of nephron destruction
    • When >75% of nephrons are lost
    • Hemodialysis: procedure for clearing wastes from blood
  28. Diabetes
    Any metabolic disorder resulting in chronic polyuria
  29. Diabetes Mellitus
    • Type 1, type 2, and gestational
    • High concentration of glucose in blood; opposes the reabsorption of water; glycosuria
  30. Diabetes Insipidus
    ADH hyposecretion, so not enough water is reabsorbed in collecting duct; risk of dehydration
  31. Diuretics
    • Any chemical that increases urine volume
    • Some increase GFR
    • Caffein dilates afferent arteriole
    • Some reduce tubular reabsorption of water
    • Alcohol inhibits ADH secretion
    • Commonly used to treat hypertension
  32. Ureters
    • Muscular tubes about 25 cm long
    • Enter on posterior surface of bladder
    • Valve prevents urine from going back into ureter when bladder contracts
  33. Adventitia
    Connective tissue connecting ureter to surround tissue
  34. Muscularis
    Smooth muscle that contracts in peristaltic waves
  35. Mucosa
    Transitional epithelium that can contract and expand
  36. Urinary Bladder
    Muscular sac on the floor of pelvic cavity, posterior to pubic symphysis
  37. Detrusor Muscle
    Three layers of smooth muscle
  38. Rugae
    Wrinkles in the mucosa of a relaxed bladder
  39. Trigone
    Triangle formed by urethra and ureters
  40. Urinary Tract Infection (UTI)
    • Cystitis: infection of urinary bladder
    • Especially common in females due to short urethra
    • Frequently triggered by sexual intercourse
    • Can spread up ureter
    • Pyelitis: infection of renal pelvis
    • Pyelonephritis: infection that reaches nephrons
  41. Renal Calculus
    • Kidney stones
    • Hard granule of calcium phosphate, calcium oxalate, uric acid, or struvite
    • Form in renal pelvis
    • Large stones can block renal pelvis or ureter, which causes pressure buildup in kidney and destroys nephrons
    • Causes: hypercalcemia, dehydration, pH imbalances, frequent UTIs, enlarged prostate
  42. Female Urethra
    • 3-4 cm long
    • Bound to anterior wall of vagina
    • External urethral orifice between vaginal orifice and clitoris
    • Internal urethral sphincter: detrusor muscle thickening that is involuntarily controlled
    • External urethral sphincter: where urethra passes through pelvis floor, under voluntary control
  43. Male Urethra
    • Approximately 18 cm long
    • Prostate urethra passes through prostate
    • Membranous urethra passes through floor of pelvic cavity
    • Spongy (penile) urethra passes through penis
    • Same two sphincters as female
  44. Voiding Urine
    • As bladder fills, detrusor muscles relax, urethral sphincters closed
    • Urination occurs when bladder contracts and both sphincters open
    • Micturition: act of urinating
    • Micturition Reflex: spinal reflex that partly controls urination