Urinary System 1

  1. Functions of the Urinary System
    • Excrete waste products from the body's fluids
    • Eliminate waste products from the body into the environment
    • Regulate the volume and pH of blood plasma
    • Regulate erythrocyte production
    • Regulates body's nutrient and electrolyte levels
    • Help the liver detoxify poisons
  2. Functions of the Kidneys
    • Filters blood plasma by returning useful chemicals to blood and eliminating waste
    • Regulates blood volume/pressure by eliminating or conserving water
    • Regulates osmolarity of blood by controlling amount of solutes eliminated
    • Secretes renin (hormone), which also controls blood pressure and electrolytes
    • Secretes erythropoietin to stimulate red blood cell production
    • Regulates CO2 concentration and pH of blood
    • Synthesize calcitriol to regulate calcium concentrations
    • Can synthesize glucose from amino acids in extreme starvation
  3. Waste
    Any substance that is useless to the body or present in excess of the body's needs
  4. Metabolic Waste
    Waste produced by the body
  5. Respiratory System Excretion
    Removes CO2 and other gases
  6. Integumentary System Excretion
    Removes water, inorganic salts, lactic acid, urea in sweat
  7. Digestive System Excretion
    Removes water, salts, CO2, lipids, bile pigments, cholesterol, food residue
  8. Urinary System Excretion
    Removes many metabolic wastes, toxins, drugs, hormones, salts, H+, water
  9. Nitrogenous Waste
    One of the vital roles of kidneys is to excrete nitrogenous waste
  10. Urea
    Formed from ammonia when proteins are broken down
  11. Creatinine
    Produced when creatine phosphate is broken down
  12. Uric Acid
    Produced when RNA is recycled
  13. Blood Urea Nitrogen (BUN)
    Measure of nitrogenous waste levels in blood
  14. Azotemia
    Elevated BUN
  15. Uremia
    Syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia from toxicity of nitrogenous waste
  16. Fibrous Capsule
    Layer of collagen covering outer surface of kidneys; provides protection from trauma and infection
  17. Perirenal Fat Capsule
    Thick layer of adipose tissue surrounding the fibrous capsule; cushions kidneys
  18. Renal Fascia
    Fibrous outer layer that anchors kidney to abdominal wall
  19. Structure of Kidney
    • Lateral surface receives renal nerves, blood vessels, and ureter (at hilum)
    • Renal Sinus: Area around hilum that contains blood and urine-collecting structures
  20. Renal Medulla
    • Renal Columns: extensions of cortex between the pyramids
    • Renal Pyramids: 6-10 per kidney
  21. Lobe of Kidney
    Pyramid plus overlying cortex
  22. Minor Calyx
    Cup at the papilla (point) of the pyramid that collects urine
  23. Major Calyx
    Convergence of several minor calyces
  24. Renal Pelvis
    Convergence of several major calyces
  25. Ureter
    Continuation of renal pelvis down to urinary bladder
  26. Blood Supply
    Kidneys receive 20-25% of cardiac output
  27. Nephrons
    • Afferent arterioles branch off of interlobular arteries, and each one supplies one nephron
    • Nephrons carry out all of the filtering/regulation functions of the kidney
    • 1.2 million in each kidney
  28. Microcirculation
    • Afferent arterioles become ball of capillaries (glomerulus)
    • Blood drained from glomerulus by efferent arterioles
    • Efferent arterioles lead to peritubular capillaries (cortex) or vasa recta (medulla)
  29. Renal Plexus
    Nerves wrapped around renal artery that go to blood vessels and tubules of nephron
  30. Sympathetic Innervation of Kidney
    • Reduces glomerular blood flow and rate of urine production
    • Stimulates kidneys to secrete renin, which stimulates water and salt reabsorption at nephron
  31. Parasympathetic Innervation of Kidney
    • From vagus nerve
    • Increases rate of urine production
  32. Nephron Structure
    • Renal Corpuscle: consists of glomerulus and glomerular (Bowman's) capsule; filters blood plasma
    • Renal Tubule: long coiled tube that converts filtrate into urine
  33. Renal Corpuscle
    • Perietal (outer) layer is epithelium
    • Visceral (inner) layer consists of podocytes that wrap around capillaries of glomerulus
    • Capsular space separates the two layers, site of glomerular filtrate collection
  34. Proximal Convoluted Tubule
    • Connected to corpuscle
    • Longest, most coiled region
    • Microvilli for absorption
  35. Loop of Henle or Nephron Loop
    • U-Shaped portion with descending and ascending limb
    • Thick segments: active transport of salts
    • Thin segments: permeable to water
  36. Distal Convoluted Tubule
    • The end of the nephron
    • Shorter and less coiled than PCT
  37. Collecting Duct
    • Receives fluid from several nephrons and takes it to medulla
    • Many converge at tip of medullary pyramid in papillary duct
  38. Cortical Nephrons
    • Most nephrons
    • Short loops, almost entirely within cortex
    • Peritubular capillaries around PCT and DCT
  39. Juxtamedullary Nephrons
    • Long nephron loops into medulla
    • Vasa recta around loop of Henle
  40. Urine Formation
    Glomerular Filtration, Tubular Reabsorption and Tubular Secretion, and Water Conservation
  41. Glomerular Filtrate
    • Fluid in capsular space
    • Blood plasma without protein
  42. Tubular Fluid
    • Fluid in renal tubule
    • Similar to glomerular filtrate, but some substances added/removed
  43. Urine
    • Fluid after it enters collecting duct
    • Tubular fluid with water content changes
  44. Glomerular Structure
    • Glomerular capillaries are fenestrated (filtration pores)
    • Substances leaving the blood in glomeruli must pass through filtration slits between podocyte "feet"
  45. Glomerular Filtration
    • Filtration pores allow everything but blood cells through
    • Basement membrane is negatively charged gel that repels anions and large molecules
    • Filtration slits also negatively charged to repel anions
  46. Filtered Molecules
    • All small molecules (<3 nm) can pass through: water, electrolytes, glucose, amino acids, fatty acids, nitrogenous wastes, vitamins
    • Some small substances prevented from crossing membrane because they are bound to protein: calcium, iron, thyroid hormone
    • Kidney infection, trauma, strenuous exercise can damage filtration membrane
    • Proteinuria: protein in urine
    • Hematuria: blood cells in the urine
  47. Glomerular Filtration Rate
    • GFR: the amount of filtrate formed per minute by the 2 kidneys combined
    • 105-125 ml/min (150-180 L/day)
    • Eliminating 1-2 L of urine per day, so 99% of filtrate is reabsorbed
    • If GFR is too high, fluid flows through renal tubules too quickly for proper reabsorption
    • Urine output rises, dehydration, electrolyte depletion
    • If GFR is too low, wastes are reabsorbed
    • GFR regulated by adjusting glomerular blood pressure
  48. Renal Autoregulation
    Nephrons control blood flow themselves (local control)
  49. Myogenic Mechanisms
    Smoot muscles in afferent arterioles passively stretch and contract to maintain stable flow of blood to glomerulus
  50. Tubuloglomerular Feedback
    • Glomerulus gets feedback about tubular fluid composition and adjusts filtration
    • Uses juxtaglomerular apparatus
  51. Juxtaglomerular Apparatus
    Structure at the end of the nephron loop that contacts afferent and efferent arterioles
  52. Macula Densa
    • Patch of epithelial cells at the end of the loop of Henle
    • Senses variations in flow of fluid composition and secretes chemical that stimulates juxtaglomerular cells
  53. Juxtaglomerular Cells
    • Smooth muscle cells in the arteriole across from macula densa
    • Dilate or constrict arterioles based on signal from macula densa
  54. Mesangial Cells
    • Between afferent and efferent arterioles and among capillaries
    • Propagate signal from macula densa to glomerulus
Card Set
Urinary System 1
Urinary System