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325
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2014-04-29 04:15:30
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  1. four layers of the tract
    • lumen
    • mucosa
    • submucoas
    • muscularis
    • serosa
  2. mucosa
    • epithelium: protection, secretion, absorption
    • lamina propria: areolar CT; blood and lymphatic vessels for nutrient absorption
    • muscularis mucosa: smooth muscle fibers, create small folds = inc SA
  3. submucosa
    • sits between two layers of muscle
    • CT: binds mucose to muscularis
    • highly vascular and contains the submucosal nerve plexus and serves the: muscularis mucosa and controlling secretion by the GI tract
  4. muscularis
    • 2 layers of smooth muscle: circular and longitudinal 
    • exception: stomach (3 layers of muscle)
    • myenteric plexus: nervous supply to muscle
  5. serosa
    • visceral layer of peritoneum
    • CT and epithelium
  6. peritoneum
    • visceral layer: lines organs
    • parietal layer: lines cavity wall
    • peritoneal cavity: space btwn layers
  7. retroperitoneal cavity
    • space behind peritoneum
    • organs which lie on the posterior walls are covered only on their anterior surfaces 
    • ex: pancreas, duodenum, kidney
  8. peritoneal folds
    • fused double layer of parietal peritoneum
    • a) mesentary: binds small intestine to abdominal wall
    • b) mesocolon: binds large intestine to posterior body wall
    • c) lesser omentum: lesser curvature of the stomach to the liver
    • d) greater omentum: greater curvature of the stomach, hangs over transverse colon, provides insulation
  9. fxn of teeth (and other processes in the mouth)
    • ingestion, mastication
    • propulsion, chemical digestion
  10. deciduous vs. permanent teeth
    • 8 months to 6 years
    • 6 years to 12 years
  11. periodontium
    • connects: alveolar socket & periosteum, cementum
    • via the: periodontal ligament
  12. function of tongue
    • ingestion, propulsion, mechanical digestion
    • positioning and mix food during chewing
    • formation of the bolus
    • initiation of swallowing, speech and taste
    • papilla- filliform, fungiform, vallate
  13. Salivary Glands
    • Parotid: Stenson's duct- serous
    • Sublingual: Wharton's duct- mixed, mostly mucous
    • Submandibular: joins Wharton's duct- mixed
    • Secondary: palate, tongue, cheeks, mucosa- mucous saliva
  14. serous vs mucous fluids
  15. fxn of salivary glands
    • keeps mucous membrane moist
    • lubricates food (mucin)
    • begins to digest starch (α­‐amylase)
  16. Buccal Phase
    • UES contracted
    • tongue presses against hard palate, forcing food bolus into oropharynx
    • involuntary phase begins
  17. Oropharynx
    • uvula and larynx rise to prevent food from entering respiratory passageways
    • tongue blocks off the mouth
    • UES relaxes allowing food to enter esophagus
  18. Food enters esophagus
    • constrictor muscles of pharynx contract
    • force food into esophagus inferiorly
    • UES contracts after entry
  19. Esophagus
    food moved through esophagus to the stomach by peristalsis
  20. Food enters stomach
    gastroesophageal sphincter opens
  21. Which parts of the digestive system require some voluntary control?
    • mouth, pharynx, upper esophagus and external anal sphincter
    • part skeletal muscle for voluntary swallowing (ingestion) and defecation (elimination)
  22. Esophagus
    • 10 inches/ 25 cm
    • UES- entrance of the esophagus
    • LES- entrane to stomach
    • purpose of sphincters? compartmentalization
  23. Where does the esophagus enter the abdominal cavity?
    • esophageal hiatus of diaphragm
    • esophagogastric junction (Z-line)
  24. stomach
    • J-shaped enlargement of the GI tract
    • 3 muscle layers: oblique, circular, longitudinal
  25. Parts of the stomach 
    • cardia
    • fundus
    • body
    • pyloric part
  26. The stomach is able to expand nearly 100 times its empty volume partly due to ______ in its walls.
    rugae
  27. in what ways does the stomach aid in digestion?
    • mechanical:
    • peristaltic mixing
    • churn food, break it into small particles and mix it with gastric gland secretions
    • "chyme"
    • chemical:
    • add chemicals to breakdown proteins
    • very little absorption
  28. neural control of GI tract
    • intrinsic control- enteric nervous system
    • myenteric plexus
    • submucosal plexus
    • extrinsic control- ANS
    • PNS: mainly stimulatory (ACh)
    • SNS: mainly inhibitory (NE)
  29. Enteric Nervous System (ENS)
    • - location? gut wall from esophagus to anus
    • - composition? cell bodies, axons, dendrites, nerve endings
    • - innervation? gut cells, sensory nerves, other neurons
    • - integration? can occur entirely within ENX or fxn independent of ANS
    • - transmitters? many excitatory and inhibitory
  30. Motor activity of the muscularis externa is directly controlled by the
    myenteric nerve plexus
  31. ENS - Myenteric Plexus
    • - location? esophagus to anus, btwn longitudinal and circular SM layers
    • - function? controls motility
  32. Stimulatory Influence of Myenteric Plexus
    • increase tonic contraction
    • increase contraction frequency/ intensity (increase propulsion)
  33. Inhibitory Influences of Myenteric Plexus
    decreased sphincter tone (relax)- pyloric sphincter, ileocecal valve, LES
  34. ENS - Submucosal Plexus
    • location? mucosal layer of esophagus to anus
    • function? local control: secretion, absorption, contraction of muscularis mucosa- creation of folds
  35. Sensory Afferent Neurons
    • stimulation of afferent neurons:
    • distension of gut wall
    • non specific irritation of gut mucosa
    • specific chemical stimuli
    • stimulation- can excite or inhibit:
    • intestinal movements
    • intestinal secretions
  36. Gastrointestinal Smooth Muscle
    • unitary smooth muscle
    • slow waves
    • spike potentials
    • muscle contractions
  37. Unitary Smooth Muscle
    • functions as syncytium:
    • large areas of SM contract as single unit
    • gap junctions:
    • low resistance pathways for ion movement
    • btwn bundles of cells and layers of SM
    • signal propagation- AP spreads from cell to cell
    • w/in and btwn muscle layers
  38. Slow Waves
    rhythmical changes in membrane potential caused by variations in sodium conductance
  39. Fixed Frequency of Slow Waves
    • interstitial cells of Cajal- pacemaker cells
    • dictates max frequency of SM contraction
    • independent of nervous/hormonal stimuli
  40. Variable amplitude of Slow Waves
    • affected by nervous/hormonal stimuli
    • inc amplitude - inc spike potential freq - inc strength of contraction
  41. Spike Potentials
    • true action potentials
    • occur when slow waves reach threshold (-40mV)
    • cause SM contraction
  42. Spike Potentials Ion Movement
    • voltage dependent calcium channels
    • ca++ entry leads to contraction
  43. Spike Potential Frequency
    • affected by nervous/hormonal stimuli
    • inc frequency: stronger contraction
  44. Peristalsis stimuli
    • distension- contraction with downstream receptive relaxation = "Law of the Gut"
    • irritation of gut epithelium
    • PNS
  45. Peristalsis Function
    • myenteric plexus required
    • atropine: dec peristalsis (blocks ACh receptors)
    • congenital absence of plexus - no peristalsis
  46. segments of small intestine proximal to distal
    duodenum, jejunum, ileum
  47. duodenum
    • first and shortest segment of SI (10 inches/ 25cm)
    • retroperitoneal cavity
    • receives chyme from stomach 
    • receives bile, pancreatic juice and enzymes through hepatopancreatic ampulla
  48. jejunum
    • 8 feet long
    • re-enters peritoneal cavity
    • upper left portion of small intestine
    • majority of digestion and absorption
  49. ileum
    • 12 ft long
    • lower right portion of small intestine
    • longest, last section of SI
    • digestion, absorption and propulsion
    • (diminished role in digestion and absorption
    • plicae and villi diminish
  50. ileocecal valve
    • point where ileum enters the cecum
    • function? prevent backflow of fecal contents from colon
  51. ileocecal sphincter
    • controls emptying of contents to cecum
    • gastroileal reflex (after meal) intensifies peristalsis, relaxes ileocecal valve
  52. cecum
    • expanded pouch at base of ascending colon
    • vermiform appendix attaches posteromedially
  53. Rectum
    • distal end of GI tract
    • internal anal sphincter- SM (involuntary)
    • external anal sphincter- skeletal (voluntary)
  54. Sphincters of GI tract
    • mouth
    • UES
    • LES
    • pyloric sphincter
    • ileocecal sphincter
    • internal anal sphincter
    • external anal sphincter
  55. Peristaltic Reflex
    stretch bowel, proximal contraction, distal relaxation
  56. Enterogastric Reflex
    from duodenum to regulate gastric emptying
  57. Gastroileal Reflex
    gastric distention relaxes ileocecal sphincter
  58. Intestino-intestinal Reflex
    over-distenion or injury of bowel segment causes entire bowel to relax
  59. Gastro and Duodenocolic Reflexes
    distension of stomach/duodenum initiates mass movement
  60. Defecation Reflex
    rectal distention initiates defecation
  61. Defecation
    • mass movements forces feces into rectum
    • distension initiates spinal defecation reflex
    • PNS signals: stimulate contraction of the sigmoid colon and rectum, relax the internal anal sphincter
    • conscious control allows relaxation of external anal sphincter
  62. Intrinsic Defecation Reflex
    • 1) distension due to mass movement stimulates stretch receptors
    • 2) spinal reflex: PNS motor (efferent) fibers contract rectal walls and relax internal anal sphincter
    • 3) if convenient, voluntary motor neurons are inhibited, allowing external anal sphincter to relax
  63. Secretory Glands
    • Single Cell Gland- mucous cells or goblet cells
    • Simple Gland- indentations in epithelium (crypts of Liberkuhn)
    • Tubular Gland- acid secreting oxyntic gland
    • Complex Gland- salivary, pancreas
  64. Control of Secretions
    • Local- tactile, distention, irritation
    • Reflex- nervous input
    • Hormonal- GI hormones
    • PNS stimulation- inc rate of secretion
    • SNS stimulation- inc or dec rate of secretion
  65. two types of glands
    gastric and pyloric
  66. Three types of Gastric Glands
    • mucous neck cells- mucus
    • peptic cells (chief cells)- pepsinogen
    • parietal cells- HCl & intrinsic factor
  67. Gastric Acid- HCl functions
    • bacteriostatic
    • converts pepsinogen to pepsin
    • begins protein digestion (with pepsin)
  68. Pepsinogen
    • inactive
    • acid converts to pepsin
    • pepsin converts more pepsinogen to pepsin:
    • proteolytic enzyme
    • optimal pH 1.8-3.5
    • reversibly inactivated > pH 5.0
    • irreversibly inactive > pH 7-8
  69. intrinsic factor
    • essential for absorption of vitamin B12
    • iliem: intrinsic factor/vitamin B12 complex absorbed
    • only indispensable substance in gastric juice
    • ileal disease, resection, atrophic gastritis
  70. lack of b12 can result in
    pernicious anemia
  71. Two types of Pyloric Glands
    • G-cells: release gastrin
    • mucus neck cells: mucous & small amounts of pepsinogen
  72. Small Intestine Overview
    • chemical digestion completed
    • SI and accessory organ secretion/enzymes used
    • nutrient absorption
    • majority of water absorbed
    • hormonal and neural controls of activity
    • 3-6 hours
  73. SI increase SA...
    • proximal part for nutrient absorption:
    • circular folds
    • villi
    • microvilli
  74. microvilli
    • projections (brush border) of absorptive cells
    • with brush border enzymes
  75. Chyme converted to what once in the large intestine?
    • chyme to semisolid stool of feces
    • due to water absorption
  76. Travel time for chyme from ileocecal valve to rectum?
    8-15 hours
  77. pancreas
    • head body and tail
    • retroperitoneal cavity: posterior and inferior to stomach
    • two ducts: accessory duct and pancreatic duct
  78. What does pancreas secrete?
    • pancreatic juice (pH8)- exocrine glands
    • hormones- insulin- endocrine
  79. Protease activation in duodenum
    • trypsiogen is activated to trypsin by brush border enzyme enteropeptidase
    • procarboxypeptidase and chymotrypsinogen are activated by trypsin
    • trypsinogen autocatalyically activated by trypsin
  80. gallbladder function
    stores and concentrates bile up to 15x until it is need in the small intestine
  81. Smooth muscle in wall of gallbladder contracts forcing bile into...
    cystic duct- bile duct- hepatopancreatic duct/ampulla- major duodenal papilla- duodenum
  82. Lobes of the liver
    • right lobe separated from left lobe by falciform ligament
    • quadrate lobe between gallbladder and left lobe
    • caudate lobe on the posterior aspect and next to vena cava
  83. major functions of liver
    • filtration and storage of blood
    • metabolism of fats, carbs, proteins
    • formation of bile
    • storage of vitamins and iron
    • formation of coagulation factors
  84. Vessels that bring blood to the liver?
    • hepatic artery: supplies oxygenated blood to the liver
    • portal vein: supplies nutrient rich blood to the liver (less oxygen than arterial blood, more than systemic venous blood)
  85. Liver circulation
    • 30% cardiac output flows through liver 
    • only 9mmHg difference in pressure
    • low resistance, low pressure, high flow
    • blood reservoir fxn
    • high lymph flow
    • macrophage system- Kupffer cells
    • cirrhosis inc resistance to blood flow
  86. hepatic circulation
    GI capillaries- GI veins- portal vein- hepatic capillaries- hepatic veins- inferior vena cava
  87. Kidney Anatomy- Layers of supportive tissue
    • 1) renal fascia- anchoring outer layer of dense fibrous CT
    • 2) perirenal fat capsule- fatty cushion
    • 3) fibrous capsule- prevents spread of infection to kidney
  88. Three layers of wall of ureter
    • 1) mucosa- line with transitional epithelium
    • 2) SM muscularis- contracts in response to stretch
    • 3) outer adventitia compose of fibrous CT
  89. Sphincters of Urethra
    • internal urethral sphincter: involuntary at bladder- urethra jxn
    • external urethral sphincter: voluntary muscle surround the urethra as it passes through pelvic floor
  90. male urethra lining epithelium
    • mostly pseudostratified columnar epithelium
    • transitional near bladder and prostate
    • stratified squamous near external urethral orifice
    • bc carries semen and urine
  91. Micturation Reflex
    • 1) stretch receptors fire
    • 2) PNS neurons fire, motor neurons stop firing
    • 3) SM contracts, internal sphincter passively pulled open, external sphincter relaxes
  92. Juxtaglomerular Apparatus
    where ascending limb joins the distal tubule
  93. nephron
    • fxnal unit of kidney
    • cannot regenerate
  94. female urethra
    transitional - stratified squamous

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