Digestive System 1

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Digestive System 1
2011-03-29 16:18:39
Digestive System

Digestive System
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  1. Functions of the Digestive System
    • Break down nutrients into a form that the body can use
    • Absorb nutrients into bloodstream
    • Eliminate parts of food that can't be digested
  2. Ingestion
    Materials enter digestive tract
  3. Digestion
    • Mechanical: Materials are crushed, sheared, and churned to allow them to fit through digestive tract and to increase surface area
    • Chemical Break down food
  4. Absorption
    Nutrients, vitamins, electrolytes move into the interstitial fluid of the digestive tract, then into the blood
  5. Compaction
    Water and indigestible residue consolidated into feces
  6. Defecation
    Feces is eliminated
  7. Digestive System Anatomy
    • Digestive tract (alimentary canal): mouth, pharynx, esophagus, stomach, small intestine, large intestine and GI tract includes stomach and intestines
    • Accessory Organs: include teeth, tongue, salivary glands, live, gallbladder, pancreas
  8. Mucosa
    Lines the lumen and consists of inner epithelium, lamina propia (loose connective tissue), and Muscularis mucosa (thin layer of smooth muscle)
  9. Submucosa
    • Thicker layer of loose connective tissue
    • Contains blood vessels, lymphatic vessels, nerves, and mucous glands
  10. Muscularis Externa
    • Two layers of muscle
    • Inner circular layer: sometimes thickens to form valves
    • Outer longitudinal layer: responsible for moving food through tract
  11. Serosa
    Thin layer of tissue between end of esophagus and beginning of rectum
  12. Adventitia
    Fibrous connective tissue in pharynx, esophagus, and rectum
  13. Peritoneal Cavity
    • Fluid-filled sac
    • Visceral peritoneum: serosa layer of GI tract
    • Parietal peritoneum: lines inner surface of the body cavity
    • Membrane secrete fluid for lubrication
    • Intraperitoneal organs are enclosed by mesentery (stomach, liver, parts of small intestine and colon)
    • Retroperitoneal organs lie against posterior body wall and are only covered by mesentery on anterior side (duodenum, pancreas, parts of colon)
  14. Mesenteries
    • Connective tissue sheets that suspend the stomach and intestines from the parietal peritoneum
    • Allows freedom of movement while still holding abdominal viscera in proper place
    • Prevents tangling (twisting) of intestines
    • Holds blood vessels and nerves in contact with GI tract
  15. Lesser Omentum
    • Mesentery that extends from the liver to the stomach
    • Stabilizes the stomach
    • Provides route for blood vessels entering and leaving the liver
  16. Greater Omentum
    • Pouch of adipose tissue that hangs from the stomach and over the small intestine
    • Provides protection and insulation
  17. Mesentery Proper
    Provides support for the small intestine
  18. Mesocolon
    • Mesentery fused to posterior body wall
    • Provides support for the colon
  19. Enteric Nervous System
    • Nervous system network in the esophagus, stomach, and intestines
    • Regulates tract motility, secretion, and blood flow
    • Can function independently of the CNS, but influenced by it
  20. Submucosal Plexus
    • In submucosa
    • Controls secretion from glands in mucosa
    • Controls movement of muscularis mucosa
  21. Myenteric Plexus
    • Parasympathetic fibers between layers of muscularis externa
    • Controls contractions of these muscles
  22. Sensory Neurons
    Monitor tension in gut wall
  23. Short (myenteric) Reflexes
    Stretch or chemical stimulation activates contractions in nearby muscularis externa
  24. Long (vasovagal) Reflexes
    Parasympathetic activation regulates digestive motility and secretion
  25. Hormonal Control
    Gastrin and secretin regulate digestion
  26. Paracrine Control
    Chemical messengers produced by digestive tract diffuse to nearby target cells
  27. Oral Cavity Functions
    • Senses taste of food
    • Mechanically processes food
    • Lubricates food with saliva
    • Begins chemical digestion of carbohydrates and lipids
  28. Cheeks and Lips
    • Hold food in mouth and push it between teeth
    • Essential for sucking and blowing
    • Consist of subcutaneous fat, buccinator muscle of cheek, and orbicularis oris of lips
  29. Cutaneous Area of Lips
    Colored like rest of face, has hair follicles and sebaceous glands
  30. Red Area of Lips
    • Red, hairless region where lips meet
    • Blood vessels very close to epidermal surface
  31. Labial Mucosa
    Inner surface of lips
  32. Labial Frenulum
    Fold that connects lip of gum
  33. The Tongue
    • Manipulates food between teeth
    • Covered in nonkeratinized stratified squamous epithelium
    • Body: anterior 2/3 in oral cavity
    • Root: posterior 1/3 in oropharynx
  34. Vallate Papillae
    Row of papillae marking boundary between body and root
  35. Terminal Sulcus
    Groove behind vallate papillae
  36. Lingual Frenulum
    Fold that attaches tongue to floor of mouth
  37. Lingual Tonsils
    Contained in the root of the tongue
  38. Intrinsic Muscles
    • Entirely within tongue
    • Produced subtle tongue movements
  39. Extrinsic Muscles
    • Insert into tongue
    • Produce strong tongue movements
  40. Lingual Glands
    • Serous and mucous glands among extrinsic muscles
    • Secrete some saliva
  41. The Palate
    Separates oral cavity from nasal cavity
  42. Hard Palate
    Anterior part supported by maxillae and palatine bones
  43. Palatine Rugae
    Ridges that help tongue hold food
  44. Soft Palate
    • Posterior part composed of muscle and glands
    • Contains uvula, which keeps food in the mouth until swallowing occurs and prevents food from entering nasal cavity
  45. Chewing
    • Masticate food into smaller pieces
    • Makes it easier to swallow
    • Increases surface area for enzymes to digest it
  46. Teeth
    • 32 adult teeth, 20 deciduous (baby) teeth
    • 16 in mandible, 16 in maxilla
    • From midline to rear-
    • 2 incisors to bite food
    • 1 canine to puncture/shred
    • 2 premolars and 3 molars to crush and grind
  47. Deciduous Teeth
    • Teeth develop beneath gums to erupt in predictable order
    • Erupt from 6-30 months
    • Replaced by permanent teeth from ages 6-25
    • Root of baby teeth dissolves as permanent tooth develops
    • Wisdom teeth (3rd molars) can be crowded against neighbors so that they can't erupt (impacted)
  48. Alveolus
    Tooth socket in the bone
  49. Periodontal Ligament
    Anchors tooth in alveolus
  50. Gingiva (Gum)
    Covers alveolar bone
  51. Crown
    Portion above gum
  52. Root
    Portion below gum
  53. Neck
    Where crown, root, and gum meet
  54. Gingival Sulcus
    Groove between tooth and gum
  55. Dentin
    Hard, yellow tissue
  56. Enamel
    Hard covering for crown formed before tooth erupts
  57. Cementum
    • Hard covering for root
    • Dentin and cementum can regenerate but enamel can't
  58. Root Canal
    Tube for nerves and blood vessels to reach pulp cavity in crown
  59. Tooth Disease
    Plaques of sugars and bacteria left on the teeth can erode enamel and dentin to for caries (cavities)
  60. Root Canal Procedure
    • Endodontic Therapy required if cavity extends into pulp
    • Pulp is removed and replaced with new material
  61. Functions of Saliva
    • Moistens mouth
    • Begins digestion of starch and fat
    • Cleanses teeth
    • Inhibits bacterial growth
    • Dissolves tastants to stimulate taste buds
    • Moistens and binds food for swallowing
  62. Saliva Components
    Mostly water
  63. Salivary Amylase
    begins starch digestion
  64. Lingual Lipase
    activated by stomach acid and digests fat after food is swallowed
  65. Mucus
    binds and lubricates food
  66. Lysozyme:
    kill bacteria
  67. Immunoglobulin A:
    inhibits bacterial growth
  68. Intrinsic Salivary Glands
    Small glands that constantly secrete saliva
  69. Extrinsic Salivary Gland
    Large glands with ducts
  70. Parotid Gland
    Anterior to earlobe
  71. Submandibular Gland
    Along Mandible
  72. Lingual Gland
    Along tongue
  73. Salivary Glands
    • Mucous cells secrete mucous
    • Serous cells secrete thin fluid full of amalyse and electrolytes
    • The fluids combine to salivary ducts
    • Salivatory nuclei in medulla and pons regulate saliva production
  74. Pharynx
    • Three pharyngeal constrictors force food downward during swallowing
    • When not swallowing, inferior constrictor remains closed to prevent air from entering esophagus
  75. Esophagus
    • Extends from pharynx to cardiac orifice of stomach
    • Passes through esophageal hiatus in diaphragm
    • Lower esophageal sphincter prevents stomach contents from entering esophagus and prevents stomach acid from eroding esophagus (heartburn)
  76. Swallowing
    • Bolus of food pushed down through mouth, pharynx, and esophagus
    • Swallowing center in medulla coordinates muscles of pharynx and esophagus through trigeminal, facial, glossopharyngeal and hypoglossal nerves
  77. Buccal Phase of Swallowing
    • Under voluntary control
    • Tongue collects flood, forms bolus, pushes it posteriorly
    • Food accumulates in oropharynx, epiglottis moves, and bolus enters laryngopharynx
    • Bolus activates tactile receptors that trigger phase 2
  78. Pharyngoesophageal Phase of Swallowing
    • Involuntary
    • Tongue, soft palate, and epiglottis/larynx block food from mouth, nasal cavity, and larynx
    • Food driven downward by pharyngeal constrictors
    • Bolus triggers peristalsis once it enters esophagus
    • Lower esophageal sphincter relaxes to let bolus enter stomach