Anatomy Lecture 18

  1. Pharynx:
    • nasopharynx
    • oropharynx
    • laryngopharynx: piriform fossa
    • pharyngeal constrictor muscles: superior, middle, inferior
    • pull the walls of the pharynx inward during swallowing
  2. Swallowing mechanism: phases:
    • buccal phase (voluntary): food pushed from oral cavity to oropharynx by tongue
    • pharyngeal phase (involuntary): elevation of soft palate, elevation of larynx against epiglottis, constriction of pharynx
    • esophageal phase (involuntary): food moved by peristaltic waves
  3. General Histological Organization of the Digestive Tract
    • four layers:
    • mucosa (three layers):
    • submucosa:
    • muscularis externa:
    • serosa:
  4. mucosa (three layers):
    • surface epithelium: type reflects function (secretion, absorption, protection)
    • lamina propria: loose connective tissue
    • muscularis mucosa: smooth muscle
  5. submucosa:
    • loose connective tissue
    • contains blood vessels, lymphatics and glands
    • submucosal (Meissners') plexus ‑ supplies muscularis mucosa and glands
  6. muscularis externa:
    • circular and longitudinal layers of smooth muscle
    • myenteric (Auerbach's) plexus ‑ between layers
    • peristalsis and segmentation
  7. serosa:
    • serous membrane that covers many structures
    • adventitia ‑ dense fibrous connective tissue that surrounds structures without a serosa
  8. Esophagusgross anatomy:
    esophageal hiatus (T10)
  9. Esophagus histology:
    • mucosa: stratified squamous
    • submucosa: contains mucus‑secreting (esophageal) glands
    • muscularis externa: upper 1/3 skeletal muscle, middle 1/3 skeletal and smooth muscle, lower 1/3 smooth muscle
    • adventitia
    • serosa: last 1‑2 cm is retroperitoneal
  10. Stomach gross anatomy:
    • regions: cardia, fundus, body, pylorus
    • lesser and greater curvature
    • lesser and greater omentum
  11. histology: of the esophagus
    • mucosa:
    • rugae
    • simple columnar (mucous) epithelium
    • gastric pits:
    • gastric glands:
    • muscularis externa:
    • serosa
  12. gastric pits:
    neck cells ‑ replace surface cells
  13. gastric glands:
    • parietal cells: ‑large, round cells with central nucleus ‑ secrete HCl and intrinsic factor
    • chief cells: ‑ cuboidal cells with basal nucleus ‑ secrete pepsinogen
    • enteroendocrine cells: ‑ produce GI hormones ‑ G cells secrete gastrin
  14. muscularis externa:
    • outer longitudinal, middle circular and inner oblique smooth muscle layers
    • pyloric sphincter ‑ thickened circular layer
  15. blood supply and drainage to the stomach:
    • blood supply: from the three branches of the celiac artery: left gastric, splenic and common hepatic
    • venous drainage: corresponding veins drain into the portal vein
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Anatomy Lecture 18