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Pharynx:
- nasopharynx
- oropharynx
- laryngopharynx: piriform fossa
- pharyngeal constrictor muscles: superior, middle, inferior
- pull the walls of the pharynx inward during swallowing
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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
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General Histological Organization of the Digestive Tract
Wall:
- four layers:
- mucosa (three layers):
- submucosa:
- muscularis externa:
- serosa:
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mucosa (three layers):
- surface epithelium: type reflects function (secretion, absorption, protection)
- lamina propria: loose connective tissue
- muscularis mucosa: smooth muscle
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submucosa:
- loose connective tissue
- contains blood vessels, lymphatics and glands
- submucosal (Meissners') plexus ‑ supplies muscularis mucosa and glands
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muscularis externa:
- circular and longitudinal layers of smooth muscle
- myenteric (Auerbach's) plexus ‑ between layers
- peristalsis and segmentation
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serosa:
- serous membrane that covers many structures
- adventitia ‑ dense fibrous connective tissue that surrounds structures without a serosa
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Esophagusgross anatomy:
esophageal hiatus (T10)
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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
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Stomach gross anatomy:
- regions: cardia, fundus, body, pylorus
- lesser and greater curvature
- lesser and greater omentum
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histology: of the esophagus
- mucosa:
- rugae
- simple columnar (mucous) epithelium
- gastric pits:
- gastric glands:
- muscularis externa:
- serosa
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gastric pits:
neck cells ‑ replace surface cells
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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
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muscularis externa:
- outer longitudinal, middle circular and inner oblique smooth muscle layers
- pyloric sphincter ‑ thickened circular layer
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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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