2.GI tract

2.GI tract

1. oral region

   • Components
     • Lip
     • Teeth
     • Tongue

2. Extrinsic glands

   • Components
     • Pancreas
     • Salivary glands
     • Liver
   • What is gland?
     • derived from epithelium tissue
     • Classification
       • Function based
         • Endocrine
         • Exocrine
           • Secretion ways
             • 1. through ducts into lumen of organ(e.g. stomach) 2. directly onto the body surfaces(e.g. skin)
       • Structural based
         • Simple Glands
           • P.4 1.Simple tubular-surface epithelium+secretory cells(e.g.large intestine) 2.Simple coiled tubular-excretory duct+secretory cells(e.g. skin) 3.Simple branched tubular-surface epithelium+excretory duct (e.g. stomach) 4. Simple acinar(e.g. urethra) 5. Branched acinar-acinar components + excretory duct (e.g. Stomach,skin)
         • Compound Glands
           • 1.Compound tubular-excretory duct+branched duct+tubular components(e.g. duodenum) 2.Compound acinar (e.g. pancreas) 3.Compound tubuloacinar (e.g. Submandi-bular salivary gland)

3. Alimentary canal

   • Components
     • Esophagus
       • Structure
         • (Inner most)1. Lamina propria & muscularis mucosae(contain a single longitudinal layer of smooth muscle)-consist a layer of losse connective tissue, a layer of smooth muscle 2.submucosa- consist collagenous fibers, blood vessels & secreting glands 3. muscularis externa-skeletal muscle (outer most)4. adventitia- composed of loose connective tissue(binds esophagus to surrounding structure)
         • lined by stratified squamous nonkeratinized epithilium
     • Large intestines
       • Mucosa
         • >simple tall columnar epithelium(for absorption) >no villi >numerous long, straight tubular intestinal cryts (many goblet cells) 
         • Submucosa
           • >connective tissue(include blood vessel and nerve plexus)
           • Mucularis Externa
             • >two layers of thin muscle(inner circular + outer longitudinal)
             • Serosa
               • >a thin layer of loose connective tissue
     • Small intestines
       • Mucosa
         • >large number of finger-like villi >cover with simple columnar epithelium >intestinal crypts
         • Submucosa
           • >consists of fibroelastic connective tissue >contains blood and lymphatic vessels
           • Muscularis Externa
             • >composed of two layers of smooth muscle(inner circular & outer longitudinal)
             • Serosa
               • >a thin layer of  loose connective tissue
       • important cells
         • surface absorptive cells
           • >for absorption proper
         • Paneth cells
           • >located at the bottom >eosinophilic granules cytoplasm >pyramidal shaped
         • Goblet cells
           • >balloon shaped >apical cytoplasm >nuclei located toward the base
     • Stomach
       • Structure
         • Muscosa
           • >epithelium with simple columnar cells >lamina propria(Between epithelium & muscularis mucosa) >muscularis mucosae:thin smooth muscle beneath the gland
           • Submucosa
             • it is coat with dense connective tissue (contain blood vessels)
             • Muscularis Externa
               • >thick muscle layer    1. inner oblique    2. middle circular    3. outer longitudinal
               • Serosa
                 • >a thin layer of loose connective tissue
           • rugae + gastric pit
             • Gastric pit-near the surface mucous cells
       • Gastric gland
         • Tubular,branched gland
         • Three regions
           • Neck
             • Mucous neck clls
               • >producing mucous >secret acidic mucus
           • Body
             • Oxyntic(parietal) cell
               • >found along length of gland >round to triangular shaped >secret HCL >eosinophilic cytoplasm
           • Base
             • Zymogenic(chief) cell
               • >locate at the base >smaller than parietal cell >basophilic cytoplasm >appear vacuolate( due to zymogen granules)
             • enteroendocrine cells
   • General structure
     • 4. adventitia
       • >outer most layer >a thin layer of connective tissue-attached adjoining structure
     • 3. Muscularis externa
       • >a think layer of smooth muscle >arrange inner circular & longitudinal layer
     • 1.Mucosa
       • >Epithlium lining >muscularis mucosae composed of smooth muscle
       • Lamina propria
       • Muscularis mucosae(outer)
       • Linking epithelium(inner)
     • 2. Submucosa
       • >dense connective tissue >may contain glands