Digestive System

Digestive System

1. histology

   • mucosa
     • (1) epithelium
       • non-k strat. squam.
         • mouth, pharynx, esoph., anus
       • simple columnar
     • (2) lamina propria
       • loose CT
       • Blood and lymphatic vessels, lymphoid tissue
       • intestinal glands/crypts (epithelium extension)
     • (3) muscularis mucosae
       • thin layer of smooth muscle
       • twitching movements, folds of sm. ints.
   • submucosa
     • BV, lymphatic vessels, *glands*
     • Meissner plexus
       • stimulate gland secretion; vasoconstrict
       • not in esoph. & stomach
   • muscularis externa
     • skeletal
       • mouth, pharynx, esoph., anus
       • for swallow and defecation
     • myentric/Auerbach plexus
       • controls muscle movement
   • outer layer
     • serosa (visceral peritoneum)
       • secretes serous; form folds that suspend organs
     • loose CT & simple. squam.
     • adventitia
       • CT blends with surrounding CT; not peritoneum
       • esophagus and retropenial organs (pancreas, duodenum)

2. ORAL CAVITY

   • function
     • ingestion
     • taste
     • mastication
       • tounge and cheek
       • depression: lateral pteryg. elevation: others
       • retraction: temporalis. protraction&sides: others
     • digestion
       • amylase
     • swallowing
     • communication
       • lips, cheek, tounge, teeth
     • protection
       • mucin & saliva for lubrication
       • epith and lysozome
   • toungue
     • muscle
       • intrisic
         • change shape
       • extrinsic
         • move & change shape
     • moves food, swallow, chew, taste, speech
   • salivary glands
     • parotid
       • serous; watery saliva
       • duct: second upper molar
     • submandibular
       • mix, more serous
       • duct: lingual frenulum
     • sublingual
       • mix, more mucus
       • duct: floor of oral cavity; 10-12
   • secretions
     • (1) serous saliva
       • moisten food
       • neutralise bacteria acids
       • flushes bacteria from oral cavity
       • weak antibacterial
     • (2) salivary amylase
     • (3) mucus
       • lubricates food
       • protects tract from digestion by enzymes
     • (4) lingual lipase

3. ESOPHAGUS

   • secretes mucus
     • lubricates wall
     • lining of esophagus from abrasion and allows food to move more smoothly through esophagus

4. STOMACH

   • secretions
     • surface mucus cells
       • alkaline mucus -> protect stomach lining
         • neutralizes acid chyme; barrier to enzymes pepsin
       • on the surface/lining of gastric pits
     • mucus neck cells
     • parietal cells (oxyntic)
       • HCl
         • antibacterial
         • inactivate amylase
         • denatures protein
         • convert pepsinogen to pepsin
       • intrinsic factor
         • binds with vit. B12 (for ileum to absorb)
     • chief cells (zymogenic)
       • pepsinogen
     • endocrine cells
       • G-cells
         • gastrin
           • increase gastric secretion
           • stimulate gastric activity and reflex
       • Enterochromaffin-like cells
         • histamine
           • stimulate acid secretion from parietal
       • somatostatin-containing
         • somatostatin
           • inhibit gastrin and insulin
     • gastric lipase
   • absorb
     • water, electrolytes, drugs (aspirin), alcohol

5. SMALL INTESTINE

   • duodenum (25 cm)
     • villi (0.5-1.5 mm)
       • lacteals
     • microvili (1 micrometer)
       • cytoplasmic extension (folds of cell membranes)
       • brush border
     • increased surface area 600 folds for efficient edigestion and absorbsion
     • cell types
       • (1) absorbtive
         • cells with microvili; produce digestive enzymes; absorb digested foods
       • (2) goblet cells
         • protective mucus
       • (3) granular/ paneth
         • antibacterial
       • (4) endocrine
         • secretin & cholecystokinin
     • intestinal glands/ crypts of Lieberkhun
       • invagination of mucosa
     • duodenal/ Brunner glands
       • coiled tubular MUCUS gland in submucosa
   • absorbed 8-8.5 L of water+solutes
   • gradual decrease in diameter, wall thickness, number of folds and vili
   • ileum
     • Peyer Patches --> Lymphatic nodules --> immune response
     • ileocaecal junction; ileocaecal sphincter (ring of smooth muscle); ileocaecal valve
   • secretion
     • mucus
       • protects wall from stomach acid & enzymes
       • adhesion for fecal matter
       • protects wall from bacteria & acid from feces
       • duodenal glands, intestinal glands, goblet cells
     • remain bound to/in the microvili
       • peptidase --> split polypeptide
       • enterokinase --> activates trypsinogen
       • sucrase
       • maltase
       • isomaltase --> seperate isomaltose to 2 glucose
       • lactose

Imagens e arquivos do mapa