Digestive tract

Digestive tract

1. Oral Cavity

   • LIP
     • Skin side
       • Straified Squamous keratinized Hair follicles,sebaceous glands, sweat glands
       • Mucous side
         • Stratified squamous non keratinized epithelium CT layer with mucous glands called labial glands
         • Labial Glands
     • Orbicularis oris
     • Lip margin
       • no keratin just a thick layer of stratum lucidum. underlying CT is rich in capillaries and sensory nerves.
   • Palate
     • Hard palate-bony                      Soft palate- muscles covered by mucous membrane Oral mucous Membrane lined with stratified squamous non keratinized epi
     • Palatine mucous gland
   • Tongue
     • Skeletal (instrinsic)3 d
       • Vertical Transverse horizontal
     • lingual glands
       • serous and mucous glands
     • superior surface
       • divided by sulcus terminalis into anterior 2/3 and posterior 1/3
       • Anterior
         • gives roughness Lingual Papillae Contain taste buds
         • Circumvallate
           • Largest in size fewest in number Anterior to sulcus terminalis Surrounded by trenches     Serous acini Von Ebner's serous
         • Fungiform
           • Large round papillae located at the tips and sides of tongue
         • Filiform
           • Most numerous cover most of the tongue conical NO taste buds
         • Folate
           • Located posterolaterally not well developed in humans
       • posterior
         • Lingual Tonsil
     • Taste Buds
       • Gustatory taste hair
         • Cells in the middle projecting hairs (microvilli) in the outer taste pore Chemoreceptor
       • Supporting/sustentacular
         • On the sides
       • Basal
         • regeneration
   • cheek
     • Buccinator
     • Buccal Glands
   • Teeth
     • Root
       • Fits inside alveolar sockets in jaw Starts at Apical foramen containous gelatinous material and blood vessels and nerves of the tooth- root pulp
     • Crown
     • Mineralized parts 3
       • Dentin-70%  organic fills the crown and root cementum hard bone that covers dentin Enamel-hardest part 95% organic

2. Digestive Tube

   • Wall 4 layers
     • Mucosa
       • Epithelium- simple columnar pits or crypts called glands Lamina propria- loose CT containg blood vessels nerves and lymphatics Muscularis Mucosa- Inner circular and outer longitudinal muscle layers of the mucousa
       • Simple columnar
         • pits depressions elevations villi crypts glands
       • Lamina propria
         • loose CT blood vessels nerves and lymphatics
       • Muscularis Mucosa
         • evacuates secretion by contraction
     • submucosa
       • support and transmission of nerves BV lymphatics
       • Meissners plexus
         • autonomic plexus controls secretion
     • Muscularis Externa
       • Inner/outer long muscles
         • Peristalsis
       • Myenteric plexus
         • Auerbachs aka controls muscle contraction
     • Adventitia/Serosa
       • SSmesothelium of the peritoneum
   • Esophagus
     • GERD
     • Mucosa
       • SSNKE smooth muscles lymphatic nodules MALT
       • Lamina propria
         • of lower end contain mucous glands that neutralize acidity
     • Submucosa
       • Facilitates the passage of bolus of food
     • Muscularis externa
       • contraction helps evacuate secretion to lumen upper thrd contain skeletal muscle lower third contain smooth muscle mixed in the middle third
     • Adventitia
       • No peritoneum until it passes through diaphragm and becomes serosa
   • Stomach
     • Rugae allow for expansion Chemical digestion HCL->chyme
     • Cardia
       • between esophagus and stomach 1st source of mucous between esophagus and stomach
     • fundus/body
       • simple columnar mucous secreting epithelium renewed every 5 daysGastric pits invag of epithelium Muscularis 3 layers Oblique- innermost Circular- middle longitudinal-outer
       • Fundic glands
         • Lamina propria open in th ebottom of the short gastric pits 5 cells
         • Mucous neck cells
           • secrete mucous
         • Parietal Oxyntic cell
           • Upper part of the glands secret HCL starts break down of protein converts pepsinogen to pepsin and bacteriostatic Instrinsic factor - b12 Pernicious anemia and subacute degeneration of spinal cord
         • Chief cell
           • bottom of fundic gland secrete pepsinogen starts fat digestionn
         • Enteroendocrine
           • Gastrin stimulating gastric secretion and motility
     • Pyloric region
       • Gate keeper Gastric pits are longer than fundic pits Simple columnar mucous secreting cells Entroendocrine cells ends at pyloric sphincter
     • Small Intestine
       • Mucosa: villi and glands
       • Factors for surface area 4
         • Surface area Villi covered with simple columnar absorptive cells enterocytes and goblet cellsLymphatic vessels called lacteals 2.microvilli- folds of cell membrane 3.plicae circularis- mucosal folds increase surface area 4. Length 7 meters
       • crypts of Lieberkuhn
         • simple columnar absorptive cells enterocytes.secrete digestive enzymes absorption of carb and protein microvilli increase surface area for absortion transport digested food from lumen to circulatory
         • Goblet Cells
           • Mucous secretion lub
         • Paneth cells
           • Antibacterial lysozymes
         • Entroendocrine cells
           • Cholecystokinin
             • contraction of gallbladder->release bile into duodenum stimulates pancreas to release pancreatic enzyme
           • Secretin
             • HCO3 from pancreas
           • Motilin
             • stimulates peristalsis
         • M cell
           • overlie Peyers patches and convery microogransims to them
       • Duodenum
         • Brunners glands in submucosa secrete alkaline mucous to protect duodenal mucosa and neutralize gastric acidity
         • Jejunum
           • Narrow Vili no brunners glands no peyers patches
       • Ileum
         • Narrow vili peyers patches in submucosa
       • Large Intestine
         • No vili Crypts Simple columnar absorptive cell with predominance of goblet cells
         • Teniae coli
           • absent in rectum and appendix 3 longitudinal bands of smooth muscle
         • Lymphocytic infiltration of mucosa
           • diffuse and nodular Cecum Appendix colon
           • Appendix
             • blind end tube immune mechanism complete layer of lymphoid follicles in submucosa short crypts few goblet cells Diffuse lymphatic infiltration of mucosa
             • Colon
               • Ascending Transverse descending Sigmoid
               • Rectum
                 • Anal Canal
                   • Stratified squamous non keratinized epithelium keratinzed at anal orifice Internal anal sphincter smooth muscle involuntary external anal sphincter voluntary

3. digestive glands

   • Salivary
     • compound tubule-alveolar gland exocrine
     • Accessory glands
       • Labial Buccal Lingual palatine mucous glands
     • Main
       • Parotid Submandibular80 serous 20 mucous  Sublingual
     • Purely Serous
       • Von Ebners Parotid- Pancreas
   • Pancreas
     • Mixed gland exocrine part purely serous glands Pacinian corpuscles in CT trabeculae Exocrine part lipases amylases peptidases  Centro acinar cells Intercalate ducts located inside acinus
     • Exocrine
       • SeroussecreteLipases AmylasespeptidasesTo Duodenum Paciniancorpuscles
     • Endocrine
       • Islets of Langerhans Secrete hormones into capillaries no ducts Beta cells Alpha cells Dcells B- Insulin lower glucose A-glucaon raise glucose D- somatostatininhibits insulin and glucagon
   • Parenchyma
     • functioning cell
     • Acini
       • Myoepithelial cells surround secretory acini
       • serous
         • pyramidal cells round central nuclei apics contains zymogen granueles-> watery secretion
       • Mucous
         • cuboidal cells secrete mucous
     • ducts
       • Intercalated duct
         • Simple cuboidal smallest intralobular. striated/secretory duct- high cuboidal cells secrete potassium and bicarb Interlobular duct- simple columnar between lobules Interlobar ducr- psuedostratified columnar
   • Liver
     • Mixed exocrine endocrine gland2ndlargest  exocrine-bile endocrine plasma proteins glucose lipoproteins
     • Hepatic Lobule
       • hexagonal pentagonal shape surrounded by portal triads
       • Portal Vein
         • Carries venous blood containg digestive products of carbs and proteins from intestine
       • Hepatic artery
         • Carries oxygenated blood and digested fats
       • Bile duct
       • Hepatoccyte
         • hepatic cell make bile
         • Blood sinusoids
           • covered y Kupffer cells and ss epi between hepatic cells
           • Bile canaliculi
             • between hepatocytes to drain bile secreted by them
             • Space of disse
               • between hepatocytes and blood sinusoids exchange of material
               • blood flow
                 • from portal vein and hepatic artery drain into blood sinusoids central vein sublobular veins hepatic veins Inferior vena cava
             • Bile flow
               • Bile Canaliculi drain bile from hepatic cells to bile duct-> hepatic ducts->cystic duct of gallbladder
               • Ampulla of Vater
                 • hepatopancreatic ampula opens to the second part of the duodenum
           • kupffer cell
             • phagocytic cell
     • Endocrine
       • Plasma proteins glucose lipoproteins
     • Exocrine
       • bile
     • capsule
       • Glissons capsule divides the liver into hepatic lobules
   • Gallbladder
     • fat imulsification
       • Bile small intestine- cholesterol
     • Colisito
       • Stimulates contraction