--- module: 084-02 language: en chapter: 84 title: "Organ Histology and Structure–Function Recognition" module_title: "Gastrointestinal, hepatic, pancreatic, renal, and endocrine histology" source_sha256: ccd77339517cb6e1239514c38ead898026127990dd47c4898f0a0409ab3d0073 --- # Gut, liver, pancreas, kidney, endocrine histology ## Gut wall plan ### Mucosa, submucosa, muscularis externa, serosa #### Mucosa: epithelium, lamina propria, muscularis #### Submucosal plexus in submucosa #### Myenteric plexus between muscle layers ### Serosa is mesothelium, adventitia binds ## Oesophagus and stomach ### Oesophagus: non-keratinised stratified squamous #### Skeletal to smooth muscle downward #### Reflux causes columnar metaplasia ### Gastric pits lined by surface mucous cells ### Parietal cells: acid and intrinsic factor ### Chief cells: basophilic, pepsinogen ### Fundus and body: short pits, long glands ### Pylorus: deep pits, G and D cells ### Inner oblique layer aids mixing ## Small intestine ### Plicae, villi, microvilli amplify surface ### Villus: lacteal, capillaries, smooth muscle ### Crypts hold stem and Paneth cells #### Paneth granules are antimicrobial ### Enteroendocrine cells release hormones basally ### Duodenum: Brunner glands ### Jejunum: prominent folds, long villi ### Ileum: Peyer patches into submucosa ## Large intestine and anal canal ### No villi, straight goblet-rich crypts ### Taeniae coli except appendix and rectum ### Appendix: extensive lymphoid tissue ### Anal canal: columnar to keratinised skin ## Liver and gallbladder ### Blood portal to central, bile opposite ### Portal tract: vein, artery, bile duct ### Sinusoids mix portal and arterial blood #### Fenestrated, no continuous basement membrane #### Space of Disse for exchange ### Kupffer cells: sinusoidal macrophages ### Stellate cells store vitamin A #### Chronic injury: matrix-producing cells ### Canaliculi sealed by tight junctions ### Acinus zones explain hypoxic vulnerability ### Gallbladder concentrates bile #### No muscularis mucosae or submucosa ## Pancreas ### Serous acini with zymogen granules ### Centroacinar cells begin intercalated ducts ### No striated ducts, unlike salivary glands ### Enzyme activation damages acini and fat ### Islet cell types need immunolabelling #### Beta insulin, alpha glucagon ## Kidney ### Cortex corpuscles, medulla loops and ducts ### Podocytes wrap capillaries with foot processes ### Barrier: endothelium, basement membrane, slits #### Injury target shapes the pattern ### Mesangial cells support and clear ### Proximal tubule: brush border, eosinophilic ### Distal tubule: pale, clear lumen ### Collecting ducts: distinct cell boundaries ### Juxtaglomerular apparatus #### Macula densa senses sodium chloride #### Granular cells release renin ## Endocrine glands ### Anterior pituitary: cords around sinusoids ### Posterior pituitary: axons, Herring bodies ### Thyroid follicles filled with colloid #### Iodination apical, release basal #### Cell height reflects activity ### C cells secrete calcitonin ### Parathyroid chief cells secrete hormone ### Adrenal cortex: three zones #### Glomerulosa: mineralocorticoids #### Fasciculata: glucocorticoids #### Reticularis: androgens ### Medulla: chromaffin cells ## Tracing flow ### Food, portal blood, bile, filtrate, hormones ### Direction links form to physiology