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Gastrointestinal System (Digestion (Hormones (Gastrin (G cells, Stimulates…

- - - - Skin
      - Camper's fascia
      - Scarpa's fascia
      - External oblique muscle
      - Internal oblique muscle
      - Transverse abdominis
      - Transversalis fascia
      - Preperitoneal fat
      - Peritoneum
  - - - Pancreas
      - Kidneys & adrenal glands
      - Ascending/descending colon
      - Most of duodenum
      - Rectum
      - Proximal ureters
  - - - Foregut
      - (Division: point point where bile duct enters duodenum)
      - Midgut
      - (Division: 2/3 across transverse colon)
      - Hindgut
    - - Mucosa
      - Submucosa
      - Muscularis externa
      - Serosa
    - - Arterial supply (branches of ascending aorta)
        
        foregut = Celiac trunk
        
        midgut = Superior mesenteric artery
        
        hindgut = Inferior mesenteric artery
      - Venous drainage
        
        Portal vein --> Liver --> Hepatic vein --> IVC
    - - Regions
        
        1) Cardia
        
        2) Fundus
        
        3) Body
        
        4) Pylorus
    - - Regions
        
        1) Duodenum
        
        2) Jejunum
        
        3) Ileum
      - Valvulae conniventes = mucosal folds of mall intestine
    - - Regions
        
        1) Cecum
        
        2) Ascending colon
        
        3) Transverse colon
        
        4) Descending colon
        
        5) Sigmoid colon
        
        6) Rectum
      - Haustra = pouches in l. intestine
    - - Extrinsic nerves
        
        Parasympathetic (vagal) & sympathetic influence on motility and secretions
      - Intrinsic/enteric nerves
        
        Myenteric plexus
        
        In muscularis externa
        
        Controls mainly smooth muscle contraction/tone
        
        Submucosal plexus
        
        Controls mainly GI secretions and blood flow
        
        In submucosa
        
        Pacemaker cells found within muscularis
  - - - Transpyloric plane - L1
      - Transtubercular plane - L5
- - - - Migrating motility complex (MMC)
      - Segmentation contractions
    - - Haustral contractions
      - Mass movement
    - - Peristalsis
  - - - Glycogenolysis
        
        breakdown of glucagon to glucose
      - Gluconeogenesis
        
        generation of glucose from non-carbohydrate carbon substrates
        
        Lactate
        
        Amino acids (from proteins)
        
        Glycerol (from lipids)
    - - Ketone bodies
      - Free fatty acids
    - - cycle of lactate <-> glucose between muscle & liver
  - - - Glucagon
        
        from alpha cells in pancreas
      - Adrenaline
        
        from adrenal medulla
      - Cortisol
        
        from adrenal medulla
  - - - Gastric lipase
      - Pepsinogen
        
        Chief cells
    - - Maltase
        
        [Maltose → 2x α-glucose]
      - Sucrase-isomaltase
        
        [Sucrose → α glucose + fructose ]
      - Lactase
        
        [Lactase → β glucose + galactose]
  - - - G cells
      - Stimulates gastric acid secretion (parietal cells)
    - - Ghrelinergic cells (called P/D1 cells in stomach)
      - Secreted when stomach is empty (stretching inhibits release)
    - - I cells
      - Stimulates release of pancreatic enzymes
    - - S cells
      - Stimulates pancreatic (bicarbonate) and bile secretions in response to low pH
    - - D cells
      - Inhibits
    - - Adipose cells
      - Acts on arcuate nucleus of hypothalamus to decrease appetite
    - - M cells
      - Increases motility (increases MMCs)
    - - K cells
      - Inhibits gastric acid secretion & stimulates insulin release
  - - - Parietal cells
    - - ECL cells