digestive system

Cards (32)

  • Digestive tract structural organisation
    From inside (lumen) to the outer surface of organs in order: mucosa, submucosa, muscularis externa, serous membrane
  • Serosa is a serous membrane with simple squamous epithelium and loose connective tissue
  • Visceral peritoneum is on the surface of much of the gastrointestinal tract
  • Adventitia: loose CT
  • Mucosa: lamina propria (loose CT containing lymphatics and immune system cells), muscularis mucosae (thin layer of CT), for secretion and absorption
  • Muscularis externa: mostly smooth muscle cells, inner circular and outer longitudina
  • Intraperitoneal organs are not really in the peritoneal cavity, they have visceral peritoneum on most of the surface and are connected to abdominal wall by a mesentery, (anchored to the posterior abdominal wall)
  • Retroperitoneal are posterior to peritoneum and may have visceral peritoneum on one or more surfaces
  • Mesentery is a double layer of serous membrane, with connective tissue and neurovascular structures between
  • pharynx parts
    nasopharynx, oropharynx, laryngopharynx
  • swallowing Involves muscular contraction called peristalsis: wave of relaxation and contraction of pharyngeal and oesophagus muscles
  • HCl results in chyme having a low pH (2-3), it is antibacterial and denatures protein
  • enzymes in stomach
    pepsinogen (into pepsin in lumen and begins protein digestion) and gastric lipase (continues lipid digestion)
  • stomach releases mucous (to protect epithelium from acidic chyme) and also releases intrinsic factor, needed for the absorption of Vitamin B12 in the intestine
     
  • small intestine from top to bottom
    duodenum, jejunum, ileum
  • small intestine Has smooth muscle contraction: segmentation which mixes contents and peristalsis which moves contents along length
  • small intestine secretions
    Secretions include intestinal cell enzymes (peptidases, disaccharidases, nucleosidases) and water, ions, and mucus
  • Chemical digestion in SI occurs in two phases: in lumen and at brush border
  • chemical digestion in SI lumen
    enzymes from pancreas break covalent bonds in macromolecules to form smaller macromolecules
  • chemical digestion in small intestine at brush border
    the intestinal epithelial cell enzymes complete digestion process prior to absorption
  • Absorption in the small intestine includes nutrients, water, and ions by: simple diffusion, facilitated diffusion, secondary active transport (relies on Na+ electrochemical gradient), or active transport.
  • Nutrients can be absorbed by enterocytes in digestive tract, then to the blood capillaries in villi, to venules, to veins
     
  • Bile: exocrine secretion produced by liver, stored, and concentrated in gallbladder
  • bile and pancreatic juice are both released into duodenum when food enters the stomach and duodenum
  • Bile salts (amphipathic) aids digestion and absorption of fat by emulsifying fats, and solubilising the digestion products (increases surface area)
  • Fats and fat-soluble vitamins to the lymphatic system:

    fatty acids, glycerol, and monoglycerides are absorbed and reynthesised into triglycerides in enterocytes, packaged into chylomicrons, travel to lymph capillaires, lymph nodes, thoracic duct, left subclavian vein, around body
  • large intestine components
    caecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal
  • Segmentation in small intestine: alternating of contraction and relaxation to move contents
  • small intestine secretions
    intestinal cell enzymes attached to microvilli (peptidases, disaccharide-ases, nucleosidases), water, ions, and mucus
  • hepatic portal venous system
    Venous blood from the gut, containing absorbed nutrients goes to hepatic portal vein, This blood flows through the liver, hepatic vein, inferior vena cava, and then the right atrium
  • enteric nervous system regulation
    sensory, motor, and inter-neurons within ganglia in walls of GIT, local control of motility and secretion in response to conditions in the lumen of the gut
     
  • endocrine regulation
    Enteroendocrine cells (distant effects) and paracrine cells (local effects), Contribute to control of motility (smooth muscle) and secretion