Digestive System Notes PDF

Chapter 23 https://me.me/i/who-would-win-the-advanced-human-one-beefy-boi-gastrointestinal-19201559  Organs of the digestive system fall into two groups: 1. Alimentary canal (gastrointestinal or GI tract or gut) ▪ Muscular tube that runs from the...

Chapter 23 https://me.me/i/who-would-win-the-advanced-human-one-beefy-boi-gastrointestinal-19201559  Organs of the digestive system fall into two groups: 1. Alimentary canal (gastrointestinal or GI tract or gut) ▪ Muscular tube that runs from the mouth to anus (approx. 9 m long) ▪ Organs: mouth, pharynx, esophagus, stomach, small intestine, large intestine, anus 2. Accessory digestive organs:  Teeth  Tongue  Gallbladder  Digestive glands: produce secretions that help break down foodstuffs ▪ Salivary glands Accessory ▪ Liver organs ▪ Pancreas have an asterisk  Processing of food involves essential activities: Ingestion: eating Propulsion (transportation): movement of food through the alimentary canal Digestion: mechanical and chemical Absorption: passage of digested fragments from lumen of GI tract into blood or lymph Defecation (elimination): elimination of indigestible substances via anus in form of feces  Abdominopelvic cavity is lined with moist serous membranes:  Parietal peritoneum  Visceral peritoneum  Mesenteries: folds of peritoneum  Support and stabilize GI tract organs  Contain blood & lymphatic vessels, nerves to supply digestive organs ▪ Greater and Lesser omentum (stomach, other organs) ▪ Mesentery proper (small intestine) ▪ Mesocolon (large intestine)  GI wall (alimentary canal) composed of four tunics  From deep to superficial they are:  Mucosa  Submucosa  Muscularis  Serosa (surrounded by peritoneum) or Adventitia (connective tissue)  What are the 4 tunics of the alimentary canal?  What are mesenteries? Name 4 different examples.  Mouth is where food is chewed and mixed saliva, that begins process of digestion  Associated organs include:  Mouth  Tongue  Salivary glands  Teeth  Mouth: Also called the oral (buccal) cavity  Bounded by lips anteriorly, cheeks laterally, palate (soft and hard) superiorly, and tongue inferiorly ▪ *Which bones make up the hard palate?  Uvula: projection on soft palate  Oral orifice is the anterior opening  Walls of mouth lined with tough cells that resist abrasion (*what kind of tissue?)  Tongue occupies floor of mouth: taste, aids in chewing, swallowing, taste  Lingual frenulum: attachment to floor of mouth  Gingivae: gums  Upper and lower lips, connected anteriorly by the superior and inferior labial frenulum  Teeth lie in sockets in gum-covered margins of mandible and maxilla  32 form between 6-12 years of age  Covered by enamel, hardest substance in body  Heavily mineralized with calcium salts and hydroxyapatite crystals  Mastication: process of chewing that tears and grinds food into smaller fragments  Teeth are classified according to shape:  Incisors (4 each row): chisel shaped for cutting  Canines (2 each row): fanglike teeth that tear or pierce  Premolars (bicuspids) (4 each row): broad crowns with rounded cusps used to grind or crush  Molars (6 each row): broad crowns, rounded cusps: best grinders  Crown: exposed area  Root: embedded in jaw (neck in between)  Cement: calcified connective tissue, covers root  Periodontal ligament: anchors tooth in socket  Pulp cavity: connective tissue, blood vessels, nerves  Dentin: bonelike material under enamel  Maintained by odontoblasts of pulp cavity  Enamel: hard, outer, calcified substance  Three pairs external to the oral cavity: 1. Parotid glands 2. Submandibular glands 3. Sublingual glands  Functions of saliva:  Cleanses mouth  Dissolves food chemicals for taste  Moistens food; compacts into bolus  Begins chemical breakdown (enzymes)  Which type of teeth are located most anteriorly? Which are located most posteriorly?  What are some of the functions of saliva?  If you ground your teeth down to wear away the enamel, what structure would be exposed?  Food passes from mouth into oropharynx and then into laryngopharynx  Air and food enter  Esophagus: Flat muscular tube, runs from laryngopharynx to stomach  Gastroesophageal (cardiac) sphincter closed when food not being swallowed (why?)  Digestion  Mechanical  HCl denatures proteins  Pepsin digests proteins  Holding area for food  Bolus processed into chyme  3 muscular layers: longitudinal, circular, oblique (extra)  4 Regions:  Cardia  Fundus  Body  Pyloris  Smooth muscle pyloric sphincter controls orifice to duodenum  Greater and lesser curvatures  Internal surface has gastric folds  4 major layers  Mucosal layer responsible for secretions  Mucosal layer:  Surface mucous cells: alkaline mucous  Mucous neck cells: acidic mucous  Parietal cells – HCl, intrinsic factor  Chief cells –pepsinogen, lipase  Enteroendocrine cells – gastrin (hormone)  What are 4 different types of cells in the stomach mucosa and what are their functions?  Small intestine: major organ of digestion and absorption, 3 sections:  Duodenum: curves around head of pancreas  Jejunum: attached posteriorly by mesentery  Ileum: attached posteriorly by mesentery; joins large intestine at ileocecal valve  Circular folds: Force chyme to slowly spiral through lumen  Villi: Fingerlike projections of mucosa  Microvilli: Cytoplasmic extensions (brush border) of mucosal cells on villi  Why is this structural arrangement important?  Ileocecal valve to anus  Shorter than small intestine but diameter greater  Site of absorption of remaining water  Contains mutualistic bacteria that aid in digestion  Storage and elimination of undigested food 1. Cecum 2. Appendix: masses of lymphoid tissue 3. Colon: longest section, several parts 4. Rectum: rectal valves stop feces from being passed with gas 5. Anal canal: opens to body exterior at anus, has internal and external anal sphincters  Liver  Gall bladder  Pancreas  Associated with small intestine  4 lobes: 1. Right lobe 2. Caudate lobe 3. Quadrate lobe 4. Left lobe  Functions:  Produces bile  Stores/ processes nutrients  Detoxification  Hepatic portal circulation: veins from small intestine Posterior  Inferior surface of the liver  Functions:  Stores bile  Concentrates bile  Cystic duct connects the gall bladder to the bile duct, merges into common hepatic duct  Exocrine functions:  Secreted into duct  Digestive enzymes: proteases, amylase, lipases, nucleases  Bicarbonate (neutralize stomach acid)  Endocrine functions:  Secreted into blood  Produces insulin and glucagon  Bile duct and pancreatic duct unite in wall of duodenum  Fuse together in bulblike structure called hepatopancreatic ampulla  Hepatopancreatic sphincter controls entry  How does the small intestine maximize surface area?  What digestive compounds are produced by the liver and the pancreas?  What may result in a blockage of the ileocecal valve?