Chapter 21: Digestive System

PHYSIO-DIGESTIVE SYSTEM-CH21 fistula-opening mucus-acidic gastric fluid-very audk digestion-uses hydrochlonc aad and pepsin. Gl disorders heartbun, indigestion, gas, Constipation. -Digestive system begins with the oral cavity-serres as a receptable for food (mwth/pharynx). -food then enters G1 tract (esophagus, stomach, small intestine, large intestini anars Stomach ans = GVT- Digestion consists of chemical and mechanical breakdown. Along the way accessory glandular organs (salivary glands, the liver, gallbladder, Pancreas) add secretions for end result of CHYME (soupy mixture of food and secretions) -Sphincters-rings of muscle that seperate the tube (Gl tract) into segments. Ediff functims. -food goes into interstitial fluid for absorption. whatever is left (or absorbed) is pooped out. -Digestive system part of external environment = prine to bactena ( bactena in intestine Commensal relationship-bactena lives in lumen without affecting the body negatively or (+) -3 Salivary glands: submandibular (under mandible), sublingual (under tounge), parstid gland -food then goes to esophagus-long harron tube from thorax abdomen. (walls are skeletal on top transition to smooth muscle) leads to Stomach. 3 Parts of stomach (ipper) fundus, Center) body, (lower) antrom)→ stomach creates chyme. Pylorus is the opening between stomach and small intestine (Guarded by Pylonic valve) which only altos small amts of chyme to go backe through at a time. *Feedback loops and stomach regulate passage of Chyme * most digestion takes place in small intestine [composed of duadenem, jejunum, ileum) 2 accessory glandular organs that help in digestion: Pancreas, liver. Whatever is absorbed in small intestine goes to Lintestine colon @ colon it forms to poop for excretion. terminal section of feces intesin Intestine rectum&ils walls distend trigger defecation refier→ feces goes out through anus through external anal sphincter (voluntary control) -Digestive system is 450cm (15ft long) -intestines aloe are 12ft. when you die, these lengths double ble longitudinal muscles relax. Fords in stomach nigae. Folds in intestine: plicae increase surface area. Intestinal mucosa-has villr (90 up) crupts (go duro)-deep pockets in the intestine gastre glands-deep pockets in stormach- Grut wall consistot 4 layers inner mucosa, submucosa, muscularis externa, serasy ①Immer mucosa-has Blaves! mucosal epithelion, lamina propia, musculars mucosa e @mucocal epithelum most vanable cells here include transporting epithelial cells (enterocytes) endonne, exoanne and stem cells. In stomach and colon-junctions are tight- In interstitial epithchum-junctions are "leaky" Gl stem cells-rapidly dinde Lifespan of Gl cells is only a couple of days-rapid turnover and cell dinsion rate ↑ risk for developing CA. lamina propia-connective tissue layer that contains nerre fibers and small 1100 and lymph vessels- Absorbed nutrients are distributed to blood and lymph here. layer has immune cells patrolling for invaders Has Peyer's Patches-psible bumps in mucosa made up of collections of lymphad tissue- ③ masculans mucosae-thin layer of smooth musde that seperates the lamina prorlu from the submucos Contraction of thic layer moves villi back and forth. 2 Submucosa middle layer of connectore tissue I large blood/lymph vessels contams submucosal plexus- the of the 2 major networks perre networks of the enteric nervous system. (Also called meissners Plexus) Submucosal plexus innervates cells in the ep thelial layer & Smooth muscle of musculans mocasal. ③ muscularis externa Oluter wall of Gl tract. Has 2 layers of smooth musde inner circular layer, outer longitudinal layer. *contraction of circular layer decreases (1) diameter of lumen *Contraction of longitudinal layer shortens (4) the tube. myentenc plexus second nerve netrark of entenc system lies between trese 2 (also called. Arverbach's plexus)-controls and coordinates musettar motor activity of the musculans externa ④ Serosy outer corening of the entire digestive tract- connective tissue membrane that is? continuation of the peritoneal membrane helps torm messenten to hold intestines ↑. Pigestire system moves nutnents, H2o, electrolytes from out in. Has 4 steps: digestion, absorption, secretion, motility. CH1-7-8 (sturdy guides) FINAL Ch22. ch.23,24 Digestion chemical and mechanical breakdown of frad 4 steps Absorption movement of substances from the lumen of Gl tract → ECF- Secretion Has 2 meanings morement of H20/1ons trom ECF to digestive tract release of substances synthesized by Gal epithelial cells into entre lumen or ECF motility movement of material in the Gy tract as aresult of muscle contraction. CHALLENGES OF DIGESTIVE SYSTEM ① Autodigestion-enzymes seureted la digestive system digest Cells of Gl tract peptic ulcers. mass balance: unable to balance fluid jorut output. ③ lack of intestinal reabsorption-(dit diarrhed for vomiting) = ↓ BIP. Defense. dit ↑ surface area theres conflict between the need to absorb and need to protect (Physiological defense mechanisms} - mucus digestire Chaymes, acids, GALT. (collection of lymphoid tissue) 91 of fluid pass through cal tract D Ally 21 enter through mouth. 71 ontar come from body waterseereted along t lons enzymes/mucus. (El epithelial cells are Polanced)