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FSCN 4612
Chapter 2: The Digestive System: Mechanism for Nourishing the Body
| Question | Answer |
|---|---|
| Main structures of the digestive system? | oral cavity esophagus stomach small & large intestine |
| Accessory organs | pancreas liver gallbladder |
| 4 layers of the lumen (tubular part of the intestine) | mucosa submuscosa muscularis externa serosa or adventitia |
| Mucosa | inner most layer of lumen interacts with food the most |
| Submucosa | connective tissue also has submucosal plexus |
| Submucosal plexus | part of the submucosa that is part of the eneteric nervous system controlling digestion |
| Muscularis externa | circulartory muscle (circular and longitudnal smooth muscle) myentaeric plexus |
| Myentaric Plexus | part of the enteric nervou systemt hat controls digestion |
| Composition of the oral cavity | mouth and pharynx |
| What are the organs of the oral cavity? | mouth pharynx salivary glands |
| Types of salivary glands | parotid submandibular sublingual |
| Salivary glands are the first level of what? | chemical digestion using amylases (MAIN source) |
| What is in saliva? | Enzymes that help to breakdown and santize foods |
| Main enzyme in saliva? | amylase |
| Function of the esophagus | moves bolus from oral cavity to stomach |
| Swallowing is what and occurs where? | moving the bolus down and in the esophogus |
| What are the 3 types of swallowing? | voluntary pharyngeal esophageal (larynx causes epiglottis to cover the glottis) |
| Peristalsis is what and where does it occur? | waves moving food down the esophagus |
| Gastroesophageal sphincter | connects the esophagus to the stomach |
| Example of a disease of the esophagus | gastrointestinal intestinal disease (GERD) |
| Is swallowing dependent on gravity? | NO! |
| Bolus | cewed food and saliva |
| 4 main regions of the stomach | cardia fundus body antrum (distal pyloric region) |
| Cardia region | GE sphincter |
| Fundus | top part |
| Antrum (DPR) | bottom; between stomach and SI |
| Function of DPR | grinds food and mixes with gastric juices to form chyme |
| DPR uses what to move chyme? | peristalsis |
| Volume of stomach full and empty? | empty: 50mL full: 1L |
| How much saliva is produced each day? | ~1L |
| What percentage of saliva is water? | 99% |
| function of saliva? | dissolves and lubricates food |
| What does saliva contain? | antibacterial and antiviral components |
| What does GERD result from? | gastric acid entering the esophagus |
| What are some potential precipitators? | smoking, chocolate, peppermint, alcohol, and peppermint cause sphincter to relax |
| If you are prone to GERD, what should you avoid? | precipitating foods and laying down after eating |
| Gastric glands of the stomach | cardiac oxyntic pyloric |
| Cells in glands | neck (mucus) cells parietal (oxyntic) cells chief (peptic or zymogenic cells enteroendocrine cells |
| Neck (mucus) cells | mucus forms barrier around tissue to prevent acid harm |
| Parietal (oxyntic) cells | secrete acid to activate the enzyme pepsinogen and secretes intrinsic facotr which binds to B12 for absorption |
| Chief (peptic or zymogenic) cells | secrete enzymes pepsinongen and breaks down proteins a little but not much |
| Enteroendocrine cells | secretes hormones in blood |
| Active state of pepsin | pepsinogen |
| composition of gastric juice | HCl enzymes mucus intrinsic factor |
| Gastric juices are made up of HCl for these reasons | converts pepsinogen to pepsin denatures proteins releases nutrients from organic complexes acts as bacteriocide |
| Denaturing of acid proteinss | acid connections become more linear and pepsinogen can cleave in |
| Release of organic complexes | form an ionic bond from food to release nutrient |
| Enzymes in the stomach | some amylase (not much) pepsin lipase |
| Mucus | provides about 2mm of pr?otection from acid |
| Why is there amylase in the stomach? | it travels with the saliva |
| What limited chemical digestion takes place in the stomach? | -initiation of protein synthesis -limited continuation of starch hydrolysis -absorption of water, alcohol, and a few drugs and minerals -HCl important for iron and IF for B12 |
| What is HCl important for? | iron |
| What is IF (intrinsic factor) important for? | B12 absorption |
| Hormones and peptide that INHIBIT gastric secretion. | PYY, GIP, secretin, somatostatin |
| Hormones and peptides that STIMULATE gastric secretion. | gastrin releasing peptide gastrin HCl |
| What is the release of HCl stimulated by? | gastrin, acetylcholine, histamine |
| Cause of peptic ulcers | H. Pylori |
| Treatment of peptic ulcers | H2 blocker= (pepcid/zantac) antagonize signals of histamine OR Proton Pump Inhibitors: (priolosec) inhibit HCl by binding receptor |
| H. Pylori | bacteria that's acid resistant and a cause of peptic ulcers |
| What can disrupt the mucus barrier? | aspirin, alcohol, ibuprofen, |
| The small intestine was made to do what? | maximize surface area to increase absorption |
| Structural aspects of SI | folds of Kerckring Villi microvilli brush border crypts of Lieberkuhn |
| Folds of Kerckring | large circular folds of mucosa |
| Villi | at the end of the folds of Kerckring; finger-like projections |
| Microvilli | hair-like extensions of the cells' plasma membranes |
| Crypts of Lieberkuhn | in between villi and replace the old villi |
| Enterocytes in the SI are replaced? | every 3-5 days they are slothed off and digested, which from that, the nutrients are used to make a new one! |
| What is the relaxation reflex of the stomach? | controlled by vagud nerve |
| Some people use a ____ to control contractions | pacemaker |
| What causes ____ contractions that move from fundus to antrum? | myoelectric complex complex; wave-like |
| What is the release of chyme regulated by? | volume and osmolarity |
| Overall gastric emptying takes how long? | 2-6 hours |
| When chyme leaves the stomach it goes where? | through to the pyloric sphincter |
| The SI is the main site of what? | digestion and absoption |
| What are the sections of the small intestine? | duodenum jejunum ileum |
| What increases intestinal secretions and motility? | vasoactive intestinal polypeptide (VIP) neuropeptide substance P, Motlin, CCK |
| Where are vasoactive intestinal polypeptides found? | in neurons within the gut |
| What decreases intestinal secretions and motility? | PYY, secretin, glucagon-like peptides |
| What are the 2 tissues that help to protect the GI tract? | MALT (mucus) GALT (gut) |
| What is the pancreas? | ductless endocrine cells that secrete hormones into the blood |
| The pancreas contains what type of enzymes? | digestive that are produced by acinar exocrine cells |
| Pancreatic juices contain | bicarbonate electrolytes pancreatic digestive enzymes |
| Contractions of the SI | segmentation and peristaltic waves |
| Segmentation | alternating contractions of circular smooth muscles, which breaks down and mixes intestinal contents |
| Peristaltic waves | progressive contractions that move SI contents distally though the SI and toward the LI |
Created by:
starryeyes213
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