Enthalpies of Formation (Section)A pound of plain M&M®

Digestion and Nutrition Study Guide 1. What are the two groups of organs that compose the digestive tract What are the specific organs within those two groups  Gastrointestinal Tract o Digests and absorbs o Mouth o Pharynx o Esophagus o Stomach o Small intestine o Large intestine o Anus  Accessory digestive organs o Teeth o Tongue o Salivary glands o Liver o Gall bladder o Pancreas 2. Distinguish/define the following ingestion, motility, secretion, digestion, absorption, and elimination.  Ingestion: introduction of food into oral cavity  Motility: voluntary and involuntary muscle contractions; mixing and moving materials through the GI tract  Secretion: producing and releasing fluid products into the GI tract  Digestion: breakdown of ingested food into smaller structures (mechanical and chemical)  Absorption: passive and active transport of digested molecules, electrolytes, vitamins, and water from the GI tract to the blood or lymph  Elimination: expulsion of indigestible components 3. Explain the two GI tract regulatory mechanisms. Also distinguish between the submucosal nerve plexus and the myenteric nerve plexus.  Submucosal nerve plexus – regulates glands and smooth muscle in the mucosa  Myenteric nerve plexus – controls GI tract motility 4. Describe in detail the four basic tunics of the GI tract What is the function of each  Four basic tunics: o Mucosa  Lines the lumen  Functions:  Secretes mucus, digestive enzymes and hormones  Absorbs end products of digestion  Protects against infectious disease  Three sublayers: epithelium, lamina propria, and muscularis mucosae o Submucosa  Dense connective tissue  Blood and lymphatic vessels, lymphoid follicles, and submucosal nerve plexus o Muscularis externa  Responsible for segmentation and peristalsis  Inner circular and outer longitudinal layers  Myenteric nerve plexus  Sphincters in some regions o Serosa  Peritoneum: serous membrane of the abdominal cavity  Visceral peritoneum on external surface of most digestive organs  Parietal peritoneum lines the body wall  Peritoneal cavity  Between the two peritoneums  Fluid lubricates mobile organs  Mesentery is a double layer of peritoneum  Routes for blood vessels, lymphatics, and nerves  Holds organs in place and stores fat  Retroperitoneal organs lie posterior to the peritoneum  Intraperitoneal (peritoneal) organs are surrounded by the peritoneum 5. What are the roles of saliva Name and describe the three types of salivary glands. Also, describe the composition of saliva.  Roles of Saliva: o Cleanses the mouth o Moistens and dissolves food chemicals o Aids in bolus formation o Contains enzymes that begin the breakdown of starch  3 types of salivary glands: o Parotid gland  Anterior to the ear external to the masseter muscle  Parotid duct opens into the vestibule next to second upper molar o Submandibular gland  Medial to the body of the mandible  Duct opens at the base of the lingual frenulum o Sublingual gland  Anterior to the submandibular gland under the tongue  Opens via 10–12 ducts into the floor of the mouth 6. Briefly describe the structure and function of the esophagus.  Esophageal mucosa contains stratified squamous epithelium o Changes to simple columnar at the stomach  Esophageal glands in submucosa secrete mucus to aid in bolus movement  Muscularis: skeletal superiorly; smooth inferiorly  Adventitia instead of serosa 7. List and describe the phases of deglutination.  Voluntary: bolus of food moved by tongue from oral cavity to pharynx.  Pharyngeal: reflex. Controlled by swallowing center in medulla oblongata. Soft palate elevates, upper esophageal sphincter relaxes, elevated pharynx opens the esophagus, food pushed into esophagus by pharyngeal constrictors’ successive contraction from superior to inferior. Epiglottis is tipped posteriorly due to pressure of the bolus, larynx elevated to prevent food from passing into larynx.  Esophageal: reflex. Stretching of esophagus causes enteric NS to initiate peristalsis of muscles in the esophagus. 8. Describe the gross anatomy of the stomach.  ANS nerve supply o Sympathetic via splanchnic nerves and celiac plexus o Parasympathetic via vagus nerve  Blood supply o Celiac trunk o Veins of the hepatic portal system 9. What are the secretions of the stomach What are the gastric glands associated with stomach tissue What role/roles do these glands play in digestion  Secretions: o Chyme: ingested food plus stomach secretions o Mucus: surface and neck mucous cells  Viscous and alkaline  Protects from acidic chyme and enzyme pepsin  Irritation of stomach mucosa causes greater mucus o Intrinsic factor: parietal cells. Binds with vitamin B12 and helps it to be absorbed. B12 necessary for DNA synthesis o HCl: parietal cells  Kills bacteria  Stops carbohydrate digestion by inactivating salivary amylase  Denatures proteins  Helps convert pepsinogen to pepsin o Pepsinogen: packaged in zymogen granules released by exocytosis. Pepsin catalyzes breaking of covalent bonds in proteins  Gastric glands: o Mucous neck cells (secrete thin, acidic mucus) o Parietal cells  HCl   pH 1.5–3.5 denatures protein in food, activates pepsin, and kills many bacteria  Intrinsic factor  Glycoprotein required for absorption of vitami12B in small intestine o Chief cells  Inactive enzyme pepsinogen  Activated to pepsin by HCl and by pepsin itself (a positive feedback mechanism) o Enteroendocrine cells (G-cells)  Secrete chemical messengers into the lamina propria  Paracrines o Serotonin and histamine  Hormones o Somatostatin and gastrin - Glands in the fundus and body produce most of the gastric juice 10. Discuss the regulation of gastric secretions. What are the three phases of gastric secretion, and what happens during these phases  Neural and hormonal mechanisms  Three phases: 1. Cephalic (reflex) phase: few minutes prior to food entry 2. Gastric phase: 3–4 hours after food enters the stomach 3. Intestinal phase: brief stimulatory effect as partially digested food enters the duodenum, followed by inhibitory effects (enterogastric reflex and enterogastrones 11. How is HCL secreted by the stomach What chemicals are necessary for maximum HCL secretion Describe the formation of HCL in the stomach.  Secretion of HCl o Parasympathetic action potentials are carried by the vagus nerves to the stomach, where enteric plexus neurons are activated o Postganglionic neurons stimulate secretion by parietal and chief cells (HCl and pepsin) and stimulate the secretion of the hormone gastrin and histamine. o Gastrin is carried through the circulation back to the stomach where it and histamine stimulate further secretion of HCl and pepsin.  Chemicals necessary for max HCl secretion: Ach, Histamine, Gastrin  Formation of HCl: within the lumen of the gastric gland, Cl- combines with H+ to form HCl. 12. Describe the gross anatomy and histology of the small intestine.  Major organ of digestion and absorption. It is the site of greatest amount of digestion and absorption of nutrients and water.  Chyme from stomach contains o Partially digested carbohydrates and proteins o Undigested fats  2–4 m long; from pyloric sphincter to ileocecal valve  Subdivisions o Duodenum (retroperitoneal) o Jejunum (attached posteriorly by mesentery) o Ileum (attached posteriorly by mesentery) 13. What are villi, microvilli, and intestinal crypts What functions do these modifications provide  Villi o Motile fingerlike extensions (~1 mm high) of the mucosa o Villus epithelium  Simple columnar absorptive cells (enterocytes)  Goblet cells  Microvilli o Projections (brush border) of absorptive cells o Bear brush border enzymes  Intestinal crypt epithelium o Secretory cells that produce intestinal juice o Enteroendocrine cells o Intraepithelial lymphocytes (IELs)  Release cytokines that kill infected cells o Paneth cells  Secrete antimicrobial agents (defensins and lysozyme) 14. Describe the secretions of the small intestine.  Mucus from goblet cells o Protects against digestive enzymes and stomach acids  Digestive enzymes: bound to the membranes of the absorptive cells o Disaccharidases: Break down disaccharides to monosaccharides o Peptidases: Hydrolyze peptide bonds o Nucleases: Break down nucleic acids  Unicellular glands o Enteropeptidase (activates trypsin)  Duodenal glands o Protect duodenum from acidic chyme  Enteroendocrine cells o CCK and secretin 15. Briefly describe water absorption in the small intestine.  95% is absorbed in the small intestine by osmosis  Net osmosis occurs whenever a concentration gradient is established by active transport of solutes  Water uptake is coupled with solute uptake 16. What are the functions of the liver  Bile production: 600-1000 mL/day. Bile salts (bilirubin), cholesterol, fats, fat-soluble hormones, lecithin o Neutralizes and dilutes stomach acid o Bile salts emulsify fats. Most are reabsorbed in the ileum. o Secretin (from the duodenum) stimulates bile secretions, increasing water and bicarbonate ion content of the bile  Storage o Glycogen, fat, vitamins, copper and iron. Hepatic portal blood comes to liver from small intestine.  Nutrient interconversion o Amino acids to energy producing compounds o Hydroxylation of vitamin D. Vitamin D then travels to kidney where it is hydroxylated again into its active form  Detoxification o Hepatocytes remove ammonia and convert to urea  Phagocytosis o Kupffer cells phagocytize worn-out and dying red and white blood cells, some bacteria  Synthesis o Albumins, fibrinogen, globulins, heparin, clotting factors 17. Describe the microscopic anatomy of the liver. What do the hepatocytes do  Microscopic anatomy: o Liver lobules  Hexagonal structural and functional units  Filter and process nutrient-rich blood  Composed of plates of hepatocytes (liver cells)  Longitudinal central vein o Portal triad at each corner of lobule  Bile duct receives bile from bile canaliculi  Portal arteriole is a branch of the hepatic artery  Hepatic venule is a branch of the hepatic portal vein o Liver sinusoids are leaky capillaries between hepatic plates o Kupffer cells (hepatic macrophages) in liver sinusoids  Hepatocytes: o Process bloodborne nutrients o Store fat-soluble vitamins o Perform detoxification o Produce ~900 ml bile per day  Yellow-green, alkaline solution containing o Bile salts: cholesterol derivatives that function in fat emulsification and absorption o Bilirubin: pigment formed from heme o Cholesterol, neutral fats, phospholipids, and electrolytes 18. Describe the regulation of bile secretion. Pay careful attention to what hormones are involved.  Bile secretion is stimulated by o Bile salts in enterohepatic circulation o Secretin from intestinal cells exposed to HCl and fatty chyme  Gallbladder contraction is stimulated by o Cholecystokinin (CCK) from intestinal cells exposed to proteins and fat in chyme o Vagal stimulation (minor stimulus)  CKK also causes the hepatopancreatic sphincter to relax 19. Describe the exocrine function of the pancreas. Specifically, how is the secretion of pancreatic juice regulated.  Exocrine function o Acini (clusters of secretory cells) secrete pancreatic juice o Zymogen granules of secretory cells contain digestive enzymes  Regulation of Pancreatic Secretion o CCK induces the secretion of enzyme-rich pancreatic juice by acini o Secretin causes secretion of bicarbonate-rich pancreatic juice by duct cells o Vagal stimulation also causes release of pancreatic juice (minor stimulus) 20. What is pancreatic juice What enzymes inactive and active are found in pancreatic juice and what role do they play in digestion  Watery alkaline solution (pH 8) neutralizes chyme  Electrolytes (primarily H3O )  Enzymes o Amylase, lipases, nucleases are secreted in active form but require ions or bile for optimal activity o Proteases secreted in inactive form  Protease activation in duodenum o Trypsinogen is activated to trypsin by brush border enzyme enteropeptidase o Procarboxypeptidase and chymotrypsinogen are activated by trypsin 21. What are the unique features of the large intestine What are the parts of the colon  Unique features o Teniae coli  Three bands of longitudinal smooth muscle in the muscularis o Haustra  Pocketlike sacs caused by the tone of the teniae coli o Epiploic appendages  Fat-filled pouches of visceral peritoneum  Ascending colon and descending colon are retroperitoneal  Transverse colon and sigmoid colon are anchored via mesocolons (mesenteries) 22. Where do the bacteria that live in the large intestine come from What purposes do they serve  Bacterial Flora o Enter from the small intestine or anus  Colonize the colon  Ferment indigestible carbohydrates  Release irritating acids and gases  Synthesize B complex vitamins and vitamin K 23. What is the major function of the large intestine  Vitamins, water, and electrolytes are reclaimed  Major function is propulsion of feces toward the anus  Colon is not essential for life 24. Describe vitamin absorption in the small intestine and large intestine and the digestion of fats.  In large intestine o Vitamin K and B vitamins from bacterial metabolism are absorbed  In small intestine o Fat-soluble vitamins (A, D, E, and K) are carried by micelles and then diffuse into absorptive cells o Water-soluble vitamins (vitamin C and B vitamins) are absorbed by diffusion or by passive or active transporters. o Vitamin B12inds with intrinsic factor, and is absorbed by endocytosis 25. What role do carbohydrates, lipids, and proteins play in human health and nutrition  Carbohydrates o Carbohydrates are present in food in the form of sugars, starch, and fiber. o Major source of fuel for making ATP  Lipids o Fat, oils, and cholesterol o Saturated fatty acids (solids at room temperature) usually come from animals  Proteins o Adequate protein formation requires 20 different types of amino acids o 9 essential amino acids are required in the diet  Some foods, such as meat, milk, and eggs, provide all 9 (complete)  Vegetables supply some essential amino acids, but are usually deficient in at least one (incomplete) 26. What are vitamins and minerals What roles do the various vitamins and minerals play in human health and nutrition  Vitamins o Organic molecules that animals require in small amounts for normal cell function, growth, and development  Many vitamins are required for the proper functioning of enzymes that control metabolic reactions in the body  Vitamins are essential nutrients that the body cannot synthesize and must be obtained in the diet  They are grouped into two categories: water soluble or fat soluble  Minerals o Elements that play many crucial roles in animal nutrition and can only be obtained in the diet or dissolved in drinking water  Calcium, magnesium, and phosphorus are major constituents of bone and teeth  Sodium, calcium, and potassium are needed for muscle contraction and the conduction of nerve impulses  Iron is a central component of hemoglobin in the blood, and iodine is found in hormones produced by the thyroid gland  Humans also require trace amounts of zinc, magnesium, copper, and chromium