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Physiology Ch.
Digestive System
| Term | Definition |
|---|---|
| Parts of the GI tract | Oral cavity, pharynx, esophagus, stomach, SI, LI, and anus |
| Where does ingestion occur? | Oral cavity |
| Motility | Involuntary and voluntary muscle contraction that mixes and moves thru GI tract |
| Mechanical digestion | Chewing and mixing |
| Chemical digestion | Specific enzymes break chemical bonds |
| Alimentary canal | Name for GI tract, food and water propelled by muscular actin |
| 4 tunics of GI tract | Muscosa, submucosa, muscularis, serosa |
| Muscosa | Innermost tunic w/ simple columnar epith for secretion/absorption. Has lamina propia and muscularis mucosae. |
| Muscularis mucosae | Thin muscle layer that may move villi |
| Submucosa | Dense ct layer of GI tract w/ submucosal nerve plexus and Peyer patches. |
| Submucosal nerve plexus | Nerves and ganglia innervating smooth muscle and glands in submucosa of GI tract |
| Peyer patches | Large aggregates of lymphatic nodules in distal SI submucosa |
| Muscularis | 3rd layer of GI tract. Has circular layer and longitudinal layer of sm and a myenteric nerve plexus. |
| Circular layer of sm in muscularis function | Contracts to narrow lumen of GI tract |
| Longitudinal layer of sm in muscularis function | Contracts to shorten tube of GI tract |
| Myenteric nerve plexus | Lies between circular and longitudinal layers of muscularis tunic of GI that controls contractions. |
| Submucosal and myenteric nerve plexi | Major network of ganglia and interconnecting neurons that will respond to changes in pH |
| Mixing | "Backward and forward" motion without directional movement. Blends material |
| Propulsion | Directional movement along GI tract occurring by peristalsis |
| Mixing and propulsion occur due to contraction of ______ tunic of GI tract | Muscularis |
| Serosa | Protective layer of GI tract with adventitia (areolar outside of peritoneal cavity) and serosa (in peritoneal cavity) |
| Enteric nervous system (ENS) | Sensory and motor neurons within submucosal and myenteric plexi that coordinates mixing and propulsion |
| Parasympathetic nervous system ______ GI activity. | Promotes |
| Sympathetic nervous system ______ GI activity. | Opposes |
| Cells at base of microvilli are highly _______. | Mitotic |
| Oral cavity and salivary glands form _____. | Bolus |
| Pharynx function | Receives bolus from oral cavity by swallowing, which the pharynx secretes mucus to facilitate. |
| Esophogus | Connects pharynx to stomach and gives more mucus |
| Stomach function | Bolus is mixed by smooth muscle with gastric secretion to form chyme. |
| Oral cavity epithelium | Stratified squamous |
| Lips | Orbicularis oris muscle attached to mucosal fold in midline called labial frenulum |
| Labial frenulum | Mucosal fold connecting lips to face |
| Palate | Roof of oral cavity |
| Transverse palatine folds | Assist tongue in manipulating materials |
| Uvula | Closes off nasopharynx during swallowing |
| Tongue | Papillae for taste and attached to floor by lingual frenulum |
| Lingual frenulum | Attaches tongue to floor of oral cavity |
| Satiety center | Part of hypothalamus that causes sensation of satiety |
| Hunger center | Part of hypothalamus that increases appetite |
| Leptin | Hormone in hypothalamus that suppresses appetite long-term |
| Salivary amylase | Produced by salivary glands to begin chemical digestion of carbohydrates (starch) |
| Intrinsic salivary glands | In oral cavity, continuously secrete saliva regardless of food. Contains lingual lipase |
| Ligual lipase | Enzyme of intrinsic salivary glands that begins breakdown of fats |
| Extrinsic salivary glands | Outside oral cavity, produce the most saliva. |
| Parotid glands | Largest extrinsic salivary gland, Conduct saliva through parotid duct to cavity. Infection of this is called mumps |
| Infection of parotid glands is called ______. | Mumps |
| Submandibular glands | 60-70% of saliva production is through these extrinsic glands |
| Sublingual glands | Extrinsic salivary gland under tongue |
| Mucous cells | Secrete mucin that forms mucus at hydration |
| Functions of saliva | Moistens food to be bolus, contains salivary amylase and antibacterial factors (lysosome and IgA antibodies) |
| Salivary secretions are regulated by ______. | Brainstem |
| Parasympathetic nervous system _______ saliva production. | Increases |
| Sympathetic nervous system _______ viscous saliva production | Increases |
| Mastication | Chewing. Controlled by mastication center in medulla and pons |
| What controls chewing? | Mastication center in medulla and pons |
| Teeth | Dention. Has exposed crown and constricted neck with roots to anchor it in dental alveoli bound by periodontal ligament. |
| What are the skeletal muscle pairs of pharynx? | Superior, middle, and inferior pharyngeal constrictors |
| Pharynx epithelium | Nonkeratinized stratified squamous |
| Esophagus length | 20cm |
| There is no chemical or mechanical processes in the ______. | Esophagus |
| Esophageal hiatus | Opening in diaphragm that the esophagus passes through |
| Upper esophageal sphincter | CLOSED during inhalation, where pharynx meets esophagus |
| Lower esophageal sphincter | Is helped by diaphragm to stop regurgitation |
| Deglutition | Swallowing. Occurs in 3 phases: Voluntary phase, pharyngeal phase, and esophageal phase |
| Voluntary phase | Initiates swallowing process and occurs after ingestion. Controlled by cerebral cortex |
| Pharyngeal phase | INVOLUNTARY reflex in swallowing. Sensory receptors signal swallowing center in medulla to constrict effectors (pharyngeal constrictors) |
| Pharyngeal constrictors cause | Elevation of larynx by extrinsic muscles to move epiglottis to cover laryngeal opening |
| Esophageal phase | Also involuntary. Bolus goes into stomach |
| Stomach is located in the ______ quadrant. | Upper left |
| Stomach begins digestion of _____. | Protein and fat |
| The stomach has ____ layers of muscle which get ______ as they go down body. | 3 (longitudinal, circular, oblique), thicker |
| Four regions of the stomach | Cardia, fundus, body, and pylorus |
| Cardiac orifice | Where cardia of stomach meets esophagus |
| Pyloric orifice | Part of stomach that opens into duodenum via pyloric sphinctor |
| Rugae | Gastric folds that allow for stomach expansion. |
| Gastric pits | Dips between rugae of stomach that contains gastric glands. |
| Stomach epithelium | Simple columnar with lamina propia |
| Parietal cells | In gastric pits, secretes intrinsic factor for vitamin B12 and HCl acid. |
| Chief cells | In gastric pits, secretes pepsinogen and gastric lipase for fat digestion |
| Gastric lipase | Enzyme in stomach produced by chief cells to digest fat |
| G-cells | Enteroendocrine cell in gastric pit that is wayyyy down at the bottom that secretes gastrin into blood |
| Surface mucous cell | In gastric pits, secretes alkaline fluid with mucin |
| Mucous neck cell | In gastric pits, secretes acidic fluid with mucin |
| Gastric juice | Contains HCl acid, mucus, pepsin, pepsinogen, and intrinsic factor. NO GASTRIN |
| Gastric emptying | Chyme from stomach moving into duodenum |
| Retropulsion | After pyloric sphincter closes, the reverse flow of some contents back towards stomach |
| _______ cells establish basic rhythm of muscular contraction in the stomach. | Pacemaker |
| Stomach breaks down _______. | Proteins |
| Small intestine (SI) | Duodenum (part of upper GI), jejunum, ileum. Receives chyme from stomach, and is where most chemical digestion and absorption happen. |
| Liver | Accessory organ of GI tract that produces bile. In R upper quadrant under diaphragm and is covered by CT capsule and visceral peritoneum |
| Gallbladder | Accessory organ of GI that stores and concentrates bile from liver |
| Pancreas | Accessory organ of GI that secretes pancreatic juice with digestive enzymes |
| Large Intestine (LI) | Primarily absorbs water, electrolytes, and some vitamins. Where feces is produced |
| Duodenum | Part of SI that receives excretions from all accessory organs |
| Duodenojejunal flexure | Where duodenum connects to jejunum |
| Jejunum | SI part that is peritoneal. Is primary region for digestion |
| Ileum | SI part that terminates at ileocecal valve with sphincter |
| SI contains _____ to slow down chyme, _____ that is most numerous in jejunum, and _____. | Circular folds, villi, lacteal |
| Lacteal | Lymphatic capillary in villus of SI that absorbs lipids |
| Intestinal crypts | Bottoms between villi in SI |
| Microvilli | Increases S.A. of SI. Has microscopic brush border containing brush border enzymes to aid digestion. Transport proteins for digestive products are also embedded here. |
| _________ muscles move villi back and forth to expose _____ epithelium surfaces in SI. | Muscularis, simple cuboidal |
| Segmentation | Back and forth movement in SI to mix chyme with accessory excretions |
| S-cells | In mucosa of duodenum that respond to pH of chyme by releasing secretin into blood |
| Secretin | Produced by S-cells of duodenum, travel to pancreas to cause digestive enzymes to be released into SI. Is released in response to increased chyme acidity and causes release of alkaline solution with bicarb in it from liver and pancreatic ducts. |
| I-cells | Respond to proteins and lipids in SI by releasing cholecystokinin (CCK), which makes pancreas work and promotes gallbladder to release bile |
| Plicae circularis | Circular folds in mucosa and submucosa of SI |
| Intestinal lands | In SI, secrete intestinal juice. Are in mucosa between villi |
| Goblet cells | Cells in SI that produce mucin. Increases in number from duodenum to ileum |
| _______ cells in SI initiate contractions of smooth muscle via _____. | Pacemaker, gap junctions |
| Migrating motility complex (MMC) | Successful waves of contractions made by pacemaker cells of SI |
| Gastroileal reflex | Where ileum contracts, sphincter relaxes (CCK helps), and moves contents into cecum in response to food in stomach. |
| Exocrine function of pancreas | Digestive enzymes and bicarbonate (HCO3-) released to neutralize pH of chyme from stomach |
| Bile | Contains bicarbonate, cholesterol, phospholipids, pigments, and salts. |
| Biliary apparatus | Network of ducts draining L&R lobes of liver: L&R hepatic ducts merge to form single common hepatic duct, which merges with cystic duct from gallbladder to make common bile duct that feeds duodenum |
| ______ are the only organs not inside peritoneal cavity. | Kidneys |
| Accessary pancreatic duct | Allows small amount of pancreatic juice into duodenum. Penetrates duodenum at minor duodenal papilla |
| Minor duodenal papilla | Where accessary pancreatic duct enters duodenum |
| Hepatopancreatic ampulla | At posterior duodenal wall where common bile duct and main pancreatic duct enter duodenum |
| Major duodenal papilla | Projection in duodenum where duct penetrates wall. Both bile and pancreatic juice enter here |
| Heptopancreatic sphinter | Regulates movement of bile and pancreatic juice into duodenum |
| R lobe of liver is ____ than the L. There are ____ lobes total in liver. | Larger, 4 |
| Round ligament | Remnant of umbilical vein and edge of falciform ligament. Attached to liver. |
| _____ and _____ lobes are in the R lobe of the liver. | Quadrate, cuadate |
| Vein that drains liver posteriorly | Inferior vena cava |
| Perta hepatis | Where blood, lymph vessels, bile ducts, and nerves enter and leave liver. Hepatic portal vein. |
| Hepatic lobules | Functional unit of liver separates by septa. Contain hepatocytes |
| Portal triads | At periphery of each lobule in liver. Hepatic artery + portal vein (perta hepatis) + bile duct |
| Central vein | At center of each lobule in liver. Merge to form hepatic veins. Blood gets to these from portal triads through hepatic sinusoids |
| Hepatic sinusoids | Where blood goes through portal triads into the central vein of liver |
| Hepatic artery | Branch of celiac trunk that feeds liver |
| Hepatic portal vein | Carries deoxyed blood from capillaries of GI, spleen, and pancreas. Mixes blood as passing through hepatic lobules |
| Hepatic veins | Enter into inferior vena cava |
| Stellate cells (Kupfter cells) | Macrophages that clear harmful substances from blood as it travels through hepatic sinusoids |
| ____ and _____ help mechanically digest lipids in pancreas. | Bile salts, lecithin |
| Blood from portal vein and hepatic artery percolate around _____ via ____ before entering central vein -> _____ -> ______. | Hepatocytes, sinusoids, hepatic vein, inferior vena cava |
| _____ of liver blood supply is through portal vein. | 80% |
| _____ of liver blood supply is via hepatic artery. | 20% |
| Cystic duct | Connects gallbladder to common bile duct. Also has sphincter |
| Pancreas endocrine function | Produces insulin to lower blood glucose and glucagon to raise it. |
| Insulin | Produces by pancreas to lower blood glucose |
| Glucagon | Produced by pancreas to raise blood glucose |
| Pancreas has a wide _____ adjacent to the _______'s curvature. | Head, duodenum |
| Pancreas has a central enlarged ____ projecting towards L lateral wall. | Body |
| Pancreas has ____ with tapers as it approaches spleen. | Tail |
| Acinar cells | In pancreas, are modified simple cuboidal epith that produce digestive enzymes. Arranged in saclike acini and organized in large clusters called lobules. |
| Lobules of pancreas | Large clusters of acini |
| Acini | Saclike groups of acinar cells |
| Pancreatic juice | Formed from secretions of acinar and pancreatic duct cells. Alkaline fluid of mostly water, bicarbonate, and digestive enzymes |
| Cholecystokinin (CCK) | Hormone from SI in response to fatty chyme that stimulates release of bile and pancreatic juice, inhibits stomach motility and relaxes sm in hepatopancreatic ampulla. |
| Cecum | First portion of LI. Intraperitoneal and extends from ileocecal valve. In lower R quadrant |
| Vermiform appendix | Sac projecting from cecum lined by lymphatic nodules. May contain good bacteria |
| Colon | 2nd part of LI forming inverted U with 4 sections (Ascending, transverse, descending, sigmoid) |
| Ascending colon | Retroperitoneal, connects to cecum. Has 90 degree L turn as approaches liver called R colic flexure |
| R colic flexure (Hepatic flexure) | 90 degree L turn of ascending colon to transverse colon |
| Transverse colon | Starts at R colic flexure, interperitoneal and ends of 90 degree downward turn called L colic flexure |
| L colic flexure (Splenic flexure) | Downward 90 degree turn from transverse colon to descending colon |
| Descending colon | Retroperitoneal on L side. Descends vertically |
| Sigmoid colon | Originates at sigmoid flexure and terminates at rectum. |
| Sigmoid flexure | Connects descending colon to sigmoid colon |
| Anal canal epithelium | Stratified squamous |
| Anal columns | Longitudinal ridges of anal canal |
| Anal sinuses | Depressions between anal columns to release mucus when pressure is asserted |
| Internal anal sphincter | Involuntary smooth muscle at base of anal canal |
| External anal sphincter | Voluntary skeletal muscle that relaxes during defication |
| No chemical processes that benefits humans occurs in the ______. | Large intestine |
| Teniae coli | Thin longitudinal bundles of sm that act like elastic in a waistband to bind LI into sacs (haustra) |
| Haustra | Sacs that make up LI |
| Omental appendices | Lobules of fat hanging off external surface of haustra of LI |
| LI has: | Mucosa with simple columnar epith, NO villi, and lots of intestinal glands to secrete mucin |
| Muscularis of cecum and colon have ___ layers of sm (and what are they). | 2; outer longitudinal and discontinuous that forms teniae coli) |
| Peristalsis in LI is ____ and ____. | Slow, sluggish |
| Haustral contractions | As LI is filled with material so that it distends, contracts to move it all to the next haustra. Slow and segmental, and increases churning when contracted |
| Mass movements | Powerful contractions involving teniae coli occurring during/just after eating. Bulk/fiber increases this. |
| Gastrocolic reflex | Initiates by stomach distention and causes mass movement |
| Defecation reflex | Filling of rectum stimulates urge to defecate. Signals spinal cord -> greater parasym output to sigmoid colon and rectum and lower output of internal anal sphincter (relaxes) |
| Feces | Final product of bacteria in LI. Contains H2O salts, epithelial cells, bacteria, undigested material |
| Monosaccharides | Glucose and fructose |
| Disaccharides | Sucrose and maltose |
| Polysaccharides | Starch and cellulose |
| Carbohydrates are digested mainly in: | Oral cavity (salivary amylase) and SI (pancreatic amylase and brush border enzymes) |
| Digestion of starch | Brush border enzymes dextranase and glucoamylase break bonds between glucose. |
| Enzymes to digest disaccharides are named for what they digest. Example | Lactase -> lactose to glucose. Lactose intolerant people have reduces lactase |
| Protein digestion | Stomach: Pepsin SI: trypsinogen, chymotrypsinogen, procarboxypeptidase (all 3 from pancreas) and enteropeptidase |
| Stomachs ____ pH from HCl of ____ cells denature proteins and converts _____ into ____. | Low, parietal, pepsinogen, pepsin |
| Trypsin | Activates chymotrypsinogen to chymotrypsin and procarboxypeptidase to carboxypeptidase |
| Carboxypeptidase | Breaks bond between amino acid w/ carboxyl group and remaining protein |
| Dipeptidase | Breaks final bond between 2 amino acids (in SI) |
| Aminopeptidase | Generates free animo acids to be absorbed across epithelial of SI |
| Lipid digestion | Stomach: lingual lipase and gastric lipase digest 30% of triglycerides w/o bile salts SI: Pancreatic lipase |
| Lingual lipase | Component of saliva that is activated in stomach to digest lipids |
| Gastric lipase | Produces by chief cells in stomach to digest lipids |
| Pancreatic lipase | Released into duodenum by pancreas to digest triglycerides. Requires emulsification to work. |
| Emulsification | Separation of large lipid droplets into smaller ones. Occurs via bile salts (which have polar head and nonpolar tail), which surrounds lipid molecules to form micelle |
| Micelle | Lipid droplets surrounded by amphipathic bile salts |
| Lipid absorption | Micelles move lipids to simple columnar epith to enter cells. In epith cells, triglycerides are reformed and wrapped in protein to become chylomicrons and released by exocytosis to enter blood to deliver to liver or lacteals. |
| Chylomicrons | Reformed lipids wrapped in proteins that form during absorption of lipids into blood |
| Deoxyribonuclease | Enzyme to digest DNA |
| Ribonuclease | Enzyme to digest RNA |
| Phosphatase | Brush border enzyme that breaks bonds to phosphate in nucleic acid for digestion |
| Nucleosidase | Brush border enzyme that breaks bonds between sugar and nitrogenous base in nucleic acid for digestion |
| _____ is the location of most water, electrolyte, and vitamin absorption from diet. | Small intestine |
| Water absorption | SI absorbs almost all. LI absorbs some, and any left gets passed in feces. |
| Electrolyte absorption | SI absorbs almost. Iron is controlled by liver chemical hepcidin. |
| Iron has ______ absorption with _____ from liver to ______ it. | Controlled, hepcidin, inhibit |
| Vitamin absorption | B12 needs intrinsic factor from parietal cells. Fat soluble goes with micelles and water soluble absorbs via diffusion/active transport in SI. |
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