Term
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Definition
| to ingest food and water, swallow and digest it, absorb the water and nurtitive substances, expel solid wastes; including secretion, barrier, and immunologic protection (from mucosa) |
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Term
| characteristics of oral cavity |
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Definition
| 1. receives food which it chews; 2. the food is moistened and acting upon by enzymes to begin process of digestion |
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Term
| organs part of oral cavity |
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Definition
| cheeks, lips, tongue, gums, teeth, tonsils, hard and soft palate, and minor and major salivary glands |
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Term
| four basic layers of tubular GI tract |
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Definition
| 1. mucosa-epithelial lining, an underlying CT (lamina propria), and a muscularis mucosa of smooth muscle; 2. submucosa-loosely arranged but coarse fibered fibroelastic CT; 3. muscularis externa-consisiting of smooth or skeletal muscule usually as inner circular and outer longitudinal arrangement; 4. fibrosa of CT or serosa of mesothelium and underlying CT |
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Term
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Definition
| lined by stratified squamous epithelium and mucosa also has lamina propria of loose CT with minor salivary glands; since some surfaces are subjected to abrasion by foods some parts maybe keratinized (gingiva and hard palate, or tongue) |
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Term
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Definition
| produce secretory products for dry food from lingual, palatal, buccal glands; lymphatic tissue also is abundant and procides a defense against infection (diffuse in nodules and tonsils) |
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Term
| function and structure of the lips |
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Definition
| used for eating, drinking, and talking; skin covering the external aspect has thin epidermis and contains hair follicles continuous with highly vascularized vermillion zone which is continuous with the inner or labial mucosa of the oral cavity which is continous with the gingival mucosa |
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Term
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Definition
| is translucent, partially keratinized, sensitive, stratified squamous epithelium appears red and warm due to tall vascular dermal papillae; has lack of glandular substance and subject to dryness |
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Term
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Definition
| lined by stratified squamous non-keratinized epithelium which closely interdigitates with underlying CT; kept moist by continuous secretion from minor salivary glands and intermittent secretions from major salivary glands (parotid, submandibular, and sublingual-secrete only on mechanical, thermal, or chemical stimuli) |
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Term
| function and structure of teeth |
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Definition
| derived from oral mucous membrane for tearing and grinding food; anatomic crown-projects about the gingiva or gum; root-fits into bony socket located in the maxilla or mandible; crown and root meet in the middle or the neck and each tooth contains a cavity called the pulp chamber and communicates witht he peridontal membrane (ligament) through the apical foramen |
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Term
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Definition
| made up of dentin, enamel, and cemuntum and in the pulp chamber contains the CT, blood vessels, and nerves) |
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Term
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Definition
| made up of small amount of organic material which is primarily GAG-protein complexes and a larger amount of inorganic material hydroxyapatite crystals; odontoblasts generate dentin and located in pulp canal and do not become trapped in dentin |
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Term
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Definition
| covers the dentin of the crown of the tooth; protein matrix produced by the ameloblasts prior to eruption of the tooth |
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Term
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Definition
| covers the root of the tooth and most resembles bone; organic matrix produced by centocytes and are embedded in the apical cemtentum and continue to form after eruption in lacunae |
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Term
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Definition
| basic secretory unit of salivary glands include acinus, intercalated duct, excretory duct |
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Term
| structue of salivary glands |
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Definition
| 1. the secretory portion can either be sac-like (acinar/alveolar) or tubular or can be intermediate; 2. excretory duct can be compound-branched duct system or simple-unbranched system |
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Term
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Definition
| arise from epithelium, the cells dedifferentiate and proliferate from signals from the mesenchymal cells, the cells grow down into modified mesenchymal cells and differentiate into duct and secretory cells, |
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Term
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Definition
| pyramidal in shape, broad base rests on basal lamina and narrow apical surface, short microvilli, protein secreting cells, joined by zonulae occludentes, adherentes, desmesosome and gap junctions form acinus with lumen in center |
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Term
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Definition
| cubodial to columnar, nuclei oval and pressed toward base of the cell, organized as tubules surrounding a lumen, produce mucous and organized as tubule may have cap of serous cells (seroud demi-lune) |
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Term
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Definition
| surrounds serous and mucous cells and contract to expel contents into ducts and into the oral cavity; jammed between epithelial cells and basal lamina; cytoplasm filled with actin, specialized type of SMC |
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Term
| path of secretory products |
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Definition
| emptied into intercalated ducts lined by cubodial cells-narrow in diameter connect acini to striated ducts; intercalated ducts join to form intralobular duct called striated duct characterized by infoldings of basal membrane with numerous mitochondira transporting water and ions; drain into larger ducts lying within the CT between lobules called interlobular ducts(psuedostratified columnar epithelium) and empty into lobar duct (stratified columnar) |
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Term
| active process of secretion |
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Definition
| calcium is released from RER after stimulation and opens K and Cl channels; once K released compensatory uptake of Na and Cl occurs-Cl exits the cell and Na enters resulting in flux of water into the lumen forming in isotonic primary saliva; in striated duct Na and CL are reabsorbed and saliva becomes hypoosmotic |
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Term
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Definition
| serine protease secreted by epithelial cells of striated duct processes many proteins in the saliva; and plasma cells secrete IgA imparting antimicrobial activity to salivary secretions and HCO3- primary buffering agent |
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Term
| characteristics of major glands |
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Definition
| parotid-tubuloalveolar glands and serous ascini; submandibular gland-mixed but mostly serous; sublingual-mixed but mostly mucous |
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Term
| function of salivary glands |
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Definition
| protection as fluid lubricant, contains IgGs and Ca binding proteins; buffering-HCO3- and PO4- and saline maintain pH; digestion-moistens bolus of food contains amylase and lingual lipase; taste-solubilizes molecules to be sensed by taste buds; antimicrobial and tooth integrity |
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Term
| function and structue of tongue |
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Definition
| involved in speech, manipulation of food and in tasting; dorsal surface subdivided into anterior two-thirds populated by three major types of paillae and posterior one third that houses lingual tonsils seperated by V-shaped depression |
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Term
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Definition
| short and conical in shape and highly keratinized (anterior dorsal surface) |
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Term
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Definition
| mushroom shaped and their epithelia house a few taste buds and are not keratinized (dorsal surface) |
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Term
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Definition
| not keratinized and 6-12 in number very large and are depressed into the surface of the tongue and surrounded by a moat-like trough-contain taste buds (anterior to sulcus terminalis) |
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Term
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Definition
| muscular organ, covered by oral mucosa and supported by a mass of interlacing bundles of skeletal muscle; suface mucous membrane firmly bound to the underlying skeletal muscle by the lamina propria; undersurface of the tongue is not keratinized, numerous mucous glands and rich supply of blood vessels |
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Term
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Definition
| intraepithelial structures composed of 40-70 cells, basal cells, and neuroepithelial cells and sustentacular cells; perception of taste sensations (5 tastes); large microvilli project from surface into taste pore where they can respond to the taste ligands and are transmitted to sensory fibers that are wrapeed around the neuroepithelial cells relayed to CNS |
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Term
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Definition
| posterior region of tongue organs of lymphoid tissue and palatine tonsils are prominent accumulations of lymphoid tissue lateral to the tongue; one of first organs of defense against organisms invading through the oral cavity; overlying epithelium invaginates to form deep crypts lined by stratified squamous epithelium; lymph is not filtered through them maybe involved in antigen recognition by B-cells and production of antobodies and are distributed through efferent lymphatics |
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Term
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Definition
| has an oral and nasal surface used in talking, breathing, and swallowing; skeletal muscle core surrounded by a mucosa; on nasal side-pseduostratified ciliated columnar epithelium with mixed glands and on the oral side a stratified squamous epithelium with mucous glands |
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Term
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Definition
| upper part is respiratory, middle is oral, and lower is laryngeal; upper part resembles respiratory system while lower part corresponds to the digestive system; epiglottis shuts off the aperture of the larynx during deglutition and structural adaptation of the pharynx is muscle and elastic tissue to move food along and avoid over distension |
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Term
| characteristics of pharynx |
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Definition
| mucosa consists of wet stratified squamous epithelium supported by a lamina propria rich in elastic fibers; in submucosal CT there are occasional seromucous glands which may extend into the muscle |
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Term
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Definition
| 1. mucosa-epithelium, lamina propria, and muscularis mucosae; 2. submucosa-loose/dense collagenous tissue that supports the overlying mucosa and contains BVs, lymphatics, and nerves; 3. muscularis externa-thick layer of smooth muscle which contains inner circular and outer longitudinal layer; 4. serosa/adeventitia-adeventitia where GI tract is attched to the abdominal or pelvic wall and serosa where gut lies freely within the abdominal cavity |
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Term
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Definition
| links the pharynx to the stomach contractions of the muscularis propels food down the esophagus; mucosal and submucosal glands lubricate and serious secretion has a antibacterial function |
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Term
| sphincters of the esophagus |
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Definition
| 1. upper-participate in swallowing; 2. lower-prevents in reflux of gastric contents |
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Term
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Definition
| 1. mucosa-nonkeratinized stratified squamous; thick muscularis mucosa and some mucous glands; 2. submucosa-coarse irregular CT, some mucous glands, submucosal nerve plexi (Meissner's); 3. muscularis externa-upper third skeletal muscle and lower third inner circular and outer longitudinal smooth muscle and middle third mixed skeletal and smooth muscle with myenteric plexi between muscle layers; 4. adeventitia/serosa-mostly fibrosa except for lowest 1 inch where it has serosa |
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Term
| epithelia changes from esophagus to stomach |
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Definition
| goes from stratified squamous epithelium to simple columnar epithelium |
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Term
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Definition
| production of gastric juice (pepsin, HCl, rennin, intrinsic factor, hormones, and mucous); mixing and storing of food and slight absorption |
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Term
| modification of general plan in stomach |
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Definition
| lining thrown into longitudinal folds called rugae (mucosa+submucosa); throughout the stomach lining it indents into the mucosa forming gastric pits |
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Term
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Definition
| and gastric glands occupy varying thickness of the gastric mucosa; glands divided into regions of isthmus to the neck and which extends into the base; cell types include surface mucous, mucous neck, parietal, chief, neuroendocrine, and stem cells |
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Term
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Definition
| narrow band between esophagus and stomach proper; glands are tubular and coiled in their terminal region cells produce mucous and lysozyme and HCL-producing parietal cells and length of pits are about equal to length of glands |
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Term
| fundus and body of stomach |
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Definition
| have shorter pits and longer glands; neck of glands consists of stem, mucous neck, and pareital cells and the base of the glands consist of parietal, chief, and enteroendocrine cells |
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Term
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Definition
| has deep pits and short coiled glands which secrete mucous, lysozyme, gastrin and somatostatin |
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Term
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Definition
| lined by simple tall columnar epithelium and nuclei are displaced to the basal surface and most of the cytoplasm is occupied by mucigen granules which give rise to layer of mucus that lubricates and protects the mucosa; only small amount of alchohol and aspirin can be absorbed by cells and between cells; renewed about every three days |
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Term
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Definition
| simple cubodial that line lumen of lower half of gastric gland; filled with coarse granules and contain pepsinogen the precursor to pepsin converted in the acid environment of the stomach; also make lipase |
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Term
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Definition
| present in mainly upper half of the glands and sometimes in the base; can be binucleate and nuclei can be large have abundent mitochonria and secretory caniculi (trenchlike invaginations of apical membrane lined with microvilli); secretion of HCl believe to occur here; basolateral membrane has receptors for histamine, gastrin, and ACh all which stimulate secretion of H+ into lumen and bicarb into interstitium; also secrete intrinsic factor |
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Term
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Definition
| fenestrated capillaries around the gastric glands facilitate bicarb delivery to protect the surface epithelial cells |
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Term
| enteroendocrine (APUD) cells |
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Definition
| peptide-producing and secreting cells that are identified based on differences in reaction to various stains; anatomically disperesed and receive local signal from the along the GI tract and send chemical messages to distant target cells found at the bases of glands |
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Term
| small intestine specializations |
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Definition
| increase SA exposed to the lumen and include 1. plicae circulares-cresentic folds involving mucosa and submucosa; 2. villi-minute fingerlike projections of mucosa; 3. innumerable crypts of Lieberkuhn-intestinal mucosal glands open into lumen at bases of villi; 4. microvilli-apical surface of cells |
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Term
| motility of small intestine |
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Definition
| controlled by ANS consists of plexuses and neurons of plexuses receive intrinsic input from the mucosa and muscle wall of the SI and extrinsic input from the CNS through PNS and SNS; contraction is coordinated to mix and mobilize contents within the intestinal segment (segmentation) and propel the intestinal contents where there is a proximal ordad contraction coordinated with a distal relaxation (peristalsis) |
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Term
| epithelium of small intestine |
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Definition
| simple columnar epithelium with an absorptive cell with a striated brush border of microvilli; goblet cells; and enteroendocrine cells-secrete secretin and CCK upon stimulation by chyme which promote pacreatic exocrine secretion and contraction of the bile duct |
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Term
| brush border of microville |
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Definition
| contain intramembraneous enzymes including lactase, maltase, and sucrase which reduce carbs to hexoses which can be transported into enterocytes |
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Term
| mechanism of absorption in small intestine |
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Definition
| take place intracellularly through lining cells so goes through transcellular route and not paracellular route |
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Term
| digestive enzymes in lumen of the small intestine |
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Definition
| pancreatic juice contributes lipase, trypsinogen, chymotrypsinogen, amylase, and lipase and contains HCO3 so it is alkaline to neutralize acid of chyme; bile acids from gall bladder help emulsify fats |
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Term
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Definition
| micelles of FAs and monoglycerides pass through apical cell membrane of absorptive cells and pass to SER; chylomicrons formed in SER by reesterfication of FAs to TGs and these pass to lacteals |
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Term
| blood circulation in small intestine |
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Definition
| arteries in serosa break up into large branches that penetrate muscularis externa and enter submucosal layer forming a large plexus these give off branches to supply villi and the crypts |
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Term
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Definition
| several types of cells 1. undifferentiated cells at the base of crypt divide and completely replace lining cells; 2. enteroendocrine cells; 3. goblet cells; 4. paneth cells located deep in the glands contain acidophilic granules which thought to contain anti-bacterial enzyme, lysozyme |
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Term
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Definition
| has mucosa, submucosa, muscularlis externa and serosa; in submucosa glands of Brunner secreting alkaline or neutral mucous with bicarb content to neutrilize acidic chyme and protect duodenal mucosa from auto digestion also secrete lysozyme and IgA (in response to feeding and PNS |
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Term
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Definition
| villi are long and glands stain dark and muscularis mucosae is quite thin; similar to duodenum except for no Brunner's glands |
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Term
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Definition
| entire thickness has plicae circularis and have Peyer's patches which are groups of many lymphatic nodules massed together |
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Term
| lymphatic nodules in GI tract |
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Definition
| appears as organized cellular aggregates have many B lymphocytes and internodular areas have mostly Tlymphocytes |
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Term
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Definition
| are lined by follicle associated epithelium consisting of M cells and enterocytes; germinal center contains IgA positive B cells, Tcells and antigen presenting cells; M cells and FAE sample the antigen from the lumen of small intestine and transport the antigens to dendritic cells or macrophage in the lamina propria; dendritic cells make way to lymph node to present antigen to T helper cell and antibodies enter circulation |
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Term
| targets of enteric nervous system |
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Definition
| smooth muscle cells, mucosal secretory cells, GI endocrine cells, microvasculature, and immunomodulatory and inflammatory cells |
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Term
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Definition
| collection of neurons in the GI tract forming a network that can control the gut independently from CNS; arise from neural crest; consists of small interconnected ganglia (submucosal and myenteric plexuses) extending entire length of the gut; PNS is excitatory and SNS is inhibitory |
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Term
| large intestine functions |
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Definition
| functions in water absorption and lubrication of feces, minor food absorption |
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Term
| modifications of general plan in large intestine |
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Definition
| mucosa-no villi but does contain crypts of Lieberkuhn and epithelial lining cells are absorptive and secretory more goblet cells are found and less paneth cells; muscularis externa-outer longitudinal smooth muscle layer is thickened as three longitudinally-running bands (taenia coli) and inner circular muscular layer is present; a serosa is present on surface the abdominal cavity and fibrosa is present on surface attached to the body wall |
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Term
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Definition
| blind extension of the colon and apex of embryonic cecum and thickened by extensive development of lymphoid tissue; villi are absent; epithelium contains few goblet cells and consists mostly of columnar cells infiltrated by lymphatic tissue |
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Term
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Definition
| terminal part of the intestinal tract has a thick mucosa with prominent veins and long crypt of liberkuhn and line predominently with goblet cells; in terminal rectum there are few simple tubular glands with simple columnar epithelial lining-changes to stratified epithelium lining the anal canal and mucosa of anal canal characterized by 8-10 longitudinal anal columns connected to valves and sinuses which prevent leakage from the anus |
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Term
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Definition
| motility pattern responsible for efficient delivery of food from mouth to stomach; involves integration and coordination of motor activity of oropharynx, upper esophageal sphincter, esophageal body, and lower esophageal sphincter |
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Term
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Definition
| bolus formation, pharyngeal clearance and protects airway |
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Term
| upper esophageal sphincter |
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Definition
| anatomical sphincter comprised of tonically contracted group of skeletal muscles seperating pharynz from the esophagus; major cricopharyngeus muscle and portions of inferior constrictor muscles and muscles of proximal esophagus; relaxes with swallowing and between serves as protective function to prevent reflux into airway |
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Term
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Definition
| muscular tube 20-25 cm in length; upper 1/3 is skeletal muscle and caudal one-half of the esophagus is smooth muscle; contraction of inner circular muscular layer produces peristaltic contraction leading to esophageal clearance of food |
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Term
| lower espohageal sphincter |
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Definition
| physiological sphincter relaxes during a swallow and between swallows the protective function limits the refluc of gastric contents |
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Term
| CNS control of swallowing |
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Definition
| resides in pontine-medullary swallowing center and the ENS can modify or amplify input from the CNS and sometimes independent of CNS |
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Term
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Definition
| contraction of mylohyoid muscle lifts back the tongue resulting in peristaltic contraction that propels food bolus into pharynx; elevation of soft palate prevents regurgitation of food in nasal passages and closure of tracheal inlets prevents aspiration of food material into the lungs; initiated voluntarily or involuntarily depends on V,VII and XII |
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Term
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Definition
| complex motor event activated by swallowing center; propulsion of food into proximal esophagus due to superior, middle, inferior constrictor muscles and larynx is displaced forward which relaxes UES (cricopharyngeus muscles); lasts about one sec and ends with downward displacement of larynx contraction of UES and resumption of respiration (pressures can reach 180mmHg) |
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Term
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Definition
| complex event characterized by sequential activation of the esophageal musculature and LES relaxation; propulsion results from contraction above and relaxation below (relaxtion is descending inhibition) |
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Term
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Definition
| esophageal perstaltic event that is preceded by the pharyhgeal phase of swallowing; velocity and force of contraction varies and depends on age, volume and temp of food (transit time 3-9 seconds); genesis of peristaltic event is efferent input from nucleus ambiguous (skeletal muscle) and dorsal motor nucleus (smooth muscle) of the vagus |
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Term
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Definition
| esophageal peristaltic event that occurs in the absence of an oral-pharyngeal phase; results from distension/irritation of smooth muscle portion of the esophagus and mediated by local reflexes in the ENS; not sensed by patient |
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Term
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Definition
| precedes the arrival of bolus to the distal esophagus and occurs in response to both primary and secondary espophageal perstalsis; genesis of high-pressure zone appears as result of inherent (myogenic) contraction of smooth muscle also partly the result of excitatory ACh input |
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Term
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Definition
| transient relaxation of the gastric fundus that accompanies primary and secondary esophageal peristalsis occuring almost simultaneously with LES relaxation |
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Term
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Definition
| initiated voluntarily or reflexively and once inititated proceeds as ccoordinated involuntary reflex; coordination of sensory input integrates within the reticular formation of the brainstem and outflow from brainstem to vagal and nonvagal nuclei mediates oral, pharyngeal, and esophageal phases of swallowing and other autonomic functions |
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Term
| afferent impulses from oropharynx |
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Definition
| travel via cranial nerves V, IX, and X to respective nuclei in brainstem |
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Term
| efferenct impulses from extravagal nuclei and nuclus ambiguous |
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Definition
| travel via nerves V, VII, IX, X, and XII and result in sequential activation of pharyngeal musculature |
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Term
| control of primary peristalsis |
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Definition
| initiated by efferent impulses from the nucleus ambiguous and dorsal motor nuclei of vagal nerve; somatic motor nerves from nucleus ambiguous activate skeletal portion of esophagus and ACh released; visceral motor efferent fibers from dorsal motor nuclei synapse on ganglion cells of ENS which innervate smooth muscle cells of the ENS and smooth muscle activation involves simultaneous release of excitatory (ACh) and inhibitory (VIP/NO) neurotransmitters from enteric neurons-ratio of excitatory to inhibtory transmitter decreases in proximal to distal direction and high inhibitory transmitter at the distal direction and LES explains relaxation of sphincter prior to arrival of food bolus |
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Term
| control of secondary peristalsis |
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Definition
| distension/irritation os smooth muscle region of esophageal body produces a peristaltic event which begins at site of stimulation and proceeds aborally accompanied by simultaneous LES relaxation; result of activation of chemoreceptors and mechanoreceptors that activate the ENS to produce a locally mediated reflex |
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Term
| transient lower esphageal relaxation |
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Definition
| LES relaxation occurs in absence of primary or secondary peristalsis but it is incomplete; origin uncertain and alteration may contribute to development of gastroesophageal reflux disease |
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Term
| major functions of the stomach |
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Definition
| begin digestion process; store ingested liquid and solid foods; reduce particle size (trituration); slowly empty partially digested meal into proximal intestine |
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Term
| reservior function of gastric motility |
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Definition
| upper portion of stomach lacks perstaltic motor activity but exhibits low resting pressure; food tends to accumulate in upper stomach w/o significant increase in intragastric pressure; accomodation is result of high compliance of upper stomach and vagally mediated inhibitory reflexes |
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Term
| trituration function of gastric motility |
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Definition
| lower part of stomach displays rhythmical, phasic peristaltic contractions designed to mix food with gastric secretions, to propel food towards the gastroduodenal junction and physically grind large particles into small particles |
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Term
| emptying function of gastric motility |
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Definition
| highly regulated process designed to ensure appropriate small intestine environment for disgestion and absorption; rate of gastric emptying regulated by small intestinal reflexes activated by physical and chemical composition of food in small intestion |
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Term
| basic generalities relate to pattern of emptying of a mixedmeal |
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Definition
| 1. liquids empty more rapidly than solids; gastric emptying of liquids is affected primarily by magnitude of intragastric pressure developed by orad; 2. digestible solid food must be first broken down to a size less than 1-2 mm prior to emptying during the digestive period-ability of perstaltic contractions to triturate solids directly related to strength of peristaltic contractions; 3. undigested food residue is not emptied during the digestive period, rather empties during the interdigestive period in response to strong peristaltic contractions generated during the migrating motor complex (MMC) |
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Term
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Definition
| high compliance, thin-walled portion of the stomach and includes the fundus and most of gastri corpus-circular smooth muscle always exhibits some level of active tone to develop intragastric pressure (primarily determinant of liquid emptying and serves as reservior upon ingestion of a meal |
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Term
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Definition
| includes part of corpus, the thick walled antrum and pyloric sphincter; pacemaker cells in the corpus exhibit spontaneous changes in membrane potential referred to as slow waves of the basic electrical rhythm of the stomach occuring at 3/minute and originate from ICC cells-spreads throughout circular smooth muscle layer and underlying basis of the phasic, perstaltic contractions; antral contractions is to mix bolus of food with gastric secretions and to triturate solid food and extent of trituration dependent upon resistance offered by pyloric sphincter |
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Term
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Definition
| when each swallow the orad stomach briefly relaxes to receive the bolus and mediated through vagal activation of inhibitory enteric neurons (VIP/NO) in wall of proximal stomach; abolished by vagotomy; and delivery of food is accompanied by only a moderate increase in intragastric pressure and termed the accommodation reflex |
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Term
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Definition
| result of distension-mediated activation of long (vago-vagal) and local inhibitory reflexes; purpose is to increase gastric compliance and promote reservoir function of the orad stomach; disruption of extrinsic vagal input to orad stomach and proximal gastric resection each significantly inhibit accomadation resulting in decreased compliance and increased intragastric pressure and increase in gastric emptying rate of liquids |
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Term
| motility of distal stomach |
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Definition
| characterized by phasic peristaltic contractions and frequency is set by underlying electrical ryhthm of the stomach; each contraction may last from 2-20 seconds and increases in force and velocity as it proceeds towards the gastroduodenal junction due to increase in muscle mass; increased velocity may reflect an increased electrical coupling between cells; solid food empties from the stomach only when the particle size has been reduced to 1-2mm and extent dependent on resistance offered by pyloric sphincter; velocity of perstaltic contractions exceeds rate of movement of gastric contents through the caudad stomach resulting in propulsion of solids towards pyloric sphincter, trituration of solids, and retropulsion of solids back towards the mid portions of the stomach |
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Term
| mechnical distension of caudad stomach |
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Definition
| only known stimulus for the initiation of caudad stomach contraction, peristalsis in initiated by activation of excitatory vago-vagal reflex (ACh); vagotomy decreases strength of antral peristaltic contractions and results in prolonged lag phase and subsequent decrease in gastric emptying rate of solids; activation of local excitatory ENS cholinergic reflexes-act in concert with long reflexes to initiate trituration-loss of these leads to virtually complete gastric stasis |
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Term
| factors in gastric emptying |
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Definition
| 1. intragastric pressure; 2. force of antral peristalsis; pyloric sphincter resistance; antro-duodenal coordination |
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Term
| control of gastric emptying |
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Definition
| involves neurohormonal negative feedback pathways activated by presence of food in small intestine; and physical and chemical composition of chyme monitored by receptors located in both proximal and distal small intestine that activate both an inhibitory neural reflex and inhibitory endocrine feedback |
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Term
| receptors in small intestine |
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Definition
| sense volume of chyme entering the small intestine-distension of small intestine slows gastric emptying; osmolarity of chyme entering the small intestine; delivery of H+ into the small intestine-as pH of small intestine decreases gastric emptying decreases; caloric density of the meal- rate of delivery of calories into the duodenum is kept within a very narrow range regardless of chemical composition of calories |
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Term
| secretion rates of stomach |
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Definition
| electrolyte composition and pH depends upon secretion rate-at low rates the gastric juice is essentially isotonic, NaCL soultion reflecting contribution of nonparietal cells and secretory rate increases contribution from parietal cells increases; at all secretory rates concentrations of H+, K+, and Cl- are higher than in plasma; excessive loss can lead to dehydration and hypokalemia, hypochloremic, and metabolic alkalosis; when parietal cell is stimulated undergoes rapid and significant morphological changes; luminal surface area increases 6-10 times increasing number and density of proton pumps in the apical surface |
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Term
| clinical analysis of gastric secretion |
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Definition
| analysis concerned with measuring the acid secretory capacity of the stomach during basal or interdigestive period (BAO=0-10mEq/hr) and in response to exogenous stimuli and can be expressed as (MAO=30-50 meq/hr) or peak acid output (PAO=50-60 meq/hr) |
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Term
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Definition
| basal acid output of the unstimulated stomach is approximately equal to 10-30% of maximal acid output; BAO evidences a circadian rhythm, with higher rates in the late evening and lower rates in the morning prior to awakening; pH is generally less than 2-reflects a tonic level of excitatory cholinergic vagal tone and histamine and gastrin may also have an excitatory effect but low pH limits the impact bc parietal cells and antral G cells evidence little or no response to physiological stimuli at pHs below 3 |
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Term
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Definition
| meal stimulated gastric acid secretion is generally divided into three phases based on location of sensory receptors responsible for initiation of secretory response-cephalic, gastric, and intestinal phase |
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Term
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Definition
| chemoreceptors and mechanoreceptors located in the nose, mouth, and oropharynx are stimulated by the taste and smeel of food and by the physical acts of chewing and swallowing-these integrate centrally in the medullary vagal nuclei and efferent preganglionic vagal fibers activate enteric neurons in the stomach parietal cell stimulated directly by ACh and indirectly by gastrin |
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Term
| direct stimulation of parietal cells |
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Definition
| efferent vagal stimulation of exocrine portion of the gastric mucosa produces the release of ACh from enteic nerves directly onto the parietal cells (M3 receptors) |
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Term
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Definition
| efferent vagal stimulation of endocrine portion of the gastric mucosa promotes the release of gastrin from antral G cells and gastrin release is a complex process involving modulation of excitatory and inhibitory mediators of gastrin release-direct release of an ENS excitatory neurotransmitter on antral G cells and ACh inhibits tonic release of somatostatin inhibitory paracrine secretion |
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Term
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Definition
| entry of food into the stomach enchances and initiates gastric secretion and accounts for 50% of gastic secretion; 1. intragastric buffering by food-buffers contained in foods neutralize the H+ ions resulting in significant rise in pH which removes inhibitory effects of low pH enhancing excitatory mediators released during cephalic phase; 2. distension-food activate vago-vagal mediated excitatory long reflexes and intrinsic neuron mediated excitatory local reflexes-serum gastrin levels rise significantly in response to distension; 3. chemical stimulation-calcium, caffeine, alcohol, and protein digestion products stimulate acid secretion via increasing gastrin release |
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Term
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Definition
| food particles in small intestine primarily release inhibitory factors, protein products evidence a slight stimulatory effect-stimulation due to release of gastrin from G cells located in proximal duodenum also inresponse to enterooxyntin and circulating amino acids may have stimulatory effect on gastric acid secretion |
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Term
| cephalic phase of gastric acid inhibition |
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Definition
| distension-mediated vagal afferent impulses from esophagus, stomach, and small intestine cause the release of substance P also GRP levels increase during a meal and both stimulate the dorsal vagal complex in medulla which sends impulses to hypothalmic cortical satiety centers and eliminates excitatory component of cephalic phase of acid secretion |
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Term
| gastric phase of gastric acid inhibition |
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Definition
| within 60-90 min minutes of ingestion acid output is maximal and buffering capacity of food has become saturated and significant amount of gastric emptying has taken place and pH drops below 3 and acid secretion decreases and is direct inhibitory effect of low pH on antral G cell and parietal cell responsiveness; and H mediated release of somatostatin from mucosal D cells which inhibits G cells and pareital cells |
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Term
| intestinal phase of gastric acid inhibition |
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Definition
| presence of acid, lipid digestion products, and hypertonic solutions in proximal small intestine stimulates hormonal and neural inhibitory feedback of gastric acid secretion; acid (secretin) and partially digested lipids (CCK) release the inhibitory hormones and decreases gastrin release and directly inhibits the activity of the parietal cell; hypertonic chyme elicits the enterogastric reflex and fat in distal small intestine releases hormone peptide YY |
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Term
| role of histamine in acid secretion |
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Definition
| potent stimulus for acid secretion; located in mast cells and cells enterochromaffin like cells and receptor on parietal cells is characterized as H2 receptor subtype; histamine potentiates ACh and gastrin and increases intracellular levels of cAMP increasing PKA activity; vs ACh and gastrin increase intracellular Ca which in turn increase PKC levels |
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Term
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Definition
| endogenous protective factors the protect from gastric inflammation, gastric erosions, and gastric ulcers |
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Term
| endogenous aggressive factors |
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Definition
| 1. HCl/pepsin; 2. bile-reflux of intestinal contents associated with gastric ulcers; 3. H. pylori- found in gastric antrum and play role in gastric ulcers |
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Term
| exogenous aggressive factors |
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Definition
| 1. alcohol-physical disruption of gastric mucosal barrier; 2. nicotine (smoking) decrease HCO3 secretion by stomach, liver, pancreas, and small intestine; 3. aspirin/NSAIDs-decrease gastric production of prostaglandins=decrease gastric mucosal barrier |
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Term
| protective factors of the stomach |
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Definition
| 1. mucous/HCO3 secretion by surface and neck cells buffers HCL; 2. mucosal blood flow-washes away acid that penetrates between cells into submucosal regions; 3. membrane integrity-low conductance to back flow of H+; 4. membrane repair |
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Term
| intrinsic factor secretion |
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Definition
| glycoprotein secreted by the parietal cell in response to ACh, gastrin, or histamine; essential fro absorption of vitamin B12 by the ileum; vitB12 ingested complexed with food protein and released in presence of gastric acid/pepsin and gastric juice has Rproteins and intrinsic factor that bind vitB12 |
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Term
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Definition
| in stomach binds preferentially to R-proteins, in upper small intestine, trypsin cleaves cobalamin from R-proteins; cobalamin has high affinty fro intrinsic factor and vitamin-intrinsic factor complex resists digestion and in the ileum complex attaches to specialized transporters-complex internalized by endocytes and complex localized into lysosome and hydrolysis and cobalamin attaches to transcobalamin II and complex leaves intestinal cells by exocytosis |
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Term
| functions of small intestine |
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Definition
| digestion/absorption, motility, feddback regulation of gastric and hepatobiliary function, and immune defense |
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Term
| small intestinal motility |
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Definition
| chyme must be mixed with bile and digestive emzymes and exposed to enterocytes for an appropriate time; and during interdigestive period undigested food must be cleansed from the small intestine; ICC generated slow waves are imnipresent in intestinal smooth muscle and must reach threshold in order for contraction and can reach threshold in absence of external stimuli and are prevented from achieving this via tonic ENS inhibitory stimuli and exhibits an orad to caudad decrease in frequency from 11-12/min in duodenum to 6-7 in terminal ileum |
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Term
| digestive pattern of small intestine |
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Definition
| delivery of chyme into the duodenum interrupts any ongoing interdigestive motilty and followed immediately by appearance of local, segmenting contractions throughout entire length of bowel and pertalsis occurs only over short distances |
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Term
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Definition
| serves to mix and circulate the chyme locally and produces the slow net forward movement of chyme as a result of the orad to aborad gradient of slow wave frequency; stimulus is distension mediated activation of preprogrammed enteric neural circuits result in contraction of orad to the distension and relaxation caudad to the distension=law of the intestine |
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Term
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Definition
| depends on the caloric content and nutrient composition of the meal |
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Term
| interdigestive motility pattern |
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Definition
| from LES to distal small intestine is characterized by periodic increases in coordinated, propagated contractions referred to as migrating motor complexes (MMCs); phase I (60-90 min) little of no contractile activity slow waves dont reach threshold; phase II-appearance of random contractile activity (30 min) sporadic spike activity; phase II-period of intense contractile activity (5-10 min) all slow waves reach threshold |
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Term
| factors resonsible for intiation and coordination of MMCs activity |
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Definition
| in esophagus and stomach-initiation requires an intact vagal input and cyclical increases in circulating levels of peptide hormone motilin may contribute; small intestine-intact ENS is required for initiation but cause of spontaneous activation of enteric neural circuitry remains unsettled |
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Term
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Definition
| proliferative, differentiate into goblet cells of entercytes; continuous secretion of Cl/H2O; no absorption; cubodial |
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Term
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Definition
| enterocytes mature as they migrate from crypt to villus tip and increased expression of transporters for absorption and decreased expression of Cl secretion proteins |
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Term
| transport of molecules across villus |
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Definition
| 1. chemical nature of material-lipid soluble (simple diffusion) or H2O soluble diffusion, active transport, or solvent drag; physical properties of cell membrane-pore size and pore charge; 3. existence of difference in electrical potential between mucosal and serosal sides |
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Term
| regional differences in absorptive capacity |
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Definition
| deuodenum/jejunum-5-6 L; ileum-2L; colon-rectum-1.5L |
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Term
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Definition
| transports across the cell membrane, nutrients-diffusion/carriers; electrolytes-diffusion/carriers; primary pathway in interdigestive period and 1/3 in digestive period |
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Term
| paracellular routes for absorption |
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Definition
| transport occurs through tight junctions connecting cells primary transport route during digestive period; ease depends on leakiness of tight junctions which have regional differences duodenum>jejunum>ileum and colon tight junctions are very tight |
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Term
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Definition
| predominat absorptive even in small intestine and colon; 1. diffusion through apical membrane sodium channels; 2. Na-nutrient coupled cotransport |
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Term
| diffusion through apical membrane sodium channels |
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Definition
| electrocehmical gradient facors diffusion of NA from gut lumen into enterocyte and Na actively extruded via Na/K pumps on BL surface; net movement of positively charged molecule from muscosal to serosal side of enterocyte is electrogenic transport and creates a potential difference with mucosa negative with respect to serosa (magnitude varies -3 to -12 mV in small intestine and -20 mV in colon-inversely related to leakiness of tight junctions); gradient created favors Cl- absorption and active pumping also creates an osmotic gradient in lateral spaces results in bulk flow of water and solvent drag of K+ and Cl-; most prominent in the colon (aldosterone sensitive channels) |
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Term
| Na-Nutrient coupled cotransport |
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Definition
| glucose, galactose, and amino acids are absorbed by a Na-dependent cotransporter; limited to small intestine highest in proximal small intestine unaffected by bacterial toxin which tend to inhibit Na and H2O absorption; bile salts and vit b12 also requre co-transport with Na localized to distal ileum |
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Term
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Definition
| most prominent in jejunum; lumenal HCO3 stimulates Na absorption via Na-H exchanger and major mechanism by which bicarb is absorbed |
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Term
| electroneutral NaCl transport |
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Definition
| located primarily in the ileum and colon by Na-Cl cotransport; Na-K-2Cl cotransport and co exchangers Na-H, Cl-HCO3; represents predominat pathways for Na reabsorption along with nutrient couple transport; this pathway is inhibited by bacterial toxins and other factors which increase cAMP or cGMP levels, Ca levels, or activate PKC |
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Term
| energy dependent absorption of sodium and absorption of other electrolyes |
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Definition
| 1. chloride-Cl absorbed as result of electrogenic Na absorption and in ileum and colon Cl-HCO3 exchangers coupled to Na-H exchanger (some not couple results in secretion of HCO3 in urine); 2. K-passive absorption in small intestine due to solvent drag, passive and active secretion occurs in colon and excess loss of fluids results in hypokalemia; 3. HCO3-passive absorption in jejunum due to Na-H exchanger and net secretion occurs in ileum and colon |
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Term
| secretion in small intestine and colon |
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Definition
| secretions derived from crypt cells; driven primarily by active transport of Cl; serosal entry via Na-K-2Cl and exits mucosa through chloride selective channels and this favors Na and water flux into gut lumen; activity can be modified by infectious pathogen, hormones, and neurotransmitters, bile salts and fatty acids |
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Term
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Definition
| result of impaired absorption due to decreased absorptive capacity and decrease digestion and infectious agents-inhibit electroneutral transport; increased secretion due to osmotic excess solute or laxative in gut lumen and secretory increased activity of crypt cells |
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Term
| parasympathetic innervation |
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Definition
| preganglionic nerve fibers arise from cell bodies in medulla and sacral region of the spinal cord and synapse on ganglion cells of intrinsic nervous system; activation is excitatory and involves ACh; inhibitor responses to PNS occur at sphincters and orad stomach; ENS inhibitory neurotransmitters are VIP and NO |
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Term
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Definition
| postganglionic fibers from the paravertebral ganglia innervate primarily the ENS and a few fibers end directly on secretory, absorptive, and smooth muscle cells organ and norephinephrine is neurotransmitter released; afferent fibers originating from the bowel wall project to the paravertebral ganglia and/or spinal cord and believed to be involved in transmission of sensory information (pain) |
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Term
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Definition
| hormone involved in acid secretion and released from antral G cells in response to distension-mediated long and local reflexes and protein digestion products |
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Term
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Definition
| pancreatic and hepatic bicarb secretion and inhibits gastric function is released from duodenum in response to acid |
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Term
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Definition
| interdigestive hormone responsible for contiuation of interdigestive pattern of motility; released from upper small intestine |
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Term
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Definition
| stimulates parietal cells-acid secretion; released from ECL cells |
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Term
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Definition
| inhibits acid secretion-inhibits gastrin released; release from antral SS cells stimulated by acid |
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Term
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Definition
| changes in tone are the result of steady state changes in Em the magnitude of the change in tone is directly proportional to the change in EM |
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Term
| frequency of phasic contractions |
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Definition
| determined by underlying spontaneous changes in smooth muscle termed slow waves, basic electrical rhythms and electrical control activity |
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