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Digestive system
| Question | Answer |
|---|---|
| gastroenterology | the medical specialty that deals with the structure, function, diagnosis, and treatment of diseases of the stomach and intestines |
| proctology | the medical specialty that deals with the diagnosis and treatment of disorders of the rectum and anus |
| 2 groups of organs that composes the digestive system | gastrointestinal tract and acessory digestive organs |
| the gastrointestinal tract | aka alimentary canal, continuous tube that extends from the mouth to anus through thoracic and andominopelvic cavities |
| organs of gastrointestinal tract | mouth, most of phayrnx, esophagus, stomach, small inestine, lg intestine |
| GI tract organs are in a state of | tonus: sustained contraction |
| acessory digestive organs | teeth, tongue,, salviary glands, liver, gallbladder, pancreas |
| accessory organs that dont come in contact with food | salivary glands, liver, gallbladder, pancreas: produce or store secretions that flow into the GI tract thrugh ducts- aids in chemical breakdown of food |
| muscular contractions of GI tract wall | phsyically break down food by churning it and prpopel food along tract from esophagus to anus- helps dissolve foods by mixing them with fluids secreted by tract |
| 6 process of digestive system | ingestion, secreation, mixing and propulsion, digestion, absorbtion, defacation |
| secretion | each day cells in GI tract secrete total of 7 liters of water acid buffers and enzymes into lumen of tract |
| motility | GI tracts capabiloity to mix and move material along its length |
| mechanical digestion | teeth cut and grind food before its swallowed then smooth muscles of tract churn nfood |
| chemical digestion | lg carb, lipid, protein, and nucleic acid molecules in food are split into smalr molecules by hydrolysis |
| few substances that can be absorbed without chemical digestion | vitamins, ions, cholesterol, and water |
| absoprtion | entrance of ingested and secreted fluids, ions, and products of digestion into the epithlial cells lining the lumen of the GI tract- pass into lymph or blood and ciculate to cells in body |
| layers of the GI tract | mucosa, submocsa, muscularis, serosa/ adventitia |
| mucosa | inner lining of GI tract- mucuous membrane |
| mucosa is composed of | layer of eptihelium in direct contact with the contents of the GI tract, a layer of connective tissue call lamina propria, thin layer of smooth muscle |
| epithelium of mucosa | in mouth pharynx, espohagus, anal canal is nokeratinized stratified squamous epthilum for protection |
| epitheliym of stomach and intestines | simple columnar epithelium which functions in secretion and absorption |
| rate of renewal of GI tract epithelial cells | every 5 to 7 days they are sloughed off and replaced by new cells |
| located among epithelial cells | exocrine cells that secrete mucus and fluid into the lumen of tract and several types of edeocrine cells called enteroendocrine cells |
| enteroendocrine cells | secrete hormones |
| lamina propria | areolar CT which has many blood and lymphatic vessels which are routes where nutrients reach tissues of body- most absorption occurs here |
| lamina propria supports | epithelium and binds to the muscularis mucosa |
| lamina propria contains | majority of cells of the mucosa associated lymphatic tissue which protect against disease |
| MALT | present all along GI tract, tonsils, sm intestine, appendix, and lg intestine |
| muscularis mucosae | thin layer of smooth muscle fibers- throws the mucous membrane of the stomach and sm intestine into many sm folds to increase surface area for digestion and abosrption |
| submucosa | areaolar CT that contains blood vessels, lymphatics and nerves and binds to the mucosa to the muscularis |
| submucosa recieves | abrobed food molecules and extensive network of neurons aka submucosal plexus, glands and lymphatic tissue |
| muscularis | of mouth, pharynx, and superior and middle pts of eshagus: skeletal muscle that produces voluntary swallowing |
| skeletal muscle forms | external anal sphincter which permits voluntary control of defecation |
| muscularis of rest of tract consists of | smooth muscle that is found in 2 sheets: inner circular and outer lngitudinal |
| serosa is found in | superficial layer found in portions of tract that are suspended in abdominopelvic cavity |
| serosa is a | serous membrane composed of areaolar CT and simple squamous eptithelium (mesothelium) |
| serosa is aka | visceral peritoneum: forms portion of the peritoneum |
| esphagus lacks | a serosa and instead only has a single layer of areolar ct called adventitia |
| GI tract is regulated by | an intrinsic set of nerves known as the enteric nervous system and by an extrinsic set of nerves that are part of the autonomic nervous system |
| enteric nervous system | brain of the gut |
| enteric nervous system consists of | 100 milion neurons that extend from the esphagus to anus that are arranged into 2 plexus myenteric and submucosal plexus |
| myenteric plexus | located between the longitudinal and circular smooth muscle layers of the muscularis |
| submucosal plexus | plexus of mmeissner: found within the submucosa |
| plexus of ENS consists of | motor neurons, interneurons, and sensory neurons |
| motor neurons of the myenteric plexus | sypply longitudinal and circular smooth muscle of muscularis and therfore controls GI tract motility: freq and strength of contraction |
| motor neuos o the submucosal plexus | supply secretory cells of the mucosal eptihelium and thus controlling the secretes of the organs of GI tract |
| interneurons of the ENS | interconnect neurons of the myecteric and submucosal plezus |
| sensory neurons of ENS | supply the mucosal epithelium, act as chemoreceptors: activated by prescence of chemicals in food, or stretch receptors: when food stretches the wall of a GI organ |
| vagus nerve supplies | parasympathetic fibers to most pts of the GI tract with exeption of the last half of lg intestine |
| last half of lg instestine is supplied by | paraysmptahtic fibers fro mthe sacral spinal cord |
| stimulation of parasympthatic nerves that innervate the GI tract causes | increase in GI secretion and motility by increasing the acitivity of ENS neurons |
| symphathtic nerves that suppy GI tract arise from | thoracic and upper lumbar regions of the spinal cord |
| smpythatic and parasymphatic nerves form | neural connections with ENS |
| symphtatic nerves that suppy GI cause | decrease in Secretion and motility by inhibiting neurons of ENS- caused by emotionssuch as anger fear and anxiety |
| GI reflex pathways | regulate GI secretion and motility in response to stimuli present in the lumen of the GI tract |
| components of GI reflex pathway | sensory receptors that are associated with sensory neurons of the ENS- axons can synapse with other neurons in ENS CNS and ANS telling them the degree of stretch and contents of GI |
| neurons of ENS CNS and ANS can | activate or inhibit GI gland sand smooth muscle- altering GI secretion and motility |
| peritoneum | largest serous membrane of the body |
| peritoneum consists of | a layer of simple squamous epithelium with an underlying supporting layer of areolar CT |
| parietal peritoneum | divides the peritoneum and lines the abdominopelvic cavity and the visceral peritoneum |
| visceral periotneuum | covers some of the organs in the cavity and is their serosa |
| peritoneal cavity | slim space containing lubricating serous fluid and is between the parietal and visceral portions of the peritoneum |
| ascites | when the peritoneal cavity may become distended by the accumulation of several liters of fluid |
| retroperitoneal organs | kidneys, colons of lg intestine, dueodenum of sm intestine, and pancreas |
| retroperitoneal | organs that are not in the peritoneal cavity lie on the posterior abdominal wall covered by peritoneum only on their anterior surface |
| peritoneum contains | large folds that weave between the viscera which binds the organs to one another and to walls of ab cavity |
| 5 major peritoneal folds | greater omentum, falciform ligament, lesser omentum, mesentery, and mesocolon |
| greater omentum | lgst peritoneal fold, drapes iver transverse colon and coils of the sm intestine. a double sheet that folds itself for 4 layers |
| greater omentum extends | downwards anterior to small intestine then turns and extends up and attaches to the transverse colon |
| greater omentum contains | good amount of adipose tissue which expands with weight gain and lymph nodes with macrophages and atinbody producing cells that combat and contains infections of GI tract |
| falciform ligament | attaches the liber to the anterior abdominal wall and diagphragm |
| liver is the only digestive organ that | is attached to the anterior ab wall |
| lesser omentum | arises as an anterior fold in the serosa of the stomach and duodenum and suspends the stomach and duodenum from the liver |
| lesser omentum is the | pathway for blood vessels entering the liber and contains the hpatic portal vein, common hepatic artery, and common bile duct with lymph nodes |
| mesentery | fan shaped fold that binds the jejunum and ileum of the sm intestine to the poserior ab wall |
| mesentery is typically | laden with fad and contributes to the large ab of obese idividuals |
| mesentery extends from the | posterior abdominal wall to wrap around the sm intestine then returning to orgin forming double layered structure |
| mesocolon | two separate folds of the peritoneum that bind the transverse colon and sigmod colon of the lg intestine to post ab wall |
| mesocolon carries | blood and lymphatic vessels to the intestine |
| the mesentery and mesoclon | holds the itnestines lossely in place allowing movement of contractions mix and move the luminal contents along the GI tract |
| mouth | aka oral or buccal cavity- formed by cheekcks, hard and soft palates and tolgue |
| cheeks are covered | externally by skin and internally by mucous membrane which consists of nonkeratinized straifiied squamous epithelium. anterior portions of the cheeks end at lips. and between skin and membrane lies buccinator muscles and FT |
| lips | aka labia- contains orbicularis oris muscle covered exyternally by skin and internally by mucous membrane |
| labial frenulum | a midline fold of mucous membrane which attaches inner surface of each lip to gum |
| oral vestibule | space bound externally by the cheeks and lips and internaly by gums and teeth |
| oral cavity proper | is the space that extends from the gums and teeth to the facues |
| palate | wall of septum that separates the oral cavity from the nsala cavity and forms the roof of the mouth |
| hard palate | anterior portion of the roof and the mouth, covered with mucous membrane |
| soft palate | forms posterior portion of the roof of the mouth- arch shaped muscular partiition between the oropharynx and nasopharynx that is lined with mucous membrane |
| uvula | hanging from the free border of the soft palate is a conical muscular process |
| during swallowing | the soft palate and uvula are drawn superiorly closing off the nasopharynx and preventing swallowed foods and liquids from entering nasal cavity |
| 2 muscular folds of soft palate | palatoglossal arch: anteriorly, extends to side of the pends to the side of the base of the tongue paltopharyngeal arch: post, extends to the side of the pharynx |
| salivary gland | gland that releaseds a secretion called saliva into oral cavity |
| glands of mucuous membrane of mouth and tongue | labial, buccal, and palatal glands, and lingual gland contribute to saliva |
| major salviary glands | lie beyond the oral mucosa into ducts that lead to the oral cavity- secrete most of the saliva |
| the three pairs of the majpr salivary glands | parotid, submandibular, and sublingual glands |
| parotid glands location | located inferior and anterior to ears between the skiin and the masseter muscle |
| parotid glands function | secretes saliva into oral cavity via parotid duct that pierces the buccinator muscle to open into the vestibule opposite to second maxillary molar tooth |
| the submandibular glands | in the floor of the mouth- contains submandibular ducts that run under mucosa and enter oral cavity proper lateral to the lingual frenulum |
| sublingual glands location and duct type | beneath the tongue and superior to the submandibular glands- has teh lesser sublingual ducts which oen into floor of the mouth in the oral cavity proper |
| saliva components | 99.5% water and .5% solutes (ions: sodium, potassium, chloride,bicarbonate, phosphate), gasses: urea, uric acid, mucus, lyzoyme, salivary amylase |
| parotid glands secrete | watery liquid containing salivary amylase |
| submandibular gland contains | similar cells found in parotid glands, mucuous cells so it secretes fluid with amylase but is also thick with mucus |
| sublingual glands contain | mucous cells so they secrete much thicker fluid with sm amount of salviary amylase |
| salivary amylase | an enzyme which is activated by chloride ions that breaks down starch in mouth into maltose, maltoriose and dextrin |
| bicarbonate and phsophate ions buffer | acidic foods that enter the mouth so saliva is only sighlty acidic |
| immunoglobulin A and enzyme lyozyme | IA: prevents attachment of microbes sothey cant penetrate the epithelium EL: kills bacteria] both of these are not present in lg enough quantities to eleimbate all oral bacteria |
| l | |
| gi tract aka | alimentary canal: 30 ft from mouth to butt holse |
| purpose of gi tract | digesetion and absorpton |
| gasteroenterologist | internal medicine MD specializing GI medicine- not surgeon |
| proctologist | surgeoun specializing in rectal and anal disorders along with GI medicine |
| general surgeons | do most GI surgery |
| organs of digestive tract | oral cavity, pharynx, espophagus, stomach, sm and lg intestine |
| accessory digestive organs | teeth, tongue, salivary glands, liver, gall bladder, pancreas |
| function of digestive system | ingestion, secretion, mixing and propulsion, digestion, absorption, defecation |
| peristalis | alternating contraction/ releaxation of smooth muscle |
| what does digestive system digest | water, enzymes, acids, buffers |
| types of digestion | mechanical: cheew, churn chemical: HCl and enzymes |
| 3 regions of mucosa (surrounds lumen) | epithelium, lamina propria, muscularis mucosa |
| epithelium layer of mucosa | stratified squamous upper or simple columnar lower> tight junctions |
| stratified squamous vs simple columnar | stratified: protection simple: absorption/ secretion |
| submucosa contains | submucosal nerve plexus which have neurons of enteric nervous system |
| submucosal nerve plexus aka | plexus of meissner: parasympthatic (motor) input- controls moevement of muscularis mucosa and gastrointestinal secretions |
| muscularis parts | oral cavity to upper pt of espohagus And in external sphincter: 1 layer of skeletal muscle (voluntary) lower pt of esphogus to internal anal sphin: double layer of smooth muscle |
| double layer of muscularis is | 2 sheets and longitduinal outer and an inner circular layer |
| myenteric plexus | in the muscularis: aka plexus of auerbach is located between 2 muscle layers |
| the myenteric plexus function | has paraympathetic and sympathetic input and it controls muscularis contractions/ relaxations and is pt of the enteric nervous system (ANSO |
| serosa | aka visceral peritoneium found in the abdominopelvic cavity and attaches areas of lower GI tract to surrounding structures |
| serosa is composed of | simple squamous empithlium (outer) and CT (inner) squamous layer: mesothelium squamous layer: serous epithelium |
| adventitia | serosa in the esophagus: only CT and no epithelial component |
| ENS can | function independentlly and is part of ANS |
| the ENS contains | 2 nerve plexus: myeteric and submucosal |
| myenteric nerve plexus | motor nerve between muscularis layers: the plexus of auerbach: symp + parasympathetic. |
| submucosal nerve plexus | sensory ( chemo and stretch) and motor (secretions: plexus of meissner and parasympathetic only |
| submucosal nerve plexus consists of | motor, sensory, and interneurons (CNS), the sensory contains stretch and chemoreceptors |
| parasympathetic stimulation of submucosal | vagal (top 1/2) and sacral (bottom 1/2) of GI tract which both cause GI stimulation and secretion and motility |
| sympathetic stimulation of submucosal | thoraco/lumbar -> GI inhibition also hypothalus and cereal input(emotion and GI inhibition) |
| greater omentum | transverse colon |
| falciform ligament | anchors liveres_> anterior ab wall |
| lesser omentum | liver-> stomach |
| mesentary | small intestine-> ab wall |
| mesocolon | lg intestine-> ab wall |
| peritonitis | result of perforated viscus |
| purpose of hard and soft palate | to prevent upward movement of food into nasal cavity |
| Uvula | upward contraction with swallowing reflex: blocks food upward |
| oral cavity initiates | digestion through mastication and food is transformed into a bolus |
| functions of salivary glands | lubrication, starts chemical breakdown, dissolves substances |
| ANS control of salivary glands | secretes saliva is presence of food and produces 1 to 1.5 liters of saliva per day |
| tongue glands secrete | lingual lipase ( activated with HCI in stomach) |
| tongue | mucuous membrane with skeletal muscle, papillae with taste buds, a midline spetum and lingula frenulum (tongue tied) |
| extrinsic tongue muscles vs intrinsic | extrinsic: maneuver food intrinsic: alster tongue shape |
| mumps virus | an RNA paramyxovirus Parotitis: parotid gland viral infection-> inflammation orchitis (testicular inflammation)-> infertility |
| number of teeth | 20 deciduous teeth: baby teeth 6 mos-> 6 years 32 adult teeth: 6- 17 years |
| adult teeth types | 8 incisors (front teeth) 4 canines: cuspids which grasp and teear 8 bicuspids: premolars 12 molars: crush and grind wisdome teeth (third molar) |
| when wisdom teeth are impacted | no room for wisdom teeth to come out |
| dental caries | tooth decay- caused by various anaerobic bacteria (strep mutans and viridians, lactobacilli) |
| teeth are made of | enamel/ dentin (bone) and pulp (loose CT/ nerve) |
| cementum/ periodontal ligmanet | ? |
| alveolar processes | bony sockets covered with gingiva (gums) |
| periodontal ligament | dense CT that connects tooth to bony socket |
| 3 regions of teeth | crown (above), neck, roots (below gum) |
| layers of teeth | dentin, cementum, pulp cavity, root canal |
| dentin | majority of tooth, calcium salts, harder than bone |
| cementum | connects roots (covers it) to periodontal ligament |
| pulp cavity | CT/Vessels/ Nerves |
| root canal | extensions of pulp cavity |
| apical foramen | where vessels and nerves enter the root canal |
| what happens from dental caries | ferment carbs-> lactic acid and dissolves enamel-> enamel/dentin/ pulp damage/ infection |
| root canal | remove pulp, file out bacteria-> apply medication seal repair crown |
| oropharynx | skeletal muscle passageway from oral cavity to esophagus |
| swallowing reflex | caused when muscular contraction pushes food blus toward the esophagus |
| water | dissolves food molecuels into solutin |
| amylase | saliva: begins breakdown of carbs |
| lipase | lingual: begins breakdown of lipids and activated by stomach HCl after swallowing |
| esophagus location | mediastinal location posterior to trachea and 10'' muscular tube |
| layers of esophagus | same four layers but serosa is called adventitia |
| muscularis of esophagus | upeer: skeletal middle: mixed lower: smooth |
| function of muscularis esophagus | secretes mucus and transports food bolus into stomach |
| the esophagus contains 2 | sphincters the UES (skeletal muscle) and the LES (smooth muscle) |
| function of esphagus | food transport only- no enzyme digestion or absorption |
| heart burn | caused by hiatal hernia/GERD where stomach moves upward through LES |
| Reflux | GERD-LES fails to close tightly after food enters stomach |
| H2 | a histamine receptor in stomach which bauses an increase in HCl release |
| esophageal cancer | squamous cell (associated with smoking) or adencarcinoma (chronic reflux aka barrets esophagus)- poor prognosis 5% survive after 5 years |
| 3 stages of swallowing | voluntary, pharyngeal, esophageal |
| voluntary stage | aka buccal phase... food in mouth goes to pharynx by yoward movement of tongue against hard palate forces food bolus into oropharynx |
| pharyngeal stage | oropharynx to esophagus- involuntary and controled by CNS brainstem: deglutition center: medulla and pons |
| pharyngeal stage contain | tactile receptors in palate and uvula that trigger the swallowing reflex |
| sequence of pharyngeal stage | uvula moves upward, epiglottis closes over trachea, UES relaxes, breathing stop temp, food bolus glides into esophagus |
| esophageal stage | esophagus to stomach: the food bolus is pushed via esophageal peristalis toward the lower esophageal sphincter, the LES relaxes and food enters |
| peristalsis | coordinated muscle contraction/relaxation |
| functions of stomach | bulk storage of ingested food, mechanical and chemical breakdown of food, production of IF, transformation of food bolus, absorption |
| chemicals of stomach | HCl, pepsin, gastrin, lipases |
| HCI | H2 receptors bind histamin which enhances effect of ACh, gastrin and more HCI secretion |
| pepsin | initiates protein digestion |
| lipases | lingual activated in stomach and gastric lipase also works in HCI |
| production of IF for | absorption of vitamin B12. IF is made by parietal cell |
| food bolus is turned into | chyme (vomit) |
| aborption of stomach | only of certain drugs (alcohol) and minimal nutrient and water absorption |
| stomach produces | mixing waves which churn the bolus then adds gastric juice to form chyme |
| mixing waves force | sm amounts of chyme into duodenum through the pyloric sphincter |
| carbs and lipids of stomach | salivary amylase, lingual lipase, gastric lipase |
| salivary amylase | remains active til pH falls below 4.5 |
| lingual lipase | becaomes activated in acidic (HCI) environment |
| gastric lipase | works in an acid environment like lingual lipase |
| pepsinogen | a stomach protein which relases pepsin which increases activity when pH is 2 (HCI) |
| pepsin function | break down complex proteins into smaller peptide chains- its proteolytic |
| HCI is involved in | carb, lipid, and protein breakdown |
| why does stomach have almost no nutrient absorption | thick alkalin mucus covering epithlial lining, no transport cells, gastric lining is relativly impermeable to water, most nutrients arent broken down yet |
| what can stomach aborb | alchol and some drugs such as aspirin |
| alcohol | relaxes LES and causes reflux (GERD) |
| 3 phases of gastric secretion and motility | chephalic, gastric, intestinal phase |
| cephalic phase | last only minutes and prepares mouth and stomach to recieve food occurs before food enters mouth, and saliva and gastric juices are released at smell, taste, sight, or thought of food (CNS) |
| cephalic phase is supressed | during depression or lack of appetitie |
| ANS of cephalic phase | parasympathetic- vagus nerve -> ACh-> secretions |
| secretions of cephalic phase | histamine, mucous cells, chief cells, G cells, parietal cells |
| histamine | synergistic (additive effect) with gastrin which stimulates parietal cells |
| ECL cell | enterochromaffin like- stimulated by gastrin and ACh |
| chief cells | releases pepsin and gastric lipase to breakk down proteins in low PH |
| G cells | release gastrin which is a hormone that stimulates chief, pariteal and ECL cells |
| Parietal cells | release HCI and IF, and ACH |
| HCI denatures and is made by | proteins and kills bacteria. made by proton pump in pH of 2 |
| Gastric phase | stimulated when food stretches stomach and occurs when food reaches the stomach and is under neural and hormonal control |
| gastric phase response type | parasympathetic via the vagus nerve (motor) because there are stretch and chemoreceptors in the stomach |
| what activaates stretch receptos | distension of the stomach with food |
| when stretch and chemoreceptors are stimulated | CNS integration with vagus output which causes mixing waves |
| what stimulates chemoreceptors | decrease in pH (stomach acid- HCI) |
| gastric empything last | 3 to 4 hours minimum and is a negative feeback regulation |
| gastric phase has hormnal regulation via | gastrin which is released by g cells in response to presence of peptides and amin acids in chyme |
| gastrin hormone travels | back to stomach via bloddstream and stimulates the parietal chief and ECL cells |
| net effect of ACH | gastrin is stimulated which stimulates parietal cell- HCl chief cell-> pepsingoen -> pepsin + gastric liapse gastrin-> ECL -> histamine -> HCL |
| intestinal phase | sympathetic response which occurs when food reaches the sm intestine and last for hours |
| intestinal phase controls | the rate at which chyme enters the small intestine |
| neural sympathetic input of intestinal phase | inhibits gastric motility |
| lipids and amino acids in small intestine cause | CCK (horomone) release which causes bile from gall bladder and pancreatic enzyme to be released which increases digestion |
| entero/gastric reflex | an inhibitory reflex which via the ANS symathetic division that occurs after duodenal stretch |
| steps following after duodenal stretch | medlla causes sympathetic output which causes pyloric sphincter constriction and gastric mixing stops |
| horomonal control of intestinal phase- where are hormones made | CCK and secretin are made in the duodenum |
| cholecystokinin- where and what is it stimulated by | CCK prodcued in duodenum by CCK cell amino acids, FAs, TGs |
| actions of CCK | increased pacreatic juice sphincter of Oddi opens, gall baldder contraction, phyloric sphincter closure, slow gastric contraction, gastric empyting |
| sphicnter of Oddi controls | bile entry into duodenum |
| gall bladder contraction causes | bile release into duodenum |
| pyloric sphicnter closure | person feels full |
| drainage system | liver/ gallbladder and pancreas |
| ampulla | open end of duct |
| secretin is realeased by | released by S cell in duodenum in response to low pH |
| secretin inhibits | chief cells and parietal cells (stops HCI production) |
| secretin stimulates | pancreas to produce and secrete a buffer called HCO3 to neutralize gastric HCI and stimulates liver to produce bile |
| helicobacter pylori | a bacteria with multiple flagella that forms a biolfilm on surface f cells (gastric mucosa) which cuases gastritis |
| helicobacter pylori symptoms | survuvies in stmach acid of pH= 2 and 80% of infected people are asymtomatic |
| helicobacter pylori causes | peptic ulcers: bores hole through stomach mucus using its corkscrew shape and causes gstric and duodenal infections and sometime stomach cancer |
| helicobacter pylori treatment | biopies 2 antibiotic combination of ampicillin and metrodizole (Flagyl) |
| pancreas has two functions | endocrine function: exocrine function: produce 1.5 liters of pancreatic juice per day |
| strucutre of pancreas | head, body, tail |
| ducts of pancreas | Wirsung, Santorini, CBD |
| ampulla of Vater | union of pancreatic and CBD |
| sphincter of Oddi | just distal to Ampulla at duodenal junction, circular band of smooth muscle |
| the pancreas | the soft, lobulated, glandular, retroperitoneal organ |
| cell types of pancreas | exocrine 99% and endocrine cells 1% |
| exocrine cells of pancreas | secrete pancreatic juice and are arragned in clusters: acini-> dust cells which release HCO3 |
| endocrine cells of pancreas | islets of langerhans-> causes insulin from beta cells and glucagon from alpha cells |
| pancreatic juice | consists mostly of water and some solutes, digestive enzymes and HCO3- |
| digestive enzymes | break down the major macromolecules |
| digestive enzymes types | pancreatic amylase, trypsin (proeolytic enzyme), pancreatic lipase, ribonuclease and deozyribonuclease |
| enzymes are synthesized as | inactive frms so autodigestion doesnt occur |
| what sitmulates pancreas | CCK and secretin does to release enzymes and HCO3- |
| panceatitis | caused by trypsin having autodigestion which causes sever pain. stimulated by alchohol, obstruction (gallstones), cystic fibrosis, and acut chronic forms |
| pancreatic cancer | most common in males of 50 yrs old, 4th leading cancer, assocatied with EtOH, smoking, genetics, pancreatitis, 5% survival |
| liver structure | 2 lobes divided by falciform ligament functional unit: hexagonal hepatic lobules, whith central vein (hepatic vein) |
| hepatocyte | primary functional cell of liver -> bile and many metabolic and synthesis functions |
| portal triad | in the liver, and arty, protal vein, and bile duct |
| kupffer cells | fixed macrophages for dead RBCs in the liver |
| liver | largest/ heaviest gland in the body that secreate bile for emulsification of lipids for increased absrption |
| fat emulsification causes | fat/water suspension lg fat particle-> sm particle-> increased SA for lipase to work |
| gallbladder function | stores and released bile but doesnt make it it als concentrates bile via H2O aborption which can cause gallstones |
| 4 layers of gallbladder | M: simple columnar with rugae for stretch S: none M: for contraction S: visceral peritoneium |
| gallbladder structure | very thin, sac like structure that stores bile until needed |
| CCK in gallbladder | stimulates bile release from gall bladder into duodenum |
| gallstones are formed by | cholesterol/ bile salt precipitates from bile |
| gallstones | duct obstruction which causes GB ischemia/infarction/infection |
| cholecystectomy | causes% dietary lipid loss, vitamin KADE loss |
| ERCP | endoscpic retrograde cholangiopacreatography |
| blood supply of liver | hepatic artery+ portal vein -> liver sinusoids drain into central vein central veins-> left and right hepatic veins-> IVC |
| portal vein of liver | drain GI tract |
| liver blood supply comes from 2 sources | arterial and portal |
| liver is common site of | intestinal cancer metastasis |
| liver secretes | about 1 liter of bile a day into lumen of duodenum from common bile duct |
| bile consists of | H2O, bilirubin (from heme breakdown), bile salts, and cholesterol |
| bile salts | important in emulsification- break lipids down into tiny droplets which make it easier for lipase to digest triglycerides |
| bile function | digestive and excretoryfunction |
| biliary drainage | hepatocyte-> make bile which goes into bile ducts of triad-> hepatic ducts -> common hepatic duct and cystic duct= common bile duct-> duodenum |
| hyperbilirubinemia | causes jaundice: yellow skin, sclera, mucous membrane |
| bilirubin is a | byproduct of Hgb breakdown |
| 3 types of hyperbilirubinemia | pre-haptic, intra-hepatic, and post hepatic |
| pre hepatic | increased production such as hemolysis |
| intra hepatic | liver disease: inability of liver to metabolize and excrete bilrubine |
| post hpatic | obstruction- eg common duct stone/ pancreatic or liver cancer |
| bille acids/ salts are | cholesterol derivatives |
| functions of liver | metabolism, detoxify drugs and hormones, excretion of bilirubin, sytnethis of bile salts, clotting factors, complement, albumin, cholesterol, sorage of fat soluble vitamins, immune, activation of VItamin D |
| what durgs and hormones does the liver metabolise and detoxify | ethanol, atnibiotics, TH, steroidal hormones |
| what vitamins does the liver store | fat solubel vitamines (KADE) and vitamin B12, iron, and copper |
| immune of liver | kupffer cells (macrophages) and RBC breakdown |
| activation of vtiamin D | works in conjuntion with skin and kidneys |
| carb metabolism of liver | regulated by insulin (anabolic) and glucagon (catabolic) glycogen sysnthesis glucogneogenesis (synthesis of glucose) |
| lipid metabolism of liver | maintains blood fatty acid, triglycerid, and choletserol levels TG storage Lipoprotein synthesis |
| protein metabolism | removes excess amino acids from bloodstream and is used for plasma protein syntheis or is stored |
| excess amino acid causes | NH3-> urea-> bloodstream -> kidney-> urine |
| small intesttine structure | ten feet long and inch diameter 3 regions: duodenum 10 ft, jejunum 3 ft, ileum 6 ft |
| ileum continues as | ileocecal valve (sphincter) into cecum (lg intestine) |
| mesentery | visceral peritoneum that connects sm intestine to ab wall |
| what happens in sm intestine | mjor events of digestion and absorption |
| small intestine recieves | chyme from stomach and secretions from the liver and pancrease that it chemically and mechanically breaks down |
| small intestine function | continues and nearly completes digesstion and 90% of all absorption occurs here |
| how does small intestine structure accommodate digestion and absorption | 10 ft long plica (circular folds), crevices, vili, microvili for increased SA to aid absroption and digestion |
| small intestine layers | same 4 layers MSMS |
| mucosa of small intestine contains | absoprtive/digestive cells, goblet cells, paneth cells, and MALT |
| absorptive/digestive cells | 1 layer of simple columnar |
| exocrine of mucosa of small intestine | from cypts of liberkuhn-> secretes intestinal juice from crevices |
| paneth cells | lysozyme, phagocytosis which regulates flora |
| MALT of small intestine | peyers patches and lympahatic follicles found in the lamina propria |
| submucosa of small intestine | brunners glands-> alkaline mucus to neutralize chyme |
| muscularis of small intestine | 2 layers of smooth muscle: concentric and longitudinal |
| serosa of small intestine | visceral peritoneum |
| what specialized structures increase surface area of small intestine | plica, villi, microvilli all 3 aid in digestion and absorption |
| plica | circular mucosal/ submucosal folds which increase SA and cuase chyme to spiral |
| villi | fingerlike projections to increase SA contains lacteals |
| lacteals | lymphatic vessls for lipid absorption found in the lamina propria of mucosa |
| microvilli | 1 micrometer, millions to increase SA aka brush border each has digestive enzymes insterted in their cell membrane |
| small intestine secretes | 1 to 2 liters of intestinal juice from cyrpts of kieberkuhn (intestinal glands) |
| secreted enzymes of small intestine | lactase, sucrease, maltase, peptidase, mucelosidase |
| some digestion of sm intestine takes place | on the mucosal surface as well as inthe lumen in the presence of intestinal juice |
| intestinal juice | added to the pancreatic juice a very liquid medium to increase absorption |
| 2 types of intestinal movements | segmentation and peristalsis |
| segmentation | localized mixing: contract and relaxation-> contriction does not propel moves chyme and forth slowly to aid in digeston |
| segmentation brings chyme into | contact with intestinal wall for absorption of nutrients |
| peristalsis | propulsion of chyme forward migrating motility complex: moves chyme to lg intestine over 3-5 hrs |
| segmentation stops | after most of a meal is absorbed |
| chyme reamins in small intestine | 3-5 hours |
| saliva and gastric juice only | paritial digestion |
| pancreatic juice + bile+ intestinal juice | work together to complete digestion of nutritents carbs proteins lipids nucelic acids are broken down into their subunit molecules |
| brush border enzymes facilitate | hydrolysis (breakdown) breaking of bonds between monomers of proteins, carbs, lipids, and nucleic acids |
| digestion of carbs starts | in oral cavity by salivary amylase and continues in the stomach |
| digestion of carbs ends in | dueodenum with pancreatic amylase and brush border enzymes |
| brush border enzymes convert | maltase - maltose-> glucose+glucose sucrase-sucrose-> glucose+fructose lactase-> lactose-> glucose+galactose |
| GI system can only absorb | monosaccharides to brush border enzymes convert di to monsaccharides |
| digestion of proteins | starts in stomach from pepsin and complete in duodenum from pancreatic juice and brush border enzymes |
| pancreatic juice involved with digestion of proteins | trypsin, chymotrypsin, elastase, peptidases |
| brush border enzymes invoved with proteins | aminopeptidase, dipeptidase with both break dipeptides into free amino acids |
| GI system can only | absorb amino acids, di- tri-peptides |
| digestion of lipids | starts in stomach with lingual and gastric lipase and completed in duodenum with pancreatic lipase |
| pacreawtic lipase | splits TGs into glycerol and fatty acids |
| during emulsfitication with bile and digestion of lipids | large lipids broken down into small globules by bile salts which enables enzymatic break down of TGs into fatty acids and monoglycerides by lipases |
| emulsification increases | SA for pancreatic lipase to work on |
| digestion of nucleic acids | occurs in small intestine with pancreatic juice, brush border enzymes, nuceosidase, and phosphatase |
| pancreatic juice contains two kinds of nucleases | ribonuclease: digests RNA deoxyribonuclease: digest DNA both DNA and RNA are broken down in to nucleotides |
| nucleotides are broke down into | nitrogenous bases ATGC (U) Sugar- ribose or deoxyribose phosphate |
| what is absorbed during digestion of nucleic acids | pentose sugar, nitrogenous bases, and phsopahte via active transprot but not entire nucleotides |
| aborption in small intestine | the passage of digest nutrients into intestinal cells and then into blood or lymph |
| absorption is via | simple diffusion, faciliateated diffuison, active transport (primary and secondary) , osomosis |
| osmosis | water moves across a semipermeable membrane |
| aborption occurs | 90% in small intestine 10% in lg intestine |
| amount of digest carbs | almost all can be digest and absorbed but cellulose remains (fiber) |
| cellulose | aka fiber: a polymer of glucose like glycogen |
| monosaccharides are absorbed from GI tract via | facilitated diffuision, secondary active transport Na/K pump and active transport |
| monosaccharides enter bloodstream via | faciliatated diffusion |
| amino acids are aborbed into intestinal epithelial cells via | acitve transport and secondary active transport- Na+ K+ pump |
| dipeptides and tripeptides | aborbed via secondary active transport into the mucosal cells and then split into single amino acids |
| amino acids diffuse | into capillaries and are transported into the liver |
Created by:
newmee32