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Digestion (Ch. 24)
The Digestive System
| Question | Answer |
|---|---|
| 7ut8rne47t894un89yb45nm9 | nvjdfshfu8y3rw ygt78349 |
| name the organs of the alimentary canal | mouth, pharynx, esophagus, stomach, small intestine, & lg. intestine |
| name the accessory digestive organs | teeth, tongue, gallbladder & glands (salivary, liver & pancreas) |
| ingestion | taking food into the digestive tract, usualy via the mouth |
| propulsion | moves food through the alimentary canal; swallowing & peristalsis |
| peristalsis | major means of propulsion; involves alternate waves of contraction & relaxation of muscles in the organ walls; main effect is to squeeze food from one organ to the next, but some mixing occurs as well |
| mechanical digestion | physically prepares food for chemical digestion by enzymes; chewing, mixing of food w/ saliva by the tounge, churning food in the stomach & segmentation |
| segmentation | rhythmic local constrictions of the intestine; mixes food w. digestive juices & increases the efficiency of absorption by repeatedly moving different parts of the food mass over the intestinal wall |
| @#$%^&*()_ | 789789789678978960#@$&*()_ |
| absorption | passage of digested end products (+ vitamins, minerals & water) fm the lumen of th eGI tract into the blood or lymph; to occur substances must first enter the mucosal cells by active or passive transort processes |
| the major absorption site is the | small intestine |
| defecation | eliminates indigestible substances from the body via the anus in the form of feces |
| list the six essential activities for processing food by the digestive system | ingestion, propulsion, mechanical digestion, chemical digestion, absorption & defecation |
| two things that apply tot eh regulatory mechanisms | 1. digestive activity is provoked by a range of mechancial & chemical stimuli; controls of digestive activity are both extrinsic & intrinsic |
| sensors (location & response) | are located in the walls of the tract organs; respond to several stimuli (streching of the organ wall by food in the lumen, osmolarity (solute concentration) & pH of the contents & presence of substrates & end products of digestion |
| receptors initiate reflexes that | (1) activate or inhibit glands that secrete digestive juices into the lumen or hormones into the blood or (2) mix lumen contents & move them along th elength of the tract by stimulating the smooth muscle of the GI tract walls |
| the walls of the alimentary canal contains | nerve plexuse; they extend & influence each other; aquires two kindes of reflexes (short & long) |
| short reflexes are | mediated entirely by the local (enteric) plexuses (so-called gut brain ) in response to GI tract stimuli |
| long reflexes are | initiated by stimuli arising within or outside the GI tract & involve CNS centers & extrinsic autonomic nerves |
| the stomach & sm. intestin contain hormone-producing cells that are distributed via the | blood to their target cells |
| peritoneum | most extensive of the serous membranes |
| visceral peritoneum | covers the external surfaces of most digestive organs & is continuous with the parietal peritoneum |
| parietal peritoneum | lines the body wall |
| peritoneal cavity | is between the two peritoneums; is a slitlike potential space containing fluid secreted by the srous membranes |
| the serous fluid | lubricates the mobile digestive organs & allows them to glide easily across one anothe & alon the body wall as they cary outh their digestive activites |
| mesentery | double layer of peritoneum -- a sheet of two serous membranes fused back to back-- that extends tot he digestive organs from the body wall; provide routes for blood vessels, lymphatics & nerves to reach the digestive visceral; they also hold organs in pla |
| retroperitoneal organs | most of the pancres & parts of the large intestine that are not suspended by a mesentery |
| intraperitoneal/peritoneal organs | digestive organs (like the stomach) that keep their mesentery & remain in the peritoneal cavity |
| peritonitis | inflammation of the peritoneum, can arise from a piercing wound of the abdomen or from a perforating ulcer that leaks stomach juices intot he peritoneal cavity, most commonly from a burst appendix |
| splanchnic circulation | arteries that branch off the abdominal aorta to serve the digestive organs & the hepatic portal circulation |
| name the four basic tunics of the alimentary canal from the lumen outward | mucosa, submucosa, muscularis externa & serosa |
| mucosa | innermost layer; lines the lumen of the alimentary canal from mouth to anus; 3 major functions secretion, absorption & protection |
| explain what secretion does during the mucosa | secretion of mucus, digestive enzymes & hormones |
| explain absorption in the mucosa | absorption of the end products of digestion into the blood |
| explain protection in the mucosa | protection against infectious disease |
| name the typical digestive mucosas sublayers | (1) a lining epithelium (2) a lamina propria (#) a muscularis mucosae |
| the epithelium of the mucosa is a | simple columnar epithelium that is rich in mucus-secreting goblet cells |
| the slippery mucus it produces protects certain digestive organs from | being digested themselves by enzymes working within their cavities & eases food passage along the tract |
| lamina propria | underlies the epithelium, is loose areolar (or reticular) connective tissue; its capillaries nourish the epithelium & absorb digested nutrients |
| MALT | the mucosa-associated lymphatic tissue are importanct in the defense against bacteria & other pathogens, which have rather free access to our digestive tract |
| peristalsis mucosae | is external tot he lamina propria, a scant layer of smoth muscle cells that produces local movements of the mucosa; Ex, twitching of this muscle layer dislodges food particles that have adhered tot eh mucosa |
| the submucosa | external tot he mucosa; moderately dense connective tissue containing blood & lymphatic vessels, lymph nodules & nerve fibers; enables the stomach to regain its normal shape after temporarily storing a large meal |
| muscularis externa/muscularis | deep to the submucosa; responsible for segmentation & peristalsis (mixes & propels foodstuffs along the digestive tract) |
| the musclaris externa layers are | the inner circular layer & an oter longitudinal layer of smooth muscle cells |
| sphincters | act as valves to prevent backflow & control food passage from one organ to the next; occurs from the circular lyer thickens |
| the serosa | protective outermost layer of the intraperitoneal organs is the visceral peritoneum; formed of areolar connevtive tissue covered w. mesothelium, a single layer of squamous epithelial cells |
| adventitia | ordinary fibrous connective tissue that binds the esophagus to surrounding sturctures; replaces the serosa (ex. esophagus which is located in the htoracic instead of abdominopelvic cavity) |
| enteric neurons | the alimentary canals own in-house nerve supply which communicate widely w. each other to regulate digestive system activity;constitute the bulk of the two mj intrinsic nerve plexuses found within the walls of the alimentary cnal; submucosal & myenteric n |
| submucosal nerve plexus | occupies the submucosa & chiefly regulates the activity of glands & smooth muscle in the mucosa tunic |
| myenteric nerve plexus | lies between the circular & longitudinal layers of smooth muscle of the muscularis externa; provide the mj nerve supply tot he G |
| the 3 types of papillae are | filiform, fungiform, & circumvallate |
| filiform papillae | give the toung surface a roughness that aids in licking semisolid foods & provide friction for manipulating foods inthe mouth (their the smallest and most numoruse); contain keratin which stiffens them & gives tounge whitish apperance |
| fungiform papillae | mushroom shaped; scattered widely; each has a vascular core that gives reddish hue |
| what is the purpose of saliva | 1)cleanses the mouth 2)dissolves food chemicals so they can be tasted 3) moistens food & aids in compacting it intoa bolus 4) contains enzymes that begin the chemical breakdown of starchy foods |
Created by:
Brina
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