2. Digestive System- throat and stomach

pharynx

nasopharynx, oropharynx, laryngopharynx

nasopharynx

posterior to nasal cavity: air passage: contain openings to auditory tubes

oropharynx

posterior to oral cavity; air and food passage

laryngipharynx

posterior to larynx; passageway to esophagus

swallowing

tongue forces food into pharynx, soft palate, hyoid, and larynx raise, tongue presses against palate, epiglottis closes, inferior constrictor muscles relax so esophagus opens, superior constrictor muscles contract and initiate peristaltic wave that forces food into esophagus. wave moves food through esophagus to stomach

esophagus

contains mucous glands in submucosa

in muscularis

superior 1/3- skeletal, middle 1/3- skeletal and smooth, inferior 1/3- smooth

lower esophageal sphincter

regulates food passage into stomach, closes to prevent regurgitation of food

stomach parts

cardia, fundus, body, pylorus

cardia

region near opening to esophagus, contains lower esophageal sphincter

fundus

rounded area that rises above cardia, temporary food storage, which sometimes contains swallowed air

body

main portion, between fundus and pylorus

pylorus

closest to small intestine, funnel shaped pyloric antrum narrows to become pyloric canal

pyloric sphincter

circular smooth muscle, controls gastric emptying

gastric secretions

surface of membrane studded with gastric pits at end of tubular gastric glands, lining has simple columnar epithelium with many mucous cells near surface

gastric cells

mucous, parietal, chief, enteroendocrine

mucous cells

Line the stomach surface and upper pits; they secrete a protective, alkaline mucus and bicarbonate to shield the stomach wall from self-digestion by acid

parietal cells

Found mainly in the fundus and body of the stomach; they secrete hydrochloric acid to sterilize food and activate enzymes, as well as intrinsic factor, which is required for vitamin B12 absorption in the small intestine

chief cells

Located deep in the base of the gastric glands; they secrete pepsinogen, an inactive enzyme that converts into active protein-digesting pepsin when exposed to stomach acid

enteroendocrine cells

Found deep in the glands and release hormones directly into the bloodstream rather than the stomach lumen

somatostatin

inhibits hydrochloric acid secretion

gastrin

increases gastric juice secretion

cholecystokinin

released by small intestine cells when proteins and fat enter small intestine, decreases gastric motility

cephalic phase

senses of food triggers para reflex, gastric juice secreted

gastric phase

food in stomach stimulates release of gastrin, stimulates secretion of gastric juice, reflex responses also stimulate gastric juice secretion

intestinal phase

food enters small intestine, stimulates intestinal cells to release intestinal gastrin, promotes secretion of gastric juice from stomach wall

pepsin

breaks down proteins

nutrients absorbed

in small intestine

stomach aborbs

SOME water, certain salts, lipid soluble drugs, alcohol

enterogastric reflex

when chyme starts to fill small intestine, stretch receptors initiate enterogastric reflex, slows stomach emptying and intestinal filling