! ! HUN3224!Spring!2012!! ! Exam!I!Study!Guide!! ! Feresin!!!I. Digestion+and+Absorption+of+Carbohydrates,+Lipids,+Proteins+The+Gastrointestinal+Tract:+physiology+• Mouth!–!esophagus!–!stomach !– !small!intestine!–!large !in te stin e !Functions!of!GI!Tract!• Makes!nutrients!available!to!cell!via:!Digestion:!hydrolysis !o f!nutrients,!food!broken!down!Absorption:!passage !o f!s imple!mo le c u le s!a cr o ss !g u t!wall!and !in to !b lo o d !( o r!ly mph)!• Elimination!of!wastes!• Protects!body!from!harmful!substances;!HCl!in!stomach!=!antibacterial!agent!• Metabolic!processes:!Metabolism!of!food!!Organs+of+GI+Tract+GI!Tract!–!Lumen!• Mucosa:!innermo st !lay e r;!3 !la y er s!o Epithelial:!in!contact!w/ !lu men;!contains!en d o c rin e !(h ormon e )!a n d !e xo c rin e !(e n z yme)!glands!o Lamina+Propria:!whit e!blood!c ells!o Muscularis+Mucosa+• Submucosa:!connective!tissue,!carries!white!blood!cells!o Network!of!nerves!–!submucosa!plexus!! ! HUN3224!Spring!2012!! ! Exam!I!Study!Guide!! ! Feresin!!o Peristalsis:!wavelike!movement;!mainly!in!esophagus!• Muscularis-Externa:!layer!whe re !p er ist als is !o cc u rs ,!movem e n t!• Serosa:!outermost!laye r!!DIGESTION:!the!following!are !the!ste ps!o f!digestio n;!I!have !includ ed !an !overall!summary!table!at!the!end!of!this!portion!of!the!study!guide!for!easier!memorization,!but!know!ALL!steps!and!details!Mouth!–!oral+cavity;+digestion+of+CHO+beg ins +he r e!• 3!salivary!secreting!glands:!parotid,!sublingual,!submandibular/submaxillary!o Sublingual!and!Submandibular!are!the!only!ones!secreting!mucus!(lubricates!and!protects!against!acid!and!erosion)!• 99%!of!saliva!is!H2O;!contains!dissolving!properties!o Saliva!components:!water,!electrolytes,!mucus,!enzymes,!antibacterial/antiviral!compounds!§ Enzymes:!§ Salivary+amylase:!produced!in!salivary!glands;!digestion!of!CHO,!hydrolyzes!alpha!1,4!linkages!§ Lingual+lipase:!only!activ at es !in !s to mach;!fat s!(s h o r t!& !med.!ch a in !tr igly c er id es )!o Lysozymes:!kill!bact e ria !o Mastication:!chewing!breaks!down!food;!increases!surface!area!§ Bolus:!ball!from!mixture!of!food!and!saliva!• Digestion!of!Starch!o Amylopectin:!(alpha!1 ,4 !lin k ag e s)!f o rms!dext rin ,!maltose!( glu c o s e!a n d !g lu c o se ),!maltotrio s e!(maltose!an d!g luco se )!o Dextrin!contains!1,6!linkage!–!harder!to!digest!o Amylase:!(alpha!1,4!link ag e s)!fo r m s !maltotrios e !an d !maltose!Esophagus:!bolus!p ro p e lle d !th r o u g h !p e rist a lsis!• Muscular!tube:!connects!back!of!mouth!to!stomach;!movement!of!food!via!peristalsis!• At!top!of!esophagus!–!some!voluntary!movemen t!• Upper!esophageal!sphincter:!opening!at!top!to!let!food!in!• Lower!esophageal!sphincter:!relaxes!to!let!food!into!stomach!o Pressure!in!sphincter!>!pressure!in!stomach!o Once!pressure!drops,!valve!will!open,!food!will!pass!o Constricts!to!keep!food!from!moving!back!up!into!esophagus!Stomach!–!holds!food;!secrete s!protein^digesting!enzymes!and!strong!acids,!wher e !p ro t e in !d ig e s tion!begins!3!types!of!muscle!o Circular,!longitudinal,!oblique!(diagonal)!• Mechanical!mixing!and!breakdown!of!food!o Formation!of!chyme!(bolus!and!gastric!juices)!• Gastric!secretions!• Absorption!of!few!fat^soluble!substances!(aspirin!and!alcoho l)!• 4!sections!(from!top!to!bottom):!cardium,!fungus,!body,!distal/antrum!o Rugae:!can!flatten ;!a llo ws!stom a c h !to !e x p an d!and!h o ld !more!• 4!types!of!cells!in!stomach!(in!gastric!juice)!o Neck!cells:!secrete!mucus!o Enteroendocrine!cells:!secrete!hormones!! ! HUN3224!Spring!2012!! ! Exam!I!Study!Guide!! ! Feresin!!o Chief!(pectic)!cells:!secrete!enz ym e s!(ga stric!lipas e,!pe psin og en )!o Parietal!cells:!Ach!secretion!a n d !IP !(n e c es sa r y!for!abso rp tio n!of!vitamin!B12 )!Lipid!Digestion!in!Stomach!• Lipids:!digested!by!lipase/lingual!lipa se !• Only!20%!of!lipid!digestion!occurs!in!stomach;!rest!occu rs!in!small!in te s tin e!• pH!in!stomach:!low!because!of!HCl!o acidity!of!HCl!inactivates!salivary!amylase!o NO!CARBOHYDRATE!DIGESTION!IN!STOMACH!Protein!digestion!in!Stomach!• Protein:!hydrolysis!to!smaller!peptides!(proteases,!peptones)!via!pepsin!ß!produced!in!gastric!glands;!released!in!stomach!o Pepsin!is!an!endopeptidase!(break!bon ds !within!protein)!o Exopeptidases!break!bonds!in!terminal!end!of!proteins!• Pepsinogen:!zymogen!–!in a c tiv e!protein!digesting!enzyme!o Zymogens:!proteolytic!enzymes!secreted!in!inactive!form !bec au se !they !will!de stroy !the !cells!that!produce!them;!they!are!activated!where!needed!o Pepsinogen!(inactive!form)!secreted!in!response!to!Ach!by!chief!(peptic)!cells!§ Activation!of!pepsinogen!by!HCl!and!pepsin!(autocatalytic!–!pepsin!can!activate!pepsinogen!as!well)!Removal!of!peptide!activates!pepsinogen.!o Activation!produces!pepsin!(active)!to!act!on !pro tein ;!hydroly ze s !to !s m a lle r!p e p tides!o HCl!will!act!upon!protein!by!denaturation!BEFORE!pepsin!§ Uncoiling!of!protein;!H^bonds!&!disulfide!bridges!broken!by!HCl!§ Bonds!left!open,!pepsin!comes!in!and!breaks!these!bonds!o Pepsinogen!1!&!2:!produced!in!body!of!stomach!(2!also!produced!in!distal!end)!• HCl:!Secreted!by!parietal!cells,!even!w h e n !s tomach!is!emp t y!o Regulated!by!Gastrin+(+)!§ Peptide!hormone!§ Release!stimulated!by!presence!of!protein!or!by!gastrin^releasing!pe ptid e!(GR P!or!bombesin)!in!response!to!Ach!§ Secreted!by!enteroendorcine!cells!• G!cells:!in!stomach/small!intestine;!proximal!end!(du o d e n um)!o Regulated!by!Acetylcholine+(+)!§ Released!in!response!to!local!reflex!of!stomach!distention!§ Vagus!nerve!stimulated,!releases!Ach,!Ach!stimulates!release!of!GRP!which!stimulates!release!of!gastrin!o GRP!also!released!by!enteric!nerves!(in!GI!tract)!o Ach!can!also!act!directly!on!gastrin!cells!§ Ach:!can!also!act!on!parietal!cells!o Regulated!by!Histamine+(+)!§ Vasoactive!Amine,!produced!by!mast!cells!o Stimulated!by!vagus!nerve!and!gastrin!as!well!o Like!gastrin!&!Ach,!has!receptor!on!parietal!cell!• Parietal!cells!have!H2!receptors:!hista m ine !will!bin d!to !form !H Cl!o Regulated!by!Somatostatin+(N)+–!a!hormone!produced!in!stomach/duodenum!§ Inhibits !H C l!s ec re tio n !§ Ach!inhibits!secretion!of!somatostatin!whereas!H+!promotes!secretion!! ! HUN3224!Spring!2012!! ! Exam!I!Study!Guide!! !
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