BIOL 373 FINAL PAPER UPDATED
COMPLETE QUESTIONS AND CORRECT
ANSWERS BUNDLED REVIEW GUIDE
●● What are some problems faced by the GI tract regarding its function?
Answer: 1. need to digest marcomolecules but not itself
-break down of barriers? -> peptic, duodenal ulcers
2. needs to allow entry of digested nutrients but not pathogens
-GI lining is largest area of contact between internal and external
environments
-protection from pathogens mediated by:
+ epithelial barrier
+ mucus
+ digestive enzymes
+ acid
+ gut associated lymphoid tissue (GALT) - needs to react to pathogens
but not foreign proteins associated with food
●● Anatomy
Answer: 1. stomach
2. small intestine - duodenum, jejunum, ileum
3. large intestine - colon, rectum
,●● Muscosal surface amatony
Answer: 1. mucosa - epithelium, lamina propria, muscularis mucosa
2. submucosa - Meissner's (Submucosal) plexus
3. smooth muscle layers - circular muscle, auerbach's (myenteric)
plexus, longitudinal muscle
4. serosa
●● Differences between small intestine and stomach anatomy?
Answer: stomach:
-gastric glands
-oblique muscle
small intestine:
-villi, crypt
-Peyer's patch (in mucosa)
●● What features increase surface area?
Answer: stomach - gastric glands
small intestine - crypts
●● What are the 2 major patterns of contraction for gut motility?
Answer: 1. peristalis - moving food from mouth to anus (forward
movement)
,2. segmental contractions - mixing/churning, maximizes exposure to
digestive enzymes and epithelium (little or no net forward movement)
these occur during/after a meal
●● Tonic vs. phasic contractions
Answer: -most gut muscle is a single unit smooth muscle, connected by
gap junctions
-certain regions are tonically contracted for minutes to hours
+ smooth muscle sphincters
+ anterior part of the stomach (keeps food from moving backwards)
-other regions undergo phasic contractions
+ posterior stomach
+ small intestine
●● Migrating motor complexes
Answer: -a series of contractions that begin in the empty stomach and
end in the large intestine (~90 minutes)
-"house keeping" function -> sweeps food remnants and bacteria out of
GI tract and into the large intestine
-between meals
●● Slow wave potentials
, Answer: -slow waves similar to pacemaker potentials in cardiac muscle
except much less frequent, and do not necessarily reach threshold
+ below threshold = no contraction
+ above threshold = opening of voltage-gated Na+ channels -> action
potentials -> contraction
-degree of contraction is graded according to amount of Ca2+ that enters
+ longer wave = more time for Ca2+ to enter = larger contraction
+ amplitude and duration of contraction influenced by: neurotransmitters
(autonomic input), hormones, paracrine factors
●● Interstitial cells of cajal
Answer: -slow wave frequency varies in different regions of the tract
+ more frequent in duodenum vs. stomach
+ set by 'pacemaker cells' between smooth muscle layers "interstitial
cells of Cajal"
●● What is secreted?
Answer: -water and ions (secreted into lumen then reabsorbed)
-enzymes
-mucus
-bile (from liver)
-saliva
COMPLETE QUESTIONS AND CORRECT
ANSWERS BUNDLED REVIEW GUIDE
●● What are some problems faced by the GI tract regarding its function?
Answer: 1. need to digest marcomolecules but not itself
-break down of barriers? -> peptic, duodenal ulcers
2. needs to allow entry of digested nutrients but not pathogens
-GI lining is largest area of contact between internal and external
environments
-protection from pathogens mediated by:
+ epithelial barrier
+ mucus
+ digestive enzymes
+ acid
+ gut associated lymphoid tissue (GALT) - needs to react to pathogens
but not foreign proteins associated with food
●● Anatomy
Answer: 1. stomach
2. small intestine - duodenum, jejunum, ileum
3. large intestine - colon, rectum
,●● Muscosal surface amatony
Answer: 1. mucosa - epithelium, lamina propria, muscularis mucosa
2. submucosa - Meissner's (Submucosal) plexus
3. smooth muscle layers - circular muscle, auerbach's (myenteric)
plexus, longitudinal muscle
4. serosa
●● Differences between small intestine and stomach anatomy?
Answer: stomach:
-gastric glands
-oblique muscle
small intestine:
-villi, crypt
-Peyer's patch (in mucosa)
●● What features increase surface area?
Answer: stomach - gastric glands
small intestine - crypts
●● What are the 2 major patterns of contraction for gut motility?
Answer: 1. peristalis - moving food from mouth to anus (forward
movement)
,2. segmental contractions - mixing/churning, maximizes exposure to
digestive enzymes and epithelium (little or no net forward movement)
these occur during/after a meal
●● Tonic vs. phasic contractions
Answer: -most gut muscle is a single unit smooth muscle, connected by
gap junctions
-certain regions are tonically contracted for minutes to hours
+ smooth muscle sphincters
+ anterior part of the stomach (keeps food from moving backwards)
-other regions undergo phasic contractions
+ posterior stomach
+ small intestine
●● Migrating motor complexes
Answer: -a series of contractions that begin in the empty stomach and
end in the large intestine (~90 minutes)
-"house keeping" function -> sweeps food remnants and bacteria out of
GI tract and into the large intestine
-between meals
●● Slow wave potentials
, Answer: -slow waves similar to pacemaker potentials in cardiac muscle
except much less frequent, and do not necessarily reach threshold
+ below threshold = no contraction
+ above threshold = opening of voltage-gated Na+ channels -> action
potentials -> contraction
-degree of contraction is graded according to amount of Ca2+ that enters
+ longer wave = more time for Ca2+ to enter = larger contraction
+ amplitude and duration of contraction influenced by: neurotransmitters
(autonomic input), hormones, paracrine factors
●● Interstitial cells of cajal
Answer: -slow wave frequency varies in different regions of the tract
+ more frequent in duodenum vs. stomach
+ set by 'pacemaker cells' between smooth muscle layers "interstitial
cells of Cajal"
●● What is secreted?
Answer: -water and ions (secreted into lumen then reabsorbed)
-enzymes
-mucus
-bile (from liver)
-saliva
