BIOL 373 Final Exam || Errorless Answers 100%.
What are the functions of the GI system? correct answers 1. digestion - break macromolecules
(nutrients) into forms that can be transported across the epithelium
2. absorption - transport nutrients, water, ions, vitamins across epithelium
3. secretion - release of enzymes into the gut lumen (heavily regulated)
4. motility - keep the gut contents moving (heavily regulated)
5. maintain water balance - balance between secretion and reabsorption
What are some problems faced by the GI tract regarding its function? correct answers 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 correct answers 1. stomach
2. small intestine - duodenum, jejunum, ileum
3. large intestine - colon, rectum
Muscosal surface amatony correct answers 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? correct answers stomach:
-gastric glands
-oblique muscle
small intestine:
-villi, crypt
-Peyer's patch (in mucosa)
What features increase surface area? correct answers stomach - gastric glands
small intestine - crypts
What are the 2 major patterns of contraction for gut motility? correct answers 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 correct answers -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 correct answers -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 correct answers -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 correct answers -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? correct answers -water and ions (secreted into lumen then reabsorbed)
-enzymes
-mucus
-bile (from liver)
-saliva
How are water and ions secreted? correct answers -mostly via membrane transporters
, -water follows osmotic gradient
-water and ions in some regions can also pass between cells (paracellular pathway)
-similar channels/transports to kidney
transporters:
Na/K ATPase, NKCC cotransporter, Cl/CHO exchanger, Na/H+ exchanger, H/K exchanger
ion channels:
-ENaC, K+ channels, Cl channels (including CFTR)
How is acid secreted? correct answers -secreted by parietal cells
1. CA forms bicarb in pariteal cells
2. basolateral side: HCO3- out and Cl- in
3. apical side: H+ out and K+ in (H+/K+ATPase), Cl- out via Cl- channel
bicarb moving out is absorbed in blood - 'alkaline tide' can be measured after a meal
How is bicarb secreted? correct answers -secreted from epithelial cells lining ducts of pancreas -
> duodenum to neutralize stomach acid
1. CA (H20 + CO2 -> HCO3- + H+) creates bicarb inside cells
2. basolateral side: Cl- in via NKCC transporter
3. apical side: bicarb secreted via Cl-/HCO3- exchanger, Cl- out via CFTR channel and reenters
via Cl-/HCO3- exchanger
How is NaCl secreted? correct answers -secreted from small intestine, colon, salivary glands
1) Na+, K+, 2 Cl- enter via NKCC transporter (basolateral side)
2) Cl- enters lumen through CFTR channel (apical side)
3) Na+ is reabsorbed (Na+/K+ ATPase) (basolateral side)
What are the functions of the GI system? correct answers 1. digestion - break macromolecules
(nutrients) into forms that can be transported across the epithelium
2. absorption - transport nutrients, water, ions, vitamins across epithelium
3. secretion - release of enzymes into the gut lumen (heavily regulated)
4. motility - keep the gut contents moving (heavily regulated)
5. maintain water balance - balance between secretion and reabsorption
What are some problems faced by the GI tract regarding its function? correct answers 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 correct answers 1. stomach
2. small intestine - duodenum, jejunum, ileum
3. large intestine - colon, rectum
Muscosal surface amatony correct answers 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? correct answers stomach:
-gastric glands
-oblique muscle
small intestine:
-villi, crypt
-Peyer's patch (in mucosa)
What features increase surface area? correct answers stomach - gastric glands
small intestine - crypts
What are the 2 major patterns of contraction for gut motility? correct answers 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 correct answers -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 correct answers -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 correct answers -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 correct answers -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? correct answers -water and ions (secreted into lumen then reabsorbed)
-enzymes
-mucus
-bile (from liver)
-saliva
How are water and ions secreted? correct answers -mostly via membrane transporters
, -water follows osmotic gradient
-water and ions in some regions can also pass between cells (paracellular pathway)
-similar channels/transports to kidney
transporters:
Na/K ATPase, NKCC cotransporter, Cl/CHO exchanger, Na/H+ exchanger, H/K exchanger
ion channels:
-ENaC, K+ channels, Cl channels (including CFTR)
How is acid secreted? correct answers -secreted by parietal cells
1. CA forms bicarb in pariteal cells
2. basolateral side: HCO3- out and Cl- in
3. apical side: H+ out and K+ in (H+/K+ATPase), Cl- out via Cl- channel
bicarb moving out is absorbed in blood - 'alkaline tide' can be measured after a meal
How is bicarb secreted? correct answers -secreted from epithelial cells lining ducts of pancreas -
> duodenum to neutralize stomach acid
1. CA (H20 + CO2 -> HCO3- + H+) creates bicarb inside cells
2. basolateral side: Cl- in via NKCC transporter
3. apical side: bicarb secreted via Cl-/HCO3- exchanger, Cl- out via CFTR channel and reenters
via Cl-/HCO3- exchanger
How is NaCl secreted? correct answers -secreted from small intestine, colon, salivary glands
1) Na+, K+, 2 Cl- enter via NKCC transporter (basolateral side)
2) Cl- enters lumen through CFTR channel (apical side)
3) Na+ is reabsorbed (Na+/K+ ATPase) (basolateral side)
