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GI > Everything Else > Flashcards

Everything Else Flashcards

1
Q

What are the 3 functional layers of GI histology

A

Muscularis mucosa
Submucosa
Muscularis propria/externa

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2
Q

What is the function of muscularis mucosa?

A

Controls shape and surface area of mucosa

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3
Q

What plexus is found in the submucosa and what is its function?

A

Submucosal plexus controls secretions and blood flow

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4
Q

What are the layers of muscularis propria, what are their functions, and what plexus is found inbetween?

A

Inner circular layer contracts to decrease diameter
Outer longitudinal layer contracts to decrease length
Myenteric plexus controls GI motility

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5
Q

What are phasic contractions? Where do phasic contractions occur in the GI?

A

Periodic contractions followed by regular periods of relaxation
Occur in esophagus, antrum, SI, and any tissue involved in mixing and propulsion

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6
Q

What are tonic contractions? Where do they occur in the GI?

A

Tonic contractions long maintained contractions without regular periods of relaxation
Occur in distal esophagus, orad, ileocecal junction, and internal anal sphincter

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7
Q

What are slow waves?
Are they AP?
Can they trigger contractions? If so where?

A

Slow waves are changes in membrane potential
Slow waves ARE NOT AP
Subthreshold slow waves can trigger weak contractions in the stomach

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8
Q

What stimulates increased amplitude and number of AP on slow waves?

A

Parasymp
Stretch
Ach

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9
Q

What decreases the amplitude and number of AP per slow wave?

A

Symp

NE

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10
Q

What are the 3 phases of the swallow reflex? Which are voluntary and which are involuntary?

A

Oral phase- voluntary
Pharyngeal phase- involuntary
Esophageal phase- involuntary

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11
Q

What is the oral phase of swallowing?

A

Voluntary phase- tongue pushes food bolus into pharynx

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12
Q

What is the pharyngeal phase of swallow reflex?

A

Involuntary
Pharynx detects bolus triggering afferent vagus n to travel to medulla and efferent vagus to return to pharynx. The soft palate elevates to close off nasal cavity, epiglottis closes off trachea, UES relaxes, and peristaltic contraction moves food into esophagus

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13
Q

What is the esophageal phase of swallow reflex?

A

Involuntary
1st peristaltic wave- continuation of pharyngeal peristaltic contraction moves food to stomach
2nd peristaltic wave- occurs only if 1st wave is unsuccessful and is under control of ENS, not vagus n, and moves food stomach. Does not require oral or pharyngeal phase to occur to be triggered and can occur following a vagotomy

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14
Q

What is GERD? What are symptoms and associated problems?

A

Gastroesophageal reflux disease
Occurs due to abnormal relaxation of LES allowing gastric contents to go into esophagus
Causes heartburn, dysphasia, and may cause Barrett’s esophagus

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15
Q

What is Achalasia?

A

Impaired peristalsis fails to relax LES so food accumulates in esophagus which will distend

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16
Q

What are the two physiological regions of the stomach? Which type of gastritis is associated with each region?

A

Orad- LES to mid body- Type A gastritis

Caudad- mid body to pylorus- Type B gastritis

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17
Q

What is receptive relaxation?

Is receptive relaxation possible following a vagotomy?

A

Receptive relaxation occurs followng swallowing reflex when the distal esophagus distends triggering a vagovagal reflex which results in the release of VIP which relaxes the LES and will decrease P and increase volume of stomach to allow passage of food
Vagotomy- receptive relaxation inhibited

18
Q

Explain mixing and digesting in the stomach and how retropulsion occurs

A

Occurs in caudad of stomach and is trigged by slow waves occuring 3-5 times per minute = 3-5 contractions per minute
Peristaltic contraction increases in velocity and force as it moves closer to pylorus and will rebound off closes pylorus and be propelled back into stomach for further mixing and digesting

19
Q

What are factors that increase gastric AP and force of contractions?

A

Parasympathetics, gastrin, and motilin

20
Q

What are factors that decrease gastric AP and force of contractions?

A

Sympathetics, secretin, and GIP

21
Q

What factors increase the rate of gastric emptying?

A

Decrease gastric distensibility
Decrease pyloric sphincter tone
Increase force of gastric contractions
Increase diameter of small intestine and inhibit segmental contractions

22
Q

What factors decrease rate of gastric emptying?

A

Increase gastric distensibility (via CCK)
Increase pyloric sphincter tone
Decrease force of gastric contractions (symp, secretin, GIP)
Increase segmental contractions in SI

23
Q

Explain purpose of enterogastric reflex?

What triggers it and how does it work?

A

Enterogastric reflex is neg feedback from duodenum to stomach to prevent premature gastric emptying
Acid- H binds receptors triggering release of secretin which inhibits gastrin and decreases gastric motility
Fat- triggers release of CCK and GIP which inc distensibility and dec motility to slow gastric empyting

24
Q

What is gastroparesis?
What is it associated with?
What is the cause?

A

Gastroparesis is gastric paralysis resulting in failure to empty stomach
Associated with type 1 diabetes
Causes by vagus n damage- either idiopathic or due to elevated blood glucose levels causing demyelination

25
Q

What are migrating myoelectric complexes (MMC)?

When do they occur and what mediates them?

A

MMCs are peristaltic contractions that occur in the stomach in 90 minute intervals during fasting periods to remove any remaining particles from stomach
Mediated by motilin

26
Q

What are segmental contractions?

A

Segmental contractions occur in the SI to mix chyme

They occur in the middle of bolus to separate it apart so that when they come back together they mix

27
Q

Do slow waves trigger contractions in SI?
What do slow waves set?
What triggers SI contractions?

A

Slow waves in SI do not trigger contractions but rather set the maximum frequency of contractions
Spike potentials trigger contractions in SI

28
Q

What are the pacemaker cells GI plexuses?

A

Interstitial cells of cajal (ICC)

29
Q

Explain the mechanism of SI peristaltic contractions

A

Enterochromaffin cells in SI detect bolus and release serotonin which binds IPANS triggering peristaltic reflex
NT released above bolus stimulate IC and inhibit OL
NT released below bolus stimulate OL and inhibit IC

30
Q

What factors stimulate SI peristaltic contractions?

A

Serotonin, insulin, gastrin, motilin

31
Q

What factors inhibit SI peristaltic contractions?

A

E, glucagon, and secretin

32
Q

What part of the brain mediates the vomit reflex?

A

Medulla

33
Q

What is the mechanism of vomiting?

A

Reverse peristalsis in SI, relax pyloric sphincter and stomach, force inspiration to increase intraabdominal pressure, relax LES, move larynx, close glottis, vomit

34
Q

What triggers the ileal sphincter to open?

What triggers the ileal sphincter to close?

A

Ileal distention opens sphincter

Cecal distention closes sphincter

35
Q

What is the name of OL muscle in the LI?

What structural feature of LI in associated with contractions?

A

OL- teniae coli

Haustra- associated with LI contractions/ not fixed

36
Q

What muscle makes up internal anal sphincter?

What muscle make sup external anal sphincter?

A

IAS- smooth muscle

EAS- striated muscle

37
Q

What are the parasymp innervations of the LI?

A

Vagus n- cecum, AC, TC

Pelvic splanchnic nerve- DC, SC, rectum

38
Q

What are the sympathetic innervations of the LI?

A

Superior mesenteric ganglion- proximal LI
Inferior mesenteric ganglion- distal LI
Hypogastric ganglion- anal canal

39
Q

How many mass movements occur in the LI per day?

A

1 to 3 mass movements per day in LI

40
Q

What is the result of poor motility in LI?

What is the result of excess motility in LI?

A

Poor motility- excess absorption, fecal compaction, constipation

Excess motility- poor absorption, loose stools, diarrhea

41
Q

Explain the rectosphincteric reflex?

A

Rectum distention, smooth muscle of LI contracts, IAS relaxes, feces pass into anal canal
EAS is under voluntary control

42
Q

What is Hirschsprung’s disease?
What is the cause?
What hormone level is low? What is the result?

A

Hirschsprung’s disease is megacolin
Due to ganglion failing to innervate LI
VIP levels low, result in muscle constriction, and fecal compaction

GI (10 decks)

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