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Physiology Block 3 > 11 - GI Motility > Flashcards

11 - GI Motility Flashcards

1
Q

What are the teeth of mastication? What is each used for and how many pounds of pressure is each capable of?

A

Incisors: in the front, used for cutting; 50 lbs of pressure

Molars: in the back, used for grinding; 200 lbs of pressure.

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2
Q

What nerve innervated the muscles of mastication?

A

Cranial nerve 5 - the motor component of the trigeminal nerve.

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3
Q

What is the chewing reflex?

A

Bolus of food inhibits muscles of mastication and lower jaw drops.

Stretch reflex is activated, leading to rebound contraction.

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4
Q

What are the three phases of swallowing? Describe the important aspects of these stages.

A
  1. Voluntary phase: Tongue propels food into pharynx
  2. Pharyngeal: Soft palate moves up (due to stim of tonsillar pillars), preventing food from entering nasal passage. Trachea comes up and epiglottis covers trachea. UES opens so food can enter..
  3. Esophageal phase - primary or secondary peristalsis
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5
Q

What is primary peristalsis?

A

Pressure is generated in the pharynx, then there’s a drop in pressure when the UES opens.

Pressure goes up in different parts of the esophagus as the bolus moves down.

Contraction behind the bolus pushes it down (Ach SubP).

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6
Q

What is receptive relaxation? What substances allow this to occur?

A

When the stomach and LES relax waiting for the bolus of food to enter.

VIP and Nirtic Oxide

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7
Q

What is secondary peristalsis? When does it occur? What stimulated this?

A

Occurs when fragments of food get stuck in the esophagus and need a sweeper to push it through.

There’s a contraction behind the bolus (SubP and Ach) and the pressure in the LES has already dropped (receptive relaxation)

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8
Q

Describe the muscles of the esophagus?

A

Proximal 1/3 is striated

Bottom 2/3 is smooth muscle

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9
Q

What contributes to the increased pressure found in the lower esophageal sphincter area?

A

The diaphragm.

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10
Q

What is a hiatal hernia? Describe the Z line. What do hiatal hernias contribute to?

A

LES at the Z-line where the two types of mucosa meet. Normally diaphragm is at the Z line.

Some people have weakness at this region and their stomach can move above the diaphragm.

Contribute to reflux.

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11
Q

What is Gastroesophageal reflux disease (GERD)? How does this compare to the anatomy of a healthy individual?
What predisposes someone to GERD?

A

Irritation of the esophagus caused by gastric reflux.

Normally LES will relax during burping, but some patients get this more commonly and it lasts longer than a burp.

Predisposition to GERD: hiatal hernia and abnormal transient LES relaxation.

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12
Q

What is achalasia?

A

Motor disorder of motility in which the LES fails to relax and food is not being emptied into the stomach from the esophagus.

Insufficient Nitric oxide and VIP produced to relax LES.

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13
Q

What is dysphagia and what are the two types?

A

Difficulty swallowing.

Oropharyngeal and esophageal dysphagia.

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14
Q

Describe oropharyngeal dysphagia: What are common characteristics and what types of illnesses cause it? What type of test is done to diagnose it?

A

Difficulty initiating swallowing with aspiration, caused by neuromuscular disorders.

Video fluoroscopy.

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15
Q

Describe esophageal dysphagia: what are common characteristics and how is it diagnosed?

A

Food gets down but there’s a problem getting into the stomach.

Luminal lesions, motility disorders.

Endoscopy or barium swallow.

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16
Q

What are rugae and where are they found?

A

Folds of the inside of the stomach.

They disappear in the antrum, which is towards the bottom of the stomach.

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17
Q

What are the function of the stomach?

A
  1. Store food
  2. Mixture of food and secretions to form chyme
  3. Controlling rate of chyme entering duodenum
  4. Acidic environment to kill bacteria and parasites
  5. Begin breakdown process of proteins by breakign down collagen
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18
Q

What is the controller of gastric motility?

A

Interstitial cells of cajal - which send waves toward the pylorus (mixing and propulsive).

These are concentrated in the body of the stomach.

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19
Q

What is the function and mechanism of the weak gastric contractions?

A

Weak contractions drive food against the closed pylorus to break it into smaller components and mixes contents.

20
Q

What is the function and mechanism of strong gastric contractions? What percentage of gastric contractions are strong?

A

Forceful enough to open the pylorus and drive food through.

Propulsive.

20% are strong.

21
Q

What are factors that promote gastric emptying?

A

Increased gastric volume leads to myenteric reflexes.

Parasympathetic stimulation.

Gastrin (weakly increases gastric contraction): main role is in acid production.

22
Q

What are factors that inhibit gastric emptying?

A

Enterogastric reflex:
1. duodenum slows emptying through ENS (myenteris plexus)

  1. Duodenum to sympathetic ganglia and back to stomach
  2. Duodenum to brain/brain stem through sensory vagus and back to stomach through motor vagus (minor role, otherwise this would increase emptying)
23
Q

What are factors that activate the enterogastric reflex?

A
  1. Distension of the duodenum
  2. Irritation or excess acidity (release of secretin which makes bicarb)
  3. Hyper or hypo-osmotic solutions
  4. Breakdown products of proteins or fats (CCK), or fats and carbs (gastric inhibitory peptide)
24
Q

What is the ultimate goal of the enterogastric reflex?

A

Slow gastric emptying by inhibiting the emptying contractions and increasing the tone of the pylorus.

25
Q

What is a normal gastric emptying time for solids and liquids?

A

solids: 75 minutes
liquids: 20 minutes

26
Q

What is gastroparesis? What are some things that can cause it?

A

When the stomach doesn’t empty and you retain food.

Can be caused by nerve damage, diabetes, or narcotic use.

27
Q

What are the functions of the small intestine? What do these functions require ?

A

Mix contents via constriction of circular muscle (sausage like breaking up of food).

Move contents from duodenum to ileocecal valve.

Both require myenteric plexus.

28
Q

How does the time it takes contents to move through the small intestines vary?

A

Usually it takes 3-5 hrs from duodenum to the ileocecal valve.

If there’s more nutrients, it will be slower (fats are slowest).

Poor nutrients: faster

29
Q

What are stimuli for propulsion in the small intestine? Describe these movements.

A

Distension, irritation, activation of chemoreceptors.

Myenteric plexus produces Ach and SubP which cause contraction proximal to bolus and

VIP and NO which cause relaxation distal to bolus.

30
Q

What hormones stimulate small intestine motility?

A

Gastrin, CCK, and Motilin

31
Q

What hormones inhibit small intestine motility?

A

Secretin and glucagon (in order to extract more glucose when there is low blood glucose).

32
Q

Describe the three components of the gastric-ileal reflex.

A

ENS: Gastric stretch stimulates small bowel motility

Parasymp NS: vago-vagal; sensory vagus back to brainstem

Sympathetic NS: to ganglia and back. Inhibits sympathetic activity and causes greater motility.

33
Q

What is the migrating motor complex (MMC) movement of the small intestine?

A

Housekeeping function, produced every 90 min in stomach and SI.

Moves undigestible material through the SI rapidly via MOTILIN.

34
Q

What is peristaltic rush movement of the small intestine? When is this normally observed?

A

Powerful, rapid movements that move contents from the SI to colon.

Usually occurs with infectious diarrhea.

35
Q

What maintains the tone of the ileocecal valve? What can relax this valve and promote small intestine emptying?

A

Acetylcholine and substance P.

Fluid (as seen in infectious diarrhea).

36
Q

What can slow down small intestine emptying into the cecum? What is an example of this?

A

Pressure or chemical irritation on the cecal end.

Appendicitis tends to tighten the ileocecal valve and inhibit small bowel emptying.

37
Q

What are the effects of poor motility and excess motility through the colon?

A

Poor motility: greater absorption and hard feces in transverse colon causing constipation.

Excess motility: less absorption and diarrhea or loose feces.

38
Q

What are the two functions of the right colon?

A

Mixing: smooth muscle contractions narrow lumen and lead to haustrations; tinea coli also contract

Propulsive: smooth muscle contractions cause disappearance of haustrations distally.

39
Q

What is the function of the left colon?

A

Storage: rectosigmoid angle acts as a barrier to keep rectum empty

Defecation.

40
Q

What are the components of the defecation reflex?

A

Enteric NS (weak): stimulates descending colon and sigmoid to have mass movement. Inhibits internal sphincter (smooth muscle) via NO and VIP.

Parasymp NS from S2-S4 levels (strong): amplifies mass movements from descending and sigmoid into rectum. Inhibits internal sphincter through pelvic nerves.

41
Q

How is constipation clinically described?

A

2 or more of the following:

  • Straining during 25% defecations
  • lumpy or hard stools in at least 25% stools
  • sense of incomplete evacuation in at least 25% of stools
  • Manual maneuvers for 25% of defecations
  • Fewer than 3/week
42
Q

What are factors that can cause constipation?

A

Extrinsic innervation (quadripalegia)

Hormones

Luminal factors (cancer)

Intrinsic motility (VIP and NO not made).

43
Q

What is Hirsprungs?

A

When there are no ganglia in a segment of the sigmoid colon so it doesn’t contract.

Like achalasia but in the colon, VIP and NO not produced.

44
Q

When describing stool with the bristol stool chart, what is type 1 and what it type 7? What is the ideal type that patients should have?

A

1 - Separate hard lumps, hard to pass

7 - Watery, no solid pieces, entirely liquid.

Ideal: 3-4

45
Q

What is a Sitz mark study?

A

When a pt is given a pill containing small rings that can be traced upon imaging in order to differentiate between a motility problem and an outlet problem.

Motility problem: they will be scattered throughout the colon

Outlet problem: accumulate in the rectum

Physiology Block 3 (17 decks)

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