GI Motility Disorders - Flashcards for Medical Students | Quizlet

1. Relaxation of the Orad region fo the stomach

2. Contraction to reduce side of bolus

3. Gastric emptying that propels chyme into small intestines

the three components of gastric motility

LES and Cardia

What section of the stomach:

-luminal secretion: mucus and HCO3-

-prevention of reflux

-entry of food

-regulation of belching

Gastric Phase

the phase of digestion that serves to sterilize, mix food, begin digestion of protein, store food for timely delivery to duodenum, and secretion of intrinsic factor

Orad

the proximal stomach

Caudad

the distal stomach

Fundus and Body

What section of the stomach:

-luminal secretion: H+, intrinsic factor, mucus, HCO3-, pepsinogens, lipase

-reservoir

-tonic force during emptying

Antrum and Pylorus

What section of the stomach:

-luminal secretion: mucus and HCO3-

-mixing, grinding, sieving

-regulation of emptying

Receptive Relaxation

• Vasovagal Reflex

• Swallowing and distension of the proximal stomach leads to relaxation to accommodate up to 1.5L of food

VIP and NO

In order to relax the stomach, what secretions must be stimulated?

Tonic Contraction

• Also mediated by the vagus nerve

• Sustained contraction compresses contents toward antrum to facilitate mixing and gastric emptying

Slow Waves

• originate at greater curvature in the mid-body and propagate circumferentially and migrate distally

• Rate of 3 per minute (slowest in the GI)

• In antrum, action potential spikes occur on top of slow waves resulting in peristaltic contractions

Peristalsis

Peristaltic wave "mixing wave" propagating distally

Retropulsion

• Terminal antral contraction spreads to pylorus which contracts

• happens with chyme proximally

• Allows for mixing and grinding

• Chyme (food) particles must be ~1mm3 in order to enter the duodenum

Increase

Parasympathetics __________________ antral contraction frequency

Decrease

Sympathetics ____________________ antral contraction frequency

Increase

Gastrin and Motlin ___________________ antral contraction frequency

Decrease

Secretin and GIP __________________ antral contraction frequency

• Proximal tone increases (Vagus)

• Antral contractions become forceful (ACh, Gastrin)

• Several milliliters of chyme are propelled through open pylorus

sequence of events for gastric emptying

Migrating Motor Complex (MMC)

during the interdigestive period, what clears any residual meal?

Carbohydrates > Protein > Fat

rates of nutrients from fastest to slowest

Slower

Solid, hypo- and hypertonic, and acidic meals empty _______________

Liquids

-empty at an exponential rate

-volume is the main determinant

Solids

-emptying has a lag phase

-influenced by composition and chewing

-can be up to 60 mins

Enterogastric Reflex (ENS)

-neural feedback where contents of the duodenum lead to decreased gastric emptying

Increased

long reflexes lead to ______________ sympathetics

CCK

-secreted in response to fatty and amino acids

-leads to decreased gastric emptying

Gastrin

-decreased ______________ from G cells of the antrum lead to decreased pyloric activity

Decreased

GIP and Secretin lead to ______________ gastric emptying

Mucus

-protective mechanism of the stomach

-phospholipids and glycoproteins

-act as a barrier to certain molecules

Bicarbonate

-protective mechanism of the stomach

-keeps the pH at the epitheial surface at 6 or 7

Epithelium of Stomach

‒ Tight junctions

‒ Maintenance of intracellular pH

‒ Prostaglandins (PGE2 and PGI2): regulate bicarbonate and mucous secretion, help maintain blood flow and cell turnover. COX-1 rate limiting step in prostaglandin synthesis.

‒ Regenerative cells and growth factors

‒ Intracellular mechanisms to prevent protein denaturation, cytotoxic insult and oxidative stress

‒ Regulation of acid secretion

Extensive Microcirculation

-protective mechanism of the stomach

-provides essential nutrients and source of HCO3- and removes waste

Nitro Oxide

-protective mechanism of the stomach

-stimulates gastric mucus

-increases mucosal blood flow

Gastritis

-occurs when there is erosion in the mucosa of the stomach

Ulcers

-occur when erosions of the stomach reach the submucosa

H. Pylori

-can evade acid environment and breach the mucous blanket, set up an inflammatory state, and is directly toxic to epithelium.

-a major causative factor in gastric ulcers

H. Pylori

-colonized gastric mucosa and releases cytotoxins

-contains urease

-inhibts somatostatin secretion

-

Cag A

-cytotoxin assoc with H. pylori

-alters signaling pathway, alters the cytoskeletal rearrangement, and alters the tight junctions between the cells

Vac A

-cytotoxin assoc with H. pylori

-causes formation of vacuoles in the cells, induces apoptosis, and causes disruption of epithelial junctions and blocks the T cells response

Delayed

______________ Gastric Emptying Causes:

-diabetes

-vagotomy

-eating disorder

-stress

-meds

-ischemia

-obstruction

Rapid

_______________ Gastric Emptying Causes:

-Gastric Surgery

-Zollinger-Ellison Syndrome

Zollinger-Ellison Syndrome

-a disease in which tumors cause the stomach to produce too much acid, resulting in peptid ulcers

-caused by gastrinoma

Gastrinoma

a tumor derived from G cells that secretes gastrin

Dumping Syndrome

-when food moves too quickly from the stomach to the duodenum

-associated with conditions following gastric or esophageal surgery

-caused by an absent or insufficienyly functioning pyloric sphincter

Vagotomy

-used to be performed in ulcer patients to control gastric acid secretion

-vagus nerves in stomach are cut to decrease secretion

Highly Selective Vagotomies (HSV)

-performed in some cases of ulcer refractory to medication

-ligating vagus nerves to the upper body and fundus

-may also impair receptive relaxation leading to early satiety and rapid emptying of liquids

Truncal Vagotomy

-the division of the anterior and posterior trunks 4-cm proximal

to the GEJ.

•Removes the acetylcholine-mediated secretion of acid from parietal cells

•Results in the accelerated emptying of liquids due to the removal of the vagally mediated receptive relaxation of the gastric fundus

•Decreases the emptying of solid

Diabetic Gastroparesis

-delayed gastric emptying

-early satiety and postprandial fullness

-rapid early phase of liquid meal gastric emptying secondary to impaired gastric accommodation to distension

Diabetic Gastroparesis

-loss of gastric neurons containing NOS

-impaired electromechanical activity in the myenteric plexus

-sensory neuropathy in the gastric wall

-abnormal pacemaker activity may generate noxious signal transmitted to CNS to evoke nausea and vomit

Pyloric Stenosis

-common cause of GI obstruction in young infants

-2nd to 6th week of life

-pylorus hypertrophies over time

-lack of pyloric inhibitory innervation leads to reduced levels of NO causing unopposed contraction

Azithromycin or Erythromycin

what drugs may increase risk for infantile hypertrophic pyloric stenosis

Ramstedt's Procedure

-definitive treatment for Pyloric stenosis

-pyloromyotomy

Delay in Gastric Emptying

what is the major effect on GI tract in pregnancy?

Progesterone

pregnancy related changes in gastric motility are related to increased levels of __________________

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