L4*-Gastric motility Flashcards
(16 cards)
Define Gastrointestinal motility and what 2 things does it involve?
Definition - The movements of the digestive system and how it transit the contents within them.
It involves coordinated contractions and relaxations of the GIT that moves content from the mouth to the anus.
Name 3 patterns of motility
-Peristalsis
-Segmentation
-Tonic contraction
What are the 2 muscle types in GIT ?
- Smooth (InV) muscles - found throughout most of the GIT. found in 2 layers: inner layer (circular) and outer layer(longitudinal)
- Skeletal (V) muscles - found in pharynx, top 1/3rd of oesophagus, external anal sphincter
what is ENS made up of ? What is the link between those 2 and the GIT ?
ENS is made up of Myenteric plexus, submucosal plexus.
-Activation of the myenteric plexus : 👆ses tonic contraction, 👆ses intensity of rhythmic contractions rate of rhythmic contractions 👆ses velocity of conduction.
-Activation of submucosal plexus : 👆ses secretory activity, modulates intestinal absorption.
1). How is the food storage related to gastric motility ?
-Storage depends on the contractions and relaxations of the smooth muscles in the stomach wall.
-when a meal is swallowed, smooth muscles in the fundus relax before the food arrives in the stomach.
-empty>50mL and full>1.5L with little👆se in pressure.
-Relaxation in the fundus is regulated by the vago-vagal reflex termed ‘receptive relaxation’ ➡ if vagal innervation is interrupted then intra-gastric pressure 👆ses.
2). How is the propulsion related to gastric motility ?
-Propulsion = movement of solid particles toward the antrum is accomplished by the interaction of propulsive gastric contractions and occlusion of the pylorus.
-These contractions propel the luminal contents toward the pylorus, which is partially closed by contraction of the pyloric musculature before delivery of the bolus.
-Sieving function > Discrimination of liquids and small particles leaving the stomach more rapidly than large particles.
3). How is grinding related to gastric motility?
Grinding definition
Once a bolus of material is trapped near the antrum, it is churned to help reduce the size of the particles - Grinding
Only a small portion of gastric material -(that contains particles smaller than 2mm) is propelled through the pylorus to the duodenum.
4). How is the retropulsion related to gastric motility?
- Most of the gastric contents are returned to the body of the stomach for pulverization and shearing of solid particles - Retropulsion
-Propulsion, grinding and retropulsion repeat multiple times until the gastric contents are emptied.
Define gastric emptying and what structure helps
-It is the process by which the contents of the stomach are discharged into the duodenum.
-Gastric emptying is regulated by ANS( vagus nerve) and gastrointestinal hormones.
- The pyrolic sphincter allow carefully regulated emptying of gastric contents and prevents regurgitaion of duodenal contents into stomach- innervated by vagus(relaxation) and sympathetics (constriction).
What are the 3 types of control of gastric emptying ?
-Cephalic phase > approach of food or food in mouth.
-Gastric phase > food in stomach
-Intestinal phase > food in duodenum, ileum or colon.
Describe cephalic phase of the controlling gastric emptying.
- An inhibitory phase - Inhibitory nerve
fibres in the vagus nerve. - Results in relaxation of stomach
enabling it to store large volumes.
Describe Gastric phase of the controlling gastric emptying
- An excitatory phase in which the stomach empties at rate proportional to the volume in it.
- Due to:
1. Myogenic reflex: stretching smooth
muscle causes reflex contraction
2. Activation of pressure receptors
which send impulses in local nerve
plexi and in the vagus nerve
3. Gastrin released in response to
peptides etc.
Describe intestinal phase of the controlling gastric emptying
An inhibitory phase.
This phase is mainly controlled through hormonal and paracrine mechanisms, activated by duodenal chemoreception.
The general scheme would be:
Low pH → activates secretion of Secretin
High fats/lipids → increase secretion of CCK
High levels of amino acids → increase secretion of Gastrin
High levels of carbohydrates → increased secretion of GIP
There are also some motor reflexes: e.g., the ileogastric reflex ➔ Chyme(partially digested food, gastric juices, and digestive enzymes entering the ileum activates pressure receptors which delays gastric emptying - via nerves in plexi.
Describe the motility of the stomach
-regulated by neural and hormonal factors
-motility influences gastric emptying
-👆sed gastric emptying results from 👆food volume, pressure, peristaltic waves, hypoglycaemia(low blood sugar level)
- 👇sed gastric emptying results from solids, fats, non-isotonic solution and hyperglycaemia(high blood sugar level).
Define Gastroparesis
- A disorder that is due to a delay in the gastric emptying in the absence of mechanical obstruction of the stomach.
- Diabetes is the most frequently identified disease linked to gastroparesis
- Underdiagnosed due to similar presentation as GORD
- Symptoms: postprandial fullness, nausea, vomiting, bloating, and upper abdominal pain.
- Treatment/management: dietary changes (several small meals/day), pro-
motility agents
Motilin is a hormonal factor that controls the motility of the stomach. When is it released?
-Motilin is released during FASTED state & also clean the stomach & finish off any undigested food.
