Gi Tract (Motility)

Front 1

Structure of the GI tract wall

Back 1

Front 2

INNERVATIONAND CONTROL OF MOTILITY
- step 1

Back 2

Stretch receptors in myentericplexus (between the circular and longitudinal muscle layers) sense the passage of a bolus and stimulate neuronesto release an unknown NT which stimulate serotonergicinterneuroneswhich then stimulate motor neuronesto release AChand cause circular muscle contraction

Front 3

INNERVATIONAND CONTROL OF MOTILITY
- step 2

Back 3

Stretch receptors also cause activation of Cholinergic interneuroneswhich in turn stimulate inhibitory neuronesto cause relaxation of circular muscle in front of the bolus and also behind the stretch receptors

Front 4

Define the term GI motility

Back 4

•Definition:
the spontaneous movements
of the digestive tube, encompassing
Contractile activity / tone
Flow / transit
Compliance

Front 5

Describe four general functions of motility

Back 5

•Propulsion
•Storage
•Mixing
–Mechanical dispersion
–Contact with digestive secretions
–Contact with absorptive cells
•Prevention of retrograde movement of contents to proximal organs
–sphincters

Front 6

Discuss motor functions of different gut regions

Back 6

- propulsion
- sotrage
- mixing
- usually more than one function to an area
- all have propulsion

Front 7

List techniques to measure gut motility

Back 7

•Radiography/fluoroscopy
•Scintigraphy
•Manometry
•Barostat

Front 8

Describe major patterns of GI motility

Back 8

- oesophagus

Front 9

Describe the neural control of gut motility

Back 9

•Most activity of GI tract takes place without perception
•mouth, UOS and striated muscle of proximal oesophagus and anus - only conscious influence
•other activities of gut proceed automatically and are controlled by autonomic NS and a network of cells in gut wall called the enteric nervous system (ENS) - ACTS LIKE A BRAIN

Front 10

Sphincters

Back 10

Front 11

Major patterns of digestive tract motility
•oesophagus:

Back 11

–primary peristalsis: response to swallowing
–secondary peristalsis: response to clear oesophagus

Front 12

Major patterns of digestive tract motility
•stomach:

Back 12

–proximal stomach: tonic receptive relaxation to accommodate food- „reservoir‟; subsequent tonic contraction to facilitate emptying
–distal stomach: phasic antral contractions grind and empty contents (0.5-1.5mm)- „antral pump‟

0.5-1.5 thus things can get stuck (eg chewing gum)

Front 13

The Stomach is Divided into Multiple Anatomic and Only Two Functional Motor Regions

Back 13

Front 14

Motility in Small Bowel

Back 14

•small bowel:
–interdigestive motor activity (migrating motor complex)
–digestive motor pattern (irregular mixing contractions)

Front 15

MMC

Back 15

rapid sequece in response to (fast irregular contraction, lumenal excluding contractions to clear the whole bowel, sweeping down th e bowel, and itgets sloer and sloer and longer and longer as it goes thorugh the bowel (it occurs spontaneusly in the stomach called the stomach brain thing)

Front 16

Interdigestive (fasting) motility of the
small bowel
Phase 1, 2, 3

Back 16

Front 17

The Migrating Motor Complex Occurs Periodically in the Interdigestive State in the Stomach and Small Intestine

Back 17

while we sleep our body is actively sweeping and clearing

Front 18

Motility in Colon & ano-rectum:

Back 18

–phasic & tonic contractions (mixing, propulsion)
–gastro-colic reflex: increased contractile activity after eating
–defaecation

Front 19

HPACs

Back 19

Front 20

Scintigraphic colonic transit

Back 20

pre and post constipation Tx

Front 21

What happens when we are fasting?

Back 21

•Small intestine almost empty
•Migrating motor complex (MMC) in stomach
–phase I: stomach quiescent
–phase II: peristaltic contractions resume
–phase III: increase force of contractions, indigestible solid leaves stomach (>1.5mm), contents swept to ileum in 1.5 hours
•MMC in small bowel
-“housekeeper” : prevent stasis and bacterial overgrowth; three phases

Front 22

What happens when we eat?

Back 22

•relaxation proximal stomach
•regular peristaltic contractions in stomach
•irregular small intestinal contractions
•increase in colonic phasic contractions
•increase in colonic tone (30%)

Front 23

Enteric nervous system

Back 23

•Controls motility and secretory functions of the intestine
•Semi-autonomous - actions modified by parasympathetic & sympathetic nervous systems - may function independently

Front 24

Three Main Types of Chemical Signaling Occur in the Enteric Nervous System

Back 24

Front 25

The peristaltic reflex

Back 25

Front 26

Autonomic control
•Parasympathetic (PSNS)

Back 26

–vagus nerve : oesophagus - ascending colon; vagus also has afferent fibres
–sacral spinal cord : pelvic splanchnic nerves - distal colon and rectum
–most important neurotransmitter is acetylcholine (Ach)

Front 27

Autonomic control
•Sympathetic

Back 27

–thoracolumbar spinal cord : sympathetic ganglia e.g. coeliac ganglia, and synapse with postganglionic nerve cells whose fibres follow mesenteric vessels and end in intramural plexus
–most important neurotransmitter is noradrenaline
–also afferents: distension, ischaemia, mucosal damage

Front 28

ENS vs Autonomic innervation

Back 28

•Isolated stomach has peristalsis! ENS
•Fasting: complex pattern, MMC cycling controlled by ENS
•Sight/chewing of food: vagus - gastric acid
•Accommodation of proximal stomach - vagus
•Fed pattern: vagus
•Tonic inhibition - sympathetic

Front 29

Symptoms of GI tract dysmotility

Back 29

•Oesophagus - heartburn, dysphagia, regurgitation, chest pain
•Stomach - dyspepsia, nausea, vomiting, anorexia, early satiety
•Small intestine - abdominal pain, bloating, abdominal distention
•Colon - abdominal pain,diarrhoea, constipation
•Anorectum - urgency, incomplete evacuation, incontinence, straining