T1 L4: Motility of the GI tract Flashcards
What are GALT cells?
Gut-associated lymphoid tissue cells are immune cells
What cells cause peristalsis in the intestines?
Interstitial cells of cajal (ICC)
What is the name of the nervous system that controls the GI motility and secretion in the intestines?
The intrinsic enteric nervous system (ENS)
What is the role of the extrinsic autonomic NS for?
It modifies the activity of the ENS
What are the 2 plexuses in the gut wall?
The myenteric and the submucosal
What nerves provide parasympathetic information to the extrinsic autonomic nervous system in the intestine?
Vagus and pelvic splanchnic nerves
What nerves provide sympathetic information to the extrinsic autonomic nervous system in the intestine?
Thoracolumbar innervation
What is Cholecystokinin CCK and what does it do?
A hormone secreted in response to protein, fat, and acid by the I cells of the small intestine. It stimulates pancreatic secretions, gallbladder contraction and growth of exocrine pancreas. It inhibits gastic emptying
What is Motilin and what does it do?
A hormone secreted in response to fat, acid, and nerves by the M cells of the duodenum and jejunum. It stimulates gastric and intestinal motility
What 3 things can cause depolarisation in the intestine?
Stretch, motilin and acetylcholine
What are the 2 types of contraction in the intestine?
Segmentation for mixing and peristalsis for propulsion. Movement is always aboral (away from the mouth)
What is Hirschsprungs disease?
A rare congenital absence of the myenteris plexus usually in the distal colon. This leads to functional obstruction and severe constipation because there’s a lack of peristalsis
What type of epithelium lines the oesophagus?
Non-keratinising stratified squamous epithelium
What type of muscle is found at the different parts of the oesophagus?
Upper part has striated skeletal muscle and the rest is smooth muscle
Where is the swallowing centre in the brain?
In the medulla oblongata and the pons in the brain stem
Describe the process of swallowing
- Soft palette elevates over posterior nares to close the nasal pharynx
- Epiglottis closes larynx
- Respiration is inhibited
- upper oesophageal sphincter relaxes
- pharyngeal muscles contraction propels bolus into the oesophagus
What nerves cause muscle contraction that propels food into the oesophagus?
Motor efferents in the trigeminal, glossopharyngeal and vagal nerves
What is secondary peristalsis in the oesophagus stimulated by?
Stretch
What innervation coordinates food moving down the oesophagus?
Intrinsic myenteric and extrinsic vagal innervation
What is Achalasia and what causes it?
The lower oesophageal sphincter fails to relax causing food to remain in the oesophagus. Its caused by a vagal or myenteric defect
What us gastro-oesophageal reflux and what causes it?
The lower oesophageal sphincter loses toning so gastric contents flows into the oesophagus. May be linked to a hiatus hernia where a portion of the stomach protrudes through the diaphragm into the thorax
What are rugae in the stomach?
Folds within the stomach
What is the pyloris of the stomach?
Where the food leaves the stomach
What is the function of the fundus of the stomach?
To be a food reservoir
What is the excitatory system for emptying the stomach?
ENS/AND neuronal stimulation and hormones like motilin
What is the inhibitory system for emptying the stomach?
ANS regulation, duodenal enterogastric reflexes and hormones like CCK and secretin
What is dumping syndrome and what causes it?
Rapid emptying of gastric contents into the small intestine. Occurs following ingestion of a large meal after a gastrectomy. Causes pallor, nausea, sweating, cramps, vertigo, and fainting.
What is gastroparesis and what causes it?
When the stomach fails to empty sometimes caused by impaired vagal stimulation to the stomach in severely diabetic patients who have developed autonomic neuropathy. Causes bloating and nausea
What are plicae circulares in the intestine?
Circular folds in the intestine
What is the migrating motor complex (MMC) in the small intestine?
A series of peristaltic contractions every 90 min between meals that sweeps the contents of the colon
What is the gastroenteric reflex?
Gastric distention activates myenteric plexus to promote small intestine peristalsis
What is the gastroileal reflex?
Gastric distention promotes peristalsis in the ileum to force chyme through the valve into the caecum
What is a peristaltic rush?
Caused by mucosal irritation. it causes the ENS and ANS neural reflexes to sweep the contents of the small intestine into the colon
What is paralytic ileus?
Loss of peristalsis following mechanical trauma
What happens in the intestine to cause vomiting?
Reverse peristalsis initiated in the distal small intestine to expel intestinal and gastric contents
What happens in the proximal large intestine compared to the distal part?
Water and electrolytes are absorbed in the proximal section and faeces are formed in the distal portion
What are taniae coli in the large intestine?
3 segments formed of longitudinal muscle which tonically contract to form haustral bulges
How many times a day do mass movements occur in the large intestine?
2/3 times a day
What is voluntarily relaxed to allow defecation?
The external anal sphincter
