Small intestine Flashcards
(35 cards)
What is the purpose of motility in the small intestine?
- mixes intestinal contents
- brings contents to mucosa for absorption
- propels contents further down GI tract
What are the 2 main types of contraction in the SI?
Segmentation: to mix chyme
Peristaltic: to propel food
What 2 parts of the GI tract are under voluntary control?
Upper oesophageal sphincter (swallowing)
External anal sphincter (defecation)
What do sympathetic (post-ganglionic) and parasympathetic (pre-ganglionic) nerves do in the GIT?
Sympathetic: inhibitory nerves to non-sphincteric muscle
Para: excitatory to non-sphincteric muscle
What are interstitial cells of Cajal?
Like pacemaker cells of the GIT, they interact with smooth muscle and set the rate for slow waves (BER)
What substances allow segmentation to occur?
Ach (vagal) and substance P: contract proximal end
NO and VIP: relax distal end
What is achalasia?
Disorder of the oesophagus, involving uncoordinated/absent contraction of oesophageal smooth muscle or incomplete relaxation of the LOS, causing swallowing disturbances.
What is the pathophysiology of achalasia?
Loss of inhibitory nitrinergic neurons in the myenteric plexus of the oesophagus, due to inflammatory destruction causing loss of peristalsis
What neurons are affected in achalasia?
Selective loss of post-ganglionic inhibitory neurons means there is no inhibition of contraction in LOS by VIP/NO.
Excitatory post-ganglionic cholinergic neurons remain, giving high LOS tone.
What is aperistalsis?
Loss of latency gradient, allowing sequential contractions by NO
What are the signs/symptoms of achalasia?
Dysphagia
Regurgitation
Weight loss
Retrosternal pain
Investigations in achalasia?
Barium swallow.
High resolution manometry
Endoscopy.
How can achalasia be treated?
Rigiflex balloon dilatation: mechanical dilation of LOS cia endoscope
Heller’s myotomy: cut muscles to LOS
Per-oral endoscopic myotomy: inner circular muscle of LOS divided through a submucosal tunnel
What is gastroparesis?
Delayed gastric empyting
What are the causes of gastroparesis?
Idiopathic Diabetes w macrovascular disease Post-viral/surgical complications Opiates Females
Symptoms of gastroparesis?
Abdominal pain
Nausea and vomiting
Weight loss
Early satiety
How is gastroparesis managed?
Small meals frequently
Liquid meals
Nutritional support
What meds can be used in gastroparesis?
D2 antagonists
Motilin agonists
5HT4 agonists
How long does food take to get from the pylorus to ileocaecal valve?
3-5 hours
Chyme moves @ 1cm/min
What is chronic intestinal pseudo-obstruction?
Signs of mechanical obstruction, without any occlusion.
Neuropathic/myopathic causes e.g. problems in Cajal cells
May need parenteral feeding
What is acute post-operative ileus?
Constipation and intolerance of oral intake, in absence of mechanical obstruction after surgery.
Pain and discomfort if prolonged.
May need open surgery or delayed enteral nutrition.
What is acute colonic pseudoobstruction?
Ogilvies syndrome
Large bowel parasympathetic dysfunction, common after cardiothoracic and spinal surgery.
May need gut rest, IV fluids, NG decompression
How long does transit take from the caecum to rectum ?
1-2 days (shorter in men)
What drugs can reduce GI motility?
Opiates
Anticholinergics
Loperamide: gut-selective Mu receptor agonist; decreases tone and activity of myenteric plexus so slows colonic transit.; increased absorption so can be used in diarrhoea
