Inflammation Of The Gut Flashcards
What are the components of the small intestine?
Duodenum, jejunum and ileum which are responsible for enzymatic digestion of food and absorption of nutrients.
Where are Peyer’s patches located?
ONLY in the ileum of the small intestine (occasionally in the distal jejunum)
How do muscular contractions occur in the GI system?
Stimulated by the pacemaker cells of the GI tract which are interstitial cells of Cajal that cause slow wave action potentials in the muscularis externa, into either tonic or phasic contraction.
What are tonic contractions?
Maintained contraction of the smooth muscle for minutes to hours, occurring in the sphincters and the stomach.
What are phasic contractions?
Rapid transient contractions without obvious changes, which is carried out by the muscularis externa in the posterior stomach and small intestine.
What is peristalsis?
Contractions occur in waves directly behind the bolus.
What is segmentation?
Pattern of GI contraction which occurs in short lengths, carried out by the longitudinal muscle. There is alternating contraction of the inner circular muscle and in other segments, relaxation of the outer longitudinal muscles in order to mix food.
What is the general composition of the small intestine?
Simple columnar epithelia lined with microvilli and a mucous layer. Contains goblet cells, Paneth cells and a crypt for proliferation of stem cells for renewal of the intestinal layer.
What are the unique features of the duodenum?
Microvilli are longer and slender. It contains Brunner’s glands in the sub mucosa which produce alkaline rich mucous fluid in response to parasympathetic stimulation.
Where are Brunner’s glands located?
Submucosa of Duodenum and Oesophagus.
What is the role of the large intestine?
Storage and elimiation of food residues, absorption of water.
Bacterial degradation of nutrients like fibre into short-chain fatty acids via fermentation.
What is the histology of the large intestine?
Simple columnar epithelium which is numerous in goblet cells. It contains absorptive enterocytes and enteroendocrine cells such as chromaffin and L cells. Contains no villi.
What are enterochromaffin cells?
Endocrine cells found in the colon that produce serotonin to stimulate gastric mucus production.
What are L cells?
Produce:
Glucagon-like peptide 1 which inhibits gastric acid secretion and promote satiety
Peptide YY cells to slow intestinal motility for satiety
They are found in the ileum and colon.
Where are Paneth cells located in the large intestine?
Only found in the right colon and limited in number compared to small intestine to limit potential damage against digestive enzymes.
Which cells are present in the lamina propia?
Inflammatory cells and fibroblasts.
What are the histological layers of the intestine?
Mucosa
Submucosa
Muscularis mucosae
Muscularis propia
Subserosa
Serosa
What is the mucosa of the intestine?
Contains the epithelial cells and the lamina propia, a layer of loose connective tissue rich in immune cells. It contains lymphoid follicles and Muscularis mucosae.
What is the Muscularis mucosae?
Thin layer of smooth muscle which controls movement of the mucosa.
What is the Submucosa?
Contains loose connective tissue of collagen, smooth muscle and adipose tissue. The enteric plexus of Meissner’s and Henle’s is found here in the jejunum and ileum.
What are Meisser’s plexus?
Enteric plexus in the Submucosa jejunum and ileum which provides parasympathetic innervation to the goblet cells for secretion.
What is the Muscularis propia?
Consists of outer longitudinal muscle and inner circular muscle for peristalsis of food. Between these layers is the Auerbach plexus.
What is the Auerbach plexus?
Responsible for innervation of the gut which lies between layers of the Muscularis propia for stimulating peristalsis.
What is the serosa?
Contains simple squamous epithelia which is high vascularised and contains lymphatic vessels and is covered by visceral peritoneum
What are the interstitial cells of Cajal?
Pacemakers of the GI tract for action potentials for slow wave phasic peristalsis, located in the Submucosa and the gap between the Submucosa and circular muscle layer.
What are the symptoms of IBD?
Pain, swelling, bloody diarrhoea, weight loss and lethargy.
How does disease present in the small intestine?
Severe abdominal pain, vomiting, weight loss due to malabsorption, and water diarrhoea.
How are abdominal symptoms assessed in history?
Changes in bowel habit
Pain or discomfort
Any wind?
Stomach distention/bloating.
How is diarrhoea assessed in a history?
Volume and consistency of stools
Number of stools per day
Acute diarrhoea vs chronic diarrhoea
Small bowel diarrhoea vs large bowel diarrhoea.
What is diarrhoea?
Passing 3 or more loose stools in one day, more frequent than usual for an individual.