Pathology of Colon Flashcards
What is the function of the small bowel?
Absorptive role
What are the functions of the large bowel?
Absorptive and secretory role
How long is the small bowel?
Approximately 6m long
How long is the duodenum?
25cm
What are the 3 parts of the small bowel?
Duodenum
Jejunum
Ileum
What are the different parts of the large bowel?
Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
How long is the rectum?
15cm
What are the different layers of the small bowel wall?
Mucosa
Submucosa
Muscularis propria
Subserosa
What are the layers of the mucosa in small bowel?
Epithelium
Lamina propria
Muscularis mucosa
What cell types are in the mucosa of the small bowel?
Goblet cells
Columnar absorptive cells
Endocrine cells
What is embedded within the mucosa of the small bowel?
Crypts that contain stem, goblet, endocrine and paneth cells
What are the projections from the epithelium of the small bowel?
Villi
What is the muscularis propria also known as?
Muscularis externa
How often is the wall of the small bowel renewed?
Every 4 to 6 days
What is different about the villi of the small bowel and the large bowel?
The large bowel does not contain any villi
What shape is the top of cells in the large bowel?
Flat, no villi
What shape are crypts in the large bowel?
Tubular
What is the difference between crypts in the small intestine and large intestine?
Crypts in the large intestine do not contain paneth cells
What is a consequence of the GI tract having a large surface area?
Large exposure to environment antigens so immune system must balance harmless ingested substances against active defect reactions to potential microbial invaders
What does dysfunction of the intestinal immune system cause?
Chronic disease
Life threatening acute conditions
What is small and large bowel peristalsis mediated by?
Intrinsic (myenteric) plexus and extrinsic (autonomic innervation) neural control
What is the myenteric plexus formed from?
Meissener’s plexus (base of submucosa)
Auerbach plexus (between the inner circular and outer longitudinal layers of the muscularis propria)
Where is the Meissener’s plexus found?
Base of submucosa
Where is the Auerback plexus?
Between the inner circular and outer longitudinal layers of the muscularis propria
What are examples of pathologies of the lower GI tract?
Inflammatory bowel disease (IBS)
Large bowel neoplasia
What does IBD stand for?
Inflammatory bowel disease
What is inflammatory bowel diseases the pathological feature of?
Ulcerative colitis
Crohn’s disease
Ischaemic colitis
Radiation colitis
Appendicities
What is idiopathic inflammatory bowel disease?
Chronic inflammatory condition resulting from inappropriate and persistent activation of the mucosal immune system driven by the presence of normal intraluminal flora
What are the 2 main diseases of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
What is the difference in where Crohn’s and ulcerative colitis can affect the GI tract?
Crohn’s can affect ny part of the GIT from mouth to the anus
Ulcerative colitis is limited to the colon
What is the pathogenesis of inflammatory bowel disease?
Strong immune response against normal flora with defects in the epithelial barrier function in genetically susceptible individuals
What percentage of people with IBD have an affected 1st degree relative?
15%
What gene mutation is associated with Crohn’s disease?
NOD2
What gene mutation is associated with ulcerative colitis?
HLA
What is the role of intetinal flora for IBD?
Specific microbe not yet identified
Defects in mucosal barrier could allow microbes access to mucosal lymphoid tissue triggering immune response
How is IBD diagnosed?
Requires clinical history, radiographic examination and pathological correlation
What is pANCA?
Perinuclear antineutrophilic cytoplasmic antibody
How does pANCA differ between Crohn’s and ulcerative colitis?
Postive in 75% of ulcerative colitis
Positive in 11% of Crohn’s disease
How does the incidence of ulcerative colitis change between males and females?
Affected equally
What age groups does ulcerative colitis peak?
20-30 years and 70-80 years
What is ulcerative colitis that is localised to the rectum called?
Proctitis
Where is ulcerative colitis more commonly spread?
Proximally
Can the appendix be involved in ulcerative colitis?
Yes