features in a Normal Large Intestinal Biopsy:
There is increase in thickness of the mucosa from the caecum (500 micrometer) to the rectum (1000 micrometer).
Crypts are aligned parallel to the crypt bases. Crypts are straight and narrow and mostly unbranched separated by a thin rim of lamina propria. The distance between the crypts and the internal diameter of the crypts are constant.
Slight variation in crypt architecture, intercryptal spacing and occasional crypt branching may occur in normal biopsies.
Crypts are deeper
in the rectum and sigmoid colon than in the proximal part of the colon.
Composed of absorptive (tall columnar), goblet and endocrine cells.
Ratio of the number of tall columnar cells to goblet cells is 4:1.
Paneth cells are usually present in the caecum & proximal colon (usually confined to the crypt bases).
Presence of Paneth cells more distally indicates metaplastic change seen in chronic infection.
The proliferative zone in the base of the crypt is composed of low cuboidal stem cells.
Surface epithelial cells overlying lymphoid follicles are more cuboidal and compactly arranged rather than columnar cells elsewhere (this should not be mistaken for dysplastic cells in ulcerative colitis).
Loose, areolar connective tissue which appears highly cellular due to the presence of chronic inflammatory cells in the superficial part of the lamina propria.
Predominantly plasma cells are present together with scattered lymphocytes (mostly T-cells).
Inflammatory cells in the deeper part and separation of crypt bases from muscularis mucosae by a band of plasma cells and lymphocytes is indicative of chronic inflammatory bowel disease.
Occasional neutrophils are present in the lamina propria of normal colonic biopsies.
Neutrophils in the surface and crypt epithelium is indicative of a pathological process.
Lymphoid follicles of B-lymphocytes are present in colonic mucosa and may extend through muscularis mucosae into submucosa.
At these points mucosal crypts extend into the mucosa forming lymphoid-glandular complexes (should not be mistaken for a pathological process).
smooth muscle layer (inner circular and outer longitudinal layer).
There is loose
connective tissue with collagen and elastic fibres. Meissner's plexus of
autonomic nerve fibres with ganglion cells are present. Detailed
examination of this layer is necessary in Hirschsprung's disease.
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