Colon

General

Anatomy & histology



Topic Completed: 1 May 2013

Minor changes: 13 October 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Colon nontumor histology

Hanni Gulwani, M.B.B.S.
Page views in 2020: 11,620
Page views in 2021 to date: 11,456
Cite this page: Gulwani H. Anatomy & histology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonhistology.html. Accessed October 15th, 2021.
Anatomy
  • 1.0 to 1.5 meters long, from terminal ileum to anal canal
  • Compared to small intestine, has greater diameter, fixed position, epiploic appendages, taeniae coli (discontinuous muscular fibers)

Regions:
  • Cecum, ascending (right sided) colon, transverse colon, descending (left sided) colon, sigmoid colon, rectum

Cecum:
  • In peritoneum, 6 x 9 cm
  • Large blind pouch arising from proximal right colon
  • Blind end directed downward, open end directed upward

Ascending colon:
  • 15 - 20 cm long
  • Posterior surface is in retroperitoneum, but anterior and lateral surfaces have serosa and are intraperitoneal

Hepatic flexure:
  • Junction of ascending and transverse colon

Transverse colon:
  • Connects ascending colon at hepatic / right colic flexure to the descending colon at the splenic / left colic flexure (Wikipedia)

Splenic flexure:
  • Junction of transverse and descending colon

Descending colon:
  • 10 - 15 cm long
  • Posterior surface is in retroperitoneum, but anterior and lateral surfaces have serosa and are intraperitoneal

Sigmoid:
  • Descending colon at origin of mesosigmoid
  • From pelvic rim to S3 vertebra

Rectum:
  • 12 cm
  • Sigmoid colon from termination of mesosigmoid
  • Also from opposite sacral promontory to upper border of anal canal
  • Becomes extraperitoneal (within the pelvis) as it passes between crura of peritoneal muscles
  • Has no serosa / peritoneal covering

Pouch of Douglas:
  • Cul-de-sac in women made up of reflection of peritoneum from rectum over pelvic wall

Taenia coli:

Epiploic appendages:
  • Pedunculated fat on lateral colon
  • Lined by mesothelium

Vasculature
  • Superior mesenteric artery supplies cecum to splenic flexure
  • Inferior mesenteric artery supplies remainder of colon to rectum
  • Numerous collaterals connect mesenteric circulation with celiac arterial axis proximally and pudental circulation distally
  • Superior hemorrhoidal branch of inferior mesenteric artery supplies upper rectum; hemorrhoidal branches of internal iliac or internal pudental artery supplies lower rectum
  • Venous drainage is similar; there is an anastomotic capillary bed between the superior and inferior hemorrhoidal veins, providing a connection between the portal and venous systems (Surg Oncol 2006;15:243)
Embryology
  • Primitive gut is divided into foregut, midgut, hindgut
  • Midgut gives rise to cecum, ascending colon and right 75% of transverse colon (also distal duodenum to ileum)
  • Hindgut develops into remainder of transverse colon to anorectal line
  • During week 6 of fetal development, endodermal epithelium of gut tube proliferates and completely occludes the lumen
  • Over the next two weeks, it vacuolates and recanalizes
  • Maturation of haustra and tenia coli start from ascending colon and progress towards sigmoid colon (Early Hum Dev 2004;78:1)
Histology
  • Composed of mucosa, submucosa, muscularis propria (externa) and serosa (perimuscular tissue in rectum)
  • Mucosa: epithelium, lamina propria and muscularis mucosa
  • Epithelium:
    • Low columnar to cuboidal cells
    • Tubules are tightly packed, have straight test tube shape (minimal branching), parallel to each other, straight luminal surface, rest on thin basement membrane, extend to muscularis mucosa; have absorptive cells and goblet cells
    • Crypts open into surface epithelium or into innominate grooves
    • Crypts are surrounded by pericryptal fibroblast sheath (fibroblasts or myofibroblasts, J Clin Pathol 1999;52:785)
    • Crypts also contain precursor cells, endocrine cells and Paneth cells in right sided colon
    • Intestinal crypt is a proliferative compartment, monoclonal, maintained by stem cells
    • Villus represents the differentiated compartment and is polyclonal as it receives cells from multiple crypts
    • Wnt signaling is important for cell proliferation, differentiation, apoptosis along the crypt-villus axis (Stem Cell Rev 2006;2:203, J Pathol 2002;197:492)
    • Paneth cells constitute the niche for Lgr5 stem cells in intestinal crypts (Transl Res 2010;156:180)
    • In colon crypts, CD24+ cells residing between Lgr5 stem cells may represent the Paneth cell equivalents (Nature 2011;469:415)
    • Colon cancer may emerge at niche of tissue stem cells (cancer stem cells) which are LGR5+, Nanong- (Acta Histochem 2013;115:320)
  • Positive stains: CDX2 (sensitive and specific for colon), CK8, CK18, CK19
  • Innominate grooves: mucosal area where several crypts open into one central crypt
  • Lamina propria:
    • Capillaries (uniform), lymphatics just above muscularis mucosa
    • Inflammatory cells present (see below)
  • Muscularis mucosa: thin and regular
  • Submucosa:
    • Loose connective tissue with submucosal plexus of Meissner
    • Minimal inflammatory infiltrate
    • Younger patients may have intramucosal lymphoid aggregates that disrupt muscularis mucosa
  • Muscularis propria: inner circular layer, myenteric plexus of Auerbach, outer longitudinal layer
  • Serosa: single layer of flat to low cuboidal mesothelial cells and adjacent fibroelastic tissue
Types of cells
  • Absorptive cells: eosinophilic cytoplasm, no mucin, shorter microvilli than small intestinal cells, basal nuclei
  • Endocrine cells:
    • Usually at base of crypts
    • Similar to cells in pancreas, lung, thyroid, urethra
    • Contain fine eosinophilic granules with secretory proteins
    • Nuclei are not basal but on luminal side of granules
    • Secretory granules are released at BASAL surface of endocrine cell or along lateral surface; NOT apical; products modulate digestive functions
  • Ganglion cells:
  • Goblet cells: contain ovoid mucoid vacuole
  • Inflammatory cells:
    • Lymphocytes (B & T), intraepithelial lymphocytes only rarely, plasma cells, histiocytes (may contain hemosiderin, mucin or "pseudomelanin" from laxatives), mast cells, occasional eosinophils (varies by geography, Mod Pathol 1997;10:363)
    • Lymphoglandular complexes when lymphoid follicles surround deep crypt epithelium extending into submucosa
    • Neutrophils not normally present
  • Interstitial cells of Cajal:
    • Associated with myenteric (Auerbach/intramuscular) plexus between circular and longitudinal muscle layers
    • Have pacemaker function which facilitates active propagation of electrical events and mediates neurotransmission
    • Have unique ultrastructure on EM with gap junctions between each other and smooth muscle cells
    • Have surface tyrosine kinase receptor c-Kit (CD117) which is essential for their development (Am J Surg Pathol 2003;27:228)
    • Kit ligand provided by neuronal cells or smooth muscle cells (J Physiol 2006;576:653, Sultan Qaboos Univ Med J 2012;12:411)
  • M cells:
  • Paneth cells:
    • Secretory epithelial cells at base of crypts in cecum and ascending colon
    • Considered metaplastic if present elsewhere in colon; granules contain antimicrobial peptides (Trends Microbiol 2004;12:394, J Biol Chem 2000;275:33969)
    • Have basophilic cytoplasm due to rough ER, numerous eosinophilic granules (larger than in endocrine cells)
  • Undifferentiated crypt cells:
    • At base of crypts
    • Precursor to other noninflammatory cells
    • Migration from crypts to surface takes 3 - 8 days
    • Process allows for rapid repair, but also makes cells sensitive to radiation and cancer chemotherapy
Diagrams / tables

Images hosted on other servers:

Cecum and appendix

Cecum and ileocecal valve

Small and large intestine

Iliac, sigmoid or pelvic colon and rectum

Female pelvis


Vascular supply of colon

M cells

Missing Image

Intestinal crypt

Microscopic (histologic) images

Contributed by Grigory Demyashkin, M.D., Ph.D.

6-8 week embryo



Contributed by Epitomics
Missing Image

MSH6

Missing Image

PMS2



Images hosted on other servers:
Missing Image

Mucosa and submucosa

Missing Image

Crypts

Missing Image

Submucosal plexus of Meissner

Missing Image

Rectum

Missing Image

Rectal folds of Morgagni


Missing Image

Normal mucosa



Pericryptal fibroblast sheath:
Missing Image

Figures c & d

Missing Image

Sheath is positive for high molecular weight caldesmon

Missing Image

Sheath is positive for alpha smooth muscle actin

CDX2



Types of cells:

Paneth cells

Missing Image

Intestinal crypt

Back to top
Image 01 Image 02