Appendix
General
Normal anatomy

Reviewer: Jaleh Mansouri, M.D., (see Authors page)

Revised: 26 January 2016, last major update August 2012

Copyright: (c) 2003-2016, PathologyOutlines.com, Inc.

PubMed Search: anatomy appendix
General
    Anatomy:
    • Commonly located in retrocecal or pelvic region
    • Arises from posteriomedial cecum, usually lies posterior to cecum or ascending colon, may overly pelvic brim and impinge on bladder; also other locations
    • Locate by following the 3 teniae coli of the large bowel, which all terminate at base of appendix
    • Same 4 layers as gut (mucosa, submucosa, muscularis externa/propria, serosa)
    • Orifice is 2.5 cm below ileocecal value; may be covered by small flap of mucosa
    • No known function; may have role in mucosal immunity

    Vasculature / lymphatics / innervation:
    • Vascular supply from posterior cecal branch of ileocolic artery, a branch of superior mesenteric artery
    • Drains into ileocolic vein, then superior mesenteric vein and portal circulation
    • Lymphatics drain into ileocolic lymph nodes
    • Innervation from vagus nerve and superior mesenteric plexus

    Mesoappendix:
    • Adipose tissue plus appendiceal vessels and occasionally small lymph nodes
    • Anchors appendix

    Abnormal positions of appendix:
    • Left-sided appendix is associated with congenital anomalies including situs inversus and midgut malrotation; appendicitis is in the differential diagnosis of left lower quadrant pain in these patients (World J Gastroenterol 2010;16:5598)
Diagrams / Tables

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Cecum, appendix and arteries

View from cecum

Micro Description
  • Large bowel type epithelium overlying lamina propria with irregularly distributed crypts (glands)
  • Rich lymphoid tissue in mucosa and submucosa that may disrupt the muscularis mucosa, obliterate the lumen and distort the crypt architecture (lymphoid tissue atrophies with age)
  • Epithelium contains occasional Paneth cells at crypt bases (basal nucleus, conspicuous nucleoli, abundant eosinophilic supranuclear granules)
  • Lamina propria also contains histiocytes, occasional eosinophils, neuroendocrine cells
  • Muscularis mucosa and submucosa may be inconspicuous
  • Muscularis propria contains complete longitudinal and circular layers and prominent ganglion cells
Micro Images

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Various images

Virtual Slides

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Normal appendix