What is the appendix and where is it located?

The appendix is a narrow, worm-like tubular structure that arises from the posteromedial wall of the caecum, about 2 cm below the ileocaecal junction. It contains abundant lymphoid tissue, earning it the nickname "abdominal tonsil."

What are the common positions of the appendix?

While the base is fixed, the rest of the appendix can vary in position. The most common orientations are retrocaecal/retrocolic (most common, ~65%) and pelvic (second most common, ~31%). Other positions include subcaecal, pre-ileal, post-ileal, and paracolic.

What is McBurney's point and why is it clinically important?

McBurney's point is a clinical landmark located at the junction of the lateral third and medial two-thirds of a line from the umbilicus to the right ASIS. It corresponds to the base of the appendix and is the site of maximal tenderness in appendicitis.

What is the blood supply to the appendix?

The appendix receives its blood supply from the appendicular artery, which is a branch of the inferior division of the ileocolic artery. This artery runs within the mesoappendix, making the tip the most ischemic and vulnerable area.

Why does appendicitis initially cause umbilical pain?

Appendicitis initially causes umbilical pain because the appendix shares the same T10 spinal segment nerve supply as the umbilical region. This creates referred pain to the umbilicus before inflammation localizes to the right iliac fossa.

What is a subhepatic appendix?

A subhepatic appendix is a developmental anomaly where the appendix is located in the right hypochondrium instead of the right iliac fossa. This occurs due to failure of caecal descent, and inflammation in this position can mimic cholecystitis.

What are the microscopic layers of the appendix wall?

The appendix wall consists of four layers: mucosa with simple columnar epithelium and goblet cells, submucosa with prominent lymphoid follicles, muscular layer with inner circular and outer longitudinal smooth muscle, and serosa of visceral peritoneum.

Vermiform Appendix – Positions & Appendicitis

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