Lecture on the Appendix

Overview and Importance

• The appendix lacks a clearly defined function but is important due to its frequency in becoming blocked and pathological.
• It is a narrow, blind-ended tube attached to the posterior medial end of the cecum.

Embryological Origin

• Derived from the embryological midgut.
• Appears during the fifth month of gestation.

Physical Characteristics

• Named "vermiform" due to its worm-like appearance (Latin: "vermes").
• Length varies between 2 to 20 cm, with an average of 8 to 10 cm.

Location

• Base of the appendix is at the point where the longitudinal tinea coli converge on the cecum.
• This knowledge aids in locating the appendix during surgery.

Anatomical Layers

• Similar structure to the large intestine:
  • Outer serosa.
  • Two layers of muscularis propria (outer circumferential longitudinal and inner circumferential).
  • Submucosa and mucosal layers.
• Distinct feature: High number of lymphoid aggregates in the submucosa, prominent in adolescence, diminishing with age.

Nerve Supply

• Innervated by sympathetic and parasympathetic branches of the autonomic nervous system.
• Carried by the ileocolic branch of the superior mesenteric plexus.
• Sympathetic afferent nerve fibers arise at the T10 level, explaining initial visceral pain in appendicitis around the central abdomen.

Blood Supply

• Supplied by the appendicular artery, branching off the ileocolic artery.
• Runs parallel with the appendix within the mesoappendix.

Location of the Appendix Base

• Typically found at McBurney's point:
  • Located two-thirds the distance from the umbilicus to the anterior superior iliac spine.
  • Named after Charles McBurney, who identified it as the site of maximal tenderness in acute appendicitis.

Variability in Appendix Tip Position

• Common positions:
  • Retroccecal (behind the cecum) - majority.
  • Pelvic - 20%.
• Rare positions:
  • Paracecal and subcecal - 2% and 1.5% respectively.
  • Pre-ileal and post-ileal - 1% and 0.5% respectively.

Clinical Significance

• Position of the appendix tip affects symptoms and signs experienced by patients, crucial for diagnosis and treatment of appendicitis.