Surgical anatomy of the right lower quadrant
The colon is about 1.5m long and originates at the confluence of the small intestine into the cecum. The cecum is located inferior to the ileocecal valve, has its own mesentery (→ mobility) with the appendicular artery and vein (← ileocolic artery← superior mesenteric artery) and is approx. 7cm long. The vermiform appendix originates on the dorsomedial wall of the cecum directly caudad of the ileocecal valve in the taenia libera. It is intraperitoneal, its length is 2–20cm and its diameter between 0.5cm and 1cm. Usually, the appendix extends from the posterior middle of the cecum to the center of the body, but its position can be quite variable, and thus also the location and severity of tenderness. This surgical condition is incorrectly referred to as "appendicitis", although from an anatomical point of view the affected organ is merely the vermiform appendix of the cecum.
Anatomical variants of the appendix:
- Descending type: Appendix extending into the lesser pelvis. In women it may be closely adjacent to the ovary.
- Medial position: Appendix between loops of the small intestine.
- Lateral position: Appendix between the lateral abdominal wall and cecum.
- Retrocecal position: Appendix turned craniad posterior to the cecum (65%)
- Anterocecal position: Appendix turned craniad anterior to the cecum.
- Subhepatic position: Appendix turned toward the liver and in contact with it.
Histologically, the mucous membrane of the appendix demonstrates the same makeup as in the large bowel. However, it has a large number of lymphatic cells and thus becomes part of the human immune system. In addition, in the wall of the appendix the 3 individual strips of longitudinal muscles (taenia) characteristic of the colon conjoin to a complete layer once again.
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