Surgical anatomy of the right lower quadrant
The large intestine (colon) is about 1.5 m long and originates at the confluence of the small intestine into the cecum. The cecum is located at the level of and inferior to the ileocecal valve, has its own mesentery (→ mobility) with the appendicular artery and vein (← ileocolic artery ← superior mesenteric artery) running within it, with a breadth of about 7 cm. The cul-de-sac tubular vermiform appendix arises from the medial wall of the cecum directly caudad of the ileocecal valve in the taenia libera. Its serous coat is complete (intraperitoneal), varies from 2 to 20 cm in length, and from 0.5 to 1 cm in diameter. Usually, the appendix extends from the posteromedial cecum to the middle of the body, but its position can be quite variable, and thus also the location and severity of tenderness in appendicitis. 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: The appendix is enveloped by loops of small intestine.
- Lateral position: The appendix courses between the lateral abdominal wall and cecum.
- Retrocecal position: The appendix turned craniad posterior to the cecum (65%).
- Anterocecal position: The appendix turned craniad anterior to the cecum.
- Subhepatic position: The appendix turned towards the liver and is in contact with it.
Histologically, the mucous membrane of the appendix demonstrates the same makeup as in the large bowel. However, it abounds with lymphatic cells and thus becomes part of the human immune system. Moreover, the longitudinal muscle layer is concentrated to form three linear bands that are equidistant from each other and make up the taenia coli.
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