ANATOMY

ANATOMY

The vermiform appendix is present only in humans, certain anthropoid apes and the wombat. It is a blind muscular tube with mucosal, submucosal, muscular and serosal layers. Morphologically , it is the undeveloped distal end of the large caecum found in many lower animals. At birth, the appendix is short and broad at its junction with the caecum, but di ff erential growth of the caecum produces the typical tubular structure by about the age of 2 years (Condon). During childhood, contin - ued growth of the caecum commonly rotates the appendix into a retrocaecal but intraperitoneal position ( Figure 76.1 ). In approximately one-quarter of cases, rotation of the appendix does not occur, resulting in a pelvic, subcaecal or paracaecal position. Occasionally , the tip of the appendix becomes extraperitoneal, lying behind the caecum or ascending colon. Rarely , the caecum does not migrate during development to its normal position in the right lower quadrant of the abdomen. In these circumstances, the appendix can be found near the gallbladder or, in the case of intestinal malrotation, in the left iliac fossa, causing diagnostic di ffi culty if appendicitis develops ( Figure 76.2 ).

Figure 76.2 Left-sided caecum and appendix due to intestinal mal rotation.