QS Study

Structure and Development of Appendix

The appendix is a small, pouch-like sac of tissue that is located in the first part of the colon (cecum) in the lower- right abdomen. When it gets infected, it’s called appendicitis. The appendix has its own blood supply in leaves of fat arising off the mesentery of the cecum.

It is usually 8 to 10 cm (3 to 4 inches) long and less than 1.3 cm (0.5 inches) wide. It is not clear whether the appendix serves any useful purpose in humans.

The appendix is covered by the following layers (from outside inwards):

(1) Serous coat.

(2) Muscular coat – Outer: Longitudinal, and Inner: Circular.

(3) Submucous coat

(4) Mucous coat: Lined by simple columnar epithelium.

Development

It develops from the lower narrow part of caecal diverticulum which arises from a distal limb of the U-shaped loop of the primitive midgut. The diameter of the appendix usually ranges from 7 to 8 mm and its length ranges between 2 and 20 cm, with an average length of 9 cm. The appendix is usually located at the lower right side of the abdomen.