Appendix, also known as vermiform, is a narrow muscular tube containing a large amount of lymphoid tissue. Its length is variable and ranges from 3 to 5 inches. The base of the appendix is attached to the cecum below the ileocecal junction, while the remainder of it is free. It has a complete peritoneal covering, which attaches to the mesentery of small intestine by a short mesentery of its own, called the mesoappendix. All the appendicular vessels and nerves pass through the mesoappendix to reach it.
Location of appendix:
The appendix lies in the right iliac fossa. It relation to anterior abdominal wall, its base is situated at the McBurney’s point. This point lies one third of the way up the line joining the right anterior superior iliac spine to the umbilicus.
Inside the abdomen, during surgical processes, the base of the appendix is easily found by finding the teniae coli of the cecum and tracing them to the base of the appendix, where they converge to form a continuous longitudinal muscle coat.
Position of the tip of appendix:
The tip of appendix is subject to considerable range of movement and as a consequence, it may be found in a number of positions. The common positions include the following:
- Hanging down in the pelvis against the right pelvic wall
- Coiled up behind cecum
- Projecting upward along the lateral side of cecum
- In front of or behind the terminal part of ileum
The first and second positions are the most common sites.
Blood supply of appendix:
The appendix receives its blood supply from the appendicular artery, which is a branch of the posterior cecal artery (branch of superior mesenteric artery). It passes to the tip of the appendix in the mesoappendix.
The appendicular vein corresponds to the appendicular artery and drains into the posterior cecal vein (tributary of superior mesenteric vein).
Lymph drainage of appendix:
The lymphatics drain into one or two intermediate nodes lying in the mesoappendix and then eventually drain into the superior mesenteric lymph nodes.
Nerve supply to appendix:
The parasympathetic and sympathetic nerves are derived from the superior mesenteric plexus. The afferent (sensory) fibers, which are concerned with the conduction of visceral pain from the appendix, accompany the sympathetic nerves and enter the spinal cord at the level of tenth thoracic segment.