Appendix- Common Positions of the Tip of the Appendix-Blood Supply-Lymph Drainage-Nerve Supply-Variability of Position of the Appendix-Why the Infection of the Appendix is very common-Pain of Appendicitis-Perforation of the Appendix

Appendix

Description

The appendix is a narrow, muscular tube containing a large amount of lymphoid tissue. It varies in length from 3 to 5 in. (8 to 13 cm). The base is attached to the posteromedial surface of the cecum about 1 in. (2.5 cm) below the ileocecal junction. The remainder of the appendix is free. It has a complete peritoneal covering, which is attached to the mesentery of the small intestine by a short mesentery of its own, the mesoappendix. The mesoappendix contains the appendicular vessels and nerves. The appendix lies in the right iliac fossa, and in relation to the anterior abdominal wall its base is situated one third of the way up the line joining the right anterior superior iliac spine to the umbilicus (McBurney’s point). Inside the abdomen, the base of the appendix is easily found by identifying 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.




Common Positions of the Tip of the Appendix

 The tip of the appendix is subject to a considerable range of movement and may be found in the following positions:
(a) coiled up behind the cecum,
(b) hanging down into the pelvis against the right pelvic wall,
(c) projecting upward along the lateral side of the cecum,
 and (d) in front of or behind the terminal part of the ileum. The first and second positions are the most common sites

Blood Supply

Arteries The appendicular artery is a branch of the posterior cecal artery.

Veins The appendicular vein drains into the posterior cecal vein.

Lymph Drainage

The lymph vessels drain into one or two nodes lying in the mesoappendix and then eventually into the superior mesenteric nodes.

Nerve Supply

The appendix is supplied by the sympathetic and parasympathetic(vagus) nerves from the superior mesenteric plexus. Afferent nerve fibers concerned with the conduction of visceral pain from the appendix accompany the sympathetic nerves and enter the spinal cord at the level of the 10th thoracic segment.

Variability of Position of the Appendix

when attempting to diagnose an appendicitis The inconstancy of the position of the appendix should be borne in mind. A retrocecal appendix, for example, may lie behind a cecum distended with gas, and thus it may be difficult to elicit tenderness on palpation in the right iliac region. Irritation of the psoas muscle, conversely, may cause the patient to keep the right hip joint flexed. An appendix hanging down in the pelvis may result in absent abdominal tenderness in the right lower quadrant, but deep tenderness may be experienced just above the symphysis pubis. Rectal or vaginal examination may reveal tenderness of the peritoneum in the pelvis on the right side.

 

Why the Infection of the Appendix is very common
?

The following factors contribute to the appendix’s predilection to infection:

■■ It is a long, narrow, blind-ended tube, which encourages stasis of large-bowel contents.

■■ It has a large amount of lymphoid tissue in its wall.

■■ The lumen has a tendency to become obstructed by hardened intestinal contents (enteroliths), which leads to further stagnation of its contents
.

Pain of Appendicitis

the pain of the appendix is produced by distention of its lumen or spasm of its muscle. The afferent pain fibers enter the spinal cord at the level of the 10th thoracic segment, and a vague referred pain is felt in the region of the umbilicus. Later, the pain shifts to where the inflamed appendix irritates the parietal peritoneum. Here the pain is precise, severe, and localized

Perforation of the Appendix

The appendix is supplied by a long small closed artery that does not anastomose with other arteries. The blind end of the appendix is supplied by the terminal branches of the appendicular artery. Inflammatory edema of the appendicular wall compresses the blood supply to the appendix and often leads to thrombosis of the appendicular artery. These conditions commonly result in necrosis or gangrene of the appendicular wall, with perforation. Perforation of the appendix or transmigration of bacteria through the inflamed appendicular wall results in infection of the peritoneum of the greater sac.