Vermiform Appendix The appendix is a narrow, muscular tube containing a large amount of lymphoid tissue. It varies in length from 3 to 5 inches.The base is attached to the posteromedial surface of the cecum about 1 inch below the ileocecal junction. The remainder of the appendix is free. It has a complete peritoneal covering, which is attached to the mesentry of the small intestine by a short mesentry of its own, the mesoappendix. The mesoappendix contains the appendicular vessels and nerves. The position of the appendix is variable, but it is usually retrocecal. The three taenia of the caecum converfge towards the point at which the appendix is attached. McBurney’s Point 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 oblique line joining the right anterior superior iliac spine to the umbilicus. This point is referred to as McBurney’s point on the spinoumblical line. Appendectomy is performed through a transverse or gridiron (muscle splitting) incision centered at the McBurney’s point in the right lower quadrant. Vasculature of Appendix The appendicular artery, a branch of the ileocolic artery supplies the appendix. The ileocolic vein drains blood from the cecum and appendix. Lymphatic Drainage The lymph vessels drain into one or two nodes lying in the mesoappendix and then eventually into the superior mesentric nodes. Nerve Supply The nerve supply to the cecum and appendix derives from the sympathetic and parasympathetic nerves from the superior mesentric plexus. The sympathetic fibres originate in the lower thoracic part of the spinal cord and the parasympathetic fibres derive from the vagus nerves. Afferent fibres from the appendix accompany the sympathetic nerves to the T10 segment of the spinal cord. Clinical Significance Appendicitis Acute inflammation of the appendix is a common cause of an acute abdomen (severe abdominal pain arising suddenly). Usually, digital pressure over the McBurney point registers maximum abdominal tenderness. Appendicitis in young people is usually caused by hyperplasia of lymphatic follicles in the appendix that occludes the lumen. In older people, the obstruction usually results from a fecalith (coprolith), a concretion that forms around a center of fecal matter. When secretions from the appendix cannot escape, the appendix swells, stretching the visceral peritoneum. The pain of appendicitis usually commences as a vague pain in the periumbilical region because afferent pain fibers enter the spinal cord at the T10 level. Later, severe pain in the right lower quadrant results from irritation of the parietal peritoneum lining the posterior abdominal wall. Extending the thigh at the hip joint elicits pain. Acute infection of the appendix may result in thrombosis (clotting of blood) in the appendicular artery, which often results in ischemia, gangrene (death of tissue), and perforation of an acutely inflamed appendix. Rupture of the appendix results in infection of the peritoneum (peritonitis), increased abdominal pain, nausea and/or vomiting, and abdominal rigidity (stiffness of the abdominal muscles). Flexion of the right thigh ameliorates the pain because it causes relaxation of the right psoas muscle, a flexor of the thigh.