LOCATION– arises from the posteromedial wall of the cecum approximately 1 to 3 cm below the ileocecal junction,
Although the location of the base of the appendix, with respect to the cecum, is constant, the position of the tip is extremely variable.
1. The appendix may pass upwards and to the right. This is paracolic or 11 o’clock position.
2. It may lie behind the caecum or colon, known as retrocolic or 12 o’clock position. This is the commonest position of appendix, about 65%.
3. The appendix may pass upwards and to the left. It points towards the spleen. This is the splenic or 2 o’clock position. The appendix may lie in front of the ileum (preileal) or behind the ileum (postileal). The preileal type is most dangerous type.
4. It may pass horizontally to the left (as if pointing to the sacral promontory) called promonteric or 3 o’clock position.
5. It may descend into the pelvis called pelvic or 4 o’clock position. This is the second most common position about 30%.
6. It may lie below the caecum (subcaecal) and may point towards the inguinal ligament called midinguinal or 6 o’clock position
Appendicular Orifice – The appendicular orifice is situated on the postero-medial aspect of the caecum 2 cm below the ileocaecal
orifice.
Peritoneal Relations – The appendix is suspended by a small, triangular fold of peritoneum, called the mesoappendix,
Blood Supply – The appendicular artery is a branch of the lower division of the ileocolic artery
Nerve Supply – Sympathetic nerves are derived from T9 and T10 segments through the coeliac plexus. Parasympathetic nerves are derived from the vagus.
Lymphatic Drainage – Most of the lymphatics pass directly to the ileocolic nodes, but a few of them pass indirectly through the appendicular nodes situated in the mesoappendix.
CLINICAL ANATOMY
- Inflammation of the appendix is known as appendicitis seen in adolescent age.
- Pain caused by appendicitis is first felt in the region of the umbilicus. This is referred pain.
- McBurney’s point is the site of maximum tenderness in appendicitis. The point lies at the junction of the lateral one-third and the medial two-thirds of the line joining the umbilicus to the right anterior superior iliac spine.