The appendix is derived from the posteromedial aspect of the cecum, and is supported by the mesoappendix, a fold of mesentery which suspends the appendix from the terminal ileum.
The position of the free-end of the appendix is highly variable and can be classified into seven main locations depending on its relationship to the ileum, caecum or pelvis. The most common position is that of a retrocecal position. They may also be remembered by their relative position on a clock face: pre-ileal (anterior to the terminal ileum, 1 or 2 o'clock), post-ileal (posterior to the terminal ileum, 1 or 2 o'clock), sub-ileal (parallel with the terminal ileum, 3 o'clock), pelvic (descending over the pelvic brim, 5 o'clock), subcecal (below the cecum, 6 o'clock), paracecal (alongside the lateral border of the cecum, 10 o'clock) and retrocecal (behind the cecum, 11 o'clock).
The vascular supply of the appendix is via branches of the superior mesenteric vessels. Specifically, the arterial supply is from the appendicular artery (derived from the ileocolic artery, a branch of the superior mesenteric artery) and venous drainage is provided by the corresponding appendicular vein. Both of these arteries and veins are contained within the mesoappendix.
The appendix is further innervated by sympathetic and parasympathetic branches of the autonomic nervous system. This is achieved via the ileocolic branch of the superior mesenteric plexus, which accompanies the ileocolic artery to reach the organ. Of particular clinical relevance is that the sympathetic afferent fibres of the appendix arise from T10 of the spinal cord - thus explaining why the visceral pain of early appendicitis is felt centrally within the abdomen.
The lymphatic fluid from the appendix drains into lymph nodes within the mesoappendix and into the ileocolic lymph nodes (which surround the ileocolic artery).
Inflammation of the appendix is known as appendicitis, and is a common cause for acute severe abdominal pain. In established appendicitis, the abdomen is most tender at McBurney's point - situated one third of the distance from the right anterior superior iliac spine to the umbilicus. This corresponds to the location of the base of the appendix when it lies in a retrocecal position.
The aetiology of appendicitis is varied, and depends on the age of the individual. In younger people, it is mostly due to an increase in lymphoid tissue size, which occludes the lumen. From the age of 30 onwards, it is more likely to be blocked due to a faecolith.
Initially, pain from the appendix and its visceral peritoneum is referred to the umbilical region. As the appendix becomes increasingly inflamed, it irritates the parietal peritoneum, causing the pain to localise to the right lower quadrant.
If the appendix is not removed, it can become necrotic and rupture, resulting in peritonitis (inflammation of the peritoneum).
The appendix is a small, finger-like pouch that is an important component of the human anatomy. It projects from the first part of the large intestine, the caecum, and has various functions and anatomical relations. It is connected to the abdominal wall and has a neurovascular supply and lymphatic drainage that are important for its functioning. Clinically, inflammation and appendicitis are the most important pathological conditions associated with the appendix, and tenderness in the right iliac fossa is the most common clinical sign suggestive of appendicitis.
The sympathetic afferent fibres of the appendix arise from T10 of the spinal cord. This explains why the visceral pain of early appendicitis is felt centrally within the abdomen. The neurovascular supply of the appendix consists of branches of the superior, middle, and inferior colic arteries as well as the iliolumbar vessels. The veins follow the course of the arteries, with the veins draining into the inferior mesenteric vein. These arteries supply the muscular and mucosal layers of the appendix.
The lymphatic fluid from the appendix drains into lymph nodes within the mesoappendix and into the ileocolic lymph nodes. These lymph nodes surround the ileocolic artery and help to flush out any potential toxins from the appendix.
Inflammation of the appendix, known as appendicitis, is a very common cause of acute, severe abdominal pain in all age groups. This pain is most tender at McBurney’s point, which corresponds to the location of the base of the appendix when it lies in a retrocecal position. This is approximately one-third of the distance from the right anterior superior iliac spine to the umbilicus. The etiology of appendicitis depends on age; in the young, it is mostly caused due to an increase in lymphoid tissue size, which occludes the lumen. From the age of 30 onwards, the appendicitis is more likely to be caused due to blockage of the lumen by a faecolith.
The pain from the appendix and its visceral peritoneum is initially referred to the umbilical region. As the appendix becomes increasingly inflamed, pain is localized to the right lower quadrant as it starts to irritate the parietal peritoneum. If the appendix is not removed, it can become necrotic and rupture, resulting in peritonitis, which is an inflammation of the peritoneum.
The appendix is an important structure of the human anatomy with various functions and anatomical relations. It is connected to the abdominal wall and has a neurovascular supply and lymphatic drainage that are essential for its functioning. Clinically, inflammation and appendicitis are the most common pathological conditions associated with the appendix and tenderness in the right iliac fossa is the most common clinical sign suggestive of appendicitis. The aetiology of appendicitis is unclear, but is thought to be related to obstruction of the lumen caused by faecolith, resulting in accumulation of fluid and bacterial proliferation, accompanied by increased tension in the peritoneum.
