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English name: vermiform
The appendix, also known as vermis, is a slender and curved blind tube, which is located at the lower right of the abdomen between the cecum and ileum. Its root is connected with the posterior medial wall of cecum, and its distal end is free and locked. Its range of activity varies from person to person, and it can extend to the abdominal cavity in any direction under the influence of mesentery. The tip of the appendix can point in all directions. Generally, the posterior position of the cecum is the most, followed by the pelvic position. The average length of the appendix is 7 ~ 9 cm, and it can also vary between 2 ~ 20 cm. The upper end of the appendix opens to the cecum, and there are also less obvious semilunar mucosal folds at the opening. The external diameter of appendix is 0.5 ~ 1.0 cm, and the internal diameter of lumen is narrow, which is only 0.2 cm at rest.
The position of the appendix root is relatively constant, and the three colon bands are downward, all of which extend to the appendix root as a sign to find the appendix. There are appendiceal arteries and veins on the mesentery of the appendix, and their roots are located in the concentrated parts of the three colonic bands. The projection of the appendix root on the body surface is generally at the lateral 1/3 of the line from the right anterior superior iliac spine to the umbilical cord, which is called the appendix point here, also called Maxwell point. When appendicitis attacks, there is often obvious tenderness here.
Generally speaking, the appendix of children is longer than that of adults relative to their height; The appendix of adult women is larger than that of men, and that of children is larger than that of women. It gradually shrinks and becomes smaller after middle age.
In the past, people thought that the appendix was a degenerate organ in the process of human evolution, which had no important physiological function and had little influence on the human body. Appendectomy has no adverse effects on the body. So after suffering from appendicitis, it can be removed, but these concepts are changing!
There are many new understandings of appendix function in modern medical research, especially the development of immunology and transplantation surgery, which suggests that clinical surgeons should strictly grasp the indications of appendectomy and be cautious about incidental appendectomy.
This function is:
The appendix is rich in lymphoid tissue and participates in the immune function of the body. According to research, the human appendix has B lymphocytes and T lymphocytes, which is equivalent to the bursa of fabricius structure of birds. It belongs to the central immune organ and undertakes two specific functions: cellular immunity and humoral immunity. According to the latest research results, the appendix also has secretory cells, which can secrete a variety of substances and digestive enzymes, hormones that promote intestinal peristalsis and hormones related to growth everywhere. In addition, the appendix has complete inner ring muscle and outer longitudinal muscle, and has a certain length and diameter. With the development of microsurgery technology, it is more and more extensive to replace the defects and strictures of ureter and urethra with autologous appendix transplantation.