Gross anatomy

Gross anatomy

The position of the base of the appendix is constant, being found at the confluence of the three taeniae coli of the caecum, which fuse to form the outer longitudinal muscle coat of the appendix. At operation, use can be made of this to find an elusive appendix, as gentle traction on the taeniae coli, particularly the anterior taenia, will lead the operator to the base of the appendix. The mesentery of the appendix or mesoappendix arises from the lower surface of the mesentery Nikolai Kulchitsky , 1856–1925, Professor of Histology , Kharkov , Ukraine, who left Russia after the Revolution of 1917 and later worked at University College, London, UK. He described these cells in 1897. Sometimes, as much as the distal one-third of the appendix is bereft of mesoappendix. Especially in childhood, the mesoappendix is so transparent that the contained blood vessels can be seen ( Figure 76.3 ). In many adults, it becomes laden with fat, which obscures these vessels. The appendicular artery , a branch of the lower division of the ileocolic artery , passes behind the terminal ileum to enter the mesoappendix a short distance from the base of the appendix. It then comes to lie in the free border of the mesoappendix. An accessory appendicular artery may be present but, in most people, the appendicular artery is an ‘end-artery’, thrombosis of which results in necrosis of the appendix (synonym: gangrenous appendicitis). Four, six or more lymphatic channels traverse the mesoappendix to empty into the ileocaecal lymph nodes.

Figure 76.3 Laparoscopic view of a normal appendix with meso- appendix displaying the appendicular artery.