The Anatomy of the Human Peritoneum and Abdominal Cavity / Considered from the Standpoint of Development and Comparative Anatomy

by George S. Huntington

Fig. 574.—Human adult. Cæcum and ileo-colic junction; well-developed ventral vascular fold, carrying appendicular artery. (Columbia University Museum, No. 1613.)

This condition is occasionally encountered. Dr. Martin, in a recent examination of the vascular supply of cæcum and appendix in one hundred subjects, found it to obtain in six instances.

Apparently the dorsal wall of the cæcum and of the proximal segment of the ascending colon remains free in these cases and does not become adherent to the parietal peritoneum. The shape of the pouch, moreover, indicates a free and unimpeded embryonal cæcal descent. The normal relative size of the two vascular folds is reversed. A good example of this variation, in the cæcum of an infant, is seen in [Fig. 516]. The same arrangement in an adult specimen is seen in Fig. 574.

In the Slow Lemur (Nycticebus tardigradus) ([Fig. 420]) the ventral artery is normally the larger of the two, extending in the ventral fold to the tip of the reduced appendix of the cæcal pouch.

(B) Fusion of ventral vascular fold with the intermediate fold, resulting in the production of a well-defined superior or ventral ileo-cæcal fossa.

Fig. 575.—Human fœtus at term. Ileo-colic junction and cæcum; ventral view. (Columbia University Museum, No. 1715.)

Normally the reduced ventral artery crosses the ileo-colic junction in a slightly developed ventral vascular fold, closely adherent to the intestine, with a very narrow free margin. The superior or ventral ileo-cæcal fossa in these cases is very shallow and confined (Fig. 574) to the ventral surface of the ileo-colic junction. Occasionally the fold is better developed and fuses with the intermediate non-vascular fold, producing a fossa of greater extent, which is bounded dorsad by the ileum, ventrad and cephalad by the ventral fold, caudad by the fusion of this fold with the intermediate reduplication, and to the right by the left wall of the cæcum. [Figs. 576], [577], [578] and [579] show this aberrant disposition of the structures in a series of adult human cæca.

Fig. 576.—Human adult. Ileo-colic junction and cæcum; ventral appendicular artery and ileo-cæcal fossa. (Columbia University Museum, No. 1614.)