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

by George S. Huntington

(a) Shape of cæcum and origin of appendix. (Type of adult cæcum.)

(b) Position, direction and peritoneal relations of the appendix.

(c) Arrangement of the vascular and serous ileo-cæcal folds.

The peculiarities encountered in any individual case usually depend upon the combination of all three of these factors, which together influence and determine the arrangement of the structures in the adult. Hence the examination of each case should be made with reference to these three points, which we will now consider in detail.

A. SHAPE OF CÆCUM AND ORIGIN OF APPENDIX. TYPES AND VARIATIONS OF ADULT CÆCUM AND APPENDIX.

The various forms of the adult cæcum are all derived by modifications from the fœtal type of the pouch.

In the embryo the cæcum is funnel-shaped, narrowing gradually and symmetrically in caliber to the root of the appendix, at which point the three colic tænia or longitudinal muscular bands of the large intestine meet. The appendix arises from the apex of the funnel, the lateral walls of which are equally and symmetrically developed. The entire pouch is of a crescentic shape, the concavity of the curve turned to the left and directed toward the caudal margin of the terminal ileum. Two subdivisions of the fœtal type are found:

Fig. 509.—Schematic table of types of human cæca.