The rumen has a very thick muscular wall and extends from the diaphragm to the pelvis. It fills most of the left side
of the abdomen. The rumen itself has two parts, a dorsal sac and a ventral sac. The dorsal (upper) sac is the larger
of the two. The rumen's rumino-reticular fold segregates it from the other parts of the stomach. The floor of each of
the rumen’s two sacs contains many finger-like projections called papillae. Each papillae many extend to one
centimeter in length. The wall of the rumen consists of two layers of smooth muscle. These muscles extend at right
angles to each other, similar to those of the esophagus.