It is the relative difficulty of digestion of cellulose. One pass and the wolf gets its nutrition, but to break down the cellulose takes more work, by the cow and the rumen microflora. The pharynx is a short, funnel shaped muscular sac between the mouth and esophagus. It is part of the digestive AND respiratory tracts. The esophagus is muscular tube that connects the pharynx to the stomach.
Muscular contractions move the food down the esophagus to the stomach.
The stomach is located in abdominal cavity between the esophagus and small intestine. It is divided into three regions, the cardiac, fundus and pylorus. Protein is the primary food component broken down in the stomach. Ask why this is important to know. The abomasum is the true stomach.