Bovine forestomachs and stomach
This is a right lateral view of the forestomachs and stomach of a bovine species. Remember, the rumen occupies most of the left abdominal cavity.
The forestomachs of the ruminant species, such as the bovine, are expanded esophageal portions of the simple stomach, and are thus lined by stratified squamous epithelium. The esophagus (A) enters the rumen (B), which is a large mixing vat that contains microorganisms for cellulose digestion and fermentation. The epithelium, despite being stratified squamous epithelium, allows the ruminal juices to perculate between the cells for absorption of the carbohydrates and volatile fatty acids. The ruminal mucosa contains numerous conical papilla to increase the surface area for absorption. The reticulum (C) has a distinct honeycomb appearance. Cellulose digestion, fermentation and absorption continues here. It is in the reticulum that wires and such end up because of the indiscriminant eating habits of these animals, and subsequently, traumatic reticuloperitonitis (Hardware Disease) may result. The omasum (D) is filled with numerous leaf-like fronds, which increase the surface area for fluid absorption. The abomasum (E) is the true stomach, containing glands as we see in the simple stomach for protein digestion (yes, even those little microorganisms left in the ingesta).