Cats have a unique digestive system that caters specifically to their carnivorous diet. In the wild, without this specialized digestive system, a cat would be unable to properly digest its prey. As a cat ages, their digestive system can slow down, resulting in illness. Whenever cats display symptoms of illness or disease, it is always best to seek out the care of a trained veterinarian.
The digestive system does not officially begin at the mouth. However, the mouth is important to starting the entire process within the body. The combination of the cat’s sharp molars, premolars, incisors and canine teeth aid in the cat’s ability to kill and devour prey quickly.
Once swallowed, the prey (or food, as it has become) travels down the cat’s esophagus. The esophagus is a small tube that travels through the neck and connects the cat’s mouth to his stomach. The esophagus is lined with muscles that create wave-like motions to help move the food down into the stomach.
At the end of the esophagus, there is a structure known as the cardiac sphincter. This sphincter, which is similar in appearance to a valve, opens and allows the food to enter the cat’s stomach.
The cat’s stomach features gastric golds which help the cat digest food. There is also stomach acid as well as a variety of digestive enzymes, which help break down the food.
Unlike popular belief, digestion does not end in the stomach. Food is only partially digested when it moves from the cat’s stomach, through a second sphincter known as the pyloric sphincter, and into the small intestine.
The feline small intestine features three sections: the duodenum (beginning,) the jejunum (the middle,) and the ileum (the end.) At the ileum, the small intestine connects to the large intestine.
While food is inside the small intestine, it is further processed by other organs in the body. The pancreas and the gallbladder both send fluids and enzymes through the pancreatic ducts that attach to the small intestine. These fluids and enzymes mix the food and further digest it. So, by the time this food reaches the middle intestine, the nutrients are ready to be absorbed.
Once the nutrients have been absorbed, the food passes into the large intestine. The large intestine, as its name suggests, is larger than the small intestine. The largest portion of this organ is the colon; though the terms colon and large intestine are often used interchangeably in veterinary (and standard) medicine.
Here, the food is now considered feces and it is stored until the cat is ready to expel it.
Washington State University: Digestive System of the Cat
Pet Education: Anatomy & Function of the Esophagus, Stomach and Intestines in Cats
Vet Info: Feline Digestive Enzymes