The food begins the journey of being digested and put to good use in the mouth. The teeth assist in the tearing of food into smaller bits. The saliva lubricates the food and assists in the swallowing of the food. Salivary enzymes do not play a huge role in this stage of digestion as cats have a limited supply of salivary enzymes
The esophagus is essentially a tube that connects the mouth (oral cavity) to the stomach. The food is swallowed and is then moved down the esophagus by muscular contractions. When the esophagus has no food, it basically collapses on itself, making it a closed space that is ready for action.
At the end of the esophagus, there is a little valve that opens when food is at the base of the esophagus. Food that enters the stomach is then mixed with acids, enzymes, and mucus. This is where proteins, fats, and carbohydrates start to be broken down. Food is then turned into a semi liquid. There is a valve at the exit area of the stomach. This controls the food leaving the stomach and entering the small intestine.
Food is then further broken down in the small intestine. Enzymes from the pancreas and the small intestine help break down the proteins, fats, and carbohydrates even further. Bile is released into the small intestine, which breaks up large fat molecules. This allows the enzymes to further break down the smaller fat molecules, being able to use them accordingly. It is in the small intestine that the proteins, fats, and carbohydrates are broken down into their simplest forms: amino acids, fatty acids, and sugars. The small intestine is covered in little hairs, called villi, where these nutrients are absorbed and enter the bloodstream, along with vitamins and minerals from the food.
The large intestine connects the small intestine to the anus. The large intestine’s primary function is to absorb any last available water and electrolytes as needed. This keeps the hydration normal and electrolyte balance level. The large intestine is also responsible for the formation and storage of the feces as it awaits removal from the body.
The liver is the largest organ in the body. The liver is responsible for the production of bile. When nutrients are absorbed by the small intestine, they go to the liver via the bloodstream. Amino acids can be rebuilt by the liver, in a way so they can be used by the body. Some of the glucose that is broken down from carbohydrates are converted and stored in the liver as glycogen. Glycogen is used as a short-term energy source. The liver is also responsible for screening the blood and making sure that no harm can come from bacteria that have been absorbed by the small intestine.
The pancreas is located near the liver, on the right side of the body. The pancreas is responsible for secreting enzymes into the small intestine. These enzymes are essential in breaking down and absorbing much needed nutrients. The three main enzymes are:
Protease: act on proteins
Amylase: act on carbohydrates
Lipase: act on fat
The pancreas also is responsible for secreting insulin directly into the bloodstream. Insulin is important because it is responsible for maintaining blood glucose (or sugar) levels. If there is no insulin being secreted by the pancreas, or not enough, the blood glucose levels will constantly be high and uncontrollable. This is known as diabetes.
The gall bladder essentially stores the bile that is created by the liver. The bile is then secreted into the small intestine from the gall bladder via a duct. Bile is a combination of bile salts, pigments, and waste products of the liver. Bile breaks up fats to the point where lipase can act on these fat molecules. The lipase breaks them down to the point where they can be absorbed by the bloodstream.