A pig has a non-ruminant type of a digestive system, which is also known as mono-gastric digestive system. This basically means that a pig has a single stomach and not multiple stomachs like cattle or sheep which are ruminants. The stomach of the pig is not divided into chambers. Hence, the pig has to be feed on grains in order to facilitate easy digestion.
The digestive system of a pig is used to break down the food that is consumed by the animal. As the food moves along the system, it is broken down in smaller and smaller particles and thereafter these tiny or minute particles are absorbed by the body. The remaining particles are eliminated from the body in the form of feces and urine.
A pig's digestive system is composed of 5 parts, namely the mouth, esophagus, stomach, the intestines. When the pig consumes food, it is first chewed in the mouth. The saliva secreted by the mouth helps to soften as well as moisten the food. In addition, the saliva has an enzyme that helps to begin the digestion of the starch contained in the food. The tongue is responsible for directing the food towards the esophagus.
The esophagus is a tube-like structure that connects the mouth and the stomach. In the esophagus, a series of contractions takes place that helps to direct the food towards the stomach. Where the esophagus joins the stomach, there is a valve that stops the food from moving backwards into the esophagus.
In the stomach, hydrochloric acid and digestive enzymes are secreted by the lining of the stomach wall. These help to chemically breakdown the food to smaller particles. It is here that the food is broken down into fats, proteins and carbohydrates. Some of the nutrients are absorbed by the stomach and they enter the bloodstream. The nutrients that cannot be absorbed are then pushed into the pyloric valve, and thereafter into the small intestine.
The small intestine of the pig is shaped like a spiral and it contain several finger like protrusions called villi. These villi aid in increasing the surface area of the small intestine. The cells lining the small intestine wall also secrete enzymes that help in breaking down the food particles further and facilitating absorption of nutrients. The first part of the small intestine is known as duodenum. It is here that the secretions by the liver and pancreas enter the digestive system. The liver secretions help to digest fat, while the pancreatic secretions help to digest fats, proteins and carbohydrates. The nutrients from the food are actually absorbed in the jejunum and ileum, which are the 2nd and 3rd part of the small intestine. The food that has not been digested is then pushed to the large intestine via the ileocecal valve.
The large intestine in the pig begins with the cecum. The large intestine is shorter in size compared to the small intestine, but it has a bigger diameter. In this part of the digestive system, water is absorbed from the remaining undigested food and the waste material that is to be eliminated from the body in the form of feces is accumulated. Though some nutrients are absorbed in the large intestine, it is mainly for storing the waste material that will ultimately form the feces. In this part of the digestive system, mucus is added to the undigested food. The mucus helps to lubricate the movement of the undigested food. With help of muscle contractions, the food is then pushed into the last part of the large intestine known as the rectum.
From the rectum, the undigested food is pushed towards the anus. Via the anus the feces is eliminated from the body.
This was a brief overview on how digestive system of a pig works. The working is very similar to the digestive system of humans.
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