The Human Digestive System -- The Alimentary Canal at Work

The alimentary canal in humans is also known as the gastrointestinal tract. It is the entire digestive tract extending from the mouth straight to the anus. It is the pathway where food is ingested and digested, and ultimately, waste is eliminated. Structures included in the alimentary canal are the following:

• mouth
  
• pharynx
  
• esophagus
  
• stomach
  
• intestines
  
• anus

An adult human male's gastrointestinal tract measures around twenty feet (6.5 meters). There are two regions that make up the alimentary canal -- the upper gastrointestinal tract and the lower gastrointestinal tract.

The upper region of the alimentary canal consists of the mouth, pharynx, esophagus, stomach, and the small intestine's uppermost section called the duodenum. Digestion begins in the mouth, also called oral cavity, where the salivary glands, tongue and teeth all work to provide initial food digestion. From the mouth, food moves down to the pharynx. The pharynx then channels the food further down into the esophagus, while at the same time making sure it doesn't go into the windpipe (trachea) instead.

Waves of involuntary muscular contraction, also called peristalsis, take place in the esophagus which pushes the food down towards the stomach. This is when the digestion process reaches its second stage. Once out of the stomach, the food goes into the duodenum. At this point, the liver and the pancreas let out their combined digestive juices.

The lower portion of the alimentary canal is where the intestines and the anus belong. The intestines are split into the small and the large intestine, each of them having three subparts. The jejunum and the ilium are the two subparts of the small intestines that belong to the lower gastrointestinal tract.

Located in the middle portion of the small intestine, the jejunum transports the food from the duodenum to the ilium, doing this through peristalsis, at the same time giving a hand in nutrient absorption. It is in the ilium where the blood picks up and takes with it all soluble molecules.

The large intestine, on the other hand, includes the cecum which links the two intestines together, the colon which takes water and salt from the food digested, and the rectum where feces are put away for later excretion. All solid waste coming out of the alimentary canal leads to the exit point, which is the anus.

Other organs that play a part in the digestive system are the liver, gallbladder and pancreas. The liver generates bile which helps to ease up the processing of the ingested food in the small intestine, while the gallbladder serves as temporary storage spot for bile. Finally, the pancreas discharges digestive enzymes which also help the small intestine do its work in the whole digestion process.