Structure and Function of the Alimentary Canal

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The mouth and the salivary glands are the beginning of the digestive tract and digestion begins before the first bite of food is taken. The salivary glands can be triggered by the smell of food, which then secrete saliva, causing the mouth to water. The saliva increases once food has actually been tasted and the structure of the salivary glands begins to relate to its function. The mouth begins to chew and break down food into small pieces that can eventually be digested. More saliva is produced in order to begin the procedure of breaking down food so that the body can absorb it. The pharynx receives the food from the mouth and swallowing is done here. Swallowing is partly a reflex and partly voluntary control, but the structure of the mouth is highly involved. The tongue and the soft palate push the food into the pharynx, closing off the trachea, allowing the food to enter the oesophagus. The oesophagus extends from the pharynx and behind the trachea to the stomach. It is a muscular tube that uses a series of contractions, known as peristalsis, to push food through into the stomach. The stomach is a hollow organ that has strong muscular walls. It holds food while it is mixed with enzymes and continuing the process of food being broken down into a usable form. The stomach secretes acid and powerful enzymes that continue the process of breaking down food. The small intestine is made up of the duodenum, jejunum and ileum. It is a long muscular tube that breaks down food using enzymes that have been released by the pancreas and bile from the liver. The continuous breaking down process is mainly done by the duodenum, while the jejunum and ileum are mainly responsible for the absorption of nutrients into the bloodstream. Peristalsis also moves food through the small intestine, mixing it with digestive secretions from the pancreas and liver. After passing through the

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