The Digestive Process - A Brief Description
A description of the digestive process of food beginning at the mouth.
The digestive process takes place in the alimentary canal, which is a muscular tube, approximately 9 metres long, beginning at the mouth and ending at the anus.
The digestive process begins in the mouth. Saliva is secreted from the three sets of salivary glands in the mouth and is mixed with the food, aided by the tongue, during the action of chewing. The aroma of food can trigger the salivary glands into action. The chewing action breaks down the food into a bolus which then passes into the pharynx and is swallowed involuntarily.
From the pharynx, the food passes into the oesophagus which is a muscular tube connecting the pharynx to the stomach. The oesophagus has a covering of elastic, fibrous tissue and the liquid and semi-solid food slides down the oesophagus, into the stomach, assisted by gravity and muscular contractions called peristalsis.
The food enters the stomach through an opening called the cardiac orifice where the lower easesophageal sphincter or cardiac sphincter opens to allow food to enter the stomach. It then closes to trap the food in the stomach.
The muscular coating of the stomach churns the food, mixing it with gastric juices and enzymes to further break down the food into a more fluid form called chime.
From the stomach, the chime moves into the small intestine.
The small intestine, which is made up of the duodenum, jejunum and ileam, acts to break down the chime with intestinal juices and enzymes released by the pancreas and secreted from intestinal glands.
The digestion of carbohydrates and protein into glucose and amino acids takes place and bile, which is excreted by the liver and stored in the gall bladder, is released into the duodenum through the bile duct. Here it mixes with the chime and digestive juices until digestion is complete. The nutrients are absorbed by the body and the residue is passed to the large intestine.
The residue from the small intestine moves into the large intestine, starting at the caecum, moving through the ascending colon, the transverse colon, the descending colon and the sigmoid colon, through to the rectum.
The large intestine processes the waste, with the aid of bacteria, by absorbing water and electrolytes from the residue which has been passed from the small intestine. Peristalsis moves the residue through the colon where water is absorbed to produce a more solid waste.
The solid waste or stool is stored in the sigmoid colon until full, when the waste moves into the rectum from where it can be expelled.
Author: Bryan Morris