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The pathway of food molecules through the alimentary canal and the process of their digestion

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The pathway of food molecules through the alimentary canal and the process of their digestion The function of the digestive system is to break down large molecules in food, such as protein and starch, into monomers that can easily be absorbed into the body and with a balanced diet it does its job efficiently. The alimentary canal is a long coiled tube that runs through the body from the mouth to the anus. It consists of associated glands, the salivary glands, the liver and the pancreas. This muscular tube is organised into several distinct regions. The overall process of nutrition can be divided into several stages. Ingestion is taking in food. Humans put food into the mouth where it is chewed. Swallowing takes it down through the oesophagus and into the stomach. Mechanical breakdown is how food is broken down into smaller pieces by chewing in the mouth and the churning action of the stomach. Digestion is the complex breakdown of foods such as carbohydrates, lipids and proteins into simpler molecules. ...read more.


Digesting protein is one of the main functions of the stomach. Pepsin breaks peptide bonds in the middles of the protein chain, which turns protein molecules into polypeptides. This process is complete when exopeptidase enzymes remove amino acids from the ends of the polypeptides. Mucous cells secrete the mucous that protects the stomach lining from digestive action of its own secretion. Food then moves from the stomach to the small intestine in the form of chyme. The small intestine is the major site of digestion and consists of the duodenum and the ileum. Enzymes and secretions flow into the duodenum from the pancreas and the liver. Pancreatic juice enters the duodenum via the pancreatic duct, this is an alkali solution and neutralises the strong stomach acid. This fluid contains several enzymes. Trypsin is an endopeptide enzyme that breaks down proteins into polypeptides. Carboxypeptidase is a polypeptide digesting enzyme that converts these into smaller peptides and amino acids. Pancreatic amylase completes the breakdown of starch to maltase. ...read more.


Each structure relates to the one before and the one after and a balanced diet is necessary for this efficiency. The mouth is a hard cavity containing teeth and the tongue, which efficiently breaks down food into a suitable state to travel through the oesophagus. The oesophagus, which is a rigid tube with a smooth surface, pushes the food to the stomach. The stomach, a muscular sac, aids in the mechanical breakdown of food. Cells in the gastric pits of the stomach aid in the chemical breakdown of food. This result is liquidation of the food in preparation for the small intestine. The small intestine is the longest section of the alimentary canal and here the most part of chemical digestion and absorption takes place. This moves the food to the large intestine. These are the final stages of digestion where the food is being prepared for egestion. The last minerals and water are taken here in this tube which is about 1.5 meters long. Finally the food is passed though the rectum and the anus, which are concerned with the compaction of faeces and the act of defecation. ?? ?? ?? ?? ...read more.

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