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This report will discuss the functions of the digestive system and outline the path food takes from ingestion to egestion. Making its way through the digestive tract and include information on the major subdivisions and accessory organs. This report will also give details on the different processes used for moving molecules and ions, including; osmosis, facilitated diffusion, active transport and co transport. The structure of each section of the digestive system and its location will be provided.
Digestion begins in the mouth. Food enters the oral cavity where mechanical digestion begins. Food is torn, broken down and is compacted into a bolus. There are three salivary glands including the large parotid gland which secretes salivary amylase, the sublingual gland which produces a secretion on mucin that acts as a buffer and lubricant and the submandibular that secrets a mixture of buffers, mucins and salivary amylase. Amylase in an enzyme which turns complex carbohydrates into disaccharides and trisaccharides. The tongue is an accessory organ made up of muscles that grips food and aids in moving it towards the posterior of the mouth to be swallowed. This is the process of ingestion when the substance is swallowed or absorbed.
Once the bolus is swallowed it enters the pharynx which is a funnel shaped tube that passes food from the mouth to the oesophagus. In the pharynx is a flap of tissue called the epiglottis that directs food to the oesophagus and air to the larynx. The oesophagus acts as a path way for the bolus and liquids from the pharynx to the stomach. It is a muscular tube that runs from the level of vertebra C6, through the thoracic cavity and entering the stomach cavity through a gap in the diaphragm. The muscles in the oesophagus contract and force the bolus towards the stomach by a peristaltic wave. The mucosa and submucosa are structured into large folds. This allows for expansion when the bolus passes through. The submucosa has oesophageal glands that secrete mucous that reduces friction on the oesophageal lining from the bolus. The bolus takes about 9 seconds to transported from the pharynx to the stomach.
Once the bolus has reached the stomach it enters the cardia which is one of the four regions of the stomach. In the cardia is abundant mucous glands that coat a secretion on the connecting oesophagus to protect it from the acid and enzymes in the stomach which are secreted from the gastric glands that are in the region called the fundas. In another region of the stomach called the body is where the food is mechanically digested by the stomach muscles that churn the food. The acids and enzymes also cause chemical digestion by breaking the food down.

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