Chemical Digestion

Physiology The mechanical and chemical digestion of carbohydrates starts in the mouth. Chewing also termed as mastication ensures that the carbohydrates crumble down into smaller pieces. There are salivary glands within the oral cavity that secrete saliva which coats the food. Saliva comprises of an enzyme salivary amylase which breaks down the bods that are found between monomeric sugars like disaccharides, oligosaccharides and starches. It also breaks down amylose and amylopectin into small glucose chains referred to as dextrin and maltose. About 5% of starches are broken down within the mouth.

There is also production of mucus by mucus cells within the salivary glad which helps the food to stick together and also lubricates food hence help in swallowing. At this stage the food is known as bolus and it is forced into the pharynx with the help of the tongue (Swartz, 2012). During swallowing, the food passes through the esophagus which is a straight tube that can easily collapse. It provides a passage of the food into the stomach from the pharynx.

The bolus is moistened and lubricated by mucus produced by mucous glands within the esophagus. The bolus then passes through the cardiac sphincter and into the first part of the stomach. The bolus contains some salivary amylase from the mouth but it does not continue breaking down the food within the stomach. This is because, the stomach environment is too acidic and salivary amylase can not work under acidic conditions. The stomach has several divisions; the cardiac section, body section, fundic section and pyloric region.

Within the stomach food is mixed and churned that helps in further digestion of the carbohydrates. Mechanical breakdown occurs through strong peristaltic contractions within the stomach. Here, the bolus is converted into a paste that is semifluid and a gastric juice referred to as chyme. This chime then moves into the pyloric sphincter into the first part of the small intestines. The small intestine has three distinct sections: duodenum, jejunum and ileum. Most of the digestion of carbohydrates occurs within the small intestines.

An enzyme known as pancreatic amylase is released from the pancreatic duct as the chime makes its way into the duodenum. The enzyme begins breaking down dextrin into shorter chains of carbohydrates. There are also some enzymes that are secreted within the intestinal cells that line the villi. These enzymes are collectively refereed to as disaccharides and they are sucrose, maltase and lactase. Sucrase breaks down the sucrose into molecules of glucose and fructose.

Maltase breaks down the bond within two the two glucose units found in maltose while lactase breaks down the bond between glucose and galactose. After the chemical breakdown of carbohydrates into single units of sugar, they are transported into the mall intestines (Swartz, 2012). The interior walls of small intestines are covered with tiny fingerlike projections known as villi. The villi increase the surface area within the intestines and play a crucial role in the.