HS 130 Anatomy and Physiology II
The gastrointestinal tract starts with the mouth, which leads to the gullet via the stomach, small intestine, large intestine, and ends at the anus. In due course of the journey, the ingested food is broken down by both physical and chemical means to release nutrients which are absorbed into the blood stream. The ingested food is physically broken down in the mouth by chewing so as to reduce its size for increased surface area over which enzymatic reaction will take place. Enzymatic reaction is known as digestion and this is defined as the chemical breakdown of the ingested complex food molecules by the action of biological enzymes, into simplest form that can be absorbed into the blood stream and assimilated into living cells. In human beings, various components of the ingested food are digested and absorbed at various sections of the alimentary canal .
The first digestion process starts at the mouth in which cooked starch is reduced into simpler sugars by the action of ptyalin. Digestion of the remaining cooked starch is completed by amylase in the small intestine where duodenum and pancreas take part. Absorption of simpler sugars as the products of digested starch, take place in the small intestine as well. The digestion of proteins starts in the stomach in which protein molecules are reduced into amino acids by the action of hydrochloric acid and the protein digestive enzymes called proteases. Digestion of the remaining proteins is completed at the small intestines by the action of trypsin, and the amino acids are absorbed into the blood stream. Digestion of lipids starts at the small intestines in which fats and oils are emulsified and digested by the enzyme called lipase into fatty acids. Vitamins and minerals are generated and absorbed in the large intestines. The discussion will focus on the digestion of ingested hamburger, French fries, and root beer in the 55 year old man's alimentary canal starting from the mouth up to the large intestines.
Hamburger is defined as a sandwich comprised of cooked ground meat, normally placed in a chopped bread roll. This meal is usually served with bacon, lettuce, onion, tomato, and bacon. Therefore the meal of hamburger consists of proteins, fats, carbohydrates and vitamins. French fries are defined as elongated pieces of deep-fried potato and therefore majorly contain carbohydrates. For the French fries to test well, common salt should be added. Root beer is a beverage that is made from a combination of cherry tree bark, vanilla, sarsaparilla root, licorice root, sassafras root bark, molasses, anise, and nutmeg among other ingredients. Root beer contains some alcohol which is as a result of fermentation. The 55 year old chewed the hamburger and the French fries before he swallowed them.
Chewing ensured reduction of large pieces into small sized pieces to increase the surface area for an accelerated enzymatic action. In due course of chewing, the hamburger and French fries are mixed with saliva which was secreted by the salivary glands. Saliva was secreted after the tongue had sensed the food in the mouth, and it was comprised of water, ptyalin enzyme, and mucus. Both hamburger and French fries contained carbohydrates in the form of starch. Some portion of moistened starch was digested by the ptyalin into simple sugars such as glucose, while the remaining portion was digested later in the small intestines.
When the chewed food boluses were fully moistened and lubricated, they were pushed by the pharynx, which is at the back of the mouth, into the esophagus and continued the journey to the stomach by a process called peristalsis. The food boluses passed over the epiglottis which is a flap of cartilage covering the windpipe to avoid entrance of food particles into the windpipe. When food boluses reached at the end of esophagus, the...
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