Biology

The food that we eat cannot be assimilated into the body in the same manner that we ingest it. It needs to be broken down through various processes aided by chemicals and anatomical structures in the human body. This paper discusses the process of digestion in the alimentary tract until it is absorbed into the body.

The food that is ingested needs to go through several processes in the body before it is assimilated into the body. These processes occur in the alimentary tract which is a long structure beginning from the mouth to the anus. There are also other important chemicals, hormones and digestive juices which are involved in this whole process. These are found in specific portions of the tract and each food is digested or broken down in specific region. Therefore, the breakdown of food is either mechanical or chemically carried out. The end result is the division of the food into very small components or sizes that can pass through into the cells (Insel, Turner and Ross, 2004).

Everyone has at one time embarked on a journey in their lifetime. In addition to this, you hope to have a smooth trip and reach your destination safely. Herbert the hamburger has prepared to go through a very long and tortuous journey of his life. Everything is in place and he only hopes to have a safe trip. The main purpose of this trip is to deliver very vital documents that are needed to a company known as Body Builders. If these documents do not reach their destination, the company dies. These documents includes Fats, Carbohydrates, Proteins and Minerals.

The journey begins in the mouth where Herbert goes through some rough machines known as the teeth. This breaks it down into small forms through mastication. The document known as carbohydrate starts to be processed in the mouth and it involves a good friend known as saliva who is the boss in this department. Saliva does this with the help of amylase. This breaks it down into simple forms. From the mouth, permission is anted to move to the next level. To do this, Herbert is rolled into a bolus by the tongue and thrown at the back of the mouth. The epiglottis prevents Herbert from going through the trachea which is a wrong route. Herbert moves down in a smooth wave known as peristalsis into the esophagus until it reaches the gate of another department known as the stomach. This gate is known as the cardiac sphincter (Insel, Turner and Ross, 2004).

In the stomach, enzymes are also involved in the digestion process. Protein digesting enzymes are known as proteases. Amino acids are the building blocks of proteins. The bonds existing between them are broken down by hydrochloric acid from gastric wall. This is followed by breakdown of amino acids by the enzyme pepsin (Insel, Turner and Ross, 2004).

The food enters the small intestines through the pyloric sphincter. In the small intestine, pancrease produces amylase which further breaks carbohydrates to lactose, sucrose and maltose. These are broken down by lactase, sucrase and maltase enzymes respectively. These three are converted to an important form known as glucose which is absorbed via the villi on the walls of the intestines and finally find its way into blood circulation. Glucose is necessary for cell metabolism and function. However, the amount of glucose is regulated by the liver with the help of hormones. Too much glucose (hyperglycemia) is transformed into glycogen and stored in the liver through the help of insulin. In cases where glucose levels are low in the blood (hypoglycemia), the reverse happens i.e. conversion of glycogen to glucose with the help of the hormone glucagon. In cases where there is no glycogen, the hormone glucagons initiate formation of glucose from amino acids or fats. This process is known as gluconeogenesis (Insel, Turner and Ross, 2004).

The digestion of fats is with the help of enzymes known as lipases. Fats are complex molecules and should be turned into small molecules. This happens with the help of lipase enzyme from the pancrease and the end result is glycerol and fatty acid molecules. In addition to this process, bile from liver enters through the bile duct and emulsifies the fat. This makes it easy for the enzyme (lipase) to break down the fats starting from the surface. Storage of the bile usually occurs in the gall bladder. The body absorbs fats through the villi that cover the small intestines. The structure of the villus is such that it has capillaries and lacteals (lymph vessels). Fatty acids and glycerol enter into the lacteals into lymphatic system and finally bloodstream. Fatty acids find its way into adipose cells for storage or as source of energy (Insel, Turner and Ross, 2004).  

Protein digestion also continues in the small intestines in duodenum. The pancrease produces protease enzyme namely trypsin. In addition, chymotrypsin is also secreted. It works in a similar manner as pepsin. The end result of breakdown of protein by trypsin is amino acids. This is done through hydrolysis with insertion of water molecule between the bonds of amino acids. This helps in separation of the bonds that hold the amino acids together. The amino acids can thus pass through the intestinal wall into bloodstream. Their importance is in the repair of structures of the body. The waste products and undigested material move to the large intestines where water is re-absorbed. From there, it moves to the cecum and out through the anus (Insel, Turner and Ross, 2004).