Human Digestive System Components and Functions
The cells of the human body need nutrients and minerals for energy and synthetic processes requirements (Smith & Morton, 2010). The nutrients and minerals are extracted from raw materials that the body consumes as food. In order to extract the required nutrients and minerals, food must go through the process of digestion. Therefore, the overall function of the human digestive system is to transfer the nutrients and minerals from food, into the cells of the body. The digestive tract is also known as the alimentary canal, gastrointestinal tract, and GI system (Rosdahl & Kowalski, 2008).
The Components of the Digestive System
The major components of the digestive system are grouped into two categories. The first one is the gastrointestinal tract. The second group is comprised of the essential organs that play a major role in breaking down food into useful nutrients and minerals. The gastrointestinal tract consists of the following:
- small intestine;
- large intestine.
The essential organs are listed as follows: 1) salivary glands; 2) liver; 3) gall bladder; and 4) pancreas.
The alimentary canal is like a tube, and it is approximately 30 feet or 9.1 meters long (Rosdahl & Kowalski, 2008). It is interesting to note that the GI tract is open to the outside at both ends. On one side is the oral cavity, and on the other end is the anus (Rosdahl & Kowalski, 2008). The entire gastrointestinal tract is lined with mucous membrane, and food travels through it in about 24 to 36 hours (Rosdahl & Kowalski, 2008). Skeletal muscles move the food ingested from the mouth to the pharynx. Smooth muscles move the same from the pharynx to the rest of the GI tract.
The Functions of the Glands
The primary function of the salivary glands, liver, gall bladder, and pancreas is to secrete juices and hormones that are required for the digestive process (Rogers, 2011). The process begins when the mouth grinds the food and mixes it with saliva (Rogers, 2011). The main function of the saliva is to provide lubrication of the upper GI tract in order to enable the movement of food from the mouth to the stomach.
The pancreas secretes pancreatic juice, which contains important digestive enzymes needed to degrade the food into smaller particles (Smith & Morton, 2010). The liver secretes bile, which is needed to break oils and natural fat (Smith & Morton, 2010). The bile produced in the liver is stored in the gallbladder (Hoffman, 2009). When the GI tract detects the presence of food, bile is squeezed out of the gallbladder into the bile ducts (Hoffman, 2009).
The Functions of the Organs in the Digestive Tract
The relaxation and contraction of the muscles sends food from the pharynx into the stomach. The stomach is a muscular and collapsible sac (Rosdahl & Kowalski, 2008). It consists of three layers of smooth muscles that enable the stomach to stir and churn food, in order to break it down into smaller pieces (Rosdahl & Kowalski, 2008). In this receptacle, gastric juices secreted from different organs are mixed with the food (Hoffman, 2009). The process continues until the food is transformed into a semi-liquid form called chyme (Hoffman, 2009).
The primary components of the GI tract are the small intestine and the large intestine. The substantial length of the small intestine requires repeated folding, so that the whole structure fits into the abdominal cavity. The small intestine is the principal organ of the GI tract. It is within this organ that enzymes and other constituents essential for digestion are produced (Rogers, 2011). The said process reduces carbohydrates, proteins, and fats into simple organic compounds that the body can absorb. The small intestine is covered by numerous folds of mucous membrane (Rogers, 2011). The surface of these mucous membranes contains tiny projections called villi and microvilli. These are primary structures needed for absorbing the simple organic compounds at the latter stages of the digestive process.
The large intestine has a wider diameter compared to the small intestine (Rosdahl & Kowalski, 2008). However, it is shorter in length. The length of the large intestine is only about 5 feet or 1.5 meters (Rosdahl & Kowalski, 2008). It is divided into three different areas called the cecum, colon, and rectum (Rogers, 2011). The main function of this organ is water reabsorption (Rogers, 2011).
The extraction of nutrients and minerals from food requires an efficient digestive system. Furthermore, a well-functioning digestive system requires the seamless integration of the organs and the digestive tract. The GI tract must work in synergy with digestive glands and organs in order to reduce food into smaller pieces. A breakdown in the system means that there is no way to extract nutrients and minerals from food. The absence of a key component of the digestive system prevents the absorption of essential nutrients that the cells need for growth and repair.
Hoffman, G. (2009). Digestive system. New York: Marshall Cavendish.
Rogers, K. (2011). The digestive system. New York: Britannica Educational
Rosdahl, C., & Kowalski, M. (2008). Textbook of basic nursing. CA: Wolters Kluwer Health.
Smith, M., & Morton, D. (2010). The digestive system: Systems of the body series. New York: Elsevier.