The Digestive System in the Human Body

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Table of Contents

Introduction
The Stomach
Large Intestines
Small Intestines
Conclusion
Works Cited

Introduction

Human biology is a field in biology that deals with nutrition, anthropology, and medicine. The body of a human being contains a digestive system that deals with the digestion and absorption of food nutrients into the body. The stomach, small intestines, and large intestines are part of the digestive system. All of them are located at different positions in the body and have different functions and structures.

The Stomach

The stomach is an organ of digestion located between the esophagus and the duodenum on the left upper part of the abdominal cavity. It is a muscular, elastic pear-shaped bag lying just below the diaphragm. It is made up of five layers. The innermost layer is referred to as mucosa. The four sections of the stomach are the fundus, cardia, body, and pylorus. It is involved in the second phase of digestion after chewing. It secretes enzymes that help in the digestion of proteins. It also secretes some acids that help in the digestion of food. The major secretions are hydrochloric acid and protease enzymes. The work of hydrochloric acid is to kill any bacteria that may be in the food and provide an acidic pH that allows proteases to work effectively (Chiras 95).

Large Intestines

The large intestines of the human body are located between the ileocecal junction and the rectum. They are about one and a half meters long and two and a half centimeters wide. The major parts of the large intestines are the caecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal (Tortora and Grabowski 46). The large intestines receive food contents and fluids from the small intestines. The large intestines help in the re-absorption of water into the body system. The water absorbed is used to maintain the fluid balance of the body. Some vitamins that are created by the bacteria in the large intestines are also absorbed. They also help in the transport of waste products in form of stool out of the body.

Small Intestines

The small intestines are located between the stomach and the large intestines. Specifically, they start at the pyloric sphincter and end at the ileocaecal valve. They are narrow and long to allow digestion and absorption of food. The standard length of the small intestines in an adult human being is five meters but they may be shorter or longer. The three parts of the small intestines are the duodenum, jejunum, and ileum (Tortora and Grabowski 49). The majority of digestion and absorption of food takes place in the small intestines. Chemical digestion takes place in the small intestines where many enzymes that facilitate digestion are secreted. In the small intestines, proteins and peptides are digested into amino acids. Lipase enzymes are used to degrade fats into glycerol and fatty acids. Some carbohydrates are also digested in the stomach to form simple sugars. The process of absorption takes place where food nutrients are diffused into the bloodstream. The small intestines have many villi that have networks of capillaries to help indigestion. Monosaccharides, amino acids, water, iron, and many others are absorbed here.

Conclusion

The digestive system in the human body mainly deals with digestion and absorption of food nutrients and fluids. The stomach is located between the esophagus and the duodenum and helps in the digestion of partially chewed food. The large intestines are located between the ileocecal junction and the rectum. They help in the absorption of water, some nutrients, and the excretion of wastes out of the body. The small intestines are located between the pyloric sphincter and the ileocaecal valve. They help in the digestion of food and absorption of food nutrients into the bloodstream.

Works Cited

Chiras, Daniel. Human Biology. Sixth Edition. London: Jones and Bartlett Punishers, 2009. Print.

Tortora, Gerald and Grabowski, Sandra. Introduction to the human body: the essentials of anatomy and physiology. Volume 1. New York: John Wiley & Sons, 2004. Print.

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The Digestive System in the Human Body

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