Digestive System: Main Issues

In the article the structure and function of the digestive system, the author provides a comprehensive analysis of how the process begins until the excretion of undigested food materials. To give the reader a good understanding, he starts by stating the main parts that make the digestive system which include the esophagus, stomach, gallbladder, small intestine, colon, rectum, and anus (Hames & Hopkin, 2009). Every part plays crucial parts which either facilitates passage, absorption of water, minerals or digested food materials. Some of the parts produce enzymes which help in the digestion process.

        The author starts by describing the process from the mouth. The digestion process begins in the mouth where food materials are broken down into small materials to facilitate easy passage in the esophagus. In the mouth, the food is also mixed with saliva which contains enzymes such as salivary amylase. Digestion of food materials such as starch starts in the mouth. The second stage of the digestion process happens in the stomach. At this point, the food is mixed with digestive enzymes such as the gastric juice. Further, in the stomach, the food is mixed with HCL which helps to kill organisms in the food.

        The small intestine comprises of three main parts which include the ileum, duodenum, and the jejunum. The size of the small intestine is about 22 foot long which increases the surface area for the absorption process (Hames & Hopkin, 2009). Further, the small intestine provides for the breakdown of food materials with the help of enzymes such as pancreatic enzyme and bile juice from the liver. The pancreas produces enzymes that help the breakdown of carbohydrates, proteins, and fats. Further, the pancreas secretes insulin hormone which helps to regulate the sugar levels in the blood. Peristalsis takes place in this place as the food is mixed with the different enzymes.

        Another important part of the digestive system is the colon. The large intestine absorbs excess water from the undigested food materials for easy storage in the rectum (Hames & Hopkin, 2009). The stool which is stored in the rectum comprises two major components; bacteria and food particles. The bacteria play essential roles in this point such as synthesizing vitamins and protecting the body from pathogens. Once the colon is full, it empties in the rectum when the process of excretion begins. Rectum connects large intestine and anus. The rectum receives the stool, notifies the brain through the CNS and holds until a person is ready to release the waste. The last part of the digestive system is the anus.

List of terms

• Enzyme-  A substance used to quicken a chemical reaction
• HCL- Hydrochloric acid
• CNS- central nervous system
• Absorption- intake of digested food material in the blood stream
• Pathogens- disease causing organism
• Duodenum- first part of small intestine
• Digestion- breakdown of food materials
• Peristalsis- rhythmical contraction of muscles
• Hormone-a regulatory substance
• Salivary amylase- an enzyme
• Excretion- process of removal of waste materials
• Secretes- To produce
• Vitamin- an organic compound
• Ileum- third part of small intestine
• Jejunum- second part of small intestine.

Reference

1. Hames, C. A. C., & Hopkin, S. P. (2009). The structure and function of the digestive system of         terrestrial animals. Journal of Zoology, 217(4), 599-627.

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