As the food is broken up, the first phase of chemical digestion occurs as saliva, which is secreted from the salivary glands. Amylase, contained in the saliva, begins the breakdown of starches into sugar. Once the food is softened by the saliva and swallowed into the esophagus, a muscular action, called peristalsis, helps to then push the food down the esophagus and into the stomach. When the food reaches the stomach, the chemical breakdown process continues where the stomach secretes gastric juice, which is made up of a protein-digesting enzyme, mucus, and strong acid (Reece, Taylor, Simon, & Dickey, 2012, p. 436) The result of this process occurring in the stomach produces a thick acidic liquid called chyme, which is the partially digested food and the digestive secretions. Peristaltic waves will continue to push the chyme toward the small intestine. The small intestine has two major functions; to break down food into smaller molecules and to absorb these molecules into the blood stream.
These functions are done with the aid of digestive secretions from the liver, pancreas, and the cells of the small intestine itself. In digestion, the role of the liver is to produce bile which is stored and concentrated in the gall bladder and released into the beginning section of the small intestine through the bile duct. Bile assists in the breakdown of lipids and the absorption of fat. The pancreas produces the digestive secretion called pancreatic juice, which like bile, is released into the beginning section of the stomach. The pancreatic juices role is to neutralize the acidic chyme and break down carbohydrates, lipids, and proteins. Pancreatic juice contains digesting enzymes; amylase, which breaks down carbohydrates; lipases, which break down lipids; and proteases, which break down proteins and peptides. Special cells lining the wall of the small intestine complete the digestive process and absorb nutrients into the blood stream. The large intestine is the next stop for the undigested food and water. By the time food reaches the large intestine, the absorption of nutrients into the blood stream is just about complete.
The large intestines main function is to remove water from the undigested matter and form solid waste that can be excreted (Kids Health). The process of digestion seems simple enough; food enters the mouth and continues down a tube through a chain of organs that breaks it down completely before it leaves the body. However, the maintenance of a system like this is anything but simple and depends on a balance of pH, the measure of hydrogen ion concentration, and helpful bacteria to maintain homeostasis. Both acidic and basic pHs are necessary at different points in digestion to maintain balance during the process. Saliva in the mouth is mildly acidic to initially breaking down the food without damaging the inside of the mouth. The stomach, in contrast, needs to be highly acidic to start the breakdown process. It is important that the small intestine has a high pH, to balance everything out, because most of the enzymes used in digestion cant function properly in acidic surroundings.
Red blood cells, which transport oxygen and hydrogen ions throughout the body; white blood cells, which fight infections in the body; platelets, which assist in blood clotting; and plasma, which transports the blood cells all help to maintain the bodys homeostasis. However, none of these could function without the nutrients supplied by the digestive system. Blood also maintains homeostasis of water, electrolytes and body temperature all by getting the nutrients necessary to function from the digestive system. Helpful bacteria, or microflora, are important to maintaining homeostasis in the digestive system. These bacteria aid in digestion, help produce vitamins, and guard against harmful bacteria. When the bacteria level in the digestive tract is thrown off or destroyed, there will be a noticeable change in the digestion process. Yogurt contains ingredients that support intestinal microflora growth and health.
During digestion, we know that carbohydrates are broken down into glucose, which enters the bloodstream. This is transported into cells to be used as energy. Insulin offsets glucose by keeping it in balance, any excess glucose is stored in the muscles and liver where it can be released when blood sugar levels drop. Excess glucose is stored as fat. Foods high in refined carbohydrates are broken down very quickly into glucose which will result in a sugar spike and rush of energy. However, this effect is not lasting and high levels of insulin are produced to counteract this. If blood sugar levels are continuously high, the body finds it harder to keep producing the necessary levels of insulin. This means that glucose is more likely to be stored as fat and there is a risk of Type 2 diabetes. The digestive system is an important part of my body. Its job is to take the food that I eat and turn it into nutrients that my body can use. If my digestive system is not working properly, my body will not be at its best, either. There are several things that I can do to help keep my digestive system healthy.
With small children, I find myself eating quickly so that I can actually eat a full meal; one thing that I can do is make it a point to take the time to eat more slowly; if I sit down to eat all of my meals, that would help with this. Because food must be broken down before my body can begin to use it, by chewing my food really well I would be assisting in this process and not make my stomach work as hard to do this. The digestive system works best when I follow a routine so I should try to eat at the same time every day, preferably several small meals throughout the day. This topic was very interesting to research because my son suffers from slow peristalsis, which effects the movement of food through his digestive system.
He does not see the effects of this every day; most days he seems fine but there are periods when his digestive system seems to shut down the peristaltic movement causing constipation, severe cramping, and vomiting. Learning how the digestive system and absorption works will help me to understand what phase of the digestion process his body might be in during these episodes. Knowing this will also allow us to better identify if there are certain foods that would aggravate this condition more so than others. With the driving force of peristalsis being the means by which food travels through the digestive system, it is easy to see how any issue interfering with this muscular movement would cause problems to each phase of digestion as well as the bodys homeostasis.
National Digestive Diseases Information Clearinghouse (NDDIC). (2012). Your digestive system and how it works. Retrieved from http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/index.aspx
Kids Health. (n.d.). A body basics article; digestive system. Retrieved from http://kidshealth.org/parent/general/body_basics/digestive.html#
Reece, J. B., Taylor, M. R., Simon, E. J., & Dickey, J. L. (2012). Campbell biology: concepts & connections (7th ed.). San Francisco, CA: Thomson/Pearson Benjamin Cummings.