Digestive System Understanding the Mechanisms

Digestive System Understanding the Mechanisms of the Digestive System All of the workings of the muscles, nerves, and in fact all of the organs and systems of the human body depend upon energy and nutrients for their continued operation. This energy and the vast majority of nutrients are pulled directly from the food that is ingested, making the operation of this system vital to the survival and success of the individual as a whole.

The digestive system works in a manner that is fairly direct in some aspects, and yet the system as a whole is highly complex and requires multiple steps and the involvement of many direct and peripheral organs in order to efficiently achieve its purpose.

Essentially, the digestive system is concerned with ingesting food items, breaking them down into usable nutritive components, absorbing these components so that they can be shipped around the body to where they are needed, and ultimately expelling any unused portion of the ingested food along with certain other waste materials/digestive by products. This entire process begins in the mouth, where several things occur to begin the digestive process.

First, the jaw and teeth are used to mechanically break down the food, creating smaller pieces that become a sort of mush due to the secretion of saliva and mucous (NGS 2010). An enzyme in saliva, salivary amylase, begins to break down a type of carbohydrate known as starches, which changes them from polysaccharides to disaccharides, and is a form of chemical (as opposed to mechanical) digestion (Discovery 2000).

The mucous secretion helps to hold the chewed food in a given mouthful into a ball, which eases the food's journey on the it's next step through the digestive process -- the esophagus. No real digestion or absorption occurs in the esophagus, but it is still an essential part of the digestive system and can be used to illustrate and explain one of the most basic functions that the digestive system performs -- the movement of food through the body.

Most of the large, hollow organs that make up the primary part of the digestive system have smooth muscles in their linings that allow for alternating contractions and relaxations, which effectively moves food through these organs in its various stages of digestion (Enchanted Learning 2010). The esophagus does nothing but move food in this manner, taking it from the mouth and pushing it through a series of well-timed contractions and relaxations that occur in a wave-like motion down the length of this tube to the stomach (NDDIC 2008).

This is the reason it is still possible to swallow upside down -- gravity isn't doing the work, the esophagus is. It is in the stomach that digestion really begins in full force, though this consists more of the breaking down of food rather than the actual absorption of nutrients. The acid mixture that exists in the stomach is highly corrosive and turns food from a still largely solid state to a more liquid and homogenous mass called chyme (Enchanted Learning 2010).

Due to the corrosive nature of this acid, a thick mucous secretion helps to protect the stomach walls and to keep the overall digestive process running smoothly instead of becoming gummed up (Enchanted Learning 2010). Also at work in the stomach is pepsinogen, an enzyme produced in the stomach lining that helps to break down proteins by targeting specific amino acids that it draws out of their configuration in these proteins (Discovery 2000).

The pyloric sphincter controls the flow of chyme from the stomach to the small intestine, and when this sphincter opens and lets the chyme flow into the duodenum -- the first section of the small intestine -- the majority of the absorption of nutrients begins to take place (NGS 2010). It is also at this point that other organs begin to play a major role in the digestive process.

The pancreas, located adjacent to the small intestine, secretes several enzymes that variously break down carbohydrates much further than they were broken down in the mouth or the proteins that began to met their demise in the stomach (NDDIC 2008). The liver produces a bile that breaks down fats and makes the constituent parts into small enough droplets that they can be suspended in water and utilized in chemical processes in the body (NGS 2010). All of this digestion takes place in the duodenum.

The small intestine continues, however, and throughout the entire small intestine are countless villi, or little finger-like hills that greatly increase the inner surface area of the smooth-muscled tube that is the small intestine (Discovery 2000). It is through the cells of these villi that the nutrients, once broken down into smaller parts by the digestive processes and enzymes, are passed through to the rst of the body (Discovery 2000).

Specifically, active chemical transport is used to carry carbohydrate and protein-based nutrients through the cell walls of the intestinal villi and lining, where they are eventually passed into the bloodstream (Enchanted Learning 2010). Similar processes take place with the components of fatty nutrients, but it is the lymph system that transports these molecules (Enchanted Learning 2010). After passing through the entirety of the small intestine, the leftover material passes into the large intestine or colon.

It is here that a great deal of the water used to lubricate the digestive process -- generally in the form of mucous and other substances that have a high water content -- is reabsorbed into the body, along with certain other mineral nutrients that might not have been absorbed through the small intestine (NGS 2010). There are also bacteria living in.