Digestion

 

††††††††††† The process of digestion is the series of physical and chemical modifications to your food that prepare the molecules that you need for further breakdown in the cells and the removal of those molecules you canít use for evacuation from the body.Digestion begins in the mouth when you take your first bite of food.The teeth crew the food into smaller pieces as the enzyme amylase, from the saliva, breaks down the polysaccharide starch into the disaccharide maltose.Chewing food helps to increase the surface area of the food so that the chemicals in your body can break them down faster.

††††††††††† Once the food has been chewed sufficiently to be able to be swallowed, the muscles of the mouth and throat push the food into the esophagus, the long, muscular tube that connects the mouth to the stomach.To avoid any dangerous complications the body has special pieces that close over any openings in the throat to prevent food from getting into places that it should not be.The uvula (that strange flap of skin that hangs at the back of the mouth) is pushed into the nasal passage behind it and plugs the hole to the sinus cavity and nose.The epiglottis folds over the windpipe preventing food and drinks from getting into the lungs.The food is transported down the esophagus by a process of involuntary muscle contractions known as peristalsis.Peristalsis allows someone to be able to swallow even when they are upside-down or sideways.Vomiting reverses the order of the contractions to bring the food up from the stomach.

††††††††††† When the food reaches the stomach a circular muscle known as a sphincter opens the top of the stomach to allow food inside.The stomach is somewhat like an elevator in that only a certain amount of food is let in at a time.Eating too fast will result in a strange sensation of food backing up in the esophagus and may lead to food and/or liquids getting into the lungs.Once the food has entered the stomach, it is mixed with an enzyme known as pepsin, produced in the pancreas.Pepsin is the enzyme responsible for breaking down proteins into their amino acid pieces.Since pepsin will only work in acidic conditions, hydrochloric acid and lactic acid are added to the mixture.To protect the lining of the stomach from being eaten away by the acids and the pepsin, special pores cover the inside of the stomach with a thin layer of mucus (similar to snot).When these pores do not work properly (due to sickness, stress, etc.) the result is a small hole in the stomach lining known as an ulcer.

††††††††††† After a few hours in the stomach, the food, now the consistency of tomato soup, is released into the small intestine for further digestion.The first fifteen centimeters of the small intestine are known as the duodenum.It is in the duodenum that the acidic stomach juices are neutralized by an alkaline (basic) solution that contains more digestive enzymes.This solution is known as bile.Bile is produced in the liver and is stored in the gall bladder.Bile breaks down the disaccharides and lipids that are left in the food.As the food is digested into its final pieces it is transported into the bloodstream by small, fingerlike protrusions on the inside of the small intestine known as villi.Villi serve only to increase the surface area of the inside of the small intestine and contain the bloodstream and the lymphatic system.The bloodstream is used to transport things like nutrients and oxygen through the body to the cells.The lymphatic system is part of the immune system and filters out impurities from the body.The small intestine is named for its diameter rather than itís length.The small intestine is about an inch (2.5cm) wide and is almost twenty feet (6m) long.Food spends most of its time in the small intestine.

††††††††††† The large intestine is the next stage of the digestive process.At the boundary between the small and large intestines the appendix can be found.The appendix does not have a use and is what we call a vestigial structure.Scientists do not know what the appendix was used for, but the leading theory supposes that it was used for adding digestive enzymes to the food thousands of years ago when the diet of humans was very different (including raw meat, heavy carbohydrates, etc.).It is in that large intestine that the excess water in the food is removed, the final chemical processes break down the last of the usable food, waste materials from the bodyís cellular processes are removed and the anaerobic bacteria do their work.The anaerobic bacteria process vitamins like A, K and D that are necessary for daily metabolic processes.

††††††††††† Whatever food and waste is left at the end of the large intestine is pushed by the strong muscles of the rectum through the two sphincters of the anus to remove them from the body.The whole process takes between twenty-four and thirty-six hours depending on what was eaten and how well your body is working.Sometimes bacteria, viruses or other pathogens disrupt the bodyís ability to digest food properly.When this occurs, the body will remove the tainted food as quickly as possible.If the food is in the stomach when the body detects the pathogen, it will cause you to vomit.If the food has passed the stomach it will generally trigger diarrhea.The reason that diarrhea is a liquid is because the excess water does not have time to be removed since your body does not want to give the pathogen time to get into your system in large enough amounts to cause damage.This is a problem because you are not getting the nutrients that are necessary and you get dehydrated.Different pathogens can take from five minutes up to thirty-six hours to affect the body.Some foods, like cellulose (fiber) cannot be digested and are good for keeping your digestive system moving.Without these foods it is likely that you will become constipated and your digestive system will slow or even stop putting out waste resulting in painful swelling of the intestines.