What is the Human Digestive System
Simple sugars are, for the most part, absorbed unchanged. However, starch, fats, and proteins generally need to be broken down by the digestive fluids before they can be utilized. A variety of enzymes perform this function, each having particular substrates upon which it can act. For example, the enzyme amylase, present in saliva, breaks down starch into sugar. Similarly, in the stomach the enzyme pepsin breaks down proteins into short peptides.
The digestive tract is composed of the organs shown in the figure at right. In the mouth, the tongue and teeth crush food and mix it with saliva. When swallowed the masticated food passes down the esophagus to the stomach. As the food passes the glottis, the epiglottis closes to prevent choking.
The stomach secretes acidic digestive fluids which aid in breaking down the food (pepsin is active only in an acidic solution).
Bile is produced in the liver and stored in the gall bladder. Within the small intestine, bile acts as a surfactant, coating lipid particles, allowing their dispersion, and thus making them accessible to the enzyme pancreatic lipase, which breaks them down into simpler molecules that can be absorbed through the walls of the intestine.
The large intestine absorbs water from the matter passed undigested through the small intestine. It then ejects the dehydrated waste from the body.
The human digestive system is one of the largest and most evolved systems in the human body. however, its complexity also opens us up to many disorders and diseases. How does it work and why does it fail so often?
The basic function of the digestive system is to convert food materials into usable energy and to provide our bodies with material its needs to grow and maintain itself. This long process has evolved to be very efficient- grabbing as many nutrients out of food as possible and leaving all unusable material to be excreted.
The organs of the digestive system on this site have been divided into early, middle, and late for simplicity sake. In the human body, the digestive system is really made up of a long, what can be thought as, tube called the Alimentry Canal or GI Tract.
The GI tract begin in the mouth and ends in the Anus. To aid the process of digestion, several accessory organs line the GI tract. These organs include the Salivary Glands, Teeth and Tongue, Liver, Gallbladder, and Pancreas. These organs produce saliva, bile, and several other important catabolic (breakdown) enzymes. These molecules are added the the orderly flow of food in the GI Tract via several ducts.
The basic strategy of digestion is to break down all food into basic molecules and then absorb the useful ones. The specific roles of each section and organ is covered at the left: early, middle, and late digestion.
Your digestive system consists of organs that break down food into components that your body uses for energy and for building and repairing cells and tissues.
Food passes down the throat, down through a muscular tube called the esophagus, and into the stomach, where food continues to be broken down. The partially digested food passes into a short tube called the duodenum (first part of the small intestine). The jejunum and ileum are also part of the small intestine. The liver, the gallbladder, and the pancreas produce enzymes and substances that help with digestion in the small intestine.
The last section of the digestive tract is the large intestine, which includes the cecum, colon, and rectum. The appendix is a branch off the large intestine. it has no known function. Indigestible remains of food are expelled through the anus.
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