These lectures cover information related to the digestive system at an 8th grade level.
Paul Buttenhoff in English
Hello my name is Paul Buttenhoff. I’m from the College of St. Catherine. Today I’m going to talk to you about selected topics concerning the digestive system. The digestive system is one of 11 major organ systems in the body. Like all organ systems it does have special functions on it’s own but it also works in collaboration with every other organ system.
The digestive system has four primary functions. First of all, the digestive system is designed to allow you to take food and beverages into your body. Second, the digestive system is designed to allow you to break down those food and beverages into smaller more useful particles that are actually usable by your body. The third function of the digestive system is absorption. Absorption involves moving tiny nutrients from the digestive system, actually into the bloodstream, so they can be transported and used by the other tissues in the body. And last, but not least, not everything that you eat is digestible and/or absorbable, the digestive system also functions in allowing you to get rid of solid waste.
The digestive system, from an anatomical standpoint, is really divided into two sub-divisions. The first sub-division will be the digestive tract, sometimes know as the gastrointestinal tract or the alimentary canal. Primarily, this is a tube that is about 30 feet in length that starts at the mouth and ends at the anus. The alimentary canal consists of an oral cavity, a throat, an esophagus, a stomach, small intestines and the large intestines. Additionally along with the alimentary canal or digestive tract, there are accessory organs in the digestive system. These are of importance but they are not part of that big 30 foot tube. The teeth, for example, are considered accessory, as are the salivary glands, the liver, the pancreas and the gallbladder.
All right, what we are going to do today is follow the fate of food or beverages as it starts in the mouth and travels through the digestive system. Food or beverages come in through the mouth and that is where the digestive processes start. Your teeth are used first of all to physically breakdown the food particles into smaller more manageable pieces. Additionally in your mouth, chemical digestion begins, especially with sugars, using saliva. Chewing will allow you to produce a very small round ball of food, known as a bolus that will be sent through your esophagus into your stomach.
Your stomach is the first primary organ in the alimentary canal. Its functions are to mix food that it receives with gastric juice. Gastric juice is a fairly nasty cocktail of chemicals that’s designed primarily to break down proteins. Foods that are higher in protein concentration will remain in your stomach, exposed to gastric juice for longer periods of time than materials that don’t have quite so much protein, which pass through to the small intestines more readily.
After food and beverages have spent time in your stomach, they then leave the stomach and enter the largest portion of your digestive system, known as the small intestine. In the small intestine chemical digestion will be very fine-tuned, will break our macromolecules, fats, sugars and proteins, down into their smallest most usable components. Food does spend quite a bit of time actually in the digestive system to facilitate this process. Once the food particles are in their smallest form they are then going to be absorbed. Absorption is a key process because without absorption, food would simply pass through your digestive system and out of your body. Absorption technically is going to involve moving the products of fats, sugars and proteins, minerals and water and a few other things, from the alimentary canal, or from this tube, actually across a few layers of tissues and into your bloodstream where they can be transported.
The large intestine is going to receive material from the small intestine and primarily when we talk about material in the large intestines, even though there is still five or six feet of journey to take before the material leaves your body, we’re primarily talking about feces. Not everything that comes into your body is digestible in the stomach or the small intestine and not everything is absorbable. The material that remains is considered a waste product and it must pass out of your body. In the large intestines, feces spend quite a bit of time and is in contact, relatively closely, with the walls of your large intestine. Your large intestine is going to do a couple of things. Primarily it’s designed to reabsorb water from the components of food. We are very stingy with water and if there is any doubt, we would rather keep it in our body and deal with it with our urinary system. In the large intestine there are also bacteria that handle functions like vitamin K production and further breaking down of amino acids and carbohydrates.
Last but not least, there are two rings of muscle at the bottom of the digestive system known as the rectum and the anus collectively. Material will move out of the body through the rectum and then through a couple of rings of smooth muscle and skeletal muscle know as the anus.