Learning about the digestive system is a unique and exciting way to discover the things your body go through on a daily basis. Let's see how it works!
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Mouth
The mouth is the beginning of the digestive tract. As a matter of fact, the first time you chew something, digestion starts here. Chewing food breaks down food molecules into smaller food molecules so that it can be digested more easily. Saliva, produced by the salivary glands, mixes with food to begin the process of digestion. The saliva contains an enzyme called amylase, which digests starch molecules into smaller molecules of the disaccharide maltose.
Esophagus
The esophagus is a thick-walled muscular tube that runs from the neck and leads to the stomach. The bolus of food moves through the esophagus with the help of peristalsis, which is a series of muscle contractions and relations which occur along the course of the intestinal tract to push food and waste products through.
Stomach
The stomach is like a sac-lunch-like organ with strong muscular walls. The stomach stores food and prepares it for further digestion. The stomach contains hydrochloric acid as well as gastric juices. The hydrochloric acid in the stomach lowers the pH to around 2, killing bacteria and denaturing proteins. Gastric pits release gastric acid, protective mucus, and enzymes. The muscular spincters control entry of the food exit of chyme (partially digest mixture). The lumen is the space in which food is stored while inside the stomach.
Small Intestine
The small intestine completes the digestion of food molecules. It contains three parts which are called the duodenum, the jejunum, and the ileum. The small intestine continues the process of breaking down food by using enzymes released by the pancreas and bile from the liver. Bile is a compound that aids in digestion of fat and eliminates waste products (stool) from the blood. Peristalsis is also at work in this organ, moving food through and mixing it up with digestive secretions. The duodenum is largely responsible for continuing the process of breaking down food, with the jejunum and ileum being mainly responsible for the absorption of nutrients into the bloodstream. Absorption is the uptake of molecules in the blood and assimilation is how the tissues are carried.
Pancreas
The pancreas aids chemical digestion by producing an alkaline solution rich in bicarbonate as well as several enzymes. These enzymes break down protein, fat, and carbohydrates from the food we eat. Among the pancreatic enzymes are trypsin and chymotrypsin, proteases secreted into the duodenum in inactive forms.
Liver
The liver has several functions, but its two main functions in the digestive system are to make and secrete bile. Bile contains bile salts, which act as emulsifiers that aid in digestion and absorption of lipids. Bile is stored and concentrated in the gallbladder. The liver also breaks down toxins that enter the body and helps balance nutrient utilization.
Gall Bladder
The gall bladder is a pear-shaped object that just sits under the liver and stores bile (as previously stated). During a meal, the gall bladder contracts, sending bile to the small intestine.
Large Intestine
The large intestine, or colon, is a 5- to 6- foot-long muscular tube that connects the cecum (the first part of the large intestine) to the rectum (the last part oft he large intestine). It is divided into ascending, transverse, and descending portions, each about one foot in length. The colon's chief functions are to absorb water and to store, process, and eliminate the residue following digestion and absorption. The intestinal matter remaining after water has been reclaimed is known as feces. Feces consist of nondigested food (such as cellulose), billions of harmless bacteria, bile pigments, and other materials. The feces are stored in the rectum and passes out through the anus to complete the digestion process.
Rectum
The rectum is an 8-inch chamber that connects the colon to the anus. It is the rectum's job to recieve waste from the colon, to let you kow there is waste to be evacuated, and to hold the waste until evacuation happens. When anything (gas or waste) comes to the rectum, sensors send a message to the brain. The brain the decides if the rectal contents can be released or not.
Anus
The anus is the last part of the digestive tract. It consists of the pelvic floor muscles and the two anal sphincters. The lining of the upper anus is specialized to detect rectal contents. It lets us know whether the contents are liquid, gas, or solid, The pelvic floor muscle creates an angle betweent he rectum and the anus that stops stool form coming out when it is not supposed to. The anal sphincters provide fine control of stool. The internal sphincter keeps us from going to the bathroom when we are asleep, or otherwise unaware of the presence of stool. When we get the urge to go to the bathroom, we rely on our external sphincter to keep the stool in until we can get to the toilet.
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