Human Anatomy and Digestion - 10 Things You Need to Know
Human Anatomy and Digestion
Digestion consists of six major processes, which occur from the time nutrients enter the body to the time waste is finally expelled. These processes include the following: ingestion, propulsion, mechanical digestion, chemical digestion, absorption and defecation. Diet plays a crucial role in digestion. If it does not contain the right amount of fiber, then the body will have a very difficult time expelling the waste once it moves into the large intestine. All of the following organs work together to make up the digestive system.
The mouth is where nutrients and liquids enter the body. When you put a piece of food in your mouth or drink a glass of water, the process of doing so is known as ingestion. Mechanical digestion starts once it enters the mouth and you begin to chew; the saliva provides a limited amount of chemical digestion, as well. The mouth, or oral cavity, consists of three major parts: the tongue, saliva and teeth. Without chewing the food into smaller pieces, it would not be able to move into the esophagus.
After liquids and food pass the mouth they enter the esophagus. This is where the process of propulsion takes place. In order for food and liquid to pass through the length of the esophagus and into the stomach, a series of muscle contractions must occur. The esophagus is designed to be a one-way passageway; in a healthy individual, the gastroesophageal sphincter, located at the base of the esophagus, prevents the contents of the stomach from reentering the esophagus.
A flexible sac, the stomach plays multiple important roles in digestion. Once food and liquids enter the stomach, it acts as a holding chamber until they are broken down. Digestion is possible in the stomach because it contains hydrochloric acid and other powerful enzymes that help break down the food. There are four distinct layers that make up the stomach wall: the inner lining, the supporting layer, the muscle layer and the serosa. As a result of the muscle layer and the hormones produced alongside the hydrochloric acid, the stomach contracts to help digest its contents.
Once the contents of the stomach have been sufficiently broken down, they are then passed into the small intestine via the pylorus. At this point, the food is only partially digested. After it is inside of the small intestine, the nutrients are absorbed into the body as it continues to be digested. There are three parts of the small intestine: the dueodenum, the jejunum and the ileum.
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Located behind the stomach, the pancreas is responsible for excreting digestive enzymes via the exocrine gland. In addition to manufacturing and excreting enzymes, it also releases the following hormones: insulin, glucagon and somastostatin. Without the enzymes that the pancreas secretes, the small intestine would not be able to digest carbohydrates and fats. These enzymes also play an important role in digesting proteins and acids, as well.
Located underneath the diaphragm, the liver is responsible for producing bile and detoxification. Considered the largest organ located inside of the body, it is divided into four parts: the right lobe, the left lobe, the caudate lobe and the quadrate lobe. In addition to detoxification, the liver is important because it helps the body metabolize fat and store carbohydrates. Without the liver, the body would shut down due to an overload of toxins.
Located on the right side of the body, the gallbladder is connected to two major organs in the digestive system: the small intestine and the liver. The primary role of the gallbladder is to release bile into the small intestine. In turn, this allows the small intestine to digest fat. Gallstones are the most common complication of the gallbladder.
Colon (Large Intestine)
Once the food is finished being digested in the small intestine, it is then passed on to the large intestine, or colon. This transfer happens via the cecum, which connects the small intestine and large intestine together. At this point, most of the nutrients have already been broken down and reabsorbed back into the body. The large intestine is responsible for ensuring that any remaining water and salt is also passed back into the bloodstream. After this happens, the result is called fecal matter, which is what moves through the large intestine and eventually leaves the body through the process of defecation. There are four major parts of the large intestine: the ascending colon, the transverse colon, the descending colon and the sigmoid colon.
After the fecal matter leaves the sigmoid colon, it enters into the rectum. In appearance, the rectum is a flexible, straight tube that extends up to 1.6 inches long. The rectum serves as a temporary holding area until the body is ready to expel the waste. As fecal matter collects in the rectum its walls expand.
When the rectum can no longer accommodate the amount of fecal matter it is storing, the waste is then expelled out of the body through the anus. Waste is prevented from prematurely leaving the rectum by the sphincter muscle. Normally contracted, the anal sphincter relaxes to allow fecal matter to exit. This process is called defecation.
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