During the digestive process, the sphincter relaxes and lets food pass into your stomach. Food goes through a significant part of the digestive process inside your stomach. You may think of your stomach as a simple pouch. For example, the digestive juices and enzymes that your stomach makes to break down food could literally dissolve most of the other organs in your body.
Your stomach contains a thick mucous lining that prevents these strong juices from eating through its walls. The stomach is also very flexible. When your most recent meal first enters your stomach, the upper part relaxes and expands.
This lets your stomach hold and process a large amount of food and liquid. During digestion, muscles push food from the upper part of your stomach to the lower part. This is where the real action begins. This is where digestive juices and enzymes break down the food that you chewed and swallowed. It prepares it to provide your body with energy. The stomach makes several digestive juices and enzymes that mix with food. This process takes longer for some types of foods than others.
Carbohydrates, for example, break down the fastest. This explains why many recommend carb-heavy foods for a quick energy boost. The ileocecal valve is a one-way valve located between the ileum and the cecum, which is the first portion of the colon.
This valve helps control the passage of contents into the colon and increases the contact time of nutrients and electrolytes essential minerals with the small intestine. It also prevents back-flow reflux from the colon up into the ileum, and helps minimize the movement of bacteria from the large intestine up into the small bowel.
The primary function of the large intestine or colon is to absorb fluids and electrolytes, particularly sodium and potassium, and to convert remaining luminal contents into more solid stool. The colon absorbs on average 1—1. Another function of the colon is to break down ferment dietary fiber to produce short chain fatty acids — substances that can be absorbed and provide added nutrition.
The first portion of the colon, the cecum, is shaped like a pouch, and is the area of storage for the contents arriving from the ileum. The second portion is the ascending colon, where fluids are absorbed and where some stool formation begins. The glands that act first are in the mouth — the salivary glands. Saliva produced by these glands contains an enzyme that begins to digest the starch from food into smaller molecules.
The next set of digestive glands is in the stomach lining. They produce stomach acid and an enzyme that digests protein. One of the unsolved puzzles of the digestive system is why the acid juice of the stomach does not dissolve the tissue of the stomach itself. In most people, the stomach mucosa is able to resist the juice, although food and other tissues of the body cannot. After the stomach empties the food and juice mixture into the small intestine, the juices of two other digestive organs mix with the food to continue the process of digestion.
One of these organs is the pancreas. It produces a juice that contains a wide array of enzymes to break down the carbohydrate, fat, and protein in food. Other enzymes that are active in the process come from glands in the wall of the intestine or even a part of that wall. The liver produces yet another digestive juice — bile. The bile is stored between meals in the gallbladder.
At mealtime, it is squeezed out of the gallbladder into the bile ducts to reach the intestine and mix with the fat in our food. The bile acids dissolve the fat into the watery contents of the intestine, much like detergents that dissolve grease from a frying pan. After the fat is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine. Digested molecules of food, as well as water and minerals from the diet, are absorbed from the cavity of the upper small intestine.
Most absorbed materials cross the mucosa into the blood and are carried off in the bloodstream to other parts of the body for storage or further chemical change. As already noted, this part of the process varies with different types of nutrients.
It is recommended that about 55 to 60 percent of total daily calories be from carbohydrates. Some of our most common foods contain mostly carbohydrates. Examples are bread, potatoes, legumes, rice, spaghetti, fruits, and vegetables. Many of these foods contain both starch and fiber. The digestible carbohydrates are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine.
Starch is digested in two steps: First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose; then an enzyme in the lining of the small intestine maltase splits the maltose into glucose molecules that can be absorbed into the blood.
Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body. Table sugar is another carbohydrate that must be digested to be useful. An enzyme in the lining of the small intestine digests table sugar into glucose and fructose, each of which can be absorbed from the intestinal cavity into the blood. Milk contains yet another type of sugar, lactose, which is changed into absorbable molecules by an enzyme called lactase, also found in the intestinal lining.
Foods such as meat, eggs, and beans consist of giant molecules of protein that must be digested by enzymes before they can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Further digestion of the protein is completed in the small intestine. Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of huge protein molecules into small molecules called amino acids.
These small molecules can be absorbed from the hollow of the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells. Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestinal cavity. The bile acids produced by the liver act as natural detergents to dissolve fat in water and allow the enzymes to break the large fat molecules into smaller molecules, some of which are fatty acids and cholesterol.
The bile acids combine with the fatty acids and cholesterol and help these molecules to move into the cells of the mucosa. In these cells the small molecules are formed back into large molecules, most of which pass into vessels called lymphatics near the intestine. These small vessels carry the reformed fat to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body. Another vital part of our food that is absorbed from the small intestine is the class of chemicals we call vitamins.
The two different types of vitamins are classified by the fluid in which they can be dissolved: water-soluble vitamins all the B vitamins and vitamin C and fat-soluble vitamins vitamins A, D, E, and K. Water and salt. Most of the material absorbed from the cavity of the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid we swallow and the juices secreted by the many digestive glands.
A fascinating feature of the digestive system is that it contains its own regulators. The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system, where they stimulate digestive juices and cause organ movement.
Two types of nerves help to control the action of the digestive system — extrinsic and intrinsic nerves. Norman Swan Gastrointestinal Health September 6, ,. Previous article Gastroscopy: examination of the upper digestive tract. Next article Liver cancer. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits.
However, you may visit "Cookie Settings" to provide a controlled consent. Cookie Settings Accept All. Manage consent. Close Privacy Overview This website uses cookies to improve your experience while you navigate through the website. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website.
We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies.
But opting out of some of these cookies may affect your browsing experience. Necessary Necessary. Necessary cookies are absolutely essential for the website to function properly. These cookies ensure basic functionalities and security features of the website, anonymously.
The cookie is used to store the user consent for the cookies in the category "Analytics". The cookies is used to store the user consent for the cookies in the category "Necessary". The cookie is used to store the user consent for the cookies in the category "Other. The cookie is used to store the user consent for the cookies in the category "Performance". It does not store any personal data.
Functional Functional. Functional cookies help to perform certain functionalities like sharing the content of the website on social media platforms, collect feedbacks, and other third-party features. Performance Performance. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors.
Analytics Analytics. Analytical cookies are used to understand how visitors interact with the website. These cookies help provide information on metrics the number of visitors, bounce rate, traffic source, etc. Advertisement Advertisement. Advertisement cookies are used to provide visitors with relevant ads and marketing campaigns.
These cookies track visitors across websites and collect information to provide customized ads. Others Others. Other uncategorized cookies are those that are being analyzed and have not been classified into a category as yet. Subscribe to the myDr Newsletter.
0コメント