what substance protects the stomach lining from damage due to digestive juices

The digestive system is a series of hollow organs joined in a long, twisting tube from the mouth to the anus (see Figure 1). Inside this tube is a lining chosen the mucosa. In the oral cavity, stomach, and minor intestine, the mucosa contains tiny glands that produce juices to help digest food.

2 solid organs, the liver and the pancreas, produce digestive juices that achieve the intestine through small tubes. In improver, parts of other organ systems (for instance, fretfulness and blood) play a major role in the digestive system.

Why is digestion important

When we swallow such things as bread, meat, and vegetables, they are not in a form that the body tin can use as nourishment. Our food and drink must be inverse into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which nutrient and drinkable are broken down into their smallest parts so that the body can use them to build and attend cells and to provide energy.

How is nutrient digested

Digestion involves the mixing of food, its movement through the digestive tract, and the chemical breakdown of the large molecules of food into smaller molecules. Digestion begins in the mouth, when nosotros chew and swallow, and is completed in the small intestine. The chemical process varies somewhat for different kinds of food.

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Movement of Food Through the System

The large, hollow organs of the digestive arrangement contain muscle that enables their walls to movement. The movement of organ walls can propel food and liquid and can mix the contents inside each organ.

Typical movement of the esophagus, stomach, and intestine is called peristalsis. The action of peristalsis looks like an ocean wave moving through the musculus.

The muscle of the organ produces a narrowing and so propels the narrowed portion slowly downwardly the length of the organ. These waves of narrowing push the nutrient and fluid in front of them through each hollow organ.

The showtime major muscle movement occurs when food or liquid is swallowed. Although we are able to commencement swallowing by pick, once the eat begins, it becomes involuntary and proceeds under the control of the nerves.

The esophagus is the organ into which the swallowed nutrient is pushed. It connects the throat above with the stomach below. At the junction of the esophagus and tum, there is a ringlike valve closing the passage betwixt the 2 organs. Even so, as the food approaches the airtight ring, the surrounding muscles relax and allow the food to pass.

The food then enters the stomach, which has three mechanical tasks to do. Beginning, the stomach must shop the swallowed food and liquid. This requires the muscle of the upper part of the stomach to relax and accept large volumes of swallowed textile.

The second job is to mix up the food, liquid, and digestive juice produced by the stomach. The lower part of the stomach mixes these materials by its muscle action. (The mixture is referred to as chyme.)

The third job of the stomach is to empty its contents slowly into the small intestine.

Several factors touch elimination of the tummy, including the nature of the food (mainly its fat and poly peptide content) and the degree of musculus activeness of the emptying tummy and the next organ to receive the contents (the pocket-sized intestine).

As the food is digested in the pocket-size intestine and dissolved into the juices from the pancreas, liver, and intestine, the contents of the intestine are mixed and pushed forward to allow further digestion.

Finally, all of the digested nutrients are absorbed through the intestinal walls. The waste products of this process include undigested parts of the food, known as cobweb, and older cells that have been shed from the mucosa. These materials are propelled into the colon, where they remain, unremarkably for a day or ii, until the feces are expelled by a bowel movement.

The Pocket-sized Intestine/Bowel

The mixture of food, liquid, and digestive juice (chyme) that passes out of the breadbasket, in a regulated controlled manner, enters into the small intestine/bowel. The average full length of the normal small bowel in adults is nearly 7 meters/22 anxiety. The small intestine has iii segments:

the duodenum,
the jejunum, and
the ileum.

Each part or section performs an of import role in nutrient absorption.

Duodenum – The chyme start enters into the duodenum where it is exposed to secretions that assist digestion. The secretions include bile salts, enzymes, and bicarbonate. The bile salts from the liver help assimilate fats and fat-soluble vitamins (Vitamin A, D, E, and K). Pancreatic enzymes help digest carbohydrates and fats. Bicarbonate from the pancreas neutralizes the acid from the stomach.

Jejunum – The chyme is then further transited downward into the 2nd or centre part of the small intestine, the jejunum. Mainly in the first half of the jejunum, the bulk (about 90%) of nutrient absorption occurs involving proteins, carbohydrates, vitamins, and minerals.

Ileum – The ileum is the last section of the small intestine and leads to the big intestine or colon. The ileum mainly absorbs water, bile salts, and vitamin B12.

The ileocecal valve is a one-style valve located between the ileum and the cecum, which is the first portion of the colon. This valve helps command the passage of contents into the colon and increases the contact time of nutrients and electrolytes (essential minerals) with the pocket-sized intestine. Information technology also prevents back-catamenia (reflux) from the colon up into the ileum, and helps minimize the movement of bacteria from the big intestine upward into the pocket-sized bowel.

The Large Intestine/Bowel, or Colon

The primary role of the large intestine or colon is to absorb fluids and electrolytes, particularly sodium and potassium, and to catechumen remaining luminal contents into more solid stool.

The colon absorbs on boilerplate 1–1.5 liters (about 1–1.5 quarts) of fluid every day and has a capacity to adapt its fluid absorption to as much as 5 liters/quarts per day if needed.

Another function of the colon is to break down (ferment) dietary fiber to produce short chain fatty acids – substances that tin can be captivated 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 2nd portion is the ascending colon, where fluids are absorbed and where some stool formation begins.

Production of Digestive Juices

The glands that act first are in the oral fissure – 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 tum lining. They produce tum acrid 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.

Subsequently the stomach empties the food and juice mixture into the pocket-sized intestine, the juices of two other digestive organs mix with the food to continue the process of digestion.

Ane of these organs is the pancreas. It produces a juice that contains a broad array of enzymes to pause down the sugar, fat, and protein in nutrient. Other enzymes that are active in the process come from glands in the wall of the intestine or fifty-fifty 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 nutrient.

The bile acids deliquesce the fat into the watery contents of the intestine, much similar detergents that dissolve grease from a frying pan. Subsequently the fatty is dissolved, it is digested by enzymes from the pancreas and the lining of the intestine.

Assimilation and Transport of Nutrients

Digested molecules of nutrient, too 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 farther chemic change. As already noted, this part of the process varies with different types of nutrients.

Carbohydrates

It is recommended that about 55 to 60 percent of total daily calories be from carbohydrates. Some of our nearly mutual foods contain mostly carbohydrates. Examples are staff of life, 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-scale intestine.

Starch is digested in two steps: First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules chosen maltose; then an enzyme in the lining of the small intestine (maltase) splits the maltose into glucose molecules that can be captivated into the blood.

Glucose is carried through the bloodstream to the liver, where it is stored or used to provide energy for the piece of work of the torso.

Table sugar is another carbohydrate that must exist 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 abdominal crenel into the blood. Milk contains however another blazon of carbohydrate, lactose, which is changed into absorbable molecules by an enzyme called lactase, also constitute in the intestinal lining.

Protein

Foods such as meat, eggs, and beans consist of behemothic molecules of protein that must be digested by enzymes before they tin can be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed poly peptide.

Further digestion of the protein is completed in the pocket-size intestine. Here, several enzymes from the pancreatic juice and the lining of the intestine carry out the breakdown of huge protein molecules into pocket-size molecules chosen amino acids. These pocket-sized molecules tin exist absorbed from the hollow of the small intestine into the claret and then exist carried to all parts of the body to build the walls and other parts of cells.

Fats

Fat molecules are a rich source of energy for the body. The first step in digestion of a fat such equally butter is to deliquesce it into the watery content of the intestinal crenel.

The bile acids produced by the liver act every bit natural detergents to dissolve fat in water and allow the enzymes to break the big fat molecules into smaller molecules, some of which are fatty acids and cholesterol. The bile acids combine with the fat acids and cholesterol and aid these molecules to motion into the cells of the mucosa.

In these cells the pocket-size molecules are formed back into large molecules, most of which pass into vessels (called lymphatics) virtually the intestine. These pocket-size vessels conduct the reformed fatty to the veins of the chest, and the blood carries the fat to storage depots in different parts of the body.

Vitamins

Another vital office of our food that is absorbed from the small-scale intestine is the form of chemicals we call vitamins. The two dissimilar types of vitamins are classified by the fluid in which they tin exist 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 textile captivated from the cavity of the modest intestine is h2o in which common salt is dissolved. The salt and water come from the food and liquid nosotros swallow and the juices secreted by the many digestive glands.

How is the digestive procedure controlled?

Hormone Regulators

A fascinating feature of the digestive system is that it contains its ain 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 dorsum to the eye and through the arteries, and return to the digestive system, where they stimulate digestive juices and cause organ movement.

The hormones that command digestion are gastrin, secretin, and cholecystokinin (CCK):

Gastrin causes the stomach to produce an acid for dissolving and digesting some foods. It is likewise necessary for the normal growth of the lining of the stomach, small intestine, and colon.
Secretin causes the pancreas to transport out a digestive juice that is rich in bicarbonate. It stimulates the tum to produce pepsin, an enzyme that digests protein, and it also stimulates the liver to produce bile.
CCK causes the pancreas to abound and to produce the enzymes of pancreatic juice, and information technology causes the gallbladder to empty.

Additional hormones in the digestive system regulate appetite:

Ghrelin is produced in the tum and upper intestine in the absence of food in the digestive arrangement and stimulates appetite.
Peptide YY is produced in the GI tract in response to a meal in the organization and inhibits appetite.

Both of these hormones piece of work on the brain to help regulate the intake of food for energy.

Nerve Regulators

Ii types of nerves help to command the action of the digestive arrangement – extrinsic and intrinsic nerves.

Extrinsic (exterior) fretfulness come to the digestive organs from the unconscious function of the brain or from the spinal cord. They release a chemical called acetylcholine and another called adrenaline. Acetylcholine causes the muscle of the digestive organs to squeeze with more force and increase the "push" of food and juice through the digestive tract. Acetylcholine also causes the stomach and pancreas to produce more digestive juice. Adrenaline relaxes the muscle of the stomach and intestine and decreases the flow of blood to these organs.

Even more than of import, though, are the intrinsic (inside) fretfulness, which make up a very dumbo network embedded in the walls of the esophagus, stomach, small intestine, and colon. The intrinsic nerves are triggered to human action when the walls of the hollow organs are stretched by food. They release many different substances that speed up or delay the movement of food and the production of juices past the digestive organs.

Source
Adapted from, "Your Digestive System and How Information technology Works"- IFFGD publications #190, from NIH Publication No. 04-2681, May 2004; and IFFGD publication #258.

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Source: https://iffgd.org/gi-disorders/the-digestive-system/