Digestive System – Concept, functions, parts, and diseases

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Digestive system
We explain what the digestive system is, its functions, and the organs that compose it. In addition, the most common diseases of this one.

What is the digestive system?

The digestive system is known as the set of organs that are in charge of the digestive process, that is, the transformation of food so that it can be absorbed and used by all the cells of the organism. In addition to humans , most of the higher animals have a digestive system that performs this function.

During digestion or the digestive process, the different types of nutrients found in the food consumed (carbohydrates, lipids and proteins ) are transformed into simpler units, thanks to the different digestive enzymes . Under these conditions, the most elementary usable parts of the nutrients can be absorbed and then transported through the blood to all the cells of the body, where they are used to obtain energy and carry out all the essential functions for the maintenance and development of life . . .

The functional process of the digestive system includes all the events that take place, from the entry of food into the mouth, to the expulsion of feces (indigestible remains) through the anus, passing through the absorption of nutrients through the intestinal walls. It is a long process, which involves a set of complex mechanisms, in which numerous organs and parts of the body are involved, and which is essential for life , given that human beings (like all animals) are heterotrophs , and therefore we can only incorporate the organic matter we need through food.

Functions of the digestive system
The digestive system fulfills various functions, but there are four main ones: transport of food, secretion of digestive juices, absorption of nutrients and excretion of feces.

Food transportation. Food enters the mouth, where it is crushed by the teeth and moistened by saliva, and becomes the food bolus, which is pushed into the esophagus with the help of the tongue. Then, through peristaltic movements (a type of muscle contraction and relaxation movement), food continues to move through the digestive tract, past the stomach, and then into the intestines.
Secretion of digestive juices. Throughout the digestive tract, food receives secretions from different organs, which allow its chemical digestion. Once in the mouth, the salivary glands secrete an enzyme that begins the transformation of sugars. The chemical digestion process continues in the stomach (thanks to the presence of gastric juices secreted there) and in the first portion of the small intestine (duodenum), where partially digested food is subjected to the action of bile and intestinal juices. and pancreatic. The enzymes and other substances present in all digestive juices allow food to be completely chemically digested, that is, to be reduced to its minimum usable units.
Nutrient absorption. Once the food is digested (reduced to its simplest forms), the nutrients are absorbed in the small intestine, then passed into the blood to be distributed throughout the body. For its part, water and some salts are absorbed in the large intestine.
stool egestion. Once the nutrients have been extracted from the food, the waste material (indigestible remains that were not used) must be expelled out of the body, which is done through the end of the digestive tract.

The digestive system is made up of the alimentary canal (which begins in the mouth and ends in the anus and is about 11 meters long) and the adjoining glands (salivary glands, liver and pancreas). Next, let’s see what are organs are part of this apparatus and the functions they perform.

Mouth and salivary glands. The mouth or oral cavity is the place where food enters the body. This organ contains different structures, such as the teeth (which allow chewing) and the tongue (which facilitates swallowing). In addition, in the mouth are the salivary glands that produce and secrete saliva. This secretion has multiple functions: it moistens the food and also contains enzymes (which start chemical digestion) and bactericidal substances.
Pharynx. It is a tube-shaped structure, which is part of both the digestive and respiratory systems : it connects the mouth with the esophagus (letting food pass through the digestive tract) and the nostrils with the larynx (letting air pass into the lungs). The pharynx has a structure called the epiglottis, which acts as a valve separating the digestive and respiratory tracts.
Esophagus. It is a muscular tube, which carries food from the mouth to the stomach, through the neck, thorax and abdomen, and passes through a hole in the diaphragm.
Stomach. Food accumulates in this organ. The cells that make up the stomach secrete gastric juices, composed mainly of pepsinogen, an enzyme precursor, and hydrochloric acid (HCl). This substance gives acidity to the medium allowing the activation of pepsinogen into pepsin (digestive enzyme that degrades proteins) and also working as a bactericide. The internal walls of the stomach are covered with a mucosa that protects them from the action of acid.
Small intestine. This first portion of the intestine, which measures between 6 and 7 meters in length , begins in the duodenum and reaches the ileocecal valve, where it joins the large intestine. The small intestine is full of villi and is the place where food is finished digesting and nutrient absorption occurs. This organ is divided into two parts. The first portion is the duodenum, which measures between 25-30 cm and is where intestinal juice secretion is produced and secretions from the pancreas and liver are received. The second portion is the jejunum-ileum, where the absorption of nutrients occurs once they have been digested.
Large intestine. It is the rest of the intestine, which culminates in the rectum and measures between 120 and 160 cm in length. This organ fulfills several very important functions for the organism: it is where feces are formed, but it is also the portion of the digestive system where water and salts are reabsorbed. In addition, the large intestine is a natural habitat for bacteria that synthesize vitamins necessary for the body.
Pancreas. This gland is in contact with the intestine and pours its pancreatic juice into the duodenum, which contains different enzymes essential for digestion. On the other hand, the pancreas also synthesizes and releases into the blood hormones that regulate the metabolism of sugars, such as insulin, which allows glucose to enter the cells.
Liver and gallbladder. The liver is the largest viscera in the body (it weighs a kilo and a half) and has multiple and varied functions. This organ produces bile, a substance necessary for the digestion and absorption of fats (allows their emulsification). Bile accumulates in the gallbladder and from there passes into the duodenum.
Year. The anal opening is where feces or fecal matter are expelled out of the human body, through controlled movements of the anal sphincter.

There are various diseases of the digestive system. Some of the main and most frequent are:

infections. Product of the entry into the intestine of bacteria or viruses that come from contaminated water or food. They can generate diarrhea, bloody stools or rectal mucus, as well as severe intestinal pain.
Parasites. Intestinal parasites are common in rural populations or in people living in poverty and are transmitted through contaminated food or water. The parasites can then migrate to other regions of the body and perpetuate the cycle if there is not proper elimination of feces.
Indigestions. The consumption of food in poor condition or contaminated with toxic or harmful substances can generate an intestinal reaction very similar to allergic reactions, with colic and usually diarrhea.
Gastritis and ulcers. The action of gastric juices and the constant consumption of irritants ( alcohol , cigarettes, citrus fruits, etc.) can lead to redness and inflammation of the stomach lining (gastritis) and, in more severe cases, to ulcers and internal sores.
Cancer. Duodenal, colon, liver or pancreatic cancer are known and aggressive forms of malignant tumors, associated with certain eating habits and which also have a high hereditary component.

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