Components of the Digestive System

The Digestive System is also known as the Digestive System or Digestive Apparatus . It is formed by a set of organs that act in the human body.

The action of these organs is related to the food transformation process, which aims to help in the absorption of nutrients.

All this happens through mechanical and chemical processes.

Organs of the human body related to the digestive system

Components of the Digestive System

The Digestive System (new nomenclature) is divided into two parts.

One of these is the digestive tube (properly speaking), formerly known as the digestive tube. It is divided into three parts: high, medium and low. The other part corresponds to the annex organs .

See in the table below the organs that make up each part of the Digestive System.

Below are more information and details about each of the components of the Digestive System.

Upper Digestive Tube

Organs and appendages of the upper digestive tract

The upper digestive tube is formed by the mouth, pharynx and esophagus.

Find out more details about each of these bodies below.

See also: Organs of the Human Body

Boca

The mouth is where the digestive system starts.

The mouth is the gateway for food to enter the digestive tract. It corresponds to a mucosa-lined cavity where food is humidified by saliva , produced by the salivary glands.

Mastication takes place in the mouth, which corresponds to the first moment of the process of mechanical digestion. It happens with teeth and tongue.

In a second moment, the enzymatic activity of ptyalin, which is salivary amylase, comes into play. It acts on the starch found in potatoes, wheat flour, rice and transforms it into smaller molecules of maltose.

See also: Salivary Glands

Pharynx

The pharynx is the organ that connects the digestive system to the respiratory system.

The pharynx is a membranous muscular tube that communicates with the mouth, through the isthmus of the throat and at the other end with the esophagus.

To reach the esophagus, food, after being chewed, travels through the entire pharynx, which is a common channel for the digestive system and the respiratory system.

In the process of swallowing, the soft palate is retracted upwards and the tongue pushes the food into the pharynx, which voluntarily contracts and takes the food to the esophagus.

The penetration of food into the airways is prevented by the action of the epiglottis, which closes the orifice of communication with the larynx.

See also: respiratory system

Esophagus

Peristaltic movement of the esophagus

The esophagus is a muscular conduit, controlled by the autonomic nervous system.

It is through waves of contractions, known as peristalsis or peristaltic movements, the muscular conduit squeezes the food and takes it towards the stomach.

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Middle Digestive Tube

The midgut tube is formed by the stomach and small intestine (duodenum, jejunum and ileum).

Find out about each of them below.

Stomach

Anatomy of the healthy stomach and a stomach with ulcer

The stomach is a large bag located in the abdomen, responsible for the digestion of proteins.

The entrance of the organ receives the name of cardia, because it is very close to the heart, separated from it only by the diaphragm .

It has a small upper curvature and a large lower curvature. The most dilated part is called the “fundic region”, while the final part, a narrow region, is called the “pylorus”.

The simple movement of chewing food already activates the production of hydrochloric acid in the stomach. However, it is only with the presence of food, of a protein nature, that the production of gastric juice begins. This juice is an aqueous solution, composed of water, salts, enzymes and hydrochloric acid.

The gastric mucosa is covered by a layer of mucus that protects it from gastric juice aggression, since it is quite corrosive. Therefore, when there is an imbalance in protection, the result is inflammation of the mucosa (gastritis) or the appearance of wounds (gastric ulcer).

Pepsin is the most potent enzyme in gastric juice and is regulated by the action of a hormone, gastrin.

Gastrin is produced in the stomach itself when food protein molecules come into contact with the organ wall. Thus, pepsin breaks down large protein molecules and transforms them into smaller molecules. These are proteoses and peptones.

Finally, gastric digestion lasts, on average, from two to four hours. In this process, the stomach suffers contractions that force the food against the pylorus, which opens and closes, allowing, in small portions, the chyme (white and foamy mass), to reach the small intestine.

See also: Enzymes

Small intestine

Attached organs that participate in the digestive process in the intestine

The small intestine is lined with a wrinkled mucosa that has numerous projections. It is located between the stomach and the large intestine and has the function of secreting the various digestive enzymes. This gives rise to small, soluble molecules: glucose, amino acids, glycerol, etc.

The small intestine is divided into three parts: the duodenum, the jejunum and the ileum.

The duodenum is the first portion of the small intestine to receive the chyme that comes from the stomach, which is still very acidic, irritating the duodenal mucosa.

Soon after, the chyme is bathed in bile . Bile is secreted by the liver and stored in the gallbladder , containing sodium bicarbonate and bile salts, which emulsify lipids, fragmenting their drops into thousands of micro droplets.

In addition, the chyme also receives the pancreatic juice, produced in the pancreas. It contains enzymes, water and a large amount of sodium bicarbonate, as in this way it favors the neutralization of chyme.

Thus, in a short period of time, the duodenum food “mush” becomes alkaline and generates the necessary conditions for intra-intestinal digestion to occur.

The jejunum and ileum are considered the part of the small intestine where the transit of the food bolus is fast, being most of the time empty, during the digestive process.

Finally, along the small intestine, after all the nutrients have been absorbed, there is a thick paste of unassimilated waste and bacteria. This paste, already fermented, goes to the large intestine.

See also: What are Lipids: Functions and Types

Lower Digestive Tube

The lower digestive tube is formed by the large intestine, which has the following components: cecum, ascending colon, transverse colon, descending colon, the sigmoid curve and the rectum.

Large intestine

The large intestine is the last organ that acts in the digestive system.

The large intestine measures about 1.5 m in length and 6 cm in diameter. It is the site of water absorption (both ingested and digestive secretions), storage and elimination of digestive waste.

It is divided into three parts: the cecum, the colon (which is subdivided into ascending, transverse, descending and the sigmoid curve) and rectum.

In the cecum, the first portion of the large intestine, food residues, already constituting the “fecal cake”, pass to the ascending colon, then to the transverse and then to the descending colon. In this portion, the fecal bolus remains stagnant for many hours, filling the portions of the sigmoid curve and the rectum.

The rectum is the final part of the large intestine, which ends with the anal canal and the anus, through which feces are eliminated.

To facilitate the passage of the fecal cake, the glands of the mucosa of the large intestine secrete mucus in order to lubricate the fecal cake, facilitating its transit and elimination.

Note that vegetable fibers are neither digested nor absorbed by the digestive system, they pass through the entire digestive tract and form a significant percentage of fecal mass. Therefore, it is important to include fiber in the diet to help the formation of feces