Digestive system

What is the digestive system?

The digestive system is the set of organs of the human body that is responsible for the digestion of food, extracting all the organic nutrients, water and energy that body cells need daily to survive.

Digestion is a process, at the same time mechanical and chemical, which consists of transforming food into products that can be absorbed by the cells of our body..

Many different organs are involved in digestion, such as the teeth, mouth, tongue, throat, stomach, small intestine, large intestine, liver and pancreas, for example.

A poor diet, little physical activity, too much stress and little hydration can cause different conditions to the different organs of the digestive system, which can considerably affect our lifestyle..

Functions of the digestive system

The digestive system works essentially in the digestion of everything we eat on a daily basis. The digestion and use of food is a relatively complex process that has many stages and the digestive system participates in many of them, with the help of other systems such as the cardiovascular and nervous.

In the end, this organ system manages to release organic, mineral and energetic compounds that are essential for cellular life, and that are used for the synthesis of proteins and lipids, for respiration and cell division, etc..

Mobility

An important aspect of digestion is the movement of food through the digestive tract as it is processed. Mobility includes ingestion, chewing, swallowing, and peristalsis:

• Ingestion refers to the moment in which we introduce food to our mouth.
• Chewing, as we can imagine from its name, involves the grinding and disintegration of food into smaller fragments; We do this with our teeth and with the help of our tongue and saliva..
• Swallowing is what happens when we swallow, it is the voluntary act of transporting the food bolus, the mixture of crushed food with saliva, from the mouth to the pharynx.
• Peristalsis, finally, consists of a series of rhythmic contractions (waves) of the digestive tract that help to move the food bolus throughout the entire canal..

Secretion

For digestion to be truly an efficient process, the digestive system has organs that are responsible for producing substances capable of promoting the hydrolysis of the molecules contained in food, this process is called "secretion".

The secretion can be of two types: exocrine and endocrine.

• Exocrine secretion has to do with the production of substances into the lumen of the intestinal tract, which is considered an "external" region of the body. The stomach, for example, secretes a large amount of gastric juices (between 2 and 3 liters per day).
• Endocrine secretion, on the other hand, has to do with the production of hormones that regulate the functions of the digestive system, the release of which occurs inside the body, especially towards the circulatory system..

Digestion

The digestive system works mainly in the process of digestion, which is the breakdown of food compounds into their smallest components, in order for them to be absorbed by the cells of our body..

This rupture is achieved gradually during the previous stages, in which certain conditions are ensured: peristaltic movements, the presence of hydrolytic enzymes, the decrease in pH, etc..

Absorption

After the food molecules have been digested and separated into their smallest fractions, the immediately most important process is absorption..

Not all the digestive system participates in this function, as it occurs especially in the intestines and involves the transit of digested products into the blood and lymph, crossing the intestinal walls, for distribution throughout the body..

Storage and disposal

The last stage of digestion in which the digestive system participates is the temporary storage of food and the elimination, in the form of feces, of food materials that could not be digested..

Parts of the digestive system (organs)

The human digestive system is divided into 2 sets of organs and structures: the alimentary canal or gastrointestinal tract and the accessory digestive organs..

Gastrointestinal tract

It is a kind of channel that internally connects the mouth with the anus; It is approximately 9 meters long, so we say that it goes completely through us, passing through the head, the rib cage and the abdominal cavity.

The organs that make up this part of the digestive system are:

• The oral cavity or mouth: the space where food can be introduced.
• The pharynx: the part of the throat that is immediately after the mouth; works in the digestive and respiratory systems (it is an area of driving).
• The esophagus: the muscular tube that connects the pharynx to the stomach.
• The stomach: the hollow muscular organ that receives chewed food as it travels through the esophagus.
• The small intestine: it is between the stomach and the large intestine, it is a kind of muscular tube and in it takes place part of the digestion and absorption of nutrients.
• The large intestine: it is directly connected to the small intestine, in which water is absorbed from undigested materials and feces are formed.

Accessory digestive organs

They are called accessories because they are not part of a continuum, as the organs of the gastrointestinal tract do. In addition, many of these are responsible for secreting substances into the gastrointestinal tract, but food does not actually pass through it as it is digested.

Some of these organs not only participate in digestive functions, but also have important endocrine functions, that is, they produce hormones and release them into our body, regulating different functions..

The main accessory organs of the human digestive system are:

• The liver: is responsible for the production of bile, an alkaline substance that participates in the digestion of fats in the small intestine.
• The gallbladder: is a hollow organ where bile derived from the liver is stored to concentrate before being released into the small intestine.
• The pancreas: has glandular functions, secretes a substance known as pancreatic juice into the small intestine; This juice contains enzymes for the degradation of proteins and carbohydrates, and bicarbonate, which neutralizes the acids derived from gastric juices from the stomach.

It is also necessary to include the teeth, tongue and salivary glands, which are actively involved in the early stages of the digestive process.

Functioning

The digestive system works as follows:

1. First we must introduce food to our mouth, where we can chew it, breaking it into small pieces and moistening it with saliva. Saliva, in addition to water, contains some enzymes that help digest certain carbohydrates and fats present in some foods. The mixture of chewed food and saliva is called Cud. Alimentary bolus.
2. The tongue helps us swallow the bolus so that it travels down the throat and esophagus to the stomach.
3. In the stomach, the food bolus mixes with gastric juices, which are very acidic, so they help break down some food molecules. The stomach is, more or less, like the drum of a washing machine, since its movements allow the relatively homogeneous mixing of everything that reaches its interior; this mixture turns into a paste called chyme.
4. The chyme, through the muscular movements of the stomach, reaches the small intestine, which is directly associated with the accessory organs: the liver, the gallbladder and the pancreas; there degradation continues to occur. The walls of the small intestine have a large surface area, specially adapted for absorption; contain a large number of folds and villi with a large number of cells that capture nutrients suspended in the intestinal lumen, absorbing them.
5. The pancreas releases pancreatic enzymes that have protease, lipase, and amylase activities for the breakdown of proteins, fats, and carbohydrates; also secretes bicarbonate, which neutralizes acids derived from the stomach.
6. The liver secretes bile, which is fundamentally involved in the digestion of fats, but it first passes through the gallbladder, where it is stored and concentrated before reaching the small intestine..
7. In the large intestine, after the cells of the walls of the small intestine have absorbed much of the nutrients released by digestion, water is absorbed and feces are produced, mainly composed of the undigested part of food.
8. The feces are expelled thanks to the peristaltic movements of the large intestine, which lead them to the colon, rectum and finally the anus.

The entire digestive system is controlled by the nervous system, particularly by the division known as the enteric nervous system, which regulates the mobility, secretion and growth of this system..

The enteric nervous system is part of the peripheral nervous system -autonomous division-, which implies that it works without us being aware of it, otherwise it would be very difficult to do anything, since we would have to continually think about digesting what we eat.

In addition, it is important to mention that the digestive system is highly irrigated by the cardiovascular system, since the blood participates in the transport of the molecules absorbed by the body and, at the same time, delivers oxygen so that the cells of the organs can work..

Digestive system diseases

Like any organ system, the digestive system is prone to a large number of diseases, some of which can be closely related to the way we eat, what we eat or the lifestyle we lead (stress seems to affect considerably to our digestive system).

Some of the most common diseases that you have surely suffered from or heard of are:

- Diarrhea.

- Threw up.

- Constipation (constipation).

- Gastric ulcers.

- Hemorrhoids.

- Reflux.

- Inflammation.

- Bacterial or viral infections.

- Parasitosis (taeniasis).

- Among other.

References

1. Chauncey, H. H., Lionetti, F., Winer, R. A., & Lisanti, V. F. (1954). Enzymes of human saliva: The determination, distribution, and origin of whole saliva enzymes. Journal of Dental Research, 33 (3), 321-334.
2. Chung, Y. C., Kim, Y. S., Shadchehr, A., Garrido, A., Macgregor, I. L., & Sleisenger, M. H. (1979). Protein digestion and absorption in human small intestine. Gastroenterology, 76 (6), 1415-1421.
3. Fox, S. I. (2009). Fundamentals of human physiology (Vol. 749). McGraw-Hill.
4. McGuinness, H. (2010). Anatomy & Physiology. Hodder Education,.
5. Netter, F. H. (1990). Atlas of Human Anatomy / Frank H. Netter. East Hannover, New Jersey, 592.
6. Stanfield, C. L., Germann, W. J., Niles, M. J., & Cannon, J. G. (2011). Principles of human physiology. Benjamin Cummings.