Mesothelium: what it is, characteristics and associated diseases.

Summary of the characteristics of the mesothelium, a membrane distributed throughout various parts of the body.

Researchers, with current knowledge, have managed to estimate that the human body houses about 30 trillion cells. Undoubtedly, each tissue has its particularities and, for example, 84% of this cell volume in our species corresponds to red Blood cells, which transport oxygen in blood. Yes, as strange as it may seem, many experts consider blood to be a type of connective tissue of a fluid nature.

Humans are 50% protein, as protein makes up half of our dry tissue and, as you can imagine, the biological system that makes us up cannot be conceived without tissue as the basic level of organization beyond the cell. It's all about perspective but, in short, without tissue organization we are nothing.

All this introduction comes to underline the diversity and importance of tissues in our body. We all know what nervous or muscular tissue is due to its clear functionality, but what comes to mind if we name the term "mesothelium"? but what comes to your mind if we mention the term "mesothelium"? If the answer is nothing, don't worry, because here we tell you everything you need to know about it.

What is the mesothelium?

Let's start directly. From a physiological point of view, the mesothelium is defined as a type of simple squamous epithelium that rests on a basal lamina supported by connective tissue.. Let us dissect each of these terms:

• Epithelium: a tissue consisting of intimately joined cells (flat or prismatic in shape), which lines the external surface of the body and certain organs.
• Simple epithelium: going one category deeper, the simple epithelium is one that consists of a single layer of cells in contact with each other by means of junctional complexes.
• Squamous (stratified) epithelium: composed of a layer of flattened (squamous) cells on a basement membrane.

That makes it clearer, doesn't it? We are talking about a really simple type of tissue: a single layer of flattened cells. To locate this curious tissue, we must emphasize that it is the outermost layer of the peritoneum.but what is it?

The peritoneum is the serous layer that lines the inside of the abdominal cavity, that is, the "hollow space" in which all our organs are housed. It is composed of two layers and, between them, there is a space (peritoneal cavity) containing about 50 milliliters of lubricating fluid that allows them to slide between each other. It is the most extensive serous membrane in the body because, in addition to lining the peritoneal cavity, it also shelters our intestines. It is estimated that, for this reason, it occupies 40-50% of the total cutaneous surface.

The mesothelial cell

We have already described the general shape of the mesothelium and its location, which is why it only remains for us to pay special attention to its basic functional unit, the mesothelial cell, to complete the picture of this unique tissue. Let's get to it.

The mesothelial cell is a flat epithelial cell of mesenchymal origin (lax connective tissue of embryonic origin) that lines the serous cavities.. These cells form a monolayer with a polygonal mosaic appearance in which certain microvilli emerge. The proteins and serous fluids trapped between these microvilli provide a low friction surface, which is an excellent contact zone between organs. On the other hand, these cells rest on a basement membrane (BM) that offers little resistance to the passage of molecules of less than 30,000 daltons.

Finally, it should be noted that mesothelial cells are very reactive. This means that they change their appearance easily. For example, when at rest they are observed in well-organized clusters of different volume, with a high nucleus:cytoplasm ratio. On the other hand, as they become activated they increase in size, forming irregular cytoplasmic protrusions and increased vacuolization. Unfortunately, this plasticity can be a problem: it is time to talk about cancer in future lines.

Functions of the mesothelium

The main purpose of mesothelial cells (and thus of the mesothelium) is to create a layer of lubricating fluid that is released between layers of lining, producing a slippery and slippery surface.producing a slippery, non-adhesive surface.

In addition to this, the mesothelium also involves the transport and movement of particles and cells between cavities. the transport and movement of particles and cells between cavities, including leukocytes, which are involved in the immune response as inflammatory mediators.Among these are leukocytes, which are involved in the immune response as inflammatory mediators. In short, it is a "passage" tissue that allows the sliding between organs and the transport of various substances and cellular bodies essential for the physiological well-being of the organism.

Mesothelioma, a cancer in the mesothelium.

Like virtually all cells in the body that grow and change, the mesothelium is a potential candidate for cancer events.. After all, cancer is nothing more than a mutation in a cell that causes it to divide uncontrollably and fail to respond to normal periods of apoptosis (cell death), giving rise to the dreaded malignant tumor.

Mesothelioma can be divided into several categories according to the site affected. Among them, we find the following.

Pleural mesothelioma

It affects the tissue surrounding the lungs, i.e. it develops in the thoracic cavity.. It can cause chest pain, painful cough, shortness of breath, unusual lumps under the skin of the chest and unexplained weight loss, among many other things.

2. Peritoneal Mesothelioma

As the name implies affects the tissue of the abdomen (peritoneum).. It causes abdominal swelling, pain in the abdomen, nausea and unexplained weight loss. Unfortunately, both types of mesothelioma are extremely aggressive and carry a not inconsiderable fatality rate.

3. Other types of mesothelioma

There are more types of mesothelioma depending on the tissue they affect. For example, pericardial mesothelioma grows in the tissue surrounding the heart, causing breathing problems and tightness. On the other hand, tunica vaginalis mesothelioma affects the lining of the testicles. Basically, any mesothelial lining is susceptible to the development of a malignant tumor.However, not all mesothelial tumors automatically result in cancer.

Distribution and epidemiology of mesotheliomas

Mesothelioma occurs in approximately 1-2 patients per million people per year. Unfortunately, people working in the construction industry (especially if they are in contact with asbestos) are up to 40 times more likely to develop mesothelioma. This aggressive type of cancer kills about 5,000 people per year in Europe and 3,000 in the USA per year.

The typical mesothelioma patient is a 60-year-old male who has been working in this type of industry for at least 30 years.. It is shocking to learn that, in most cases, it usually takes 20 to 40 years after exposure to asbestos (in vinyl, cars and building materials) for cancer to develop.

For this reason, the World Health Organization (WHO) has recommended that all countries in the world stop using this material in construction. Unfortunately, in 2010 this organization estimated that, despite global bans, 125 million people around the world are still in close contact with asbestos. In addition to mesothelioma, this material also causes asbestosis (cicatricial lesions in the lung and pleura) and lung cancer, as well as possible metastasis of asbestos.as well as possible metastases from these types of malignant tumors.

Summary

As you have seen, the mesothelium is a very simple structure with many secrets to unravel. For the sake of understanding (and in a final, more familiar note), we can say that it is a simple layer that allows sliding between organs and the transport of substances, from proteins to specialized immune bodies, passing through many other cell types.

Mesotheliomas are a very rare type of malignant tumor in the general population but, unfortunately, they occur almost exclusively in people who have worked on construction sites in contact with asbestos. If you have a history of labor/physical work and notice strange lumps in any soft part of your body, abdominal swelling, and continuous coughing, see your doctor promptly.

Bibliographic references:

• Mesothelial cells, Clínica Universidad Navarra (CUN). Retrieved December 26 https://www.cun.es/diccionario-medico/terminos/celula-mesotelial
• Mesothelial cells...The great challenge of cytology, onkos.es. Retrieved Dec. 26 at https://www.onkos.es/blog/las-celulas-mesoteliales-el-gran-reto-de-la-citologia.
• Martín, L. B., Pereira, P. P., Lista, F. S., & Castañón, L. B. (2013). Mesothelioma of the tunica vaginalis. Archivos Espanoles de Urologia, 66(4), 384-388.
• Mesothelioma, Mayoclinic.org. Retrieved December 26 at https://www.mayoclinic.org/es-es/diseases-conditions/mesothelioma/symptoms-causes/syc-20375022.
• Mesothelioma, medlineplus.org. Retrieved Dec. 26 from https://medlineplus.gov/spanish/ency/article/000115.htm#:~:text=It%20is%20a%20little%20cancerous%20tumor%20little,%C3%B3n%20prolonged%20exposure%20to%20asbestos.
• WHO warns about asbestos exposure of 125 million people, UN News. Retrieved December 26th from https://news.un.org/es/story/2010/08/1197561
• Panadero, F. R. (2015). Diagnosis and treatment of malignant pleural mesothelioma. Archives of Bronchopneumology, 51(4), 177-184.