THE CONNECTIVE SYSTEM

Psychoneuroendocrinoimmunology

In 1981, R. Ader published the volume "Psychoneuroimmunology" definitively sanctioning the birth of the "homonymous discipline. The fundamental implication concerns the" unity of the human organism, its psychobiological unity no longer postulated on the basis of philosophical convictions or therapeutic empiricisms. but the result of the discovery that so different compartments of the human organism work with the same substances.
The development of modern investigation techniques has made it possible to discover the molecules which, as the famous psychiatrist P. Pancheri defined them, constitute: "the words, phrases of the communication between the brain and the rest of the body". In light of recent discoveries, today we know that these molecules, defined neuropeptides, are produced by the three main systems of our organism (nervous, endocrine and immune). Thanks to them, these three great systems communicate, like real networks, with each other not in a hierarchical way but, in reality, in a bidirectional and widespread way; essentially forming a real global network. Any event concerning ourselves concerns these systems, which act or react accordingly, in close and constant reciprocal integration.
In reality today, as we will try to demonstrate in this report, we know that another system, consisting of cells with poor capacity for contraction and poor electrical conduction but capable of secreting a surprising variety of products in the intercellular space, has an essential influence on physiology. of our organism by integrating with other systems: the connective system.

Connective tissue

The connective tissue develops from the embryonic mesenchyme tissue, characterized by branched cells comprised in an "abundant amorphous intercellular substance. The mesenchyme derives from the intermediate embryonic sheet, mesoderm, very widespread in the fetus where it surrounds the developing organs and interpenetrates them. The mesenchyme, in addition to producing all kinds of connective tissue, it produces other tissues: muscle, blood vessels, epithelium and some glands.

- Collagen fibers
They are the most numerous fibers, they impart white color to the tissue in which they are present (eg tendons, aponeuroses, organ capsules, meninges, corneas, etc.). They form the scaffolding of many organs and are the strongest components of their stroma (supporting tissue). They have long, parallel molecules, which are structured into microfibrils, then into long, tortuous bundles held together by a cemented substance containing carbohydrates. fibers are very resistant to traction undergoing a completely negligible elongation.
Collagen fibers are mainly composed of a scleroprotein, collagen, by far the most widespread protein in the human body, accounting for 30% of total proteins. This basic protein is able to modify itself, according to the environmental and functional requirements, assuming varying degrees of rigidity, elasticity and resistance. Examples of its range of variability include the integument, basement membrane, cartilage and bone.
- Elastic fibers
These yellow fibers predominate in the elastic tissue and therefore in areas of the body where particular elasticity is required (eg ear, skin). The presence of elastic fibers in the blood vessels contributes to the efficiency of blood circulation and is a factor that has contributed to the development of vertebrates.
The elastic fibers are thinner than the collagen fibers, they branch and anastomose forming an irregular reticulate, they easily yield to traction forces, resuming their shape when traction ceases. The main component of these fibers is the scleroprotein elastin, somewhat younger, in evolutionary terms, than collagen.
- Reticular fibers
They are very thin fibers (with a diameter similar to that of collagen fibrils), which can be considered as immature collagen fibers into which they largely transform. They are present in large quantities in the embryonic connective tissue and in all parts of the organism in which collagen fibers are formed. After birth they are particularly abundant in the scaffolding of the hematopoietic organs (eg spleen, lymph nodes, red bone marrow) and constitute a network around the cells of the epithelial organs (eg liver, kidney, endocrine glands).

The connective tissue is morphologically characterized by various types of cells (fibroblasts, macrophages, mast cells, plasma cells, leukocytes, undifferentiated cells, fat cells or adipocytes, chondrocytes, osteocytes, etc.) immersed in an abundant intercellular material, defined MEC (extracellular matrix), synthesized by the same connective cells. ECM is composed of insoluble protein fibers (collagen, elastic and reticular) and a fundamental substance, erroneously defined as amorphous, colloidal, formed by soluble complexes of carbohydrates, largely bound to proteins, called acid mucopolysaccharides, glycoproteins, proteoglycans, glucosaminoglycans or GAG (hyaluronic acid, coindroitin sulfate, keratin sulfate, heparin sulfate etc.) and, to a lesser extent, by proteins, including fibronectin.
Cells and intercellular matrix characterize various types of connective tissue: connective tissue proper (connective tissue), elastic tissue, reticular tissue, mucous tissue, endothelial tissue, adipose tissue, cartilage tissue, bone tissue, blood and lymph. Connective tissues therefore play several important roles: structural, defensive, trophic and morphogenetic, organizing and influencing the growth and differentiation of surrounding tissues.

Extra-Cellular Matrix (MEC)

The conditions of the fibrous part and of the fundamental substance of the connective system are partly determined by genetics, partly by environmental factors (nutrition, exercise, etc.).
Protein fibers are in fact able to change according to environmental and functional needs. Examples of their spectrum of structural and functional variability include the integument, basement membrane, cartilage, bone, ligaments, tendons, etc.
The fundamental substance continuously varies its state, becoming more or less viscous (from fluid to sticky to solid), according to specific organic needs. Detectable in large quantities as joint synovial fluid and ocular vitreous humor, it is actually present in all tissues.
The connective tissue varies its structural characteristics through the piezoelectric effect: any mechanical force that creates structural deformation stretches the inter-molecular bonds producing a slight electrical flux (piezoelectric charge). This charge can be detected by the cells and lead to biochemical changes For example, in bone, osteoclasts cannot "digest" piezoelectrically charged bone.