Examples of Tissue Level

When we talk about tissue level, we refer to the different tissues that make up the body of living beings, that is, to the various degrees of cellular organization that operate to fulfill a specific function. For instance: the skin, the heart, the brain.

These tissues can be made up of cell sets of the same or several types, of similar embryonic origin, that are distributed in a regular way and show a coordinated physiological behavior.

Not all living things have this level of biological organization, fruit of centuries of evolution and cellular differentiation. Only vascular plants and multicellular animals (metazoans) have specialized cellular tissues, based on four different tissue levels, which are:

  • Epithelial tissue. It is the cell group that covers the body’s surfaces, “covers” the outermost parts of the organs and the body itself, and is in charge of secretion and absorption. It gives rise to the glands and constitutes the physical limit of the body, its outermost layer that faces the elements.
  • Connective tissue. Also called connective tissue, it is responsible for the support and integration of the various systems that make up the body. Through it the neurovascular network (blood and neuronal) spreads, and forms the various organs and appendages of the body of the living being. It can be specialized like bone tissue, or non-specialized like mucous or gelatinous.
  • Muscle tissue. As its name indicates, this tissue level deals with the structures that mobilize the body, which give it the necessary strength to move around or to undertake the most diverse tasks, such as keeping the blood circulation going (such as the heart). These tissues are usually highly specialized, which is why their cells are known as “fibers” and have an unusual elasticity.
  • Nervous tissue. The control tissue of the body, made up of billions of neurons and supporting cells (glial) interconnected in a vast network of transmission of electrical impulses that allow the action and coordination of the parts of the body, as well as the perception of the surroundings, the accumulation of experiences and other reasoning and reaction processes characteristic of higher living beings.

It is possible to find more or less specialized tissues within each of these levels, performing point functions and diverse. All, absolutely all the cells of the body are part of one of these four levels of tissue organization.

Examples of tissue level

  1. The skin. Considered the “largest organ in the body”, this outer and superficial layer of tissue belongs to the epithelial level. In it, processes of absorption of ambient humidity or ambient heat energy take place, as well as segregation of sweat and other lubricating substances.
  2. The heart. As we said before, this organ is made up almost entirely of muscle fibers, which allow it to keep pumping blood more or less quickly throughout our lives. This means that it is part of the muscular level, although it also contains connective and nerve cells that provide structure and regulate its functioning.
  3. Brain. Main part of the Central Nervous System (CNS), the body’s “computer” obviously belongs to the nervous tissue level, made up of neuronal and glial cells. It is in charge of processing data, attending to conscious and unconscious processes, managing reflexes, regulating the levels of the body and it is enclosed and protected in the cranial vault (which belongs to the connective tissue).
  4. Joints. Composed mainly of cartilage, they are part of the connective tissue, a meeting point between large muscle and bone stripes. It is a specialized connective tissue, however: it lacks blood vessels, it is almost all extracellular matrix and has the conditions of elasticity and resistance to serve as a cushion between the bones and cushion the possible impact.
  5. The ribs. Obviously made of bone, they also belong in this classification to connective tissue, since they provide support to the body, protect the organs of the rib cage and mark the necessary structure of the torso. However, it is not the only thing they do: they also, like all bones, secrete red blood cells and other substances in the body that originate in the bone marrow.
  6. Exoskeletons. Although the human body does not have one (instead, it has an endoskeleton, that is, an internal one), certain arthropods, protists, and fungi have a covering of chitin, a protein that they secrete to harden their epithelium and generate an external defense shield. . This tissue, known as chitin tissue, is not very specialized and can be considered a type of connective tissue.
  7. Body fat. The so-called adipose tissue, which is made up of body fats in their diversity (good and bad, light and dense) is part of the connective tissue level, since they not only fulfill the role of being energy reservoirs (glucose), but also provide support , union and structure to various organs and segments of the body.
  8. The sebaceous glands. These are tiny organelles that secrete lubricating material on the skin (sebum), the obstruction of which leads to the well-known acne disease. In this sense, they are part of the epithelial tissue level, since they are part of the outer layer of the body and their functions have the task of ensuring its preservation: guaranteeing that it is moist, lubricated and protected.
  9. Capillaries. These conduits through which blood travels in the body are made up of tissue belonging to both the epithelial tissue (the outer surface of the interior of the capillaries, for example) and connective tissue (the bulk of the “tunnel” that constitutes the capillary). It is a good example of how various tissue levels come together to do their job.
  10. Nose. Similarly, the nose is nothing more than a set of cells with two levels: the conjunctiva, since it is made up almost entirely of cartilage; and the epithelial, since it is covered with skin and sweat and sebaceous glands.