We explain what the tissues of the human body are and the characteristics of the epithelial, muscular, connective and nervous tissues.
What are the tissues of the human body?
With the term “tissue”, in biology and medicine, we normally refer to organic materials made up of a huge set of cells distributed regularly, which together fulfill the same purpose determined and have a common embryonic origin. In simpler terms, tissues are the types of meat or pulp of the body, made up of cells of different types but with the same physiological purpose.
The organization of the body into tissues It is typical of the most complex living beings. It is distinguished from those that group together in cellular colonies, as is the case of sponges, capable, for example, of regrouping and recovering their structure on the other side of a sieve through which we separate them. This does not happen with tissue cells, firmly connected to each other and in a relationship of mutual interdependence.
The human body, as well as that of animals and complex multicellular life forms, is made up of tissues of different types, responsible for diverse functions and with their own characteristics, to the study of which the discipline of histology is dedicated. The four main tissue types of the human and animal body are detailed below.
Epithelial tissue
This is what the fabric is called made up of multiple densely packed cells that make up the skin that is, the limits of the body itself.
Its name comes from what we call this type of cortex: the epithelium, and although in other animals it fulfills clearer defensive functions (for example, through scales), in the case of mammals they are stratified cellular groups of two types. :
- Squamous cells: They are the most external, flattened in shape.
- Cuboidal cells: They are located deeper in the epithelium, the shape of which resembles a cube.
One of its functions is to protect internal tissues from the action of environmental elements, infections and attacks from competitors (as far as possible). In addition, it has the ability to lubricate and protect itself, and is also found lining the small intestine, where it helps the absorption of nutrients, and also the internal glands, where they secrete some enzymes and hormones.
muscle tissue
Muscle tissue is that which gives our body solidity, structure and defined shape, and which also gives the body its complex range of voluntary and involuntary movements. It is made up of elastic cells capable of deforming and recovering their shape, called myocytes, and can be classified into three tissue subtypes, which are:
- Skeletal muscle tissue. That which is subject to the will of the mind, such as that of our arms and legs, or facial muscles, and that is composed of cylindrical and multinucleated cells, up to 30 cm in length, equipped with a large number of mitochondria to manage the energy necessary for body movements. Together, they build striated muscles, attached by a tendon to the bones of the body.
- cardiac muscle tissue. As its name indicates, we are referring to the muscles of the heart, composed of cardiomyocytes, elongated and branched cells, equipped with a central nucleus, and capable of forming terminal junctions with a high level of specialization, which facilitate the transmission of nervous impulses. Its function is to operate as a hydraulic pump to keep blood circulating through the body. For that reason, it does not obey our mind at all.
- smooth muscle tissue. Composed of leimocytes, spindle-shaped mononucleated cells, without striations or tubular systems, they are found in the walls of hollow viscera (stomach, bladder, uterus, intestine, etc.) and most of the blood vessels. Its contractions do not obey the mind, but operate automatically.
Connective or connective tissue
In this case, a diverse group of organic tissues that are formed from the embryonic mesoderm are brought together under this same name, and that respond to the primary function of providing support and systemic integration to the human body. That is, it keeps everything together and everything in its place.
Connective tissue can be of various types, depending on its functions in the body. First of all, we can distinguish between specialized connective tissues, which fulfill specific and specific functions (such as bone, cartilaginous, blood or lymphatic tissue) and non-specialized ones, which simply provide support and physical structure with their presence ( such as adipose or fibrous tissue).
On the other hand, we must also differentiate between:
- dense connective tissue or fibrous. Composed of collagen, it holds things in place in a specialized way, whether it’s muscles attached to bones (tendons and ligaments), or certain tissues separated from others (such as the capsules of certain internal organs).
- Loose connective tissue. Endowed with abundant extracellular content, it fulfills specific roles depending on the type: mucosal connective tissue, endowed with defensive and structural roles; the reticular connective tissue, composed of collagen and which makes up many lymphoid nodes and organs; and the mesenchymal connective tissue, which makes up the embryonic mesenchyme and provides specialized cells to all tissues.
nervous tissue
It is made up of nerve cells, that is, neurons and glial cells, and It makes up both the brain and the spinal cord, in addition to the vast network of nerve endings that make up the nervous system of our body.
These are generally highly sensitive cells, capable of reacting to external and internal stimuli and transmitting information through their connections. So, It efficiently and quickly links the entire body with the brain
This tissue is responsible for processing our movements, through the somatic system that links the nerves with the skeletal muscles and executes conscious orders, or the autonomic system, which operates automatically and is in charge of the smooth and cardiac muscles.
Continue with: Central nervous system
References
- “Tissue (biology)” on Wikipedia.
- “Tissue types” in Medline Plus.
- “Basic tissues of the human body: tissue types and classification” (video) in MD Guide.
- “Tissues of the Human Body” in cK-12.
