There are several types of different tissues in the human body. All of them play their role in our life. One of the most important is connective tissue. Its specific gravity is about 50% of the mass of a person. It is a link that connects all the tissues of our body. Many functions of the human body depend on its state. The different types of connective tissue are discussed below.
General information
Connective tissue, the structure and functions of which have been studied for many centuries, is responsible for the work of many organs and their systems. Its specific gravity is from 60 to 90% of their mass. It forms the supporting frame, called the stroma, and the outer integument of the organs, called the dermis. Main Features of Connective Tissues:
- common origin from mesenchyme;
- structural similarity;
- execution of support functions.
The main part of the hard connective tissue is of the fibrous type. It is made up of elastin and collagen fibers. Together with the epithelium, connective tissue is an integral part of the skin. At the same time, shecombines it with muscle fibers.
Connective tissue is strikingly different from others in that it is represented in the body by 4 different states:
- fibrous (ligaments, tendons, fascia);
- hard (bones);
- gelatinous (cartilage, joints);
- liquid (lymph, blood; intercellular, synovial, cerebrospinal fluid).
Also representatives of this type of tissue are: sarcolemma, fat, extracellular matrix, iris, sclera, microglia.
The structure of connective tissue
It includes immobile cells (fibrocytes, fibroblasts) that make up the main substance. It also has fibrous formations. They are intercellular substance. In addition, it contains various free cells (fat, wandering, obese, etc.). Connective tissue contains an extracellular matrix (base). The jelly-like consistency of this substance is due to its composition. The matrix is a highly hydrated gel formed by macromolecular compounds. They make up about 30% of the weight of the intercellular substance. At the same time, the remaining 70% is water.
Classification of connective tissues
The classification of this type of fabric is complicated by their diversity. So, its main types are subdivided, in turn, into several separate groups. There are such types:
- Actually connective tissue, from which fibrous and specific tissue is isolated, characterized by special properties. Firstis divided into: loose and dense (unformed and formed), and the second - into fatty, reticular, mucous, pigmentary.
- Skeletal, which is divided into cartilage and bone.
- Trophic, which includes blood and lymph.
Any connective tissue determines the functional and morphological integrity of the organism. She has the following characteristics:
- fabric specialization;
- versatility;
- multifunctionality;
- adaptability;
- polymorphism and multicomponent.
General functions of connective tissue
Different types of connective tissue perform the following functions:
- structural;
- ensure water-s alt balance;
- trophic;
- mechanical protection of the skull bones;
- formative (for example, the shape of the eyes is determined by the sclera);
- ensure the consistency of tissue permeability;
- musculoskeletal (cartilaginous and bone tissue, aponeuroses and tendons);
- protective (immunology and phagocytosis);
- plastic (adaptation to new environmental conditions, wound healing);
- homeostatic (participation in this important process of the body).
In the general sense of the function of the connective tissue:
- shaping the human body into shape, stability, strength;
- protection, covering and connecting internal organs to each other.
The main function contained in the connective tissueintercellular substance supporting. Its basis ensures a normal metabolism. Nervous and connective tissue provides interaction between organs and various body systems, as well as their regulation.
The structure of different types of fabrics
The structure of connective tissue varies depending on its type. It consists of different cells and intercellular substance. A distinctive feature of such tissue is its high regenerative capacity. It is characterized by plasticity and good adaptation to changing environmental conditions. Any types of connective tissue grow and develop due to the reproduction and transformation of young undifferentiated cells. They originate from the mesenchyme, which is embryonic tissue formed from the mesoderm (middle germ layer).
The intercellular substance, called the extracellular matrix, contains many different compounds (inorganic and organic). It is on their composition and quantity that the consistency of the connective tissue depends. Substances such as blood and lymph contain intercellular substance in liquid form, called plasma. The cartilage matrix has the form of a gel. The intercellular substance of bones and tendon fibers are solid insoluble substances.
The extracellular matrix is represented by proteins such as elastin and collagen, glycoproteins and proteoglycans, glycosaminoglycans (GAGs). It may include structural proteins laminin and fibronectin.
Loose and dense connectivecloth
These types of connective tissue contain cells and extracellular matrix. There are much more of them in loose than in dense. The latter is dominated by various fibers. The functions of these tissues are determined by the ratio of cells and intercellular substance. Loose connective tissue performs a predominantly trophic function. At the same time, it also participates in musculoskeletal activities. Cartilaginous, bone and densely fibrous connective tissue perform a musculoskeletal function in the body. The rest - trophic and protective.
Loose fibrous connective tissue
Loose unformed fibrous connective tissue, the structure and functions of which are determined by its cells, is found in all organs. In many of them, it forms the basis (stroma). It consists of collagen and elastic fibers, fibroblasts, macrophages, and a plasma cell. This tissue accompanies the vessels of the circulatory system. Through its loose fibers, the process of metabolism of blood with cells occurs, during which the transfer of nutrients from it to the tissues occurs.
There are 3 types of fibers in the intercellular substance:
- Collagens that go in different directions. These fibers have the form of straight and wavy strands (constrictions). Their thickness is 1-4 microns.
- Elastic, which is slightly thicker than collagen fibers. They connect (anastomose) with each other, forming a wide-braided network.
- Reticular, distinguished by their subtlety. They are intertwined in a mesh.
The cellular elements of loose fibrous tissue are:
- Fibroplasts being the most numerous. They are spindle shaped. Many of them are equipped with processes. Fibroplasts are able to multiply. They take part in the formation of the basic substance of this type of tissue, being the basis of its fibers. These cells produce elastin and collagen, as well as other substances related to the extracellular matrix. Inactive fibroblasts are called fibrocytes. Fibroclasts are cells that can digest and absorb extracellular matrix. They are mature fibroblasts.
- Macrophages, which can be round, elongated and irregular in shape. These cells can absorb and digest pathogens and dead tissue, and neutralize toxins. They are directly involved in the formation of immunity. They are divided into histocytes (quiescent) and free (wandering) cells. Macrophages are distinguished by their ability to amoeboid movements. By their origin, they belong to blood monocytes.
- Fat cells capable of accumulating a reserve supply in the cytoplasm in the form of drops. They have a spherical shape and are able to displace other structural units of tissues. In this case, dense adipose connective tissue is formed. It protects the body from heat loss. In humans, adipose tissue is predominantly located under the skin, between the internal organs, in the omentum. It is divided into white and brown.
- Plasma cells found in tissuesintestines, bone marrow and lymph nodes. These small structural units are distinguished by their round or oval shape. They play an important role in the activity of the body's defense systems. For example, in the synthesis of antibodies. Plasma cells produce blood globulins, which play an important role in the normal functioning of the body.
- Mast cells, often referred to as tissue basophils, are characterized by their granularity. Their cytoplasm contains special granules. They come in a variety of shapes. Such cells are located in the tissues of all organs that have a layer of unformed loose connective tissue. They include substances such as heparin, hyaluronic acid, histamine. Their direct purpose is the secretion of these substances and the regulation of microcirculation in tissues. They are considered immune cells of this type of tissue and respond to any inflammation and allergic reactions. Tissue basophils are concentrated around blood vessels and lymph nodes, under the skin, in the bone marrow, spleen.
- Pigmented cells (melanocytes), having a highly branched shape. They contain melanin. These cells are found in the skin and iris of the eyes. By origin, ectodermal cells are isolated, as well as derivatives of the so-called neural crest.
- Adveptitial cells located along blood vessels (capillaries). They are distinguished by their elongated shape and have a core in the center. These structural units can multiply and transform into other forms. It is at their expense that the dead cells of this tissue are replenished.
Dense fibrous connective tissue
Tissue refers to connective tissue:
- Dense unformed, which consists of a significant number of densely spaced fibers. It also includes a small number of cells located between them.
- Densely designed, characterized by a special arrangement of connective tissue fibers. It is the main building material of ligaments and other formations in the body. For example, tendons are formed by tightly spaced parallel bundles of collagen fibers, the spaces between which are filled with the ground substance and a thin elastic network. This type of dense fibrous connective tissue contains only fibrocytes.
Elastic fibrous tissue is also isolated from it, of which some ligaments (voice) are composed. Of these, shells of round vessels, walls of the trachea and bronchi are formed. In them, flattened or thick, rounded elastic fibers run parallel, and many of them are branched. The space between them is occupied by loose, unformed connective tissue.
Cartilage tissue
Connective cartilage tissue is formed by cells and a large amount of intercellular substance. It is designed to perform a mechanical function. There are 2 types of cells that make up this tissue:
- Oval-shaped chondrocytes with a nucleus. They are in capsules around which intercellular substance is distributed.
- Chondroblasts, which are flattened young cells. They are oncartilage periphery.
Specialists divide cartilage tissue into 3 types:
- Hyaline found in various organs such as ribs, joints, airways. The intercellular substance of such cartilage is translucent. It has a uniform texture. The hyaline cartilage is covered by the perichondrium. It has a bluish-white tint. The skeleton of the embryo consists of it.
- Elastic, which is the building material of the larynx, epiglottis, walls of the external auditory canals, the cartilaginous part of the auricle, small bronchi. In its intercellular substance there are developed elastic fibers. There is no calcium in such cartilage.
- Collagen, which is the basis of the intervertebral discs, menisci, pubic articulation, sternoclavicular and mandibular joints. Its extracellular matrix includes dense fibrous connective tissue, consisting of parallel bundles of collagen fibers.
This type of connective tissue, regardless of location in the body, has the same coverage. It's called the perichondrium. It consists of dense fibrous tissue, which includes elastic and collagen fibers. It has a large number of nerves and blood vessels. The cartilage grows due to the transformation of the structural elements of the perichondrium. At the same time, they are able to quickly transform. These structural elements turn into cartilage cells. This fabric has its own characteristics. Thus, the extracellular matrix of mature cartilage does not have blood vessels; therefore, its nutrition is carried out with the help ofdiffusion of substances from the perichondrium. This fabric is distinguished by its flexibility, it is resistant to pressure and has sufficient softness.
Connective tissue of bone
Connective bone tissue is particularly hard. This is due to the calcification of its intercellular substance. The main function of connective bone tissue is musculoskeletal. All the bones of the skeleton are built from it. Main fabric structural elements:
- Osteocytes (bone cells), which have a complex process shape. They have a compact dark core. These cells are found in bone cavities that follow the contours of osteocytes. Between them is the intercellular substance. These cells are unable to reproduce.
- Osteoblasts, which are the structural element of the bone. They are round in shape. Some of them have multiple cores. Osteoblasts are found in the periosteum.
- Osteoclasts are large multinucleated cells involved in the breakdown of calcified bone and cartilage. Throughout a person's life, a change in the structure of this tissue occurs. Simultaneously with the decay process, the formation of new elements occurs at the site of destruction and in the periosteum. Osteoclasts and osteoblasts are involved in this complex cell replacement.
Bone tissue contains intercellular substance, consisting of the main amorphous substance. It contains ossein fibers that are not found in other organs. Connective tissue refers to tissue:
- coarse fibrous, present in embryos;
- lamellar, available in children and adults.
This type of tissue consists of such a structural unit as a bone plate. It is formed by cells located in special capsules. Between them there is a fine-fibrous intercellular substance, which contains calcium s alts. Ossein fibers, which are of considerable thickness, are arranged parallel to each other in the bone plates. They lie in a certain direction. At the same time, in neighboring bone plates, the fibers have a direction perpendicular to other elements. This ensures greater durability of this fabric.
Bone plates located in different parts of the body are arranged in a certain order. They are the building material of all flat, tubular and mixed bones. In each of them, the plates are the basis of complex systems. For example, a tubular bone consists of 3 layers:
- Outer, in which the plates on the surface are overlapped by the next layer of these structural units. However, they do not form complete rings.
- Medium, formed by osteons, in which bone plates are formed around blood vessels. At the same time, they are arranged concentrically.
- Internal, in which a layer of bone plates limits the space where the bone marrow is located.
Bones grow and regenerate thanks to the periosteum that covers their outer surface, consisting of connective fine-fibrous tissue and osteoblasts. Mineral s alts determine their strength. With a lack of vitamins or hormonal disorders, the calcium content is significantly reduced. The bones form the skeleton. Together with the joints, they represent the musculoskeletal system.
Diseases caused by weak connective tissue
Insufficient strength of collagen fibers, weakness of the ligamentous apparatus can cause serious diseases such as scoliosis, flat feet, joint hypermobility, prolapse of organs, retinal detachment, blood diseases, sepsis, osteoporosis, osteochondrosis, gangrene, edema, rheumatism, cellulite. Many experts attribute weakened immunity to the pathological condition of the connective tissue, since the circulatory and lymphatic systems are responsible for it.
