There are approximately 206 bones in the human body, but few people know their structure and understand why they are so strong. But the main role in this is played by osteon. These are the structural units from which the bones of the limbs, ribs, vertebrae, etc. are built. It has another name - the Haversian system.
Structure of bone
Only because of the joint action of the skeleton and muscles of our body, we are able to move, and this is their main function. There are, of course, additional ones - hematopoiesis, microelement metabolism, storage (fat reserve). They mainly have the following structure - special bone cells and intercellular substance, the outer covering (periosteum), and the bone marrow is located in the inner part.
Any bone consists of two components - compact and spongy substance. The first is placed along the periphery, the second - in the center, and consists of bone crossbars, located not randomly, but in strict accordance with the external influence on the bone in a particular area.
Composition of bone
Combination of organic (30-40%) and inorganic (60-70%)substances is a feature of the composition of the skeleton. Inorganic substances include s alts of different chemical composition: calcium phosphate and carbonate, magnesium sulfate and others. All of them dissolve in acids, after its impact only organic substances remain in the bone, and the bone looks and feels like a sponge.
Fats, mucoproteins, glycogens and collagen fibers (represented by ossein, osseomucoid, elastin) can be isolated from organic substances. If the bone is burned, its shape will be preserved, but it will become brittle and easily crumble when pressed.
It is the combination of substances of different origin that makes the bone hard, strong, but at the same time elastic.
Types of bones
By difference in structure they are divided into:
- tubular. There are long ones and short ones. Consist of two epiphyses and a diaphysis, the shape is trihedral or cylindrical;
- spongy - consisting mainly of spongy tissue surrounded by a solid substance;
- flat. They are two flat plates, between which there is a spongy substance, for example, the bone of the scapula;
- mixed. Bones, consisting of several parts of a complex shape. They vary in form and function. For example, the thoracic vertebrae consists of three parts - the body, the arch and the process.
Cellular structure of bone
Having examined the bone tissue at the cellular level, we can distinguish three main forms of cells that differ in structure and perform their functions:
- Osteoblasts are young large cells,which are of mesenchymal origin. Cylindrical shape, the core is located eccentrically. Each cell has a process to contact neighboring osteoblasts. The main functions are to synthesize the intercellular substance and be responsible for its mineralization.
- Osteocytes are the next stage in the development of osteoblast bone cells, they are found in bone that has already ceased to develop. The cell body is small compared to osteoblasts, and the number of processes is large, and can vary even in the same bone. The core also decreased in size and became more dense. The cell seems to be walled up in a mineralized intercellular substance (lacunae).
- Osteoclasts are large cells that can be over 80 microns in size. The nuclei are not one, but several, since they are formed from several macrophages that have merged with each other. Since the osteoclast is in constant motion, its shape is constantly changing. On the side of the bone that needs to be destroyed, there are numerous processes on the cell that seem to “resorb” the bone, taking all the s alts from it and destroying the matrix.
These three types of cells, together with amorphous matter and ossein fibers located in free space, are ordered and form plates, which in turn form osteons, intercalary and general plates.
Structural structure of bone
The diaphysis consists of two structural units: the Haversian system, or osteon, is the main part - and insertion plates. The structure of the osteon is very complex. Bone platesrolled into cylinders of different diameters. These cylinders are nested in each other, and in the center there is a so-called Haversian channel. Nerves and blood vessels pass through this canal.
Osteon is not a separate structural unit, it repeatedly anastomoses between other units, as well as with the periosteum and vessels of the bone marrow. After all, the blood supply of all osteons originates precisely from the circulatory network of the periosteum, and then passes into the blood vessels of the bone marrow. Nerve endings run parallel to the blood vessels.
Any osteon is located, photo confirmation of this, in the tubular bone parallel to the long side, and in spongy bones - perpendicular to the force of compression and stretching.
Each bone is built from its individual number of units such as the osteon, biology justifies such a structure by the fact that the load on each of them is different. The femur is subjected to a large compressive load when walking, the number of Haversian systems in it is 1.8 pcs. per square millimeter. Moreover, 11% is the share of Haversian channels.
Osteons are always separated by intermediate plates (they are also called intercalary). This is nothing more than a destroyed bone osteon that has become unusable for one reason or another. After all, the process of destruction and construction of new Haversian systems is constantly going on in the bones.
Osteon functions
Let's list the functions of the osteon:
- basic building block of bone tissue;
- gives strength;
- protectionnerve ending and blood vessel.
It becomes clear that the osteon is a structure that plays one of the main roles in our movement, without it the skeleton could not fulfill its intended purpose - to support organs, tissues and the body in space.
