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. He has one more name - Haversian system.
Bone structure
Only due to the combined 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, exchange of microelements, storage (fat reserve). Mostly they have the following structure - special bone cells and intercellular substance, the outer coating (periosteum), and the bone marrow is located in the inner part.
Any bone consists of two components - compact and spongy. The first is located on the periphery, the second - in the center, and consists of bone bars not located randomly, but in strict accordance with the external effect on the bone in a particular area.
Bone composition
The combination of organic (30-40%) and inorganic (60-70%) substances is a feature of the composition of the skeleton. Inorganic substances include salts of different chemical composition: phosphate and calcium carbonate, magnesium sulfate and others. All of them dissolve in acids, after its exposure only organic substances remain in the bone, and the bone in appearance and touch resembles a sponge.
Fats, mucoproteins, glycogens and collagen fibers (represented by ossein, osseomucoid, elastin) can be distinguished from organic substances. If the bone is burned, its shape will be preserved, but it will become brittle and when crushed, it will easily crumble.
It is a 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 and short. Consist of two epiphyses and diaphysis, the shape is trihedral or cylindrical;
- spongy - composed mainly of spongy tissue surrounded by solid matter;
- flat. They are two flat plates between which a spongy substance, for example, a scapula bone, is located;
- mixed. Bones, consisting of several parts of complex shape. They are different in form and function. For example, the thoracic vertebra consists of three parts - the body, the arch and the appendix.
Bone structure
Having examined 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 that are of mesenchymal origin. The cylindrical shape, the core is eccentric. Each cell has a process to come into contact with 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 bone cells of osteoblasts; they are found in the bone, which has already stopped developing. The cell body is small compared to osteoblasts, and the number of processes is large, and can vary even in the same bone. The nucleus also decreased in size and became more dense. The cell is as if walled up in the intercellular mineralized substance (lacunae).
- Osteoclasts are large cells whose sizes can reach more than 80 microns. There are not one, but several nuclei, since they are formed from several macrophages merged together. 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 “dissolve” the bone, taking all salts 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, insertion and general plates.
Bone structure
The diaphysis consists of two structural units: the Haversian system, or osteon - this is the main part - and insertion plates. The structure of osteon is very complex. Bone plates are folded into cylinders of different diameters. These cylinders are nested in each other, and in the center passes the so-called Haversian channel. Nerves and blood vessels pass through this channel.
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 to all osteons originates precisely from the circulatory network of the periosteum, and then passes into the vessels of the bone marrow. Parallel to the blood vessels are nerve endings.
Any osteon is located, photo of which is confirmed, in the tubular bone parallel to the long side, and in the spongy bone - perpendicular to the compressive and tensile forces.
Each bone is built from its individual number of units such as osteon, biology justifies this structure by the fact that the load on each of them is different. The femur is subjected to a large compression load when walking, the number of havers systems in it is 1.8 pcs. per square millimeter. Moreover, 11% is the share of Haversian canals.
Osteons are always separated by intermediate plates (they are also called insertion plates). This is nothing more than a destroyed osteon of the bone, which became unusable for one reason or another. Indeed, the process of destruction and construction of new havers systems is constantly going on in the bones.
Osteon functions
We list the functions of osteon:
- the basic building unit of bone tissue;
- gives strength;
- protection of the nerve ending and blood vessel.
It becomes clear that osteon is a structure that performs one of the main roles in our movement; without it, the skeleton would not be able to fulfill its direct purpose - to maintain organs, tissues and body in space.