Osteon is the structural unit of bone: structure and function

There are about 206 bones in the human body, but few know their structure and understand why they are so strong. But the main role in this plays osteon. These are the structural units of which the bones of extremities, ribs, vertebrae, etc. are built. He also has one more name - the Havers system.

Structure of the 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 - hematopoiesis, micronutrient metabolism, reserve (reserve of fat). Mainly have the following structure - special cells of bone and intercellular substance, outer covering (periosteum), and in the inner part is located bone marrow.

Any bone consists of two components - a compact and spongy substance. The first is located on the periphery, the second - in the center, and consists of bone beams located not chaotically, but in strict accordance with the external impact 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 impact, only organic substances remain in the bone, and the bone looks like a sponge in appearance and touch.

Among organic substances, fats, mucoproteins, glycogen and collagen fibers (represented by ossein, ossseomucoid, elastin) can be isolated. If the bone is burned, its shape will be preserved, but it will become fragile and easily crumble when pressed.

It is the combination of substances of different origin that makes the bone firm, firm, but at the same time elastic.

Types of bones

By difference in the structure are divided into:

• Tubular. There are long and short. Consist of two epiphyses and diaphysis, the shape is triangular or cylindrical;
• Spongy - mainly 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 complex shape. There are different in form and function. For example, the thoracic vertebra consists of three parts - a body, an arc and an appendage.

Cellular structure of bone

Having examined bone tissue at the cellular level, we can distinguish three basic forms of cells that differ in structure and fulfill their functions:

1. Osteoblasts are young large cells that have a mesenchymal origin. Cylindrical form, the nucleus is located eccentrically. 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.
2. Osteocytes are the next stage in the development of osteoblast bone cells, they are found in the bone, which has already ceased to develop. The body of the cell 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 denser. The cell seems to be immured in the mineralized substance intercellular (lacunae).
3. Osteoclasts are large cells, the size of which can reach more than 80 microns. The nucleus is not one, but several, since they are formed from several, merged macrophages. Since the osteoclast is in constant motion, its shape is constantly changing. From the side of the bone that you need to destroy, there are numerous processes on the cell that seem to "dissolve" the bone, taking all the salts out of it and destroying the matrix.

These three types of cells, together with the amorphous substance and the ossein fibers located in the free space, are arranged and form plates, in turn, forming osteons, intercalary and general plates.

Structural structure of bone

Diaphysis consists of two structural units: Havers system, or osteon, is the main part - and intercalary plates. The structure of the osteon is very complicated. The bone plates are folded into cylinders of different diameters. These cylinders are nested inside each other, and in the center passes the so-called Havers channel. In this channel, the nerves and blood vessels pass.

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 from the bloodstream of the periosteum, and then passes into the bone marrow spermatozoa. Parallel to the blood vessels there are also nerve endings.

There is any osteon, photo evidence, in the tubular bone parallel to the long side, and in the spongy - perpendicular to the force of compression and stretching.

Each bone is built from its individual number of units such as 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 load on compression when walking, the number of havers systems in it is 1.8 pcs. Per square millimeter. And 11% is the share of Havers channels.

Osteons are always separated by intermediate plates (they are also called intercalary plates). It is nothing but a broken bone osteon that has become unusable for one reason or another. After all, the process of destruction and construction of new Havers systems is constantly going on in the bones.

Functions of osteon

We list the functions of osteon:

• The basic building unit of bone tissue;
• Gives strength;
• Protection of the nerve end and vessel carrying blood.

It becomes clear that osteon is a structure that performs one of the main roles in our movement, without it the skeleton could not fulfill its direct purpose - to maintain organs, tissues and the body in space.