Classification of bones

The basis of the classification of bones laid down the following principles: the form (the structure of the bones), their development and function. Distinguish the following groups of bones: long (tubular), short (spongy), flat (broad), mixed (abnormal) and airborne.

Long bones form a solid limb base. They perform the functions of long bony levers. These bones are in the form of tubes. The diaphysis (the body of the bone) is usually cylindrical or trihedral. Thick ends of a long tubular bone are called epiphyses. On the epiphyses are articular surfaces covered with articular cartilage.

Epiphyses participate in the formation of connections with adjacent bones. A section of bone located between the diaphysis and the epiphysis is called a metaphysis. This section of bone corresponds to the epiphyseal cartilage, which is stiffened in the course of postnatal development, located between the diaphysis and the epiphysis. Due to the metaphyseal cartilage zone, the bone grows in length. Among the tubular bones it is customary to allocate long (humeral, femoral, etc.) and short (metacarpal and metatarsal) bones.

Short, or spongy, bones are located in those parts of the skeleton where significant bone mobility is combined with a large mechanical load (carpal and tarsal bones). To short bones also include sesamoid bones located in the thickness of some tendons. Sesamovidnye bones like a kind of blocks increase the angle of attachment of the tendon to the bone and, accordingly, the force of muscle contraction.

Flat bones form cavity walls, perform protective functions (bones of the skull, pelvis, sternum, rib). These bones have significant surfaces for the attachment of muscles.

Mixed bones are built complex, their parts are similar in appearance to different in form bones. Thus, in the vertebra, for example, his body is referred to spongy bones, processes and an arc - to flat bones.

Airborne bones contain cavities lined with mucous membranes and filled with air. Such cavities have some bones of the skull (frontal, wedge-shaped, latticed, temporal, maxillary). The presence of cavities in the bones facilitates the mass of the head. Cavities also serve as a voice resonator.

On the surface of each bone there are irregularities. This is the place of the beginning and attachment of muscles, fasciae, ligaments. Elevations, appendages, hillocks are called apophyses. Their formation is facilitated by the traction of muscle tendons. In areas where the muscle is attached with its fleshy part, there are usually depressed areas (pits).

In places where the vessels or nerves adhere, there are furrows and cuttings on the surface of the bone. Triangular tubular bones denote pointed edges and flat surfaces between them, near the flat bones, edges, corners, and also surfaces are distinguished.

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