They are stem cells of bone tissue and are located in the inner layer of epiosseum and endosteum.

The cells are small, spindle-shaped, with oval or elongated nuclei and less cytoplasm, which is weakly alkaline.

Can differentiate into osteoblasts and chondroblasts

Arranged in a single layer on the surface of bone tissue. The cell body is short columnar or cuboidal, with small protrusions on the cell surface, round nucleus, and basophilic cytoplasm.

It synthesizes and secretes organic components in the bone matrix to form osteoid, and itself is embedded in it and transforms into bone cells. Osteoblasts also secrete a variety of cytokines to regulate the formation, absorption and metabolism of bone tissue.

The cell body is flat oval or star-shaped, with few organelles, and the nucleus is round or oval, centered.

The spaces where bone cells are located are called bone lacunae; the spaces occupied by protrusions are called bone canaliculi

Osteocytes participate in calcium and phosphorus metabolism

Distributed at the edge of bone tissue, it is a multinucleated giant cell (mononuclear phagocyte system) formed by the fusion of multiple blood monocytes. The cell body is large, with wrinkled edges (microvilli) formed on the bone side; the number of nuclei ranges from 2 to 50, and the cytoplasm is eosinophilic.

Osteoclasts release a variety of hydrolases and organic acids, which can dissolve and absorb bone matrix and participate in the process of bone growth and reconstruction.

Organic ingredients (osteoid)

Inorganic ingredients (bone salts)

The various components of bone matrix together form a thin lamellar structure

The collagen fibers in the same bone plate are parallel to each other, and the fibers between adjacent bone plates are vertical. This structure increases the strength of the bone.

In the backbone of long bones, as well as on the surface of long bone epiphyses, short bones, flat bones and irregular bones, the bone plates are arranged regularly and have many layers.

Inside the epiphyses of long bones, short bones, flat bones and irregular bones, layers of irregular bone plates form a large number of needle-like or lamellar bone trabeculae. They are criss-crossed to form a porous three-dimensional network structure, forming cancellous bone.

They are bone plates arranged around the inner and outer surfaces of the backbone, and are called inner ring bone plates and outer ring bone plates respectively. The outer ring bone plates are thicker and arranged more neatly around the backbone; the inner ring bones are thinner and arranged irregularly.

Located between the inner and outer ring bone plates, it is the main supporting unit of long bones.

Each bone unit is cylindrical and consists of 10 to 20 layers of Haversian bone plates arranged in concentric circles surrounding a central canal (Haversian canal).

The central canal is connected to the perforating canal, its wall contains periosteum tissue, and its lumen contains capillaries and nerves.

In the cross-sectional specimen of the bone unit, there is a strong refractive contour line, which is a bonding line.

It is an irregular bone plate located between bone units or between bone units and ring bone plates.

Outer layer

inner layer

Lining the perforating canal, central canal, medullary cavity surface and trabecular bone surface, it is composed of a layer of flat osteoprogenitor cells and a small amount of connective tissue