Chondrocytes

cartilage matrix

No blood vessels, lymph, nerves

Cartilage matrix: collagen fibrils (type 2 collagen) and amorphous matrix (containing 3 types of glycosaminoglycans: polyhyaluronic acid, chondroitin sulfate and keratan sulfate, as well as a variety of glycoproteins)

Chondrocytes: rich rough endoplasmic reticulum and well-developed Golgi apparatus. Under the electron microscope, many protrusions and wrinkles can be seen on the surface. There are many glycogen and lipid droplets. They mainly obtain energy through glycolysis.

Except for articular cartilage and retroosseous cartilage, hyaline cartilage is surrounded by a thin layer of dense connective tissue called perichondrium.

The surface is smooth, with synovial fluid attached, and is elastic, which can reduce friction during joint movement. Osteoarthritis: Decreased type 2 collagen, proteoglycans, and water in articular cartilage, while increased matrix metalloproteinases

Organic matter: a large amount of collagen fibers (type 1 collagen) and a small amount of amorphous matrix, containing macromolecular proteoglycans and various glycoproteins

Inorganic matter: bone salts (calcium, magnesium, phosphorus, etc.), mainly in the form of hydroxyapatite crystals

In the bone matrix of lamellar bone, collagen fibers are thin, regularly arranged in layers, and closely combined with bone salt crystals and matrix to form bone plates. The fibers of two adjacent bone plates are perpendicular to each other.

Osteoprogenitor cells: differentiated from mesenchymal cells, actively divide and differentiate into osteoblasts when bone tissue grows and remodels or when fractures heal.

Osteoblasts: Active secretion function, synthesize and secrete collagen fibers and organic matrix, form unmineralized extracellular matrix called osteoid, also secrete some growth factors and cytokines, regulate bone formation, absorption, metabolism

Osteocytes (embedded in the bone matrix, others located on the surface of the bone tissue): individually dispersed between or within the bone plates, gap junctions, have osteogenesis and osteolysis, play an important role in Ca2 balance, and are sensitive to growth hormone

bone covering cells

Osteoclasts: located in resorption pits, multinucleated eosinophils, microfilaments, ruffled edges, lysosomes, capable of dissolving and absorbing bone matrix, participating in bone reconstruction and maintaining blood calcium balance, sensitive to calcitonin and parathyroid hormone

ring bone plate

bone unit

interosseous plate

Main function: protect and nourish bone tissue and provide new osteoblasts for bone growth or repair