Osteocyte

An osteocyte, a star-shaped cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...

, is the most abundant cell found in compact bone

Bone

Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

. Cells contain a nucleus

Nucleus

Nucleus may refer to:*the Atomic nucleus,*Cell nucleus, the control center of a cell, which contains the cell's chromosomal DNA-Other science uses:*Nucleus , a central nervous system structure composed mainly of gray matter* In linguistics:...

 and a thin ring of cytoplasm. When osteoblast

Osteoblast

An osteoblast is a mononucleate cell that is responsible for bone formation. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix...

s become trapped in the matrix they secrete, they become osteocytes. Osteocytes are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi

Canaliculus (bone)

Canaliculi are microscopic canals between the various lacunae of ossified bone. The radiating processes of the osteocytes project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do not entirely fill up the canaliculi. The remaining space is known...

, which are used for exchange of nutrients and waste. The space that an osteocyte occupies is called a lacuna

Lacuna (histology)

In histology, a lacuna is a small space containing an osteocyte in bone or chondrocyte in cartilage.-Bone:The Lacunæ are situated between the lamellæ, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots...

 (Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...

 for a pit).

An osteocyte, a star-shaped cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...

, is the most abundant cell found in compact bone

Bone

Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

. Cells contain a nucleus

Nucleus

Nucleus may refer to:*the Atomic nucleus,*Cell nucleus, the control center of a cell, which contains the cell's chromosomal DNA-Other science uses:*Nucleus , a central nervous system structure composed mainly of gray matter* In linguistics:...

 and a thin ring of cytoplasm. When osteoblast

Osteoblast

An osteoblast is a mononucleate cell that is responsible for bone formation. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix...

s become trapped in the matrix they secrete, they become osteocytes. Osteocytes are networked to each other via long cytoplasmic extensions that occupy tiny canals called canaliculi

Canaliculus (bone)

Canaliculi are microscopic canals between the various lacunae of ossified bone. The radiating processes of the osteocytes project into these canals. These cytoplasmic processes are joined together by gap junctions. Osteocytes do not entirely fill up the canaliculi. The remaining space is known...

, which are used for exchange of nutrients and waste. The space that an osteocyte occupies is called a lacuna

Lacuna (histology)

In histology, a lacuna is a small space containing an osteocyte in bone or chondrocyte in cartilage.-Bone:The Lacunæ are situated between the lamellæ, and consist of a number of oblong spaces. In an ordinary microscopic section, viewed by transmitted light, they appear as fusiform opaque spots...

 (Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...

 for a pit). Although osteocytes have reduced synthetic activity and, like osteoblasts are not capable of mitotic division, they are actively involved in the routine turnover of bony matrix, through various mechanosensory mechanisms. They destroy bone through a rapid, transient (relative to osteoclast

Osteoclast

An osteoclast is a type of bone cell that removes bone tissue by removing its mineralized matrix and breaking up the organic bone . This process is known as bone resorption...

s) mechanism called osteocytic osteolysis.  Osteoblasts/osteocytes develop in mesenchyme

Mesenchyme

Mesenchyme, or mesenchymal connective tissue, is an example of reticular connective tissue, a type of loose connective tissue, which is derived from all three germ layers and located within the embryo . Mesenchyme is characterized morphologically by a prominent ground substance matrix containing a...

. Hydroxyapatite

Hydroxylapatite

Hydroxylapatite, also called hydroxyapatite, is a naturally occurring mineral form of calcium apatite with the formula Ca₅₃, but is usually written Ca₁₀₆₂ to denote that the crystal unit cell comprises two entities. Hydroxylapatite is the...

, calcium carbonate and calcium phosphate is deposited around the cell.

External links

• - "Cartilage and Bone and Bone Histogenesis: cells of* - "Cartilage and Bone and Bone Histogenesis: compact bone"* Histology at ou.edu