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Each lacuna is occupied during life by a branched cell, termed an osteocyte, bone-cell or bone-corpuscle. Lacunae are connected to one another by small canals called canaliculi. A lacuna never contains more than one osteocyte. Sinuses are an example of lacuna.
The cell body varies in size from 5–20 micrometers in diameter and contain 40–60 cell processes per cell, [4] with a cell to cell distance between 20–30 micrometers. [3] A mature osteocyte contains a single nucleus that is located toward the vascular side and has one or two nucleoli and a membrane. [ 5 ]
In bone, osteoclasts are found in pits in the bone surface which are called resorption bays, or Howship's lacunae. Osteoclasts are characterized by a cytoplasm with a homogeneous, "foamy" appearance. This appearance is due to a high concentration of vesicles and vacuoles. These vacuoles include lysosomes filled with acid phosphatase.
The Haversian canals surround blood vessels and nerve cells throughout bones and communicate with osteocytes (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculi. This unique arrangement is conducive to mineral salt deposits and storage which gives bone tissue its strength.
Diameter of canaliculi in human bone is approximately 200 to 900 nm. [1] In bovine tibia diameter of canaliculi was found to vary from 155 to 844 nm (average 426 nm). [ 2 ] In mice humeri it varies from 80 to 710 nm (average 259 nm), while diameter of osteocytic processes varies from 50 to 410 nm (average 104 nm).
Intra-cellular features are characteristic of a synthetically active cell. The cell density of full-thickness, human, adult, femoral condyle cartilage is maintained at 14.5 (±3.0) × 10 3 cells/ mm 2 from age 20 to 30 years. Although chondrocyte senescence occurs with aging, mitotic figures are not seen in normal adult articular cartilage.
The primary cells of cartilage are chondrocytes, which are in a matrix of fibrous tissue, proteoglycans and glycosaminoglycans. [2] [3] As cartilage does not have lymph glands or blood vessels, the movements of solutes, including nutrients, occur via diffusion within the fluid compartments contiguous with adjacent tissues. [2]
A primary ossification center is the first area of a bone to start ossifying. It usually appears during prenatal development in the central part of each developing bone. In long bones the primary centers occur in the diaphysis/shaft and in irregular bones the primary centers occur usually in the body of the bone. Most bones have only one ...