Exam 2 Review:  Chapter 6:  Osteon System

osteon = Haversian system - The structural unit for formation and remodeling of compact bone consisting of a series of concentric lamellae of bony matrix formed sequentially by sets of osteocytes located within lacunae in each layer of matrix which retains in the center a central canal containing areolar connective tissue, blood and lymphatic vessels and nerve fibers.  [See Figs. 6.5 & 6.6, pp. 182-183]

central canal = Haversian canal - The central compartment or tunnel in the osteon which contains areolar connective tissue, blood and lymphatic vessels and nerve fibers.

concentric lamellae - The thin cylindrical plates, or layers of bone matrix (produced by osteoblasts) around the minute vascular central canals in compact bone, which in cross-section produce a pattern of circles of different size, one within another, having a common center.

canaliculi - Any small canals or ducts in the body, such as the minute channels in compact bone through which extend the cytoplasmic processes of individual osteocytes such that the osteocytes are in contact with one another and with their capillary blood supply.

perforating canal = Volkmann's canal - Any compartment or tunnel which connects with and runs perpendicular to the central canal in an osteon (which also contains areolar connective tissue, blood and lymphatic vessels and nerve fibers) and serves as a connection between an osteon and the systemic circulation by connection to blood vessels in the periosteum, the endoosteum or a medullary space.

circumferential lamellae - The thin parallel plates, or layers of bone matrix (produced by osteoblasts) located just deep to the periosteum and just superficial to the endosteum which extend around the entire diaphysis of long bones and effectively resist twisting stresses exerted on the shaft.

interstitial lamellae - The thin plates, or layers of bone matrix (produced by osteoblasts) observed between osteons in compact bone, which in cross-section are variable in shape and orientation; these lamellae represent remnants of circumferential lamellae or earlier osteons partially replaced during remodeling.

Circumferential Lamellae are seen under the Periosteum of Compact Bone; their numbers will increase with Appositional Growth (growth in width).  Deeper in the Compact Bone you will see the pattern of osteons with their Concentric Lamellae.  Osteons are continually replaced by Bone Remodeling.

 1.