Bone Biology Medical Animation

       Bone is a highly specialized form of connective tissue which gives the body is shape and provides structural integrity for the systems contained within. The interior of bone is composed of bone marrow. It is surrounded by two major types of bone tissue; cortical bone (or compact bone), which forms the hard outer shell of bone, and trabecular bone, the spongy-looking center. Osteons are the functional subunits of compact bone and contribute to bone strength; these structures are composed of successive concentric lamellae, forming a series of tubes containing blood vessels and nerves known as Haversian canals.

       Bone is an active and dynamic tissue which is continually being built, broken down and rebuilt during the lifespan of an individual through a process known as bone remodeling. Bone remodeling is dependent on the balance of the principle cells of the bone tissue, osteoclasts and osteoblasts. Osteoclasts are derived from hematopoetic stem cells residing in the bone marrow and spleen which once stimulated become mononuclear cells which further differentiate into preosteoclasts, immature osteoclasts and ultimately mature osteoclasts in a manner dependent on the expression of a series of cytokines includingmacrophage colony stimulating factor (M-CSF) and receptor activator of nuclear factor κB (RANKL). Osteoclasts are the most abundant cells within the bone, actively removing bone through the secretion of acid and proteases in a process known as resorption. Meanwhile, the bone cell responsible for forming new bone tissue is known as the osteoblast, derived from pluripotent mesenchymal stem cells.Together, osteoclasts and osteoblasts assemble themselves into discrete temporary anatomic structures, known as basic multicellular units (BMUs) which carry out bone remodeling.Within the Haversian canal, osteoclasts form the leading edge or “cutting cone” of the BMU, excavating tunnels within the bone, approximately 250-300uM in diameter, and are followed by a group of mononuclear reversal cells, believed to prepare the exposed bone surface for deposition or newly formed bone. Osteoblasts then re-fill these tunnels, laying deposits of un-mineralized bone matrix known as osteoid. Remodeling of the trabecular bone, though sequentially similar to the process within the Haversian canal, involves the removal and replacement of pancake-like packets of bone, instead of the excavation and re-filling of tunnels within bone.

       In conclusion, bone is a dynamic tissue that is capable of self-repair that is continually remodeled during the course of an individual’s lifespan. Central to this process are bone cells known as osteoclasts and osteoblasts, which form temporary structures enabling the coupling of resorption and formation processes. A variety of factors can influence bone remodeling including mechanical loading, age and corticosteroid therapies which can result in perturbation of BMU dynamics subsequent metabolic bone disease.

Bone Biology


Osteoblasts and Osteoclasts animation
Bone is a living organ that is continuously being reshaped in a process called remodeling. In this process, cells called osteoclasts resorb bone tissues whereas cells called osteoblasts deposit new bone tissue. Osteoblasts can become trapped within the bone matrix they secrete, promoting their differentiation into osteocytes. These cells are thought to play an important role in sensing bone load. Under high loading conditions, osteoblasts increase bone mass, whereas under low loading conditions, osteoclasts remove bone tissue, optimizing its structure. This medical animation forms part of a series of nine animations that Random42 developed for an interactive website on the processes that occur within bone:


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bone body medical animation
This is an image of the thoracic cage which forms the core portion of the human skeleton- the skeleton forms part of the muscoskeletal system and also gives the body is shape and physical support for the systems contained within.
This is an image of an osteoclast; these cells are derived from monocytes within the bone marrow and are responsible for resorbing bone tissue; resulting in the release of calcium phosphate and other minerals during bone remodeling.
This is an image of the cell surface of an osteoclast; here osteoprotegerin (OPG), a decoy receptor for the receptor activator of nuclear factor kappa B (RANK) ligand whose production is stimulated by estrogen is shown bound to the RANK ligand.
This is an image of osteocytes, which are derived from osteoblasts which become embedded within the bone matrix and are found distributed within the concentric lamellae.