What´s Endochondral Ossification?

| - osteoblasts begin to replace the fibrocartilage splint with spongy and compact bone, forming a bulge that is initially wider than the original bony shaft

One of the key elements of regulating skeletal growth is the Osteoclasts. The Osteoclasts are responsible for initiating the bone remodeling cycle. Blood vessels and nerves are able to penetrate the bone once the chondrocytes die

Cartilage doesn’t contain any nerves or blood vessels and is surrounded by a layer of dense irregular connective tissue, the perichondrium (Marieb, 176). Bones contain various types of tissues which makes them organs. They are used for support, protection, movement, mineral storage, and blood cell formation (Marieb, 178-179).

The skeletal system is made up of cartilage and bone. Both bone and cartilage are connective tissues, that is, they are composed of cells in a matrix with intracellular fibers. Just imagine connective tissue as a gelatin salad with grapes and coconut. The grapes would represent cells, the gelatin the support material for matrix, and the pieces of coconut the intracellular fibers. By changing the amounts of each ingredient and adding extra substances, we can produce a material that is very hard like bone and can withstand weight or softer like cartilage which can be used as a cushioning material. In this exercise, we will examine a fresh raw chicken bone to study bone

Longitudinal bone growth occurs at the epiphyseal plate, which is a thin layer of cartilage between the epiphyseal and metaphyseal bone at the distal ends of the long bones. Bone growth is the result of maturation, growth of chondrocytes, their production of bone matrix, and finally calcification (47). The growth plate is a complex structure consisting of different layers of cells, as shown in figure 3. The most immature cells, the stem cells, are found towards the epiphyseal end of the growth plate in the stem cell zone, or resting zone; the proliferating zone contains more mature chondrocytes and the hypertrophic zone contains the larger chondrocytes. The resting stem cells in the resting zone are recruited, whereupon proliferation and differentiation

When the point of two or more bones comes together, it is called a joint. We are able to make a movement because the present of joints which are designed to allow movement and to assimilate shock from the movement such as running or walking. Furthermore, cartilage is an elastic and though tissue that covered the ends of the bones. The capsule act as protection centre which joints is surrounded by it. A type of tissue called synovium produces synovial fluid lined the joint capsule (Magro, C., M., and Crowson, A., N., 2003). The fluid is clear in substances that help the cartilage and bones inside the joint capsule easily lubricated and nourished. The disease process leading to rheumatoid arthritis begins here. The protective sac consists of lubricating liquid known as synovial fluid. Other than to cushioning joints, cartilage is a slippery tissue located at the ends of the bones also get nutrients and oxygen which is supplied by the fluids. Cartilage also is the structural protein in the body, which is composed primarily of collagen. The functions of this cartilage is form a mesh to give protection and flexibility to the joints. In rheumatoid arthritis, continuous inflammation of the synovium is occurred caused by an abnormal immune system response that secrete destructive molecules (Paleolog, 2002). As a result, collagen dramatically destroyed thus make the joint space

Otosclerosis is a disease of the bone of the middle and inner ear. The term is otosclerosis is derived from oto, meaning “of the ear” and sclerosis, meaning “abnormal hardening of body tissue.” Otosclerosis is caused when one of the bones in the middle ear, the stapes, becomes stuck in place. When the stapes is unable to vibrate, sounds are unable to travel through the ear and hearing becomes impaired.

Adding to the involvement of joint tissues, osteoarthritis has been characterized by a failure of the repair process of damaged cartilage due to changes in the joint. This leads to a formation of a matrix that cannot handle normal mechanical stress. Thus, the tissue enters a cycle in which degeneration dominates the makeup of extracellular

Osteoarthritis, also known as degenerative joint disease, affects around 26 million Americans (Litwic 2013). It is an inflammation of the joints resulting from cartilage degradation. Cartilage is a firm connective tissue that is made up of chondrocytes that produce an extracellular matrix made up of collagen fibers, chondroitin sulfate, and elastin fibers. It forms rapidly, but it is avascular so there are no blood vessels running through it to provide the chondrocyte cells with oxygen and nutrients. To obtain nutrients, the nutrients diffuse through a connective tissue that surrounds cartilage called the perichondrium, in order to reach the center of the cartilage. Due to this avascular factor, self-repair of cartilage is much slower than

The joint cartilage deteriorates and reactive new bone forms at the margins and sub Chandra areas of the joints. The degenerations results from damage to the Chandracytes. Cartilage softens with age narrowing the joint space. Mechanical injury erodes Articuler cartilage leaving the underlying bone unprotected this causes sclerosis or thickening and hardening of the bone underneath the cartilage. Cartilage particles irritate the synovial lining, which becomes fibrotic and limits joint movement. Synovial fluid may be forced into defects in the bone, causing cysts, newbone, called Osteophyte (bone spurs). Forms at joint margins as the Articular cartilage erodes, causing gross attention of the bony contours and enlargement of the joint.”

They undergo a mineralization process to calcify the bone into a harden material. First, the matrix of the bone, a mixture of both collagen and water, plus other organic components are first laid down first. Osteoblast cells secrete type 1 collagen, glycoproteins, proteoglycans, membrane-enclosed vesicles with alkaline phosphatase and toehr associated enzymes as well as a product known as osteoid into the matrix. The osteoblast secretions bind with calcium with high affinity and enzymes hydrolyze phosphate ions from various macromolecules creating a high concentration of ions. The high ion concetrations causes calcium phosphate crystals to form and grow to mineralize further into a compound known as hydroxyapatite. Hydroxoapatie surround collagen fibers and merge into a solid bony

Clavicular osteolysis is a type of shoulder injury. It happens in the area where the collarbone attaches to the top of the shoulder blade (acromioclavicular joint, or AC joint). Repeated stress may cause tiny breaks (microfractures) on the end of the collarbone (clavicle). This leads to loss of bone cells in the end of the clavicle.

The growth plates are a cartilaginous tissue found at the distal ends of the long bones between the metaphyseal and epiphyseal bone (Fig 1). They consist of three principal zones of chondrocytes: the resting zone, the proliferative zone and the hypertrophic zone, where the hypertrophic chondrocytes are the most differentiated (Fig 1) (16,17). Longitudinal bone growth of the long bones occurs at the growth plates through a process called endochondral ossification. In this process the chondrocytes proliferate, become more differentiated and finally become hypertrophic. The hypertrophic chondrocytes enlarge and secrete matrix proteins which form a scaffold for the formation of bone tissue (18). Terminal hypertrophic chondrocytes undergo apoptosis

The notochord, flexible rodlike structure of mesodermal cells that is the principal longitudinal structural element of chordates and of the early embryo of vertebrates, in both of which it plays an organizational role in nervous system development. In later vertebrate development, it becomes part of the vertebral column. The notochord derives during gastrulation (infolding of the blastula, or early embryo) from cells that migrate anteriorly in the midline between the hypoblast and the epiblast (inner and outer layers of the blastula). These cells coalesce immediately beneath the developing central nervous system. With the formation of the vertebral column, the notochord is incorporated into the column as the centres of the intervertebral discs, called the nuclei pulposi, which cushion the vertebrae This nucleus is later surrounded by circularly arranged fibers that form the anulus fibrosus. The anulus fibrosus and nucleus pulposus together constitute the intervertebral disc which is a soft tissue that made of fibrocartilaginous material. The annulus fibrosus is made of strong material of tightly packed parallel collagen type I fibrils. The inner aspect of the annulus fibrosus is poorly organized and contains both collagen type I and II and aggregating proteoglycans. Inside that protective covering is the nucleus pulposus which is a jelly-like substance known as mucoprotein gel. The nucleus of the disc acts as a shock absorber, absorbing the impact of the body's activities and keeping the two vertebrae separated. It is the remnant of the

Transforming growth factor is one of the earliest biological activity factors that can induce cartilage generation. It is initially described as a role in the proliferation and differentiation of chondrocytes. At the same time, it stimulates the expression of type II collagen and proteoglycan in MSCs and promotes chondrocyte proliferation , the ability to regulate MSCs differentiation and extracellular matrix synthesis. It has also been shown that TGF-β pretreatment of the periosteum of adult rabbit injury joints can improve the quality of osteogenesis in osteochondral tissue[44]. Zhang [45] also found that TGF-β can induce chondrogenic differentiation of stem cells, Stem cell chondrogenesis and overgrowth involving TGF-β pathway and IL-1β, dynamic pressure can induce cartilage formation and inhibit the excessive growth of cartilage.