Ossification

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

Bone is a living tissue and made up of cartilage. Fibrodysplasia ossificans progressiva bone appears as normal bone tissue, but it develops in the wrong places. Osteogenesis and ossification are medical terms which refer to the formation of bone. Most bones in the human body grow and heal up after a break through endochondral bone formation, which is how FOP bones grow. Cartilage forms first and then the bone will eventually take the place of cartilage.

This is called a flare-up. These nodules often develop after a child experiences some sort of trauma to the body, such as a bump or fall. In most cases, the nodules transform into bone during a painful process known as heterotopic ossification (HEO). A flare-up is the first clinical indication of the tissue metamorphosis, which involves the catabolism of soft connective tissues (including aponeuroses, fascia, ligaments, tendons and skeletal muscles) and their replacement by extraskeletal bone through heterotopic ossification. When the body starts to generate this new bone, the patient usually experiences tissue swelling, joint stiffness and serious discomfort. These flare-ups can last as long as six to eight weeks and usually a small fever accompanies them. Heterotopic ossification is typically seen first in the dorsal, axial, cranial and proximal regions of the body, and later in the ventral, appendicular, caudal and distal regions. These lesions slowly replace the body's muscles with normal-looking

Bone is surrounded by a thin membranous layer of soft tissue called periosteum (Singh, 2017). When the bone breaks it bleeds from torn ends because of the disruption of the supplying blood vessels. And quite naturally the periosteum is also torn. A fracture hematoma forms and white blood cells march in to clean up the area that is injured. The periosteum is the primary source of osteoblasts, which plays a huge role in fracture healing (Singh, 2017). After the hematoma formation, the next step is callous formation with the formation of cartilage and bone and then the remodeling phase consisting of the osteoclasts and the osteoblasts reshaping the bone to its original state (Patton, 2012).

Heterotopic ossification(HO) is a condition that occurs when there is bone present in soft tissue. Heterotopic ossification is often caused after instances of musculoskeletal trauma, after an event that has caused injuries to the spine, or severe brain injury in some cases.

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

Bones never finish growing. It is renewed throughout life by a twopart remodeling process, resorption and formation. During resorption, osteoclast cells break down minerals and remove old bone tissue. During formation, osteoblast

Fibrodysplasia Ossification Progressiva is a rare connective tissue disorder that is characterized by development of bone in parts of the body it should not be present. It localized in most of the skeletal, muscular system affecting the joints of the body thus making their ROM difficult. FOP mesomorphs the soft connective tissue into bone and progressively degrades ROM and eventually locks the joints, making movement not an option, it starts with the neck, shoulders, elbows, hips, knees, wrists, and ankles, and most likely in that order. Some extreme cases the rib cage becomes a cocoon-like shell linking the ribs together.

Bone morphogenetic proteins and TGF-β are responsible for differentiation of MSCs into osteoblasts. Major bone forming cells is known as osteoblasts. They secrete bone proteins of the matrix, including osteocalcin, collagen type I (col-I) and osteonectin (52). They are also responsible for the mineralization of the matrix, via ALP (alkaline phosphatase) expressed on their surface.

Ossification is the transitional process through which cartilage and fibres form bone. The primary ossification centre is the initial site of bone formation in the shafts of long bone. At the primary ossification centre the osteoclast forms the bone marrow cavity and the osteoblast forms the bone. The secondary ossification centre occurs after the primary ossification centre is visible and ossification continues to occur at this site. The primary ossification centre occurs at the diaphysis and the secondary ossification centre occurs at the epiphysis. The primary ossification centre appears in week 8 of the intra uterine life and the secondary ossification centre appears during the first year of postnatal life. The diaphysis of the primary

Osteoblasts helpt the ossification of the bones and more in particularly the lengthening of the bones. Ossification is a development process taking place between 0 and 20 years to gradually harden and lengthen the bones. Young children have more flexible cartilage. Osteoblasts absorb calcium from the blood and lay it down as small plates in the cartilage in both directions. This causes the bone to

The first stage starts with osteoblastic activation of osteoclast differentiation, fusion, and activation. The second stage or reversal stage begins after the formation of resorption lacunae, since the osteoclasts leave the area and mononucleated cells of uncertain origin appear and “clean up” the organic matrix remnants left by the osteoclast. This stage takes about 2-4 weeks, and the third stage is when osteoblasts begin filling the lacunae with new bone and this stage takes between 4-6

The process of degeneration in Osteoarthritis is followed by more thickening of the subchondral bones, later new bone outgrowths at the joint margin which we call the osteophytes. Most of the patient will suffer from pain and impaired mobility, decrease in the muscle strength and limitation in daily life

This is done to regulate the onset of hypertrophic chondrocytes. First, the process starts off when the cranial neural cells proliferate and condense to make nodules in response to bone morphogenic protein (BMP) signals from the head epidermis. High levels of BMPs will make cartilage from the nodules. Low levels of BMP will produce pre-osteoblast progenitor cells that express the Runx2 transcription factor and mRNA for collagens 2 and 4. These cells will eventually downregulate Runx2 and begin expressing the osteopontin gene making it look like a cartilage cell, hence the name chondrocyte-like osteoblast. IHH and PTHrP will start receiving negative feedback signals telling them to stop chondrocyte differentiation. PTHrP, which is secreted from perichondrial cells and chondrocytes at the end of long bones, acts on receptors of the chondrocyte to keep them proliferating and delay the production of IHH. IHH is in charge of coordinating endochondral bone growth. IHH will induce patch and Gli proteins to then initiate synthesis of PTHrP, which will block the recruitment of more chondrocytes and reducing bone

The bones that are developed from endochondral ossification are referred to cartilaginous bones which occur in long bones and are essential during growth of lengthy bone. It proceeds via condensation of mesenchymal cells and gets differentiated into chondroblasts instead of osteoblasts. A cartilage template is produced by the activity of chondroblasts and serves as a template for the development of long bones such as femur and tibia. The cartilage template becomes surrounded by a membrane called perichondrium, which contains osteoprogenitor cells. As proliferation increases, the template begins to grow. The chondroblasts can secrete an extracellular matrix composed of collagen and proteoglycans. The chondroblasts