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These bones are located just beyond the wrist and serve as a link to the phalanges, or finger bones, at the end of the limbs. In the lower body, the femur is a prominent bone positioned between the hip and knee. As the longest bone in the human body, it plays a pivotal role in forming the upper part of the knee joint.
Bone is broken down by osteoclasts, and rebuilt by osteoblasts, both of which communicate through cytokine (TGF-β, IGF) signalling. Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. [1]
That bone marrow is a priming site for T-cell responses to blood-borne antigens was first described in 2003. [13] Mature circulating naïve T cells home to bone marrow sinuses after they have passed through arteries and arterioles. [14] They transmigrate sinus endothelium and enter the parenchyma which contains dendritic cells (DCs).
The primary center of ossification is the area where bone growth occurs between the periosteum and the bone. Osteogenic cells that originate from the periosteum increase appositional growth and a bone collar is formed. The bone collar is eventually mineralized and lamellar bone is formed.
Bone tissue is removed by osteoclasts, and then new bone tissue is formed by osteoblasts. Both processes utilize cytokine (TGF-β, IGF) signalling.In osteology, bone remodeling or bone metabolism is a lifelong process where mature bone tissue is removed from the skeleton (a process called bone resorption) and new bone tissue is formed (a process called ossification or new bone formation).
The long bone category includes the femora, tibiae, and fibulae of the legs; the humeri, radii, and ulnae of the arms; metacarpals and metatarsals of the hands and feet, the phalanges of the fingers and toes, and the clavicles or collar bones. The long bones of the human leg comprise nearly half of adult height.
A long bone is one that is cylindrical in shape, being longer than it is wide. However, the term describes the shape of a bone, not its size, which is relative. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges).
Osteochondroprogenitor cells are progenitor cells that arise from mesenchymal stem cells (MSC) in the bone marrow. They have the ability to differentiate into osteoblasts or chondrocytes depending on the signalling molecules they are exposed to, giving rise to either bone or cartilage respectively.