11. Bone
It is a mineralized connective tissue that exhibits four types of cells namely osteoblasts, bone lining cells, osteocytes, and osteoclasts. Bones have many functions. They support the body structurally, protect our vital organs, and allow us to move. Also, they provide an environment for bone marrow, where the blood cells are created, and they act as a storage area for minerals, particularly calcium. Bones are mostly made of the protein collagen, which forms a soft framework. The mineral calcium phosphate hardens this framework, giving it streghth. It is divided into Compact Bone (cortical) – a hard outer layer that is dense, strong and durable, and Cancellous Bone (trabecular or spongy) – consists of a network of trabeculae or rod-like structures. It is lighter, less dense, and more flexible.
Bone tissue is continuously remodeled through the concerted actions of bone cells, which include bone resorption by osteoclasts and bone formation by osteoblasts, whereas osteocytes act as mechanosensors and orchestrators of the bone remodeling process under the control of (e.g growth factors, cytokines, calcitonin, and estrogen)