Gives Shape and support to our body

In most vertebrate animals, a bone is a stiff organ that is a component of the skeleton. Bones protect the body’s other organs, create red and white blood cells, store minerals, provide the body structure and support, and allow for motion. Bones have a complicated internal and exterior structure that comes in a range of forms and sizes. They’re light but tough, and they’re useful for a variety of things.

Bone tissue (osseous tissue), is a form of specialised connective tissue that is hard tissue. Internally, it comprises a honeycomb-like structure that aids in bone stiffness. Different kinds of bone cells make up bone tissue. Osteoblasts and osteocytes play a role in the production and mineralization of bone, whereas osteoclasts play a role in bone tissue resorption. Bone tissue is made up of two forms of mineralized tissue: cortical bone and cancellous bone. Bone marrow, endosteum, periosteum, nerves, blood vessels, and cartilage are among the other forms of tissue present in bones.

There are around 300 bones in the human body at birth; many of them fuse together throughout growth, leaving a total of 206 different bones in the adult, not including several tiny sesamoid bones. The femur, or thighbone, is the biggest bone in the body, while the stapes, or middle ear bone, is the smallest.

Structure of Bones

Bone is not evenly solid; instead, it is made up of a flexible matrix (30%) and bonded minerals (70%) that are intricately braided and continually reshaped by a group of specialised bone cells. Bones are quite robust and sturdy while being lightweight due to their unique composition and design.

The elastic collagen fibres, also known as ossein, make up 90 to 95 percent of the bone matrix, with the rest being pulverised material.

Collagen’s flexibility promotes fracture resistance. The binding of an inorganic mineral salt, calcium phosphate, in a chemical arrangement known as calcium hydroxylapatite hardens the matrix. Bone mineralization is what gives bones their stiffness. The tissue is braided into two primary patterns inside a single bone, known as cortical and cancellous bone, each having its unique look and properties.

Cortex

Cortical bone, often known as compact bone because it is significantly denser than cancellous bone, makes up the hard outer layer of bones. It is responsible for the hard outer layer (cortex) of bones. The cortical bone, which accounts for 80% of the total bone mass in an adult human skeleton, gives bone its smooth, white, and solid look. It helps bones perform their primary activities, which include supporting the entire body, protecting organs, providing mobility levers, and storing and releasing chemical components, mostly calcium. 

Trabeculae

Cancellous bone, also known as trabecular or spongy bone, is an open cell porous network that makes up the interior tissue of the skeletal bone. Cancellous bone is less dense and has a larger surface-area-to-volume ratio than cortical bone. It becomes weaker and more flexible as a result of this. It is also ideal for metabolic processes such as the exchange of calcium ions due to its larger surface area. Cancellous bone is most commonly seen around joints, at the extremities of long bones, and in the inside of vertebrae. 

Marrow

In red bone marrow, bone marrow is also known as myeloid tissue. It may be found in basically any bone that has cancellous tissue. All such bones are loaded with red marrow or hematopoietic marrow in new-borns, but as the child grows older, the hematopoietic fraction diminishes in amount and the fatty/ yellow portion known as Marrow Adipose Tissue (MAT) rises. In adults, red marrow is usually present in the femur, ribs, vertebrae, and pelvic bones’ bone marrow. 

Deposition

Osteoblasts, which produce both collagen and ground material, lay down the extracellular matrix of bone. These secrete collagen fibrils after synthesising collagen within the cell. Collagen fibres polymerize quickly to create collagen strands. They are called “osteoid” because they have not yet been mineralised. Calcium and phosphate precipitate on the surface of the strands, turning into hydroxyapatite crystals within days to weeks. 

Types of Bones 

• Long bones have a diaphysis (shaft) that is significantly longer than its breadth, as well as an epiphysis (rounded head) at either end of the shaft. They are largely compact bones, with a little quantity of marrow in the medullary cavity and spongy, cancellous bone at the ends. 
• Short bones are generally cube-shaped and contain a spongy centre surrounded by a thin shell of compact bone. Wrist and ankle bones are both short bones.
• Flat bones have two parallel layers of solid bone sandwiching a layer of spongy bone. They are thin and typically curved. The sternum, like the majority of the bones in the cranium, is a flat bone. 
• Sesamoid bones are tendons-encased bones. Because they operate to pull the tendon away from the joint, the angle of the tendon is increased, increasing the muscle’s leverage. The patella and the pisiform are two sesamoid bones. 
• Irregular bones do not fall into any of the categories listed above. They are made up of thin layers of compact bone that surround a spongy centre. Their forms are irregular and intricate, as the name implies. 

Conclusion

Our body’ structure is provided by bones. There are 206 bones within the mature human skeleton. Bones are composed of connective tissue that is calcium-reinforced, as well as specialised bone cells. Most bones are found with a bone marrow which helps in producing blood cells. Bones cooperate with muscles and joints to stay our bodies together and permit us to maneuver freely. The musculoskeletal system is what it’s called. Brain, heart, and lungs are sensitive organs protected by the skeleton while supporting and shaping the body. Bones contain the majority of our calcium supply. The body is continually constructing and destroying bone tissue as required. For bone health, Exercising, a balanced diet and the proper levels of several hormones are necessary.