What is a Bone

In several vertebrate animals, a bone is a hard structure, which is part of the skeleton. Bones protect the body’s major organs, generate red and white blood cells, contain minerals, offer structural support, and allow mobility to the human body. Bones have a complicated internal and exterior structure and exist in various forms and sizes. They are lightweight, while also being sturdy and durable, and they perform various tasks.

Bone is living tissue that makes up the skeleton of the human body. There are three forms of bone tissue, which include:

• Cancellous tissue
  These are sponge-like tissues that are present inside the bones.
• Compact tissue
  This is the outer, harder tissue of bones.
• Subchondral tissue
  This is the smooth tissue at the end of the bones which is covered with another type of tissue, called cartilage. Cartilage is a specialised and flexible connective tissue found in adults. It is a type of tissue from which most bones develop, during the infant or child stage of development.

There are around 300 bones in the human body at birth, but many of them fuse during 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, located in the middle ear, is the smallest.

Bones are composed of a structure of protein called collagen, and a mineral called calcium phosphate, which hardens and strengthens the structure. While other body parts require calcium, bones release some of it into circulation. Some vitamins and minerals, particularly vitamin D and calcium, directly impact how much calcium is stored in the bones.

Bone Tissue

Bone tissue (also called osseous tissue), commonly known as bone in the plural form, is a specific subset of connective tissue, that is hard tissue. Internally, it has a honeycomb-like structure that contributes to the rigidity of the bone. Different kinds of bone cells make up bone tissue.

Osteoblasts and osteocytes are engaged in bone production and mineralization, while osteoclasts are involved in bone resorption. Modified (flattened) osteoblasts are transformed into liner cells that form a protective cover on the surface of the bone.

The mineralized structure of bone tissue contains an organic component, primarily collagen, known as ossein, and an inorganic element of bone mineral composed of different salts. Bone tissue is mineralized tissue, which has two varieties: cortical bone and cancellous bone. Marrow, endosteum, nerves, periosteum, blood vessels, and cartilage are all tissue forms that are present in bones.

Functions of a Bone

These are the functions of a bone:

• Bones shape and support the body, as well as protect various organs. Bones also function as a mineral storage site and the medium (marrow) to create and store blood cells.
• Bones function as mineral stores for the body, particularly calcium and phosphorus.
• Bone marrow is found in the ligamentous region of bones. Haematopoiesis is the process through which bone marrow generates blood cells. The bone marrow produces red blood cells, platelets, and white blood cells.
• Bones perform several mechanical purposes. The skeleton is made up of the bones in the body. They serve as a framework for the body and a connection site for skeletal muscles, ligaments, tendons, and joints, all of which work together to create and transfer forces, allowing individual body parts, or the entire body, to be moved in a three-dimensional environment.
• Phosphate metabolism is controlled by the bone through the release of fibroblast growth factor 23 (FGF-23), which works on the kidneys to limit phosphate reabsorption.
• Toxic substances and other foreign elements can also be stored in bone tissues, eliminating them from circulation and limiting their effects on other tissues. These might be progressively released for excretion later on and thus, helps in detoxification.

Bone Diagram

This bone diagram will provide an illustration of the human skeleton and will help us visually understand the functions of different bones:

Different Types of Bone Cells

The different types of bone cells are:

• Hematopoietic
  This is a type of bone cell found inside the bone marrow. Its main function is to produce white blood cells, red blood cells, and platelets. 
• Osteoclast
  This is a very large cell formed inside the bone marrow. Its main function is to remove and absorb unwanted tissues.
• Osteoblast
  This is found inside the bone, and its function is to create new bone tissues.
• Osteocyte
  This is a type of bone cell found inside the bone. Its main function is to help maintain the bone as living tissue.

Bone Pain Causes

Bone cancer is the most common cause of bone pain. This condition commonly affects the long bones of the upper arms and legs, although it can affect any bone. Primary bone cancer occurs when cancer cells begin in the bone.

Pain caused by bone cancer may present with the following symptoms: initial discomfort in the afflicted bone, escalation to chronic pain or pain that appears and disappears in the affected bone, and persistent pain at night or while resting.

Conclusion

Bones provide structural support to our bodies, and also aid in forming the shape of our bodies. Despite their low weight, bones are strong enough to sustain our complete body weight. Bones also safeguard the organs of the body. The skull protects the brain and shapes the face. Bones, therefore, have a lot of uses and perform important functions in our day-to-day lives.