What are bones?

Bones are a form of extremely specialized connective tissue, consisting of a mix of a dense organic matrix and inorganic mineral component. They are characterized by their hardness and mechanical resistance. Bones are segments of varying shape, size and density, all of which constitute to form the skeletal system.

Depending on their shape formations, bones can be divided into long bones, flat bones, short bones and irregular bones.  Long bones develop mainly in length (such as the femur, tibia, fibula, radius, ulna, humerus); flat bones are characterized by having higher length and width than thickness (such as bones of the skull, shoulder blades, sternum); short bones are developed in a similar way in all three dimensions (such as the carpus and tarsus); and irregular bones are characterized by not having any dominant morphological element (such as in the case of the vertebrae). Under normal circumstances, bones stop growing when an individual has reached late teens or early twenties.


What are long bones?

Longs bones are hard, dense bones that provide structure and mobility. A long bone has a shaft and two ends. The femur, tibia and fibula are considered long bones in the lower limbs, and the humerus bone, ulna bone and radius bone are considered long bones in the upper limbs. The surface of long bones is covered by the periosteum, a membrane connecting the processes responsible for bone growth and callus formation in fractures. The compact bone (or cortical), which is a layer of dense bone, is located below the periosteum; and underneath the compact bone, is the location of the spongy bone (or trabecular), which contains bone marrow responsible for the production of blood cells.


What are flat bones?

Flat bones are formed by a thin layer of spongy bone tissue inside of which is located bone marrow. This spongy layer is then wrapped by two sheets (one for each side) of cortical or compact bone tissue. Examples of flat bones include the shoulder blades, sternum and bones of the skull and pelvis.


What are short bones?

Short bones or court, are characterized by their development in a manner similar to all three dimensions (recall the shape of a cube), such as by poor mobility and the presence of numerous facet joints. Inside of the human skeleton, short bones are those which make up carpus and form the tarsus. They are formed from spongy tissue wrapped by a sheet of compact bone tissue.


What are irregular bones?

Irregular bones are bones which serve various purposes in the body, such as protecting the nerve tissue and maintaining pharynx and trachea support. They are classified as neither long, nor short nor flat and fall into the group of vertebrae and hip bone (also called coaxiale bone).


What function do bones serve?

Bones perform different functions throughout the body:

  • They are spares and storage of minerals such as calcium, phosphorus, sodium and magnesium, essential for regulating many physiological mechanisms.
  • They provide form and support to the body parts of which they are composed from.
  • They provide support and stability even in the absence of motion.
  • They have important extensive protection features (such as the skull protecting the brain).
  • The bone marrow in them is capable of producing blood cells (white blood cells, red blood cells, platelets).
  • By interacting with the muscles and tendons, they allow movement of the limbs.