Structure of Bone

Structure of the Bone

The human skeleton is composed of both compact and spongy bone. These bones are vital structures that provide support and protect the organs in the body.
A bone is primarily made up of bone tissue, a type of dense connective tissue. It is responsible for the strength and rigidity of bones.

Parts of a Bone

Long bones like the femur (thigh bone) and humerus (upper arm bone) have a distinct structure with different parts.
The main shaft of these long bones is called the diaphysis. It is largely made up of compact bone tissue, providing strength and resistance to bending or twisting forces.
The broad ends of long bones are known as the epiphyses. These contain spongy bone tissue, which is lighter and less dense than compact bone. This spongy bone contains red marrow, which produces blood cells.
A thin layer of hyaline cartilage, called the articular cartilage, covers the region of the epiphyses where the bone forms a joint with another bone. This cartilage reduces friction and absorbs shock at the joints.
The external surface of the bone is covered in a tough fibrous tissue called the periosteum. This contains blood vessels and nerves and also serves as an attachment site for muscles.
Inside the diaphysis is the medullary cavity, a hollow space that houses the bone marrow. Bones contain two types of marrow: red marrow for the production of blood cells and yellow marrow primarily for fat storage.

Compact and Spongy Bone

Compact bone is the hard outer layer that gives bones their white, smooth, solid appearance.
Compact bone comprises closely packed osteons or cylindrical structures. Each osteon contains a central canal (the Haversian canal) surrounded by concentric layers of calcified matrix, the lamellae.
Spongy bone (trabecular bone) makes up the interior of bones. It is more flexible than compact bone and contains a series of trabeculae or columns that look like a honeycomb.
Spongy bone also contains marrow cavities filled with either red or yellow marrow.

Understanding and remembering the structure of the bone can provide a foundation for further learning about the skeletal system, joint types and how they all function together to maintain the structural integrity of the body.