Internal Structure Of Long Bone
Internal Structure of Long Bones
Long bones, as the name suggests, are longer than they are wide. They are one of the types of bones classified based on their shape, and they play a crucial role in the skeletal system. Examples of long bones include the femur, tibia, fibula, humerus, ulna, and radius.
A long bone is primarily composed of two parts: the diaphysis and the epiphysis.
1. Diaphysis: The diaphysis, or the shaft, is the long, hollow, tubular structure that runs between the proximal and distal ends of the bone. The diaphysis is composed of a thick layer of compact bone, a dense and hard form of osseous tissue. Inside the diaphysis is the medullary cavity, which is filled with yellow bone marrow in an adult.
2. Epiphysis: The wider section at each end of the bone is called the epiphysis. Internally, the epiphysis is filled with spongy bone, another type of osseous tissue. Red bone marrow fills the spaces between the spongy bone in some long bones. Each epiphysis meets the diaphysis at the metaphysis.
3. Metaphysis: The metaphysis is the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone. When the bone stops growing in early adulthood (approximately 1821 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.
4. Endosteum: The medullary cavity has a delicate membranous lining called the endosteum. This is where bone growth, repair, and remodeling occur.
5. Periosteum: The outer surface of the bone is covered with a fibrous membrane called the periosteum. The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum.
6. Articular Cartilage: In the region where the epiphyses meet other bones to form joints, the epiphyses are covered with articular cartilage, a thin layer of hyaline cartilage that reduces friction and acts as a shock absorber.
The internal structure of long bones is a marvel of nature’s engineering, providing strength, flexibility, and the ability to withstand stress. The intricate design of these bones allows them to perform their functions effectively, contributing to our ability to move and interact with our environment..