At the end of each long bone is a wider area known as the epiphysis. This is filled with spongy bone and red marrow. Each epiphysis meets the diaphysis at the metaphysis, which is a narrower area that consists of the epiphyseal plate, which is the growth plate of the bone. When the person stops growing, the epiphyseal plate becomes ossified and defined as the epiphyseal line. There is a membranous lining called the endosteum inside the bone in the medullary cavity. This is where bone repair, remodeling, and bone growth occur. The outer membrane of bone is called the periosteum, which contains the blood vessels, lymph vessels, and nerves that supply the compact bone. Tendons and ligaments attach to bones at the periosteum. It covers the entirety of bone except where the epiphyses for joints; this is where the articular cartilage covers bone instead. Flat bones are slightly different from long bones. They have two layers of compact bone that sandwiches a spongy layer called the diploe. The inner layer can protect the internal structure, such as the brain in the cranial bones, even if the outer layer gets fractured.
BONY MARKINGS There are many different markings on bone, of which there are three types: •
Articulations—also referred to as joints, where two bones meet to facilitate movement.
•
Projections—these will stick out of a bone and is often where tendons and ligaments attach.
•
Holes—this is a groove or opening in the bone where nerves and blood vessels enter the bone.
Types of articulations include the following: •
Head—such as the head of the femur, in which there is a prominent rounded surface at one end
•
Facet—this is a flat end of the bone, such as the facet joint of a vertebral bone
72
