Bones have many different types of markings that are associated with muscle attachment points, joints, and passageways for vessels and nerves.
Viewing the external anatomy of bone reveals that each bone is not completely smooth. In fact, bones often have many protrusions coming off of them. Each of these is called a bone marking, which is one of several structures used to determine where muscles and ligaments attach, as well as where and how bones join together. Bone markings fall into one of three categories: surfaces, depressions, and projections. A surface is the outer area of a bone that forms joints, the places where two or more bones come together. Joints can be immovable, such as those found in the bones that make up the skull, or they can be fully movable, such as those found where the arm meets the shoulder. A depression is a dip or trench within the bone surface that allows for nerves and blood vessels to pass through. A foramen, a type of depression, is a hole in the bone through which nerves and blood vessels pass. An example is the mandibular foramen, which is an opening in the lower jaw that allows nerves and blood vessels to pass into the teeth. A projection is an area of the bone that sticks up off the surface. These areas are the sites of muscle and ligament attachment, such as the mastoid process, which is the place where certain neck muscles attach to the skull.
Major Types of Bone Markings
|Bone Marking||Definition||Type of Bone Marking||Example|
|Crest||Raised border or ridge||Projection||Iliac crest found on the bones of the hips|
|Process||Any raised area of bone||Projection||Mastoid process where muscles from the jaw connect to the temporal bone behind the ear|
|Facet||Flat surface of joint||Surface||Articular facets of vertebrae|
|Head||Rounded projection that forms joint||Surface||Head of the femur (leg bone)|
|Fissure||Crack-like opening for blood vessels||Depression||Auricular fissure in temporal bone that carries the vagus nerve|
|Foramen||Hole in the bone through which blood vessels and nerves pass||Depression||Foramen of the vertebrae|