The occipital bone is one of eight bones that make up the cranium, or skull. It is located at the back of the head, just above the neck. This four-sided bone has a curve in at the base of the skull. An opening in this bone allows the brain stem to connect with the spinal cord. The occipital bone joins with the temporal and parietal bones to make up the back part of the skull.
The occipital is generally made up of three distinct parts. The posterior section of the bone is often triangular in shape, with the apex pointing upwards. This section of the bone is convex, giving the back of the skull its roundness. On either side of the opening for the brain stem, known as the foramen magnum, two large, bony protuberances, generally known to anatomists as the condyles, allow the muscles of the neck to connect with the back of the skull.
The condyles are convex and articulating, making them capable of movement. Muscle tissue connects the occipital condyles to the atlas, or the first cervical vertebra at the top of the neck. The occipital condyles allow the head and neck to move together. The posterior and anterior condylar foramina are generally located in front of and behind the condyles. These small openings allow nerve fibers to penetrate the occipital bone and connect to the nerves of the spinal cord.
This bone often has a large bump in the center of the posterior section. This bump is generally known as the external occipital protuberance. The protuberance is usually located in the center of a ridge of bone that anatomists may refer to as the superior curved line. An inferior curved line is typically located below the superior curved line. The external occipital crest vertically bisects the superior and inferior curved lines, beginning at the external occipital protuberance and ending at the foramen magnum.
The occipital bone is slightly articulative with the bones around it. It connects with the parietal bones, which form the top of the skull. It also connects with the sphenoids, which form the temples. Finally, the occipital connects with the temporals, which form the sides of the skull.