The human ear is a complex structure that extends beyond the visible external flap, or auricle. The region immediately behind the auricle has a precise anatomical designation. Understanding this area involves recognizing the combination of bone and soft tissue that makes up this part of the head. This article clarifies the formal terminology for this region, detailing the structures that lie just beneath the skin.
Identifying the Area
The anatomical term for the space immediately posterior to the auricle is the mastoid region. This region encompasses the skin, underlying muscle, and the bone structure beneath. It is bordered by the external ear canal in front and the occipital region of the skull in the back.
This area is externally marked by a palpable bony prominence that many people can feel. This bump is a projection of one of the skull’s major bones. Its location and underlying structures make the mastoid region a point of reference in medicine and anatomy.
The Underlying Bone Structure
The bony prominence that is easily felt behind the ear is called the mastoid process. This conical or pyramidal projection is an extension of the temporal bone of the skull. The temporal bone is a large, irregularly shaped bone that forms the side and base of the skull.
The mastoid process is not solid bone, but instead contains numerous small, air-filled cavities known as mastoid air cells. These air cells are connected to the middle ear cavity by a small passage. This structure helps regulate air pressure within the middle ear and may also help lighten the weight of the skull.
The mastoid process serves as an anchor point for several muscles in the neck and head. Muscles such as the large sternocleidomastoid, which is involved in head rotation and neck flexion, attach directly to the mastoid process. This bony projection is larger in males than in females and contributes to the overall contour of the head.
Other Key Structures in the Region
Beyond the bone, the mastoid region contains soft tissue structures. A network of small, bean-shaped organs, the lymph nodes, are situated here. Specifically, the posterior auricular lymph nodes (also called mastoid lymph nodes) are located just behind the ear and on the surface of the mastoid process.
These nodes are part of the body’s immune system, acting as filters that collect lymph fluid from the scalp, the upper ear, and the external ear canal. When the body is fighting an infection, such as a cold or an ear infection, these lymph nodes can swell and become tender. The swelling is a common change in the mastoid region that prompts people to seek information.
The facial nerve (Cranial Nerve VII), which controls the muscles of facial expression, also passes through this area. This nerve passes close to the mastoid process and exits the skull near the bone’s lower tip. Due to the close proximity of the nerve to the bone, surgical procedures or severe infections in this region require careful consideration to prevent potential damage to the facial nerve.