The occipitalis muscle, often discussed in the context of scalp movement and facial expression, is a paired muscle located at the back of the head. It forms the occipital belly of the epicranius and plays a specific role in moving the scalp and skin over the cranium. Understanding its location, structure, and function provides insight into how we express emotion and how tension in this area can contribute to common physical ailments.
Anatomical Location and Structure
To understand what the occipitalis muscle does, one must first look at where it is and how it is built. This muscle is situated on the posterior part of the skull, covering the occipital bone. It is thin and quadrilateral in shape, lying just beneath the skin and superficial fascia of the scalp. The muscle fibers run horizontally and originate from the superior nuchal line of the occipital bone and the mastoid process of the temporal bone.
Connection to the Epicranius
Anatomically, the occipitalis does not work in isolation. It is one of two parts of the epicranius, the other being the frontalis muscle located on the forehead. These two muscles are connected by a broad tendon known as the epicranial aponeurosis, or galea aponeurotica. This structure acts as a flexible bridge, allowing the forces generated by the occipitalis to be transmitted across the scalp to the frontalis and vice versa.
Mechanics of Movement
The primary action of the occipitalis muscle is to retract the scalp, pulling it posteriorly. When both sides of the muscle contract simultaneously, they pull the scalp backward. This movement is often subtle in humans compared to other animals, but it is essential for adjusting the position of the scalp and skin. Additionally, the muscle works in conjunction with the frontalis to raise the eyebrows and wrinkle the forehead, creating expressions of surprise or concentration.
Role in Facial Expression
While the occipitalis is located at the back of the head, its influence on facial expression is significant. Through the epicranial aponeurosis, tension in the occipitalis can create a downward pull on the frontalis. This interaction allows for the fine-tuning of expressions such as frowning or raising the upper lip. The coordinated effort between the frontalis and occipitalis allows for a wide range of non-verbal communication cues.
Associated Nervous System Control
The function of the occipitalis muscle is governed by the facial nerve, specifically the posterior auricular branch. This nerve provides the necessary motor signals to initiate contraction. Because the muscle is involved in conscious movements like raising the scalp or wrinkling the forehead, it is classified as a skeletal muscle, meaning it is under voluntary control, although some reflexive actions may occur.
Clinical Significance and Common Issues
Issues involving the occipitalis muscle are often related to tension and musculoskeletal stress. Tightness in this muscle can contribute to tension headaches that originate at the base of the skull. Trigger points within the muscle can refer pain to the temples and the top of the head. Stretching and massaging the scalp can help alleviate this tension, highlighting the muscle's role in overall physical comfort.
Relation to Hair and Scalp Health
The tension of the occipitalis muscle can also influence the health of the scalp and hair follicles. Chronic pulling or tension in the muscle may contribute to conditions like traction alopecia in extreme cases, where constant tension damages the hair roots. Maintaining flexibility in the muscle supports healthy blood flow to the scalp, which is essential for nourishing hair follicles and promoting growth.
