The helicis major is an intrinsic muscle of the external ear (auricle). It is one of the small muscles found within the auricular cartilage and plays a limited role in the movement of the ear in humans. Like other auricular muscles, the helicis major is considered vestigial, meaning its function has diminished over the course of evolution.
Location
The helicis major is located along the anterior (front) part of the helix, which forms the outer rim of the ear. It runs from the spine of the helix to the upper portion of the helix, within the cartilaginous framework of the auricle. Its placement is adjacent to the helicis minor, though it extends higher up along the helix’s curvature.
Structure and Anatomy
Location and Position
The helicis major is situated on the anterior surface of the auricle, extending along the outer rim of the ear, known as the helix. It lies near the superior portion of the helix, starting at the spine of the helix and following the ascending curve upward. Its position places it adjacent to the helicis minor, which is located at the root of the helix. The helicis major is slightly larger than the helicis minor and spans a greater length along the ear’s cartilaginous rim.
Origin
The helicis major originates from the anterior aspect of the auricular cartilage. Specifically, it begins from the region known as the spine of the helix, a slight prominence found at the junction of the helix and the antihelix, which forms part of the ear’s cartilaginous framework.
Insertion
The muscle fibers of the helicis major travel upward and outward, inserting into the upper section of the helix. Its insertion is along the cartilaginous edge of the helix, helping define the shape and contour of this outer ear structure. This positioning also allows the helicis major to span a broader portion of the helix compared to the helicis minor, which is restricted to the lower region.
Fiber Composition
Like the helicis minor, the helicis major is composed of striated skeletal muscle fibers. These fibers are organized in a narrow, elongated pattern and run parallel to the curve of the helix. The muscle fibers are fine and relatively weak, reflecting the limited movement capacity of the auricle in humans.
Blood Supply
The helicis major receives its blood supply from branches of the superficial temporal artery and posterior auricular artery, which also supply the surrounding structures of the external ear. These small arteries ensure the muscle receives sufficient blood flow for its minimal role in ear movement and structural maintenance. Venous drainage from the auricle, including the helicis major, follows the course of the arterial supply and drains into the external jugular vein.
Innervation
The innervation of the helicis major is provided by the auricular branch of the facial nerve (cranial nerve VII). This nerve supplies motor control to the intrinsic and extrinsic muscles of the ear, including the helicis major. Although the muscle’s function is vestigial, the facial nerve ensures the muscle receives proper neural signals.
Adjacent Structures
The helicis major is in close anatomical proximity to several other intrinsic muscles of the ear, such as the helicis minor, tragicus, and antitragicus. It is also directly connected to the cartilaginous framework of the helix and surrounded by skin. The muscle’s location places it along the outermost edge of the ear, where it contributes to the external contour and shape of the auricle.
Function
Limited Role in Auricular Movement
The helicis major is one of the intrinsic muscles of the auricle, but its function in humans is extremely limited. Like the helicis minor, the helicis major has a vestigial role, meaning it has lost much of its evolutionary function over time. In many animals, particularly mammals with more mobile ears, this muscle contributes to the movement and positioning of the auricle. However, in humans, the auricular muscles, including the helicis major, do not significantly contribute to ear movement.
Subtle Adjustments in Ear Structure
Although humans generally cannot move their ears independently, the helicis major may play a minor role in maintaining the shape of the auricle. Its attachment to the cartilaginous helix could allow it to assist in small adjustments to the tension of the outer ear structure. These changes would be imperceptible and serve no functional purpose in hearing, but they might help keep the helix in its defined shape.
Possible Involvement in Minor Ear Movements
In rare individuals who retain some ability to move their ears, the helicis major might contribute to very small movements of the auricle. This movement could involve the elevation or slight rotation of the helix, though it is not noticeable in most people. The helicis major is thought to work in conjunction with other intrinsic and extrinsic auricular muscles when ear movement occurs.
Evolutionary Remnant
The helicis major is a remnant of the more functional auricular muscles seen in other animals. In many mammals, such as cats, dogs, and primates, the ability to move the ears is crucial for detecting sound from different directions. The helicis major in these animals helps to rotate or pivot the ear to capture sound more effectively. Over time, as humans evolved and relied more on the internal structures of the ear and the brain’s processing of sound, the need for external ear movement diminished, leaving the helicis major as a vestigial structure.
Contribution to Auricular Stability
Though its functional capacity is minimal, the helicis major may provide slight reinforcement to the cartilage of the helix. By exerting minor tension along the outer rim of the ear, it could help stabilize the cartilaginous framework and maintain the ear’s external form. However, this function is largely structural rather than motor in humans.
Clinical Significance
The helicis major muscle, though vestigial and functionally insignificant in most humans, can have clinical relevance in certain scenarios:
- Surgical Considerations: In otoplasty (cosmetic ear surgery) or auricular reconstruction, the helicis major and its attachment to the cartilage must be considered to preserve or restore the natural shape of the helix. Surgeons must carefully handle the muscle and surrounding cartilage to avoid affecting the aesthetic outcome of the ear.
- Injury and Trauma: In cases of trauma to the external ear, such as lacerations or cartilage damage, the helicis major might be involved. While not critical for ear function, damage to the muscle or its surrounding structures could alter the ear’s appearance or complicate healing.
- Congenital Deformities: Rarely, deformities involving the helix may involve the helicis major. In such cases, surgical correction may need to take the muscle’s anatomy into account to achieve a normal ear shape.
