What is the action of the Cleidomastoid muscle?

The primary actions of the Cleidomastoid muscle are the rotation of the head to the opposite side and flexion of the neck. This powerful muscle plays a vital role in the complex movements of the head and cervical spine.

Understanding the Cleidomastoid Muscle's Role

The Cleidomastoid muscle is a significant superficial muscle located in the neck. Its strategic positioning allows it to perform a variety of actions that are essential for daily activities, from simply looking around to more complex head movements.

Key Actions Explained:

• Head Rotation: When one Cleidomastoid muscle contracts, it causes the head to turn, or rotate, towards the opposite side. For instance, if your right Cleidomastoid muscle contracts, your head will turn to the left. This action is crucial for peripheral vision and situational awareness.
• Neck Flexion: When both Cleidomastoid muscles contract simultaneously, they work together to flex the neck, which means bringing the head forward towards the chest. This action is involved in nodding, looking down, or bringing your chin to your sternum.

Characteristics and Functionality

As one of the largest and most superficial muscles in the cervical region, the Cleidomastoid muscle is easily palpable and visible, especially when the head is turned. Its functionality is integral to posture, balance, and the dynamic range of motion of the head.

• Innervation: The Cleidomastoid muscle receives its nerve supply from the accessory nerve (Cranial Nerve XI), which is critical for its ability to contract and perform its actions effectively. Damage to this nerve can impair the muscle's function.

Summary of Actions

To summarize the actions of the Cleidomastoid muscle:

These actions demonstrate the muscle's importance in various everyday movements and its contribution to overall head and neck mobility.