Question

Match each function to a muscle of the head and neck in the key. a. trapezius b arhicularis aculi c. masseter Moves head and scapula

Short answer

The muscle that moves the head and scapula is the trapezius. The arhicularis aculi (orbicularis oculi) and masseter are not involved in head and scapula movement, as they control eyelid movement and facial expressions, and facilitate chewing and biting, respectively.

Step-by-step solution

T1: Function of Trapezius

The trapezius muscle is a large, diamond-shaped muscle located in the upper part of the back and neck. Its primary functions are to support the weight of the arm, move the scapula (shoulder blade), and facilitate head movement by extending, rotating, and tilting the head.

T2: Function of Arhicularis Aculei

The arhicularis aculi (properly known as orbicularis oculi) is a thin, circular muscle around the eye that controls eyelid movement and contributes to facial expressions. It does not participate in head or scapula movement.

T3: Function of Masseter

The masseter muscle is a thick, powerful muscle located in the cheek area responsible for chewing and biting by moving the lower jaw. It does not participate directly in head or scapula movement. Now, we can match each muscle to its primary function in relation to head and scapula movement. a. trapezius: Moves head and scapula (as it supports the weight of the arm, moves the scapula, and facilitates head movement) b. arhicularis aculi (orbicularis oculi): Not involved in head and scapula movement (as it controls eyelid movement and contributes to facial expressions) c. masseter: Not involved in head and scapula movement (as it is responsible for chewing and biting by moving the lower jaw)

Key concepts

Trapezius Muscle

The trapezius muscle is a significant muscle located in the upper back and neck region. It's uniquely shaped like a diamond and spans a large portion of the back and neck area. This muscle plays several important roles in bodily movement and function:

• **Head Movement**: It helps in extending and rotating the head, which is crucial for looking around and maintaining posture.
• **Scapula (Shoulder Blade) Movement**: The trapezius is vital for moving your shoulder blades. It assists in shrugging your shoulders, raising the arm, and even pulling the shoulders back.
• **Arm Support**: By supporting the shoulder blade, it indirectly supports arm movements, which is essential for lifting objects and other activities requiring strength.

Stretching and strengthening exercises for the trapezius can improve posture and alleviate neck and upper back pain. Its role is crucial in daily activities that require both mobility and stability of the upper body.

Orbicularis Oculi Muscle

The orbicularis oculi is a delicate, circular muscle that is essential for eye function and facial expression. Surrounding the eye socket, it’s primarily responsible for:

• **Eyelid Movement**: This muscle enables you to blink, which keeps the eyes moist and free from debris. It is also involved in tightly closing the eyelids to protect the eyes from injury or bright light.
• **Facial Expressions**: By contracting and relaxing, the orbicularis oculi helps express emotions like smiling or squinting, allowing subtle and complex changes in facial appearance.

Unlike the trapezius, it does not contribute to head or scapula movement. However, its ability to control the eyelids makes it essential for eye protection and non-verbal communication.

Masseter Muscle

Situated in the cheek area, the masseter muscle is one of the strongest muscles in the body, crucial for chewing. Despite its power, it does not involve head or scapula movement. Its primary functions include:

• **Chewing**: The masseter muscle elevates the lower jaw, allowing the teeth to come together and grind food, an essential process for digestion.
• **Biting**: This muscle generates the necessary force to bite through and crush food.

This muscle is vital for everyday tasks like eating and speaking, and jaw exercises can help maintain its strength and function. Proper alignment and function of the masseter are essential for oral health and well-being.