Several muscles act to move and/or stabilize the scapula. Which of the following are small rectangular muscles that square the shoulders as they act together to retract the scapula?
a. Levator scapulae
b. Rhomboids
c. Serratus anterior
d. Trapezius

Verified step by step guidance

1. Step 1: Understand the function and shape of each muscle listed in the options. The question asks for small rectangular muscles that act together to retract the scapula and square the shoulders.
2. Step 2: Recall that the levator scapulae primarily elevates the scapula and is not rectangular in shape; it is more strap-like.
3. Step 3: Consider the rhomboids, which are small, rectangular muscles located beneath the trapezius. They retract (pull back) the scapula and help to square the shoulders.
4. Step 4: Note that the serratus anterior is a fan-shaped muscle that protracts the scapula, moving it forward, so it does not fit the description.
5. Step 5: Recognize that the trapezius is a large, broad muscle that also helps move and stabilize the scapula but is not small or rectangular; it has a more triangular shape.

Key Concepts

Scapular Retraction

Scapular retraction refers to the movement of pulling the shoulder blades (scapulae) toward the spine. This action is important for posture and upper limb movement, involving muscles that stabilize and move the scapula medially.

Rhomboid Muscles

The rhomboids are small, rectangular muscles located between the spine and the scapula. They function primarily to retract and elevate the scapula, helping to 'square' the shoulders by pulling the scapulae toward the vertebral column.

Muscles of the Scapula

Several muscles influence scapular movement, including the levator scapulae (elevates scapula), serratus anterior (protracts scapula), and trapezius (moves scapula in multiple directions). Understanding their roles helps identify which muscle performs specific actions like retraction.