Dance Anatomy & Kinesiology

The Upper Extremity 383

Rhomboids

The rhomboid (rhomboid, diamond shaped) muscles are paired muscles that lie beneath the trapezius

muscle (figure 7.9). They derive their name from the fact that they are shaped like a rhombus (G. rhom-

bos). They are often divided into the thinner and weaker upper portion called the rhomboid minor and

the thicker and stronger lower portion called the rhomboid major. The rhomboids run down and outward

from the spine to the medial border of the scapulae. Their line of pull is similar to that of the trapezius

except that their attachment is onto the medial border of the scapula. Hence, when the rhomboids

contract they produce downward rather than upward rotation of the scapula. They can also elevate and

adduct the scapula. Since downward rotation of the scapula accompanies shoulder adduction or exten-

sion, the rhomboids are used when these motions are performed forcefully or against resistance.

Palpation: Have a partner stand with the back of his or her right hand against the low back, and place

your fingers under the lower portion of the medial border of the right scapula. Then have your partner

lift his or her right hand backward (away from the back), and you will feel the rhomboids contract to

produce the necessary downward rotation of the scapula.

Attachments and Primary Actions of Rhomboids

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Rhomboids

(ROM-boidz)

C6 or C7 to T4 or T5

spinous processes

Medial border of scapula from

spine to inferior angle

Scapular elevation

Scapular adduction

Scapular downward rotation

Attachments and Primary Actions of Serratus Anterior

Muscle Proximal attachment(s) Distal attachment(s) Primary action(s)

Serratus anterior

(ser-A-tus an-TEER-ee-or)

Lateral, outer aspect of

lower 8 to 9 ribs

Inferior angle and medial

border of scapula

Scapular abduction

Scapular upward rotation

Scapular depression (lower fibers)

Serratus Anterior

The serratus anterior (serratus, saw) is named for

its serrated, or saw-toothed, anterior margin and

can be seen on the anterolateral rib cage below the

armpit. It actually runs from the lower eight or nine

ribs under the scapula to attach onto the inferior

angle and the entire length of the medial margin of

the scapula (figure 7.10). Part of the anterior portion

of this muscle is covered by the pectoralis major,

and posteriorly it is covered by the scapula. The

lowest four or five slips interdigitate with fibers of the

external oblique abdominal muscles. The serratus

anterior effectively attaches the medial scapula to

the front of the thorax. The line of pull makes it an

effective abductor of the scapula. The lower fibers

of the serratus anterior and the trapezius also form

a force couple for upward rotation of the scapula

(figure 7.11), used when one lifts the arms to the

side (shoulder abduction) and to the front (shoulder

flexion). In addition, the lower fibers of the serratus

anterior can assist with scapular depression.

Functionally, the serratus anterior has been

shown to be active in pushing movements,

FIGURE 7.10 Anterior scapular muscles: serratus

anterior and pectoralis minor (left shoulder, deep view).

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