Rhomboid Minor Muscle; Origin, Nerve Supply, Function - Health

Rhomboid Minor Muscle is a small skeletal muscle on the back that connects the scapula with the vertebrae of the spinal column. Located inferior to levator scapulae and superior to rhomboid major, it acts together with the latter to keep the scapula pressed against the thoracic wall. It lies deep to trapezius but superficial to the long spinal muscles.^[rx]

Rhomboid Major Muscles often simply called the rhomboids, are rhombus-shaped muscles associated with the scapula. There are two rhomboid muscles on each side of the upper back. The large rhombus-shaped muscle, located under the trapezius muscle in the upper part of the thoracic region of the back, and also the small muscle, in the same way, participate in the movement of the scapula.

Rhomboid major muscle
Rhomboid minor muscle

At a Glance of Rhomboid minor

Function – Retracts and rotates the scapula
Origin – Spinous processes of C7 to T1 vertebrae
Insertion – Medial border of the scapula
Innervation – Dorsal scapular nerve (C5)

Anatomy of Rhomboid Minor Muscles

Origin and Insertion

The rhomboid minor arises from the inferior border of the nuchal ligament, from the spinous processes of the seventh cervical and first thoracic vertebrae, and from the intervening supraspinous ligaments. It is inserted into a small area of the medial border of the scapula at the level of the scapular spine.^[rx]

Innervation and Blood supply

The nerve supply comes from the dorsal scapular nerve, with most of its fibers derived from the C5 nerve root and an only minor contribution from C4 or C6. ^[rx]The rhomboid minor gets its arterial blood supply from the dorsal scapular artery.

Functions of Rhomboid Major Muscles

Together with the rhomboid major, the rhomboid minor retracts the scapula when trapezius is contracted. Acting as a synergist to the trapezius, the rhomboid major and minor elevate the medial border of the scapula medially and upward, working in tandem with the levator scapulae muscle to rotate the scapulae downward. While other shoulder muscles are active, the rhomboid major and minor stabilize the scapula. ^[rx]
The rhomboid major helps to hold the scapula (and thus the upper limb) onto the ribcage. Other muscles that perform this function include the serratus anterior and pectoralis minor.
Both rhomboids (major and minor) also act to retract the scapula, pulling it towards the vertebral column.
The rhomboids work collectively with the levator scapulae muscles to elevate the medial border of the scapula, downwardly rotating the scapula with respect to the glenohumeral joint. Antagonists to this function (upward rotators of the scapulae) are the serratus anterior and lower fibers of the trapezius. If the lower fibers are inactive, the serratus anterior and upper trapezius work in tandem with rhomboids and elevators to elevate the entire scapula.

References

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