The rhomboid major is a

skeletal muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of m ...

on the back that connects the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...

with the

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e of the

spinal column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordates ...

. In human anatomy, it acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column.

Structure

The rhomboid major arises from the spinous processes of the

thoracic vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

T2 to T5 as well as the supraspinous ligament. It inserts on the medial border of the scapula, from about the level of the scapular spine to the scapula's inferior angle. Rhomboideus major muscle

The rhomboid major is considered a superficial back muscle. It is deep to the

trapezius The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...

, and is located directly inferior to the rhomboid minor. As the word ''rhomboid'' suggests, the rhomboid major is diamond-shaped. The ''major'' in its name indicates that it is the larger of the two rhomboids.

Variation

The two rhomboids are sometimes fused into a single muscle.

Nerve supply

The rhomboid major, like the rhomboid minor, is innervated by the ventral primary ramus via the dorsal scapular nerve (C5).

Blood supply

Both rhomboid muscles also derive their arterial blood supply from the dorsal scapular artery.

Function

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 vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

. The rhomboids work collectively with the

levator scapulae muscle The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. As the Latin name suggests, its main function is to lift the scapula. Anatomy Attachments The muscle descends diagonally from its origin to its inserti ...

s 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 levators to elevate the entire scapula.

Clinical significance

If the rhomboid major is torn, wasted, or unable to contract, scapular instability may result. The implications of scapular instability caused by the rhomboid major include scapular winging during scapular protraction, excessive lateral rotation and depression of the scapula, as the antagonistic action by the rhomboid major is absent. With scapular instability, movement in the upper extremity is limited as the scapula cannot guide the desired movement of the arm and shoulders. Pain, discomfort, and limited range of motion of the shoulder are possible implications of scapular instability. Treatment for scapular instability may include surgery followed by

physical therapy Physical therapy (PT), also known as physiotherapy, is one of the allied health professions. It is provided by physical therapists who promote, maintain, or restore health through physical examination, diagnosis, management, prognosis, pat ...

or occupational therapy. Physical therapy may consist of stretching and endurance exercises of the shoulder.

Pilates Pilates (; ) is a type of mind-body exercise developed in the early 20th century by German physical trainer Joseph Pilates, after whom it was named. Pilates called his method "Contrology". It is practiced worldwide, especially in countries suc ...

and

yoga Yoga (; sa, योग, lit=yoke' or 'union ) is a group of physical, mental, and spiritual practices or disciplines which originated in ancient India and aim to control (yoke) and still the mind, recognizing a detached witness-consciou ...

have been also suggested as potential treatment and prevention of scapular instability.

Other animals

The muscles of the shoulder can be categorized into three topographic units: the scapulohumeral, axiohumeral, and axioscapular groups. Stretching from the spine to the scapula, rhomboid major forms part of the latter group together with rhomboid minor, serratus anterior, levator scapulae, and trapezius. The trapezius has evolved separately, but the other muscles in this group evolved from the first eight or ten ribs and the transverse processes of the cervical vertebrae (homologous to the ribs). Functional demands have resulted in the evolution of individual muscles from the basal unit formed by the serratus anterior. In primitive life forms, the main function of the axioscapular group is to control the movements of the vertebral border of the scapula: fibers concerned with the dorsal movement of scapula evolved into the rhomboids, those with ventral motion into serratus anterior, and those with cranial movements into levator scapulae.

Additional images

References

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External links

Video: Anatomy, Function & Dysfunction Rhomboid MusclesDissection video: Superficial Back Review showing the rhomboids with the neurovascular unit
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Rhomboid muscle back problems
{{Authority control Muscles of the upper limb