The rhomboid major is a

skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...

of the back that connects the

scapula The scapula (: 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 either side ...

with the

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e of the

spinal column The spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmen ...

. It originates from the

spinous process Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

es 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 vertebra (anatomy), vertebrae of intermediate size between the ce ...

T2–T5 and

supraspinous ligament The supraspinous ligament (also known as the supraspinal ligament) is a ligament extending across the tips of the spinous processes of the vertebra of the vertebral column. Anatomy The supraspinous ligament connects the tips of the spinous proces ...

; it inserts onto the lower portion of the medial border of the scapula. It acts together with the rhomboid minor to keep the scapula pressed against thoracic wall and to retract the scapula toward the vertebral column. 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.

Structure

Origin

The rhomboid major arises from the spinous processes of the

T2–T5 as well as the

Insertion

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

Innervation

The rhomboid major, like the rhomboid minor, is innervated by the ventral primary ramus via the

dorsal scapular nerve The dorsal scapular nerve is a branch of the brachial plexus, usually derived from the ventral ramus of cervical nerve C5. It provides motor innervation to the rhomboid major muscle, rhomboid minor muscle, and levator scapulae muscle. Dorsal ...

(C5).

Blood supply

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

Relations

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 human spine, spine and laterally to the spine of the scapula. It moves the scapula and ...

, and situated directly inferior to the rhomboid minor.

Variation

The two rhomboids are sometimes fused into a single muscle.

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 spinal column, also known as the vertebral column, spine or backbone, is the core part of the axial skeleton in vertebrates. The vertebral column is the defining and eponymous characteristic of the vertebrate. The spinal column is a segmente ...

. The rhomboids work collectively with the

levator scapulae muscle The levator scapulae is a slender skeletal muscle Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous s ...

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 a healthcare profession, as well as the care provided by physical therapists who promote, maintain, or restore health through patient education, physical intervention, disease preventio ...

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

yoga Yoga (UK: , US: ; 'yoga' ; ) is a group of physical, mental, and spiritual practices or disciplines that originated with its own philosophy in ancient India, aimed at controlling body and mind to attain various salvation goals, as pra ...

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 early 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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{{Authority control Muscles of the upper limb