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Serratus posterior superior muscle

The serratus posterior superior is a thin, quadrilateral muscle located at the upper back beneath the rhomboid muscles. It plays a supportive role in elevating the upper ribs during inspiration and is considered part of the intermediate group of back muscles. Although small, it can be visualized on advanced imaging studies, and its precise anatomical knowledge is important for radiologists, clinicians, and surgeons.

Anatomy and Description

  • The muscle is flat, thin, and lies deep to the rhomboids and superficial to the erector spinae muscles.

  • Its fibers run downward and laterally from the vertebral column toward the upper ribs.

Origin

  • Arises from the lower part of the ligamentum nuchae

  • Spinous processes of the C7, T1, T2, and T3 vertebrae

Insertion

  • Attaches to the superior borders and external surfaces of the 2nd to 5th ribs, just lateral to their angles

Function

  • Elevates the 2nd to 5th ribs, aiding in deep inspiration

  • Stabilizes the upper posterior thoracic wall

Nerve Supply

  • Intercostal nerves (anterior rami) of the 2nd to 5th thoracic spinal nerves (T2–T5)

Artery Supply

  • Supplied primarily by the intercostal arteries, especially the posterior intercostal arteries

Vein Supply

  • Venous drainage is via the corresponding posterior intercostal veins

MRI Appearance

  • T1-weighted images: The serratus posterior superior muscle appears as an intermediate to low signal intensity structure compared to subcutaneous fat, similar to other skeletal muscles.

  • T2-weighted images: Muscle displays low signal intensity relative to surrounding fat; increased signal may indicate pathology such as edema or myositis.

  • STIR sequences: The muscle is normally low signal; any high signal indicates edema, inflammation, or injury.

CT Appearance

  • The muscle is seen as a thin, soft tissue structure deep to the rhomboids and superficial to the thoracic wall.

  • Appears with soft tissue attenuation, distinguishable from adjacent fat and bone.

MRI images

Serratus posterior superior muscle mri axial image

MRI image

serratus posterior superior muscle anatomy MRI axial image -img-00000-00000

MRI image

serratus posterior superior muscle anatomy MRI axial image -img-00000-00000_00001

CT images

serratus posterior superior muscle anatomy CT axial image -img-00000-00000_00002