Levatores breves costarum

At a glance

English

Levatores breves costarum

Latin (TA2)

Levatores breves costarum

System

Muscle

Region

Trunk

Side

Paired, left and right

About the levatores breves costarum

The levatores costarum, or rib elevators, are a row of small, flat, triangular muscles on each side of the back of the thorax. They lie deep to the long extensor muscles of the back, close against the necks of the ribs. Every one of them has a short member, a levator brevis, and the lowest few also have a second, longer slip, the levator longus, which skips a rib.

Each short levator starts at the tip of a transverse process, from the seventh cervical vertebra down to the eleventh thoracic vertebra. It widens as it passes downward and outward, much like the external intercostal muscles beside it, and attaches to the outer face of the rib directly beneath its vertebra. The attachment lies lateral to the tubercle but short of the angle of that rib, so the muscle covers the back of the costotransverse joint. The fibres run in the same direction as the external intercostals and are sometimes regarded as their hindmost portion.

Their name suggests that they lift the ribs, and they can do so to a small degree, helping to widen the chest when breathing in. Their leverage is poor, however, because they are attached so close to the joints between ribs and vertebrae. They are more likely to act as fine adjusters of the vertebral column, assisting slight extension, side bending and rotation of the thoracic spine, and to provide the nervous system with information about joint position. Their many sensory endings fit this role.

The short levators are supplied by branches of the dorsal rami of the eighth cervical to eleventh thoracic spinal nerves, the same nerves that supply the deep muscles of the back. Their blood comes from the dorsal branches of the posterior intercostal arteries. Because they are small and deep, they are seldom examined on their own, but they may contribute to localised pain and stiffness at the back of the ribs.

Attachments, action and supply

Origin

Tips of the transverse processes of C7 and T1-T11.

Insertion

Outer surface of the next rib down, between its tubercle and angle.

Action

Weakly elevate the ribs; assist extension, side bending and rotation of the thoracic spine and sense its position.

Nerve supply

Dorsal rami of C8-T11 spinal nerves.

Blood supply

Dorsal branches of the posterior intercostal arteries.