The serratus posterior inferior muscle, also known as the posterior serratus muscle, is a muscle of the human body.

Structure

The muscle is situated at the junction of the thoracic and lumbar regions. It has an irregularly quadrilateral form, broader than the

serratus posterior superior muscle The serratus posterior superior muscle is a thin, quadrilateral muscle. It is situated at the upper back part of the thorax, deep to the rhomboid muscles. Structure The serratus posterior superior muscle arises by an aponeurosis from the l ...

, and separated from it by a wide interval. It arises by a thin aponeurosis from the

spinous processes 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 characteristic i ...

of the lower two

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

and upper two or three

lumbar vertebrae The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...

. Passing obliquely upward and lateralward, it becomes fleshy, and divides into four flat digitations. These are inserted into the inferior borders of the lower four ribs, a little beyond their angles. The thin aponeurosis of origin is intimately blended with the

thoracolumbar fascia The thoracolumbar fascia (lumbodorsal fascia or thoracodorsal fascia) is a deep investing membrane throughout most of the posterior thorax and abdomen although it is a thin fibrous lamina in the thoracic region. Above, it is continuous with a simil ...

, and aponeurosis of the

latissimus dorsi muscle The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from L ...

Function

The serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the trunk. This movement of the ribs may also contribute to inhalation and forced

expiration Expiration or expiration date may refer to: Expiration Expiration may refer to: *Death *Exhalation of breath, breathing out *Expiration (options), the legal termination of an option to take an action *Shelf life, or the time after which a product ...

of air from the

lungs The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side ...

Additional images

References

External links

* - "Intermediate layer of the extrinsic muscles of the back, deep muscles." * {{Authority control Muscles of the torso

Structure

Function

Additional images

See also

References

External links