The serratus posterior inferior muscle, also known as the posterior serratus muscle, is a
muscle
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
of the
human body
The human body is the entire structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently Organ (biology), organs and then Organ system, org ...
.
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 ...
, and separated from it by a wide interval.
It arises by a thin
aponeurosis
An aponeurosis (; : aponeuroses) is a flattened tendon by which muscle attaches to bone or fascia. Aponeuroses exhibit an ordered arrangement of collagen fibres, thus attaining high tensile strength in a particular direction while being vulnerable ...
from the
spinous processes
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 spinal ...
of the
lower two thoracic
The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of 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 ...
and upper two or three
lumbar vertebrae
The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe t ...
.
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 complex, multilayer arrangement of fascial and aponeurotic layers forming a separation between the paraspinal muscles on one side, and the muscles of the posterior abdomina ...
, 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 dorsi'') comes from ...
.
Function
The serratus posterior inferior draws the lower ribs backward and downward to assist in rotation and extension of the
trunk
Trunk may refer to:
Biology
* Trunk (anatomy), synonym for torso
* Trunk (botany), a tree's central superstructure, and the stem of woody plants
* Trunk of corpus callosum, in neuroanatomy
* Elephant trunk, the proboscis of an elephant
Comput ...
.
This movement of the ribs may also contribute to
inhalation
Inhalation (or inspiration) happens when air or other gases enter the lungs.
Inhalation of air
Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...
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
lung
The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...
s.
Additional images
See also
*
Serratus anterior muscle
The serratus anterior is a muscle of the chest. It originates at the side of the chest from the upper 8 or 9 ribs; it inserts along the entire length of the anterior aspect of the medial border of the scapula. It is innervated by the long tho ...
*
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 ...
References
External links
* - "Intermediate layer of the extrinsic muscles of the back, deep muscles."
*
{{Authority control
Muscles of the torso