The innermost intercostal muscle is a layer of

intercostal muscles Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size of ...

. It may also be called the intima of the internal intercostal muscles. It is the deepest muscular layer of the

thorax 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 ...

, with

muscle fibres A muscle cell is also known as a myocyte when referring to either a cardiac muscle cell (cardiomyocyte), or a smooth muscle cell as these are both small cells. A skeletal muscle cell is long and threadlike with many nuclei and is called a musc ...

running vertically (in parallel with the

internal intercostal muscles The internal intercostal muscles (intercostales interni) are a group of skeletal muscles located between the ribs. They are eleven in number on either side. They commence anteriorly at the sternum, in the intercostal spaces between the cartilage ...

). It is present only in the middle of each

intercostal space The intercostal space (ICS) is the anatomic space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it. Structures in intercostal space * several kind ...

, and often not present higher up the

rib cage The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi ...

. It lies deep to the plane that contains the

intercostal nerves The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and dif ...

and intercostal vessels, and the

. The diaphragm is continuous with the innermost intercostal muscle.

Additional images

File:Innermost intercostal muscles animation.gif, Innermost intercostal muscle (shown in red). Animation. File:1114 Thorax zoom.png, A cutout of the thoracic wall showing the three layers of intercostal muscle - from the left wall.

References

External links

* - "Thoracic Wall: The Intercostal Nerve and Vessels" * - "Transverse section of thorax." * Muscles of the torso {{muscle-stub