Corpus: Innermost intercostal muscles
1. Definition
The innermost intercostal muscles are skeletal muscles belonging to the intercostal musculature.
2. Anatomy
The innermost intercostal muscles are the deepest layer of the intercostal muscles and split off from the internal intercostal muscles between the costal angle and the cartilage-bone junction. The intercostal nerve and intercostal artery serve as anatomical markers, separating the internal intercostal muscles from the innermost intercostal muscles. Both the innermost and internal intercostal muscles are enveloped by the internal thoracic fascia.
3. Innervation
The innermost intercostal muscles are innervated segmentally by the intercostal nerves arising from the spinal cord segments Th1-11.
4. Function
The primary function of the innermost intercostal muscles is to assist in expiration by lowering the ribs, thereby contributing to the decrease in thoracic volume necessary for exhalation.