serratus posterior

Intermediate layer of upper and lower back muscles. They are separated from each other by a wide interval.

(Components)
• serratus posterior superior: A thin, quadrilateral muscle, situated at the upper back part of the thorax, deep to the rhomboid muscles.
• serratus posterior inferior: An irregularly quadrilateral muscle, broader than the serratus posterior superior, situated at the junction of the thoracic and lumbar regions.