serratus Definition

any of three muscles of the thorax that have complex origins but arise chiefly from the ribs or vertebrae:

serratus anterior

serratus posterior inferior

a thin muscular sheet of the thorax that arises from the first eight or nine ribs and from the intercostal muscles between them, is inserted into the ventral side of the medial margin of the scapula, and acts to stabilize the scapula by holding it against the chest wall and to rotate it in raising the arm

serratus anterior

a thin quadrilateral muscle at the junction of the thoracic and lumbar regions that arises chiefly from the spinous processes of the lowest two thoracic and first two or three lumbar vertebrae, is inserted into the lowest four ribs, and acts to counteract the pull of the diaphragm on the ribs to which it is attached

a thin quadrilateral muscle of the upper and dorsal part of the thorax that arises chiefly from the spinous processes of the lowest cervical and the first two or three thoracic vertebrae, is inserted into the second to fifth ribs, and acts to elevate the upper ribs