Cat information:
pectoralis major
origin: manubrium,
the first three divisions
of the sternum and the
median raphe
insertion: greater tubercle and along a line
to the pectoral ridge of
humerus
nerve: anterior thoracic
action: adducts arm
Note that is muscle can be tagged in three places!
Human information:
pectoralis major (sternal division)
origin: sternum, costal
cartilages of ribs 1-6
insertion: lateral lip of bicipital groove
of humerus
nerve: lateral and medial pectoral
(C7, 8, and T1)
action: extends humerus to
approximately 90 degrees
Human information:
pectoralis major (clavicular division)
origin: anterior surface of
medial third of clavicle
insertion: lateral lip of bicipital groove
of humerus
nerve: lateral pectoral (C5 and C6)
action: flexes humerus to
approximately 90 degrees
action together: adduction, internal (medial) rotation,
horizontal adduction of arm
Note that the pectoralis major is one of the five muscles in the group we refer to as the muscles that move the arm (not including the rotator cuff muscles). The above drawing of the origin and insertion might help visualize this information (red is the origin, blue the insertion). Both divisions are on the same origin/insertion drawing.
COPYRIGHT
2009 by William C. Johnson II
ALL RIGHTS RESERVED!