Ventral view, left side

Ventral view, left side

Craniolateral view, left side

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!

Anterior view, right side Anterior view of origin and insertion, right side

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
 

Anterior view, right side

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!