📝 STANDARD DESCRIPTION:
Type: Extrinsic, Deep Layer
Subtypes: Descending (manubrium), Transverse (sternal), Deep/Ascending (sternum/xiphoid)
Insertion: Greater/lesser tubercles of humerus; deltoid crest
Function: Adduct limb; prevent abduction during weight bearing; assist in advancing trunk (deep part) or limb (superficial).
📚 DETAILED DESCRIPTION:
THE BRISKET STABILIZERS
The pectoral complex anchors the limb to the sternum, preventing limb abduction (splaying) during weight bearing and assisting in propulsion.
SUPERFICIAL PECTORAL (PECTORALIS SUPERFICIALIS):
• Descending Part: Originates from manubrium of sternum; inserts on humeral crest
• Transverse Part: Originates from ventral sternum (sternebrae 1-6); inserts on deltoid fascia
• Function: Adduct the limb and assist in protraction
DEEP PECTORAL (PECTORALIS PROFUNDUS/ASCENDENS):
• Origin: Ventral surface of sternum, xiphoid cartilage, abdominal fascia—extensive caudal origin
• Insertion: Lesser and greater tubercles of humerus plus medial tubercle via aponeurosis
• Function: Strong retractor of the non-weight-bearing limb; when limb is fixed, advances the trunk (propulsion)
ANTI-ABDUCTION CRITICAL FUNCTION: Prevents the limb from abducting (moving laterally away from body) during the stance phase. In a heavy bovine, failure via deep pectoral tear results in 'splayed' leg appearance.
SUBCLAVIUS: In ox, this is a reduced narrow band from first costal cartilage blending into brachiocephalicus; unlike the robust equine version, it is vestigial and considered functionally part of the deep pectoral complex.
// COMPARATIVE ANALYSIS
| HORSE |
Deep pectoral (ascending) is massive; subclavius is distinct and robust. |
| DOG |
Deep pectoral has distinct abdominal attachment; accessory head common. |
CLINICAL RELEVANCE
Deep Pectoral Tear: Rare but causes limb abduction inability, 'sprawling' gait. Mastitis Extension: Infections can track along pectoral fascia to forelimb lymphatics.
