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Encyclopedia > Pectoralis major
Contents

Location

The clavicular head of the pectoralis major takes its origin from the anterior surface of the medial half of the clavicle. The sternocostal head takes its origin from the anterior surface of the sternum, the superior six costal cartilages, and the aponeurosis of the external oblique muscle.


The muscle fibres then converge and inserted into the lateral lip of the intertubucular groove of the humerus


Action

Clavicular head : flexes the humerus
Sternocostal head : extends the humerus


As a whole, the pectoralis major adducts and laterally rotate the humerus. It also draws the scapula anteriorly and inferiorly.


Innervation

  • lateral and medial pectoral nerves
  • the clavicular head is innervated by nerves from C5 and C6
  • the sternocostal head is innervated by nerves from C7, C8 and T1

Blood supply

pectoral branch of the thoracoacromial trunk


  Results from FactBites:
 
IV. Myology. The Muscles Connecting the Upper Extremity to the Anterior and Lateral Thoracic Walls. Gray, Henry. 1918. ... (1805 words)
As the fascia leaves the lower edge of the Pectoralis major to cross the floor of the axilla it sends a layer upward under cover of the muscle; this lamina splits to envelop the Pectoralis minor, at the upper edge of which it is continuous with the coracoclavicular fascia.
Below this it is thin, and at the upper border of the Pectoralis minor it splits into two layers to invest the muscle; from the lower border of the Pectoralis minor it is continued downward to join the axillary fascia, and lateralward to join the fascia over the short head of the Biceps brachii.
—The Pectoralis major is supplied by the medial and lateral anterior thoracic nerves; through these nerves the muscle receives filaments from all the spinal nerves entering into the formation of the brachial plexus; the Pectoralis minor receives its fibers from the eighth cervical and first thoracic nerves through the medial anterior thoracic nerve.
  More results at FactBites »

 
 

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