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Pectoralis Major Muscle - want to learn more about it?

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Pectoralis Major Muscle

The pectoralis major muscle is a strong, fan-shaped muscle of the shoulder joint. It decisively shapes the surface anatomy of the breast. Furthermore it participates in forming the anterior wall of the axilla. The innervation is carried by the medial and lateral pectoral nerves (C5-T1), direct branches of the brachial plexus.

This muscle is also important because of its function as the accessory breathing muscle. This happens during all conditions that interfere with breathing process, such are many lung diseases like asthma, bronchitis, bronchiolitis, obstructive and restrictive lung diseases. In those states, the pectoralis major helps with the expanding of the chest.

Key Facts
Origin Clavicular part: medial half of the clavicle
Sternocostal part: sternum, 2nd to 7th costal cartilages
Abdominal part: anterior layer of the rectus sheath
Insertion Greater tubercle of the humerus
Innervation Lateral pectoral nerves (branches of the brachial plexus)
Vascularization Pectoral branch of the thoracoacromial artery
Function Adduction and anteversion of the shoulder, medial rotation of the arm, retroversion of the arm
Antagonist Deltoid muscle
Clinical relations Aplasia, Polan syndrome

This article will discuss all the important anatomical and clinical aspects related to the pectoralis major muscle.

Recommended video: Pectoralis major muscle
Origins, insertions, innervation and functions of the pectoralis major muscle.

Parts/Divisions

Due to its various origins the muscle is subdivided in three parts:

  • Clavicular part - medial half of the clavicle
  • Sternocostal partsternum, 2nd to 7th costal cartilages
  • Abdominal part - anterior layer of the rectus sheath

All fibers insert together at the crest of the greater tubercle located at the proximal humeral shaft. Due to the different courses of the muscle fibers, the insertion has a recess which is open to the top preventing the muscle from overstretching. The triangular depression between the pectoralis major muscle, deltoid muscle and clavicle is called infraclavicular fossa (Mohrenheim’s fossa). Here the cephalic vein passes through the subfascia within the deltopectoral groove.

Functions

The pectoralis major muscle is the most important muscle for the adduction and anteversion of the shoulder joint which is why it is also known as the “breaststroke muscle”. It rotates the upper arm inwards (medial rotation) and makes a powerful stroke movement (retroversion) when the arms are elevated (e.g. in wood-chopping). If the arms are fixed the muscle lifts the trunk which can be helpful in climbing or during inspiration (inspiratory breathing muscle).

Clinical Notes

Aplasia of the pectoralis major muscle is one of the most common muscular malformations. In Poland syndrome there is embryonic malformation of the thoracic wall, which is accompanied by a defect of the pectoralis major muscle in combination with other malformations of the upper extremities (e.g., malformations of the fingers). The muscle can be partly or completely missing. Depending on the degree of severity, the adduction and anteversion of the shoulder joint are made more difficult (for example, the crossing of the raised arms). In addition, affected persons have visibly distorted breasts due to the aplasia of the muscle, which is why a plastic-surgical reconstruction can be used therapeutically.

Pectoralis Major Muscle - want to learn more about it?

Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster.

Sign up for your free Kenhub account today and join over 852,397 successful anatomy students.

“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

Show references

References:

  • D. Drenckhahn/J. Waschke: Taschenbuch Anatomie, 1.Auflage, Urban & Fischer Verlag/Elsevier (2008), S.31-32
  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.302-303, 374-376
  • W. Graumann/ D.Sasse: CompactLehrbuch der gesamten Anatomie – Band 2 – Bewegungsapparat, Schattauer Verlag (2003), S.271-273
  • F. Gohlke/A. Hedtmann: Orthopädie und Orthopädische Chirurgie, 1.Auflage, Thieme Verlag (2002), S.178-180

Author & Layout:

  • Achudhan Karunaharamoorthy
  • Christopher A. Becker
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the ventral trunk

Main muscles of the trunk

Muscles of the arm and the shoulder

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