Muscles of the thorax – Musculi thoracis
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Muscles
The muscles of the thorax are organised into three groups: the thoracohumeral muscles, which insert on the upper limb, the proper muscles of the thorax, which are the main muscles of respiration, and the diaphragm. 1 Thoracohumeral muscles 1.1 Pectoralis major (musculus pectoralis major) 1.2 Pectoralis minor (musculus pectoralis minor) 1.3 Serratus anterior (musculus serratus anterior) 1.4 Subclavius (musculus subclavius) 2 Proper muscles of the thorax 2.1 Intercostal muscles (musculi intercostales) 2.1.1 External intercostal muscles (musculi intercostales externi) 2.1.2 Internal intercostal muscles (musculi intercostales interni) 2.1.3 Innermost intercostal muscles (musculi intercostales intimi) 2.2 Transversus thoracis (musculus transversus thoracis) 2.3 Levatores costarum (musculi levatores costarum) 3 Diaphragm (diaphragma)
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The anterior axillary fold (plica axillaris anterior) is formed by the tendon of the pectoralis major. The subclavius is functionally considered to be part of the pectoralis major.
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1.4 1.2
1.1
2.1.1
Clinical notes 1.3
The subclavius protects the vessels and nerves that run under the clavicle. This is important in fractures of the clavicle. All three parts of the pectoralis major tend to shorten and must be evaluated and exercised separately. Trigger points in the sternocostal part of the pectoralis major may cause hypersensitivity of the nipple and areola.
2.1.1
2.1.2 2.1.3
3
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The trigger point of cardiac arrhythmia is a trigger point situated in the sternocostal part of the pectoralis major under the 5th rib 3–4 cm laterally from the midline. It may cause a sense of palpitations, but there is no underlying cardiac pathology. The pectoralis minor may compress some branches of the axillary artery and distal parts of the brachial plexus. This muscle is usually examined in abduction and lateral rotation of the shoulder. Shortening of the pectoralis minor leads to protraction of the arms. A hypertonic pectoralis minor is associated with pain in the infraclavicular region. Trigger points in the serratus anterior may lead to problems with breathing. Such patient may suffer from a lack of air and may even complain of painful inspiration. The pain may radiate to the ulnar part of the arm, forearm and hand.