MSK - Muscles of the Pectoral Region Flashcards Preview

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Flashcards in MSK - Muscles of the Pectoral Region Deck (17)
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How many muscles lie in the pectoral region?

What are their names?


Pectoralis Major

Pectoralis Minor

Serratus Anterior


What is the most superficial muscle of the pectoral region? What is is shaped like?

Pectoralis Major

Fan Shaped


How many heads does the Pectoralis Major have?

What are their names?

Where do they attach?

2 heads

Clavicular head - Attaches to the clavicle

Sternocostal head - Attaches to the sternum and ribs

Fibres from both can be found attaching to the intertubecular groove of the humerus


Where does the Pectoralis Major originate from?

Anterior surface of sternal half of clavicle, anterior half of sternum and as low down as sixth of seventh rib


What actions are the two heads capable of?

What further action is the clavicular head capable of?

Together - Adduction and Medial Rotation of the Humerus

Clavicular Head - Flexion


What nerves innervate the Pectoralis Major?

Where are they derived from?

Medial and Lateral Pectoral nerves

Brachial Plexus


What muscle lies posterior to the Pectoralis Major?

Pectoralis Minor


What shape is the Pectoralis Minor?

Triangular Shape


Where does the Pectoralis Minor originate from?

Where does it attach to?

Anterior surface of ribs 3-5

Attaches to corocoid process of Scapula


What nerve innervates the Pectoralis Minor

Medial Pectoral Nerve


What is the main action of Pectoralis Minor?

Stabilises scapula by drawing it inferiorly and anteriorly against thoracic wall


What muscle is found more laterally in the chest than the Pectoralis Major and Minor muscles and forms the medial wall of the axilla?

Serratus Anterior


Where does the Serratus Anterior originate from?

Where does it attach to?

Serratus Anterior is composed of strip of muscle that originate from ribs 2-8

Attach to costal surface of the medial border of the scapula

(Note: Medial border of costal surface of Scapula has been expertly spray painted in green. Not to be confused with the Acromion which is also shaded a green colour)


What is the Serratus Anterior innervated by?

Long Thoracic Nerve


What is the action of the Serratus Anterior?

Rotates the Scapula which allows abduction of the arm above 90°

Also holds Scapula against thoracic wall (ribcage) which is useful when upper limb reaches anteriorly in actions such as punching. Hence, the Serratus Anterior is the "boxer's muscle"


What has happened to this individual?

"Winged Scapula"

Damage to the Long Thoracic Nerve

Serratus Anterior no longer innervated, Scapula no longer held against rib cage


How might Winged Scapula occur?

Trauma to the shoulder

Repetiive movements involving the shoulder

Structures becoming inflamed and pressing on the Long Thoracic nerve