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What is the primary action of the whole pectoralis major muscle?
Which nerve primarily supplies the pectoralis minor muscle?
What muscle helps with deep inspiration by raising the ribs when the scapula is fixed?
Where does the pectoralis major muscle insert?
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What is the action of the subclavius muscle?
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Which part of the pectoralis major muscle is responsible for extending the flexed arm?
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What fascia forms a suspensory ligament of the axilla?
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Which ribs does the pectoralis minor muscle originate from?
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Which structure is part of the axillary fascial septum?
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Which muscle does the long thoracic nerve supply?
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What is the primary action of the serratus anterior muscle?
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Which artery is associated with the acromiothoracic region?
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Which digitations of the serratus anterior muscle insert into the inferior angle of the scapula?
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Which of the following structures does NOT pierce the clavipectoral fascia?
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How does the serratus anterior muscle assist in respiration?
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Which feature is characteristic of the fascia surrounding the subclavius muscle?
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Study Notes
Pectoralis Major Muscle
- Origin:
- Clavicular head: anterior surface of medial half of clavicle
- Sternocostal head: anterior surface of sternum, front of the upper 6 costal cartilages, and aponeurosis of external abdominal oblique muscle
- Insertion: by a bilaminar tendon into the lateral lip of bicipital (inter-tubercular) groove of humerus
- Nerve Supply: medial and lateral pectoral nerves
- Action:
- Clavicular head: flexion, adduction, and medial rotation of the arm
- Sternocostal head: extension, adduction, and medial rotation of the arm. Involved in swimming, rowing, and climbing with latissimus dorsi muscle
- Whole muscle: adduction and medial rotation of the arm
Pectoralis Minor Muscle
- Origin: anterior surfaces of 3rd, 4th, and 5th ribs close to their costal cartilages
- Insertion: medial border and upper surface of coracoid process of scapula
- Nerve Supply: medial pectoral nerve
- Action:
- Protraction and depression of the shoulder girdle
- Downward rotation of the scapula
- Helps in deep inspiration by raising the ribs when the scapula is fixed
Subclavius Muscle
- Origin: upper surface of 1st costo-chondral junction
- Insertion: groove in the middle 1/3 of the inferior surface of the clavicle
- Nerve Supply: nerve to subclavius (C5)
- Action: steadies the clavicle during excessive movements of the shoulder girdle
Clavipectoral Fascia
- Site: strong sheet of deep fascia located between the subclavius muscle (above) and pectoralis minor muscle (below), deep to the upper part of pectoralis major muscle
- Attachments:
- Above: splits to enclose subclavius muscle, then attaches to the inferior surface of clavicle
- Below: splits to enclose pectoralis minor muscle, then continues downwards to form "suspensory ligament of axilla," which fuses with axillary fascia
- Medially: attaches to 1st and 2nd costal cartilages
- Laterally: attaches to coracoid process of scapula, where it blends with the coraco-clavicular ligament
Structures Piercing Clavipectoral Fascia
- Cephalic vein
- Lateral pectoral nerve
- Acromiothoracic artery
- Lymph vessels from infraclavicular lymph nodes to apical axillary lymph nodes
Serratus Anterior Muscle
- Origin: arises by 8 digitations from outer surfaces of the upper 8 ribs
- 1st digitation arises from the 1st and 2nd ribs as well as fibrous arch between the ribs
- Insertion: ventral surface of the medial border of the scapula
- 1st digitation inserts into the superior angle
- 2nd and 3rd digitations fan out to insert into the whole length of the medial border
- Lower 5 digitations insert into the inferior angle
- Nerve Supply: nerve to serratus anterior (long thoracic nerve) from C5, 6, and 7. Descends on the outer surface of the muscle in the mid-axillary line.
- Action:
- Whole muscle:
- Powerful protraction of the scapula (as in boxing)
- Fixation of the scapula to the chest wall (as in pushing against resistance)
- Helps in deep inspiration by elevation of the ribs when the scapula is fixed (accessory muscle of inspiration)
- Lower 5 digitations:
- With upper and lower fibers of trapezius, rotates the scapula upwards.
- Depresses the shoulder girdle.
- Whole muscle:
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Description
This quiz covers the anatomy of the pectoralis major and minor muscles, detailing their origins, insertions, nerve supply, and functions. Test your knowledge on how these muscles contribute to arm movements and shoulder activities.
