Pectoralis Major Muscle

Pectoralis Major Muscle

Question 1. Enumerate the muscles of the pectoral region.
Answer.

• Pectoralis major
• Pectoralis minor
• Subclavius

Question 2. Give the origin, insertion, nerve supply, and actions of the pectoralis major muscle.
Answer.

Pectoralis Major Muscle Origin

• Clavicular head: From the anterior surface of the medial 1/2 of the clavicle.
• Sternocostal head arises from:
• • Anterior surface of the sternum up to the 6th costal cartilage.
  • Medial parts of the 2nd to 6th costal cartilages.
  • Aponeurosis of the external oblique muscle.

Pectoralis Major Muscle Insertion

By a bilaminar tendon onto the lateral lip of the bicipital groove in a ‘U-shaped manner’ with two laminae continuous with each other inferiorly.

Pectoralis Major Muscle Nerve Supply

Medial and lateral pectoral nerves.

Pectoralis Major Muscle Actions

Adduction and medial rotation of the shoulder.

Question 8. Give the origin, insertion, nerve supply, and actions of the pectoralis minor muscle.
Answer.

Pectoralis Minor Muscle Origin

Arises from the 3rd, 4th, and 5th ribs anteriorly near their costal cartilages.

Pectoralis Minor Muscle Insertion

Medial border and upper surface of the coracoid process of the scapula.

Pectoralis Minor Muscle Nerve Supply

Medial and lateral pectoral nerves (C6–C8).

Pectoralis Minor Muscle Action

• Pectoralis Minor Muscle draws the scapula forward across the chest wall along with the serratus anterior.
• Pectoralis Minor Muscle depresses the shoulder as in bringing the arm down from the ‘above head position’.