Pectoral Muscles Anatomy

Pectoral Muscles

The pectoral muscles are a group of muscles located in the pectoral region, which include:

Pectoralis Major

• Origin: Medial clavicle, sternum, and costal cartilages
• Insertion: Lateral lip of bicipital groove of humerus
• Actions:
  • Adduction of the arm
  • Flexion of the arm
  • Medial rotation of the arm
• Innervation: Lateral and medial pectoral nerves

Pectoralis Minor

• Origin: Third to fifth ribs
• Insertion: Coracoid process of scapula
• Actions:
  • Depression of the scapula
  • Forward tilt of the scapula
• Innervation: Lateral pectoral nerve

Serratus Anterior

• Origin: First to ninth ribs
• Insertion: Costal surface of scapula
• Actions:
  • Rotation of the scapula
  • Abduction of the arm
• Innervation: Long thoracic nerve

Subclavius

• Origin: First rib
• Insertion: Inferior surface of clavicle
• Actions:
  • Depression of the clavicle
  • Stabilization of the clavicle
• Innervation: Nerve to subclavius

Pectoral Muscles

• Located in the pectoral region

Pectoralis Major

• Originates from the medial clavicle, sternum, and costal cartilages
• Inserts into the lateral lip of the bicipital groove of humerus
• Performs three main actions: • Adduction of the arm • Flexion of the arm • Medial rotation of the arm
• Innervated by the lateral and medial pectoral nerves

Pectoralis Minor

• Originates from the third to fifth ribs
• Inserts into the coracoid process of scapula
• Performs two main actions: • Depression of the scapula • Forward tilt of the scapula
• Innervated by the lateral pectoral nerve

Serratus Anterior

• Originates from the first to ninth ribs
• Inserts into the costal surface of scapula
• Performs two main actions: • Rotation of the scapula • Abduction of the arm
• Innervated by the long thoracic nerve

Subclavius

• Originates from the first rib
• Inserts into the inferior surface of clavicle
• Performs two main actions: • Depression of the clavicle • Stabilization of the clavicle
• Innervated by the nerve to subclavius

Chest Wall Structure in the Pectoral Region

Bony Landmarks

• Sternum is a long, flat bone located in the center of the chest
• There are 12 pairs of ribs that curve outward and backward from the spine to the sternum
• Costal cartilages connect the ribs to the sternum
• Thoracic vertebrae (T1-T12) form the posterior aspect of the chest wall

Muscles of the Chest Wall

• Pectoralis major is a large, fan-shaped muscle that covers the anterior chest wall
• Pectoralis major has two parts: sternal head and clavicular head
• Pectoralis minor is a small, triangular muscle located deep to the pectoralis major
• Serratus anterior is a muscle that originates on the surface of the scapula and inserts on the costal cartilages
• There are three layers of intercostal muscles between the ribs: external, internal, and innermost intercostal muscles

Other Key Structures

• Intercostal spaces are the spaces between the ribs where blood vessels and nerves pass
• The mammary gland is located in the subcutaneous tissue of the anterior chest wall
• The axillary fold is a fold of skin and fascia that marks the boundary between the chest and arm