Muscle Origins, Insertions, and Actions

Anterior Muscles

Deltoid

• Description: A triangular muscle forming the rounded contour of the shoulder.
• Origin: Clavicle, Acromion, and Scapula.
• Insertion: Humerus. Specifically, into the deltoid tuberosity on the lateral aspect of the humerus.
• Joint Crossed: Shoulder (Glenohumeral joint).
• Action:
  • Flexion and extension of the shoulder (Glenohumeral joint).
  • Abduction of the arm.
  • Medial and lateral rotation of the arm.

Pectoralis Major

• Description: A large, fan-shaped muscle covering the upper portion of the chest.
• Origin: Clavicle, Sternum, Ribs.
• Insertion: Humerus. Specifically, into the intertubercular groove of the humerus.
• Joint Crossed: Shoulder (Glenohumeral joint).
• Action:
  • Adduction of the arm.
  • Medial rotation of the arm.

Rectus Abdominis

• Description: A paired muscle running vertically on each side of the anterior wall of the abdomen.

Abdominal External Oblique

• Description: A paired muscle located on the lateral and anterior aspects of the abdomen.

Iliopsoas

Biceps Brachii

• Description: A two-headed muscle located in the anterior compartment of the arm.
• Origin: Scapula. Specifically, the short head originates from the coracoid process, and the long head originates from the supraglenoid tubercle.
• Insertion: Radius. Specifically, into the radial tuberosity.
• Joints Crossed: Shoulder and Elbow.
• Action:
  • Flexion of the elbow.

Brachialis

• Description: A muscle located deep to the biceps brachii in the anterior compartment of the arm.
• Origin: Humerus. Specifically, the anterior surface of the distal humerus.
• Insertion: Ulna. Specifically, into the ulnar tuberosity and coronoid process.
• Joint Crossed: Elbow.
• Action:
  • Flexion of the elbow.
• Note: Strong elbow flexor.

Pronator Teres

Brachioradialis

Quadriceps Femoris

Adductor Muscles

Peroneus Longus

Tibialis Anterior

Peroneus Brevis

Posterior Muscles

Trapezius

• Description: A large, flat, triangular muscle of the upper back and posterior neck.
• Origin: Cervical and Thoracic vertebrae.
• Insertion: Scapular edge of the clavicle.
• Joint Crossed: Shoulder.
• Action:
  • Elevation of the shoulder girdle.
  • Retraction of the shoulder girdle.
  • Depression of the shoulder girdle.
  • Rotation of the shoulder girdle.

Latissimus Dorsi

• Description: A broad, flat muscle of the middle and lower back.
• Origin: Thoracolumbar fascia (TLF), Lumbar vertebrae, Sacral vertebrae, Iliac crest, Ribs, and Scapula.
• Insertion: Humerus. Specifically, into the intertubercular groove of the humerus.
• Joint Crossed: Shoulder (Glenohumeral joint).
• Action:
  • Adduction of the arm.
  • Medial rotation of the arm.
• Origin: Ribs
• Insertion: Scapular
• Joint Crossed: Shoulder Girdle
• Action:
  • Protraction of the shoulder girdle.
  • Rotation of the shoulder girdle.
  • Elevation of the shoulder girdle.

Biceps Femoris

Semitendinosus

Semimembranosus

Gastrocnemius

Soleus

Rotator Cuff

Summary Table