Essential Muscle Anatomy: Origin, Insertion, and Action Reference

Major Muscle Origin, Insertion, and Action (OIA)

Muscles of the Neck and Torso

Sternocleidomastoid

• Origin (O): Manubrium of sternum and medial clavicle
• Insertion (I): Mastoid process
• Action (A): Rotates the head (unilaterally)

Pectoralis Major

• Origin (O): Sternum, medial clavicle, and costal cartilages 2-6
• Insertion (I): Intertubercular sulcus of the humerus
• Action (A): Flexes and adducts the arm

Trapezius

• Origin (O): Occipital bone, ligamentum nuchae, and C7-T12 vertebrae
• Insertion (I): Clavicle, acromion, and scapular spine
• Action (A): Elevates, superiorly rotates, retracts, and depresses the scapula

Latissimus Dorsi

• Origin (O): Spinous processes of T7-L5, ribs 10-12, and iliac crest
• Insertion (I): Intertubercular sulcus of the humerus
• Action (A): Extends, adducts, and medially rotates the arm

Rectus Abdominis

• Origin (O): Xiphoid process and costal cartilage of ribs 5-7
• Insertion (I): Pubic symphysis and pubic crest
• Action (A): Flexes the trunk, compresses abdominal viscera, and aids in forced expiration

Muscles of the Upper Limb

Triceps Brachii

• Origin (O): Posterior humerus and scapula
• Insertion (I): Olecranon process of the ulna
• Action (A): Prime mover of elbow extension (extends arm and forearm)

Biceps Brachii

• Origin (O): Coracoid process of the scapula (short head) and supraglenoid tubercle of the scapula (long head)
• Insertion (I): Radial tuberosity
• Action (A): Elbow and arm flexion (long head), forearm supination and flexion

Brachialis

• Origin (O): Distal half of the anterior humerus
• Insertion (I): Coronoid process (on the ulna) and the ulnar tuberosity
• Action (A): Flexes the forearm

Muscles of the Lower Limb

Rectus Femoris (Quadriceps Group)

• Origin (O): Anterior inferior iliac spine
• Insertion (I): Tibial tuberosity
• Action (A): Extends the leg at the knee and flexes the thigh at the hip

Vastus Medialis (Quadriceps Group)

• Origin (O): Femur
• Insertion (I): Tibial tuberosity
• Action (A): Leg and knee extension

Vastus Lateralis (Quadriceps Group)

• Origin (O): Greater trochanter of the femur
• Insertion (I): Tibial tuberosity
• Action (A): Prime mover of knee extension

Biceps Femoris (Hamstring Group)

• Origin (O): Ischial tuberosity (long head) and femur (short head)
• Insertion (I): Lateral condyle of the tibia
• Action (A): Extends thigh at the hip (long head) and flexes the knee (short head)

Semitendinosus (Hamstring Group)

• Origin (O): Ischial tuberosity
• Insertion (I): Medial side of the proximal tibia
• Action (A): Extends the thigh at the hip and flexes the leg and knee

Semimembranosus (Hamstring Group)

• Origin (O): Ischial tuberosity
• Insertion (I): Medial condyle of the tibia
• Action (A): Extends thigh at the hip and flexes leg and knee

Gastrocnemius

• Origin (O): Medial and lateral condyles of the femur
• Insertion (I): Calcaneus
• Action (A): Plantar flexes the foot and flexes the leg