Human Muscle Anatomy: Origin, Insertion & Action

Understanding Key Human Muscles and Their Functions

Temporalis

• Origin: Along temporal lines of the skull.
• Insertion: Coronoid process of the mandible.
• Action: Elevates the mandible.

Masseter

• Origin: Zygomatic arch.
• Insertion: Ramus of the mandible.
• Action: Elevates the mandible and closes the jaw.

Sternocleidomastoid

• Origin: Attaches to the sternal end of the clavicle and manubrium.
• Insertion: Mastoid region and lateral nuchal line of the skull.
• Action: Flexes the neck.

Pectoralis major

• Origin: Cartilage of ribs 2-6, sternal body, and medial clavicle.
• Insertion: Greater tubercle and intertubercular groove of the humerus.
• Action: Flexion, adduction, and medial rotation at the shoulder.

Biceps brachii

• Origin: Coracoid process of the scapula.
• Insertion: Tuberosity of the radius.
• Action: Flexion at the elbow and shoulder, supination.

Flexor carpi radialis

• Origin: Medial epicondyle of the humerus.
• Insertion: Second and third metacarpal bones.
• Action: Flexion and abduction at the wrist.

Flexor carpi ulnaris

• Origin: Medial epicondyle of the humerus.
• Insertion: Pisiform, hamate, and fifth metacarpal bones.
• Action: Flexion and adduction at the wrist.

Rectus abdominis

• Origin: Superior pubis around the symphysis.
• Insertion: Costal cartilages of ribs 5-7 and xiphoid process.
• Action: Depresses ribs, flexes the spine, and compresses the abdomen.

Iliacus

• Origin: Iliac fossa of the ilium.
• Insertion: Femur distal to the lesser trochanter.
• Action: Flexion at the hip.

Adductor longus

• Origin: Inferior pubic ramus anterior to the adductor brevis.
• Insertion: Linea aspera of the femur.
• Action: Adduction, flexion, and medial rotation at the hip.

Sartorius

• Origin: Anterior superior iliac spine.
• Insertion: Near the tibial tuberosity.
• Action: Flexion at the knee; flexion and lateral rotation at the hip.

Rectus femoris

• Origin: Anterior inferior iliac spine and superior acetabular rim.
• Insertion: Tibial tuberosity by the patellar ligament.
• Action: Extension at the knee, flexion at the hip.

Tibialis anterior

• Origin: Lateral condyle and proximal shaft of the tibia.
• Insertion: First metatarsal and medial cuneiform.
• Action: Flexion at the ankle and inversion of the foot.

Extensor hallucis longus

• Origin: Anterior fibula.
• Insertion: Superior distal phalanx of the great toe.
• Action: Extension of the great toe.

Extensor digitorum longus

• Origin: Lateral condyle of the tibia and anterior fibula.
• Insertion: Superior phalanges of digits 2-5.
• Action: Extension of digits 2-5.