Gross Anatomy of Muscles

Cranial Aponeurosis

Connects to the frontalis and occipitalis; forms the scalp.

Occipitalis

Located at the back of the head; immovable.

Frontalis

Raises eyebrows and wrinkles the forehead.

Temporalis

Closes the jaw; elevates the mandible.

Orbicularis Oculi

Responsible for blinking, squinting, and winking.

Nasalis

Flares nostrils; used when smelling deeply.

Zygomaticus

Runs diagonally; helps with smiling (includes major and minor).

Buccinator

Runs horizontally across the cheek; compresses cheek to keep food between teeth.

Masseter

Strongest jaw muscle; helps with chewing and elevates the mandible.

Orbicularis Oris

Closes the lips; used in kissing.

Platysma

Pulls mouth downward (sad face expression); superficial muscle.

Sternocleidomastoid

Rotates head and helps lift head when lying down (one side at a time).

Trapezius

Moves the scapula (elevation and retraction); located in the upper back.

Deltoid

Covers the shoulder; abducts the arm.

Pectoralis Major

Located in the chest; responsible for shoulder flexion and arm adduction.

Biceps Brachii

Main muscle for elbow flexion; works when arm is supinated (palm up).

Brachialis

Lies deep to the biceps; works in both supination and pronation.

Triceps Brachii

Main muscle for elbow extension.

Brachioradialis

Assists in wrist flexion and helps stabilize the elbow.

External Oblique

Runs diagonally; involved in trunk rotation and flexion (intermediate layer).

Internal Oblique

Also runs diagonally (opposite direction); deeper than external.

Transversus Abdominis

Runs horizontally; deepest abdominal muscle; compresses abdomen.

Rectus Abdominis

Runs vertically ('six-pack'); flexes the spine and stabilizes the pelvis.

Serratus Anterior

Located on the ribs; abducts and stabilizes the scapula (think: boxing motion).

Latissimus Dorsi

Large lower back muscle; helps with arm adduction and extension (think: swimming).

Erector Spinae

Runs from skull to pelvis; helps with back extension and posture.

Quadratus Lumborum

Located in the lower back (lumbar region); helps stabilize and extend the spine.