muscles

Masseter Muscle Superior Attachment

Zygomatic arch

Masseter Muscle Inferior Attachment

Angle and ramus of mandible

Masseter Muscle Action

Elevates and protracts the mandible; prime mover of elevation for chewing.

Sternocleidomastoid Muscle Superior Attachment

Mastoid process of temporal bone

Sternocleidomastoid Muscle Inferior Attachment

Manubrium of sternum & sternal end of clavicle

Sternocleidomastoid Muscle Action

Bilaterally flexes neck; unilaterally rotates head to opposite side.

Rectus Abdominis Muscle Superior Attachment

Xiphoid process of sternum

Rectus Abdominis Muscle Inferior Attachment

Superior surface of pubis near symphysis

Rectus Abdominis Muscle Action

Flexes the vertebral column and compresses the abdominal wall.

Trapezius Muscle Superior Attachment

Occipital bone & ligamentum nuchae

Trapezius Muscle Inferior Attachment

Clavicle, acromion, spine of scapula

Trapezius Muscle Action

Elevates, retracts, depresses, and rotates the scapula.

Deltoid Muscle Proximal Attachment

Clavicle, acromion, spine of scapula

Deltoid Muscle Distal Attachment

Deltoid tuberosity of humerus

Deltoid Muscle Action

Abducts the arm; flexes/medially rotates (anterior), extends/laterally rotates (posterior).

Elbow Flexion Prime Movers

Biceps brachii, Brachialis, Brachioradialis

Elbow Extension Prime Movers

Triceps brachii and Anconeus

Shoulder Abduction Main Mover

Deltoid (middle fibers)

Shoulder Abduction Initiator

Supraspinatus (first 15°)

Shoulder Adduction Prime Movers

Pectoralis major, Latissimus dorsi, Teres major

Hip Flexion Muscles

Iliopsoas (iliacus + psoas major), Rectus femoris, Sartorius

Hip Extension Muscles

Gluteus maximus and Hamstrings

Knee Extension Prime Movers

Quadriceps group (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius)

Knee Flexion Assisting Muscles

Hamstrings (biceps femoris, semitendinosus, semimembranosus) and Gastrocnemius

Common Musculoskeletal Injury - Unhappy Triad

Involves ACL, medial meniscus, and MCL injuries.

Common Musculoskeletal Injury - Shoulder Separation

Injury to the acromioclavicular joint.

ACL Function

Prevents anterior tibial translation, crucial for knee stability.

PCL Function

Prevents posterior tibial translation, important for knee stability.

Ankle Inversion Sprain Impact

Tears lateral ligaments; anterior talofibular ligament most commonly affected.

Disc Herniation

Occurs when the nucleus pulposus protrudes, compressing spinal nerves.