Muscle Anatomy Notes

Muscles Overview

  • Important for anatomy and physiology identification and understanding.

  • Know the origins, insertions, and actions for lab tests.

Muscles of the Head and Neck

Frontalis

  • Action: Raises eyebrows, wrinkles forehead

  • Origin: Galea aponeurotica

  • Insertion: Skin of eyebrow, nose

Occipitalis

  • Action: Tenses and retracts the scalp

  • Origin: Occipital bone, mastoid

  • Insertion: Galea aponeurotica

Temporalis

  • Action: Elevate mandible

  • Origin: Temporal lines of skull

  • Insertion: Coronoid process of mandible

Zygomaticus Major

  • Action: Elevates/retracts the corner of mouth (smile muscle)

  • Origin: Zygomatic bone

  • Insertion: Corner orbicularis oris

Nasalis

  • Action: Compresses bridge of nose, elevates nostril corners

  • Origin: Maxillary bone, cartilage

  • Insertion: Bridge of nose

Buccinator

  • Action: Compresses cheeks, creates suckling action (infants)

  • Origin: Maxillary bone, mandible

  • Insertion: Orbicularis oris

Orbicularis Oculi

  • Action: Closes eyelids

  • Origin: Medial orbit bones

  • Insertion: Skin of eyelid

Orbicularis Oris

  • Action: Closes lips, puckers, shapes lips for speech

  • Origin: Maxillary bone, mandible

  • Insertion: Mucosa of lips

Mentalis

  • Action: Elevates/protrudes the lower lip (pout)

  • Origin: Fossa on mandible

  • Insertion: Skin of chin

Sternocleidomastoid

  • Action:

    • Both together: flex neck

    • Each singly: rotate/turn head

  • Origin: Sternum (manubrium), clavicle

  • Insertion: Mastoid process

Platysma

  • Action: Tenses skin of neck, depresses mandible

  • Origin: Superior thorax (between acromion process & cartilage rib #2)

  • Insertion: Mandible, skin of cheek

Muscles of the Back and Shoulders

Semispinalis Capitis

  • Action:

    • Both together: extend head

    • Each singly: extends/tilts head

  • Origin: Processes lower cervical and upper thoracic vertebrae

  • Insertion: Occipital bone

Trapezius

  • Action:

    • Elevates clavicle

    • Adducts, elevates, retracts, depresses scapula

  • Origin: Occipital bone, all cervical and thoracic vertebrae

  • Insertion: Clavicle, scapula

Latissimus Dorsi

  • Action: Extends, adducts, and medially rotates shoulder

  • Origin: Lower thoracic, lumbar, and sacral vertebrae, ribs 8-12

  • Insertion: Humerus – intertubercular groove

Deltoid

  • Action: Abducts, flexes, extends, and rotates shoulder

  • Origin: Clavicle, scapula

  • Insertion: Humerus (deltoid tuberosity)

Muscles of the Chest

Pectoralis Major

  • Action: Flexes, adducts, and medially rotates at shoulder

  • Origin: Clavicle, sternum (body), costal cartilage ribs 2-6

  • Insertion: Humerus – greater tubercle & intertubercular groove

Pectoralis Minor

  • Action: Depresses and protracts shoulder, rotates scapula downward

  • Origin: Ventral surfaces of ribs 3-5

  • Insertion: Coracoid process – scapula

Muscles of the Abdomen

Rectus Abdominis

  • Action: Compresses abdomen, flexes vertebral column anteriorly, depresses ribs

  • Origin: Pubic crest/symphysis

  • Insertion: Xiphoid and costal cartilage for ribs 5-7

External Oblique

  • Action:

    • Both together: compress abdomen

    • One side at a time: flex spine laterally

  • Origin: Lower 8 ribs

  • Insertion: Iliac crest, linea alba

Internal Oblique

  • Action:

    • Both together: compresses abdomen

    • One side at a time: flex spine laterally

  • Origin: Iliac crest

  • Insertion: Linea alba, lower ribs, xiphoid process

Transverse Abdominis

  • Action: Compresses abdomen

  • Origin: Iliac crest, costal cartilage of lower ribs, thoracolumbar fascia

  • Insertion: Pubis, linea alba

Muscles of the Lower Extremity

Gluteus Maximus

  • Action: Extends and laterally rotates the thigh

  • Origin: Ilium, sacrum, coccyx

  • Insertion: Femur

Gluteus Medius

  • Action: Abducts and medially rotates the thigh

  • Origin: Ilium

  • Insertion: Femur - greater trochanter

Quadriceps Group

  • Includes: Rectus femoris, Vastus medialis, Vastus lateralis, Vastus intermedius

  • Action: All extend knee

  • Origin: Varies by muscle, generally from femur, pelvis

  • Insertion: Patella and tibia via patellar tendon

Hamstrings Group

  • Includes: Biceps femoris, Semitendinosus, Semimembranosus

  • Action: Flexes knee, extends thigh

  • Origin: Ischial tuberosity, linea aspera of femur

  • Insertion: Varies by muscle; generally include fibula and tibia

Tibialis Anterior

  • Action: Dorsiflexes and inverts foot

  • Origin: Tibia (lateral condyle)

  • Insertion: Medial cuneiform and 1st metatarsal

Gastrocnemius

  • Action: Plantar flexes, inverts foot, adducts foot, flexes knee

  • Origin: Femoral condyles

  • Insertion: Calcaneus via the calcaneal tendon

Soleus

  • Action: Plantar flexes, inverts foot, adducts foot

  • Origin: Fibula, tibia

  • Insertion: Calcaneus via the calcaneal tendon

Fibularis (Peroneus) Longus

  • Action: Everts foot, plantar flex foot, supports arch

  • Origin: Tibia, fibula

  • Insertion: 1st metatarsal bone, medial cuneiform

Study Tips

  • Use anatomy models for visual aids.

  • Write out muscle names, origin, insertion, and action repeatedly.

  • Quiz yourself or use flashcards to reinforce memory.