Comprehensive Human Muscular Anatomy Laboratory Guide and Model Atlas
Head and Neck Musculature
A. Frontalis (Frontal Belly of Epicranius / Occipitofrontalis):
Superficial muscle located across the frontal bone of the forehead.
Function: Elevates the eyebrows and wrinkles the skin of the forehead horizontally (expressions of surprise or curiosity).
B. Temporalis:
Fan-shaped masticatory muscle situated within the temporal fossa superior to the zygomatic arch.
Function: Elevates and retracts the mandible to close the jaw during mastication.
C. Orbicularis Oculi:
Sphincter muscle composed of concentric fibers encircling the orbital perimeter.
Function: Closes the eyelids, blinking, squinting, and drawing tears medially toward the lacrimal sac.
D. Orbicularis Oris:
Circular multilayered sphincter muscle surrounding the oral fissure.
Function: Compresses, closes, purses, and protrudes the lips ("kissing muscle").
E. Buccinator:
Deep, horizontal quadrilateral muscle forming the anterior wall of the cheek, located deep to the masseter and facial adipose tissue.
Function: Compresses the cheeks against the molar teeth during mastication to keep food on occlusal surfaces; expels air forcibly (whistling, blowing).
F. Masseter:
Thick, powerful, rectangular superficial muscle of mastication spanning from the zygomatic arch to the angle and ramus of the mandible.
Function: Prime mover of mandibular elevation, generating powerful biting and chewing forces.
G. Sternocleidomastoid:
Two-headed strap-like muscle of the neck with sternal and clavicular origins that inserts into the mastoid process of the temporal bone.
Function: Unilateral contraction produces ipsilateral cervical lateral flexion and contralateral rotation of the head; bilateral contraction causes cervical flexion.
H. Platysma (Not Shown on Model):
Broad, thin, superficial sheet muscle extending from the upper thoracic and deltopectoral fascia across the clavicle to the inferior border of the mandible and corner of the mouth.
Function: Tenses the skin of the anterior neck, depresses the mandible, and draws down the lower lip and corners of the mouth.
Thoracic and Abdominal Wall Musculature
Thoracic Wall Musculature:
Deltoid (A): Large, multipennate, triangular muscle covering the shoulder joint; primary abductor of the arm past the initial .
Pectoralis Major (B in Model 1; A in Model 2): Thick, fan-shaped muscle covering the upper anterior chest with clavicular and sternocostal heads inserting onto the lateral lip of the intertubercular sulcus of the humerus; adducts, flexes, and medially rotates the humerus.
Pectoralis Minor (C in Model 1; B in Model 2): Thin, flat triangular muscle lying deep to pectoralis major, running from ribs 3–5 to the coracoid process of the scapula; depresses the scapula and stabilizes it against the thoracic wall.
Serratus Anterior (D): Broad, fan-shaped muscle with distinct serrated slips arising from the external lateral surfaces of ribs 1–8 and inserting onto the anterior aspect of the medial border of the scapula; prime protractor of the scapula and anchors the scapula against the thoracic cage ("boxer's muscle").
External Intercostals (E): Eleven pairs of muscles occupying intercostal spaces; fibers run obliquely inferoanteriorly ("hands in pockets"); elevates the ribs to expand thoracic cavity volume during quiet inspiration.
Internal Intercostals (G): Eleven pairs of muscles located deep to the external intercostals; fibers run obliquely inferoposteriorly, perpendicular to the external intercostals; depresses the ribs during forced expiration.
Abdominal Wall Layers (Superficial to Deep):
Rectus Abdominis (F in Thorax Model 1; C in Model 2; A in Cadaver): Segmented, paired strap-like muscle separated along the midline by the linea alba and divided horizontally by tendinous intersections; flexes the vertebral column, compresses abdominal viscera, and stabilizes the pelvis.
External Oblique (D in Torso Model 2; B in Cadaver Abdomen): Most superficial of the three lateral flat muscles; fiber orientation runs inferomedially; unilateral contraction rotates the trunk to the opposite side; bilateral contraction flexes the vertebral column and compresses abdominal contents.
Internal Oblique (E in Torso Model 2; C in Cadaver Abdomen): Intermediate muscle layer lying directly deep to the external oblique; fiber orientation runs superomedially, roughly perpendicular to external oblique fibers; assists in ipsilateral trunk rotation, trunk flexion, and intra-abdominal pressure generation.
Transversus Abdominis (D in Cadaver Abdomen): Deepest of the three flat anterolateral abdominal muscles; fiber orientation runs horizontally (transversely); compresses abdominal viscera and stabilizes the core and lumbar spine without flexing or rotating the trunk.
Posterior Trunk and Shoulder Musculature
Superficial and Intermediate Extrinsic Back Muscles:
Trapezius (E in Torso Model; A in Posterior Cadaver): Large, superficial triangular muscle spanning from the external occipital protuberance and nuchal ligament down through the spinous processes of C7–T12, inserting onto the lateral clavicle, acromion, and spine of the scapula; elevates (upper fibers), retracts (middle fibers), and depresses (lower fibers) the scapula.
Latissimus Dorsi (H in Torso Model; E in Posterior Cadaver): Broad, flat muscle of the lower back originating from the spinous processes of T7–T12, thoracolumbar fascia, iliac crest, and lower ribs, inserting into the floor of the intertubercular groove of the humerus; powerfully extends, adducts, and medially rotates the humerus ("swimmer's muscle").
Rhomboid Minor (G in Torso Model; F in Posterior Cadaver): Small cylindrical muscle superior to rhomboid major running from spinous processes C7–T1 to the medial border of the scapula at the level of the scapular spine; retracts and stabilizes the scapula.
Rhomboid Major (F in Torso Model; G in Posterior Cadaver): Broad parallel-fibered muscle running from spinous processes T2–T5 to the medial border of the scapula below the spine; retracts and downwardly rotates the scapula.
Scapular and Posterior Shoulder Muscles:
Deltoid (H in Posterior Cadaver): Posterior fibers originate along the spine of the scapula; extends and laterally rotates the arm.
Teres Major (A in Torso Model; D in Posterior Cadaver): Thick muscle originating from the posterior surface of the inferior angle of the scapula, inserting onto the medial lip of the intertubercular groove of the humerus; adducts, extends, and medially rotates the arm (functions synergistically with latissimus dorsi; not a rotator cuff muscle).
Rotator Cuff Musculature (SITS Group - Posterior/Scapular Components):
Spine of Scapula: Crucial osseous dividing landmark separating the supraspinous fossa from the infraspinous fossa.
Supraspinatus (C in Torso Model; A in Proximal Posterior Arm Model): Sits superior to the spine of the scapula within the supraspinous fossa; inserts onto the superior facet of the greater tubercle of the humerus; initiates the first of arm abduction.
Infraspinatus (D in Torso Model; B in Posterior Cadaver; B in Proximal Posterior Arm Model): Occupies the infraspinous fossa inferior to the scapular spine; inserts onto the middle facet of the greater tubercle of the humerus; powerful lateral (external) rotator of the arm and stabilizes the glenohumeral joint.
Teres Minor (B in Torso Model; C in Posterior Cadaver; C in Proximal Posterior Arm Model): Narrow, elongated muscle situated along the inferior aspect of the infraspinatus and superior to the teres major; inserts onto the inferior facet of the greater tubercle; laterally rotates the arm and stabilizes the glenohumeral joint.
Teres Major (D in Proximal Posterior Arm Model): Located inferior to teres minor; acts as an adductor and internal rotator.
Deltoid (E in Proximal Posterior Arm Model): Envelops the lateral glenohumeral articulation.
Triceps Brachii (F in Proximal Posterior Arm Model): Located along the posterior brachium; extends the forearm.
Musculature of the Upper Limb
Arm (Brachium) Compartmental Musculature:
Subscapularis (F in Anterior Arm Model): Large, triangular rotator cuff muscle covering the anterior costal surface of the scapula (subscapular fossa); inserts onto the lesser tubercle of the humerus; primary medial (internal) rotator of the arm and anterior dynamic stabilizer of the glenohumeral joint.
Deltoid (G in Anterior Arm Model; A in Cadaver Arm): Caps the shoulder joint; provides abduction, flexion, and extension of the humerus.
Biceps Brachii (D in Anterior Arm Model; B in Cadaver Arm; E in Posterior Arm Model): Two-headed muscle of the anterior compartment of the arm (long head originating from supraglenoid tubercle, short head from coracoid process); inserts onto the radial tuberosity and bicipital aponeurosis; primary flexor of the elbow joint and powerful supinator of the radioulnar joints.
Triceps Brachii (E in Anterior Arm Model; C in Cadaver Arm; D in Posterior Arm Model): Three-headed extensor occupying the posterior compartment of the arm (long head, lateral head, medial head); inserts via a common tendon onto the olecranon process of the ulna; prime extensor of the forearm at the elbow joint.
Anterior Forearm (Antebrachium) - Superficial Flexor Compartment:
Brachioradialis (A): Located along the anterolateral/radial border of the forearm; originates from the lateral supracondylar ridge of the humerus and inserts near the radial styloid process; acts as a powerful flexor of the forearm when semi-pronated ("beer-drinking muscle").
Flexor Carpi Radialis (B): Medial to brachioradialis; originates from the medial epicondyle of the humerus via the common flexor tendon and inserts onto the bases of metacarpals II and III; flexes and abducts (radial deviation) the hand at the wrist.
Flexor Carpi Ulnaris (C): Most medial muscle of the superficial flexor compartment; originates from the medial epicondyle and olecranon, inserting onto the pisiform, hook of hamate, and metacarpal V; flexes and adducts (ulnar deviation) the hand at the wrist.
Posterior Forearm (Antebrachium) - Extensor Compartment:
Extensor Carpi Radialis (C): Located laterally along the radial side; extends and abducts the hand at the wrist.
Extensor Digitorum (B): Central superficial muscle of the posterior forearm; divides into four distinct tendons that insert via the extensor expansion onto digits 2 through 5; primary extensor of the digits and wrist.
Extensor Carpi Ulnaris (A): Located along the medial/ulnar border of the posterior forearm; inserts at the base of metacarpal V; extends and adducts (ulnar deviation) the hand at the wrist.
Pelvic, Hip, and Gluteal Musculature
Iliopsoas Complex and Lateral Hip Stabilizers:
Psoas Major (A): Long, thick muscle originating from the bodies and transverse processes of T12–L5 vertebrae; traverses inferiorly deep to the inguinal ligament.
Iliacus (B): Broad, fan-shaped muscle filling the iliac fossa of the pelvis.
Iliopsoas Integration:
The common tendon inserts onto the lesser trochanter of the femur.
Function: Prime, most powerful flexor of the thigh at the hip joint; flexes the trunk onto the thigh during a sit-up.
Tensor Fasciae Latae / TFL (D in Pelvis Model; E in Cadaver Anterior Leg; H in Anterior Thigh Model): Originates from the anterior superior iliac spine (ASIS) and anterior iliac crest, inserting directly into the fascia lata / iliotibial band; flexes, abducts, and medially rotates the thigh, and tenses the lateral fascia to stabilize the extended knee.
Fascia Latae / Iliotibial Tract (G in Pelvis Model; F in Cadaver Anterior Leg): Deep, dense fibrous aponeurotic sheath enveloping thigh muscles; thickens laterally into the iliotibial band (IT band) running from iliac crest to Gerdy's tubercle on the lateral tibial condyle.
Gluteal Musculature Layers:
Superficial Layer:
Gluteus Maximus (A in Gluteal Model; F in Pelvis Model; A in Posterior Thigh Model): Largest, heaviest muscle of the body; originates from ilium, sacrum, and coccyx, inserting into the gluteal tuberosity of the femur and iliotibial band; prime extensor and lateral rotator of the thigh (active during climbing stairs, running, rising from sitting).
Gluteus Medius (B in Gluteal Model; E in Pelvis Model): Intermediate, fan-shaped muscle located superior and deep to gluteus maximus; inserts onto the lateral surface of the greater trochanter of the femur; primary abductor and medial rotator of the thigh; prevents pelvic drop on the contralateral side during single-leg stance.
Deep Layer (Exposed when Gluteus Maximus and Medius are Removed):
Piriformis (C): Pear-shaped muscle originating from the anterior surface of the sacrum and passing through the greater sciatic foramen to insert onto the superior border of the greater trochanter; primary anatomical landmark dividing the supra- and infrapiriform spaces (sciatic nerve exits immediately inferior to it); laterally rotates the extended thigh and abducts the flexed thigh.
Gluteus Minimus (D): Deepest, smallest gluteal muscle lying entirely beneath gluteus medius; inserts onto the anterior border of the greater trochanter; abducts and medially rotates the thigh in synergy with gluteus medius.
Musculature of the Thigh
Anterior (Extensor) Compartment of the Thigh:
Sartorius (A in Anterior Thigh Model; G in Cadaver Anterior Leg; C in Pelvis Model): Longest muscle in the human body; slender, ribbon-like muscle crossing diagonally from the ASIS to the medial surface of the proximal tibia (pes anserinus); flexes, abducts, and laterally rotates the thigh at the hip; flexes the leg at the knee ("tailor's position").
Quadriceps Femoris Group: Four-headed muscle group inserting via the common quadriceps tendon, through the patella, and via the patellar ligament onto the tibial tuberosity; prime extensor of the knee:
Rectus Femoris (C in Anterior Thigh Model; C in Cadaver Anterior Leg): Fusiform superficial central muscle originating from the anterior inferior iliac spine (AIIS); uniquely crosses two joints, flexing the hip and extending the knee.
Vastus Lateralis (D in Anterior Thigh Model; D in Cadaver Anterior Leg; B in Posterior Thigh Model): Largest vastus belly; forms the anterolateral bulk of the thigh; extends the knee.
Vastus Medialis (B in Anterior Thigh Model; B in Cadaver Anterior Leg): Teardrop-shaped muscle on the anteromedial thigh; extends the knee and prevents lateral patellar tracking.
Medial (Adductor) Compartment of the Thigh:
Adductor Longus (E in Anterior Thigh Model): Triangular muscle situated in the anteromedial groin; adducts, flexes, and medially rotates the thigh.
Adductor Magnus (F in Anterior Thigh Model; F in Posterior Thigh Model): Massive triangular muscle comprising an adductor portion (innervated by obturator nerve) and a hamstring portion (innervated by sciatic nerve); powerful adductor, flexor, and extensor of the hip.
Gracilis (G in Anterior Thigh Model; A in Cadaver Anterior Leg; G in Posterior Thigh Model): Slender, superficial vertical strap-like muscle of the medial thigh; originates from pubic body and inferior ramus, inserting into the pes anserinus of the proximal tibia; adducts the thigh and flexes the leg.
Posterior (Flexor / Hamstring) Compartment of the Thigh:
Biceps Femoris (C): Lateral hamstring muscle consisting of a long head (originating from ischial tuberosity) and short head (originating from linea aspera of femur); common tendon inserts onto the head of the fibula; extends the hip, flexes the knee, and laterally rotates the flexed knee.
Semitendinosus (D): Medial hamstring characterized by a long, cord-like distally placed tendon; originates from ischial tuberosity and inserts onto the pes anserinus of the medial proximal tibia; extends the hip, flexes the knee, and medially rotates the flexed leg.
Semimembranosus (E): Broad, flat, membrane-like medial hamstring lying deep and slightly medial to semitendinosus; originates from ischial tuberosity, inserting onto the posterior medial condyle of the tibia; extends the hip, flexes the knee, and medially rotates the flexed leg.
Musculature of the Lower Leg and Foot
Anterior Compartment of the Leg:
Tibialis Anterior (E in Lower Leg Model): Thick, superficial muscle situated immediately lateral to the sharp anterior border of the tibia; originates from lateral condyle and upper lateral shaft of tibia, inserting onto medial cuneiform and base of metatarsal I; primary dorsiflexor and inverter of the foot.
Lateral Compartment of the Leg:
Fibularis Longus / Peroneus Longus (D in Lower Leg Model; C in Cadaver Lower Leg): Superficial lateral leg muscle originating from the head and upper lateral shaft of the fibula; its long tendon passes behind the lateral malleolus and courses across the plantar foot to insert on the medial cuneiform and metatarsal I; everts the foot and assists in plantarflexion.
Posterior (Plantarflexor) Compartment of the Leg:
Gastrocnemius (A in Lower Leg Model; A in Cadaver Lower Leg): Most superficial, two-headed (medial and lateral) muscle forming the proximal bulk of the calf; originates from the medial and lateral condyles of the femur; crosses two joints to flex the knee and powerfully plantarflex the foot.
Soleus (B in Lower Leg Model; B in Cadaver Lower Leg): Broad, flat, multipennate muscle situated directly deep to gastrocnemius; originates from the posterior proximal tibia and fibula; prime mover of plantarflexion, especially critical for posture, upright stability, and walking.
Triceps Surae & Tendinous Insertion:
Calcaneal Tendon / Achilles Tendon (C in Lower Leg Model; D in Cadaver Lower Leg): Thickest, strongest tendon in the human body; unites the gastrocnemius and soleus to insert onto the posterior tuberosity of the calcaneus; transmits tensile forces required for walking, running, and jumping.
Systematic Summary of Anatomical Identifications
Cranial & Cervical Regions:
Frontalis: Forehead wrinkler / eyebrow elevator.
Temporalis & Masseter: Primary elevators of the mandible for mastication.
Orbicularis Oculi & Oris: Circular sphincters of the orbit and mouth.
Buccinator: Cheek compression during chewing/blowing.
Sternocleidomastoid: Lateral flexion and contralateral rotation of head.
Platysma: Broad superficial anterior neck tensor from mandible to clavicle.
Thoracoabdominal Wall:
Pectoralis Major & Minor: Superficial vs. deep anterior chest wall muscles.
External & Internal Intercostals: Intercostal space muscles controlling costal elevation (inspiration) and depression (expiration).
Serratus Anterior: Scapular protraction along the lateral thoracic cage.
Rectus Abdominis: Medial longitudinal abdominal flexor with tendinous intersections.
External Oblique, Internal Oblique, Transversus Abdominis: Three-tiered muscular wall arranged from superficial to deep with distinct fiber trajectories (inferomedial, superomedial, and transverse).
Dorsal Scapular & Glenohumeral Region:
Trapezius & Latissimus Dorsi: Superficial extrinsic back muscles.
Rhomboid Minor & Major: Scapular retractors anchored to the medial scapular margin.
Supraspinatus, Infraspinatus, Teres Minor, Subscapularis: Rotator cuff muscles (SITS) providing dynamic glenohumeral stabilization.
Teres Major: Adductor, extensor, and internal rotator positioned inferior to teres minor.
Brachium & Antebrachium:
Biceps Brachii: Anterior arm flexor and supinator.
Triceps Brachii: Posterior arm extensor.
Brachioradialis: Lateral semi-pronated elbow flexor.
Flexor Carpi Radialis & Ulnaris: Superficial flexors mediating wrist flexion and deviations.
Extensor Digitorum, Extensor Carpi Radialis & Ulnaris: Posterior compartment wrist and digit extensors.
Pelvic Girdle & Lower Extremity:
Iliopsoas (Psoas Major + Iliacus): Primary hip flexor complex.
Gluteus Maximus, Medius, Minimus: Progressive superficial-to-deep abductors, extensors, and rotators of the hip.
Piriformis: Landmark lateral rotator traversing the greater sciatic notch.
Tensor Fasciae Latae & Fascia Lata / IT Band: Lateral hip and knee stabilization.
Quadriceps Femoris (Rectus Femoris, Vastus Medialis, Vastus Lateralis): Knee extensors.
Sartorius & Gracilis: Biarticular strap muscles inserting at the pes anserinus.
Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus): Knee flexors and hip extensors.
Tibialis Anterior: Anterior leg dorsiflexor and inverter.
Fibularis Longus: Lateral leg evertor.
Gastrocnemius, Soleus, Calcaneal Tendon: Triceps surae plantarflexion complex.