Human Muscular Anatomy: Origins, Insertions, Actions, and Innervations

Vocabulary flashcards covering human body muscle groups, including actions, origins, insertions, and nerve innervations.

External Intercostals

Muscle responsible for inspiration (expanding ribcage); originates at the inferior border of a rib, inserts at the superior border of the rib below, and is innervated by intercostal nerves.

Pectoralis Major

Muscle responsible for shoulder flexion, adduction, and internal rotation; originates at the medial ½ of clavicle and sternum, inserts into the bicipital groove, and is innervated by the medial pectoral n. & lateral pectoral n.

Trapezius Muscle Subdivisions

Back muscle innervated by Accessory n. (CN 11). Upper Trapezius performs scapular elevation & upward rotation; Middle Trapezius performs scapular retraction; Lower Trapezius performs scapular depression & upward rotation.

Latissimus Dorsi

Muscle responsible for shoulder extension, shoulder adduction, and internal/medial rotation; originates at T7-L5 spinous processes, posterior surface of sacrum, iliac crest, and lower 3 ribs, inserts at medial lip of bicipital groove of humerus, and is innervated by the thoracodorsal n.

Erector Spinae Group (ILS)

Muscle group performing extension & lateral flexion of spine. Consists of Iliocostalis (most lateral), Longissimus (intermediate), and Spinalis (**most medial).

Transversal Spinalis Group (SMR)

Group that protects back, provides stabilization, contralateral rotation, and prevents spasms. Composed of Semispinalis (Most lateral & superficial), Multifidus, and Rotatores (Most medial & deep).

Sternocleidomastoid

Neck muscle responsible for bilateral neck flexion, lateral bending, and unilateral rotation to the opposite side; originates on the sternum & clavicle, inserts on the mastoid process, and is innervated by Accessory n. (CN 11), 2nd & 3rd cervical nerves.

Serratus Anterior

Muscle responsible for scapular protraction & upward rotation; originates on ribs 1-8, inserts on the anterior surface of medial border of scapula, and is innervated by the long thoracic n.

Supraspinatus

Rotator cuff muscle responsible for shoulder abduction; originates in the supraspinous fossa of scapula, inserts on the greater tubercle of humerus, and is innervated by the suprascapular n.

Infraspinatus

Rotator cuff muscle responsible for shoulder lateral/external rotation and horizontal abduction; originates in the infraspinous fossa of scapula, inserts on the greater tubercle of humerus, and is innervated by the suprascapular n.

Subscapularis

Rotator cuff muscle responsible for shoulder internal/medial rotation; originates in the subscapular fossa of the scapula, inserts on the lesser tubercle of humerus, and is innervated by upper subscapular n. & lower subscapular n.

Biceps Brachii

Arm muscle responsible for elbow flexion, shoulder flexion & abduction (weak synergist), and radioulnar supination; originates at the coracoid process of scapula (short head) & supraglenoid tubercle (long head), inserts at radial tuberosity & bicipital aponeurosis into deep fascia on medial forearm, innervated by musculocutaneous n.

Triceps Brachii

Muscle performing forearm extension, shoulder extension, and adduction; consists of long head (origin: infraglenoid tubercle), lateral head (origin: above radial sulcus), and medial head (origin: below radial sulcus), all inserting into olecranon process of ulna, innervated by radial n.

Brachioradialis

Forearm muscle responsible for arm flexion, pronation & supination (to mid-position); originates at lateral supracondylar ridge, inserts at styloid process of radius, and is innervated by radial n.

Flexor Digitorum Profundus

Forearm flexor responsible for flexion of distal phalanx of each finger; originates at anterior/medial surface of proximal 2/3 of ulna, interosseous membrane, aponeurosis of flexor carpi ulnaris, inserts at distal phalanx of each finger, innervated by lateral half from median n. and medial half from ulnar n.

Palmar Interossei (PAD)

Intrinsic hand muscles responsible for digit adduction (PAD), flexing MCP joints/extending IP joints for digits 2-4; innervated by ulnar n.

Dorsal Interossei (DAB)

Intrinsic hand muscles responsible for digit abduction (DAB), flexing MCP joints/extending IP joints for digits 2-4; innervated by ulnar n.

Lumbricals (Hand)

Intrinsic hand muscles responsible for flexing MCPs/extending IPs (L-shaped flexion at MCP joint); originate from flexor digitorum profundus tendons, innervated by median n. (I & II) and ulnar n. (III-IV).

Rectus Abdominis

Abdominal muscle responsible for flexing trunk and lateral flexion; originates at xiphoid process of sternum, inserts at pubis, and is innervated by thoracoabdominal nerves.

Iliopsoas

Primary hip flexor muscle group causing anterior pelvic tilt; composed of Iliacus (origin: iliac fossa, innervated by femoral nerve) and Psoas Major (origin: lumbar vertebrae, innervated by L1, L2, L3 anterior rami), inserting onto the femur.

Quadriceps Femoris Group

Thigh muscle group consisting of Rectus femoris (origin: AIIS), Vastus intermedius (origin: anterior femur), Vastus medialis, and Vastus lateralis; action is knee extension (plus hip flexion for Rectus femoris), inserting via quadriceps tendon/patellar tendon into tibial tuberosity, innervated by femoral n.

Hamstrings Group

Posterior thigh muscle group consisting of Biceps femoris, Semitendinosus, and Semimembranosus; primary actions are knee flexion and hip extension; innervated mainly by the sciatic n.

Tibialis Anterior

Leg muscle responsible for dorsiflexion; originates at lateral condyle of tibia and interosseous membrane, inserts at medial surface of 1st cuneiform & base of 1st metatarsal, innervated by deep branch of common peroneal n.

Gastrocnemius

Superficial leg muscle responsible for plantar flexion and knee flexion; originates at medial and lateral femoral condyles, inserts at calcaneus via Achilles tendon, innervated by tibial n. (sciatic n.).