Muscles: Neck, Torso, and Pectoral Limb

Vocabulary practice flashcards covering anatomical movements, skeletal muscle naming rules, and muscles of the neck, back, thorax, abdomen, and upper limb.

Muscle Origin

The muscle attachment point that remains relatively fixed during contraction, typically situated proximally or medially.

Muscle Insertion

The muscle attachment point that moves during contraction, typically situated distally or laterally.

Sternocleidomastoid

A two-headed anterolateral neck muscle originating on the manubrium of the sternum and medial clavicle, inserting into the mastoid process and superior nuchal line; it flexes and laterally rotates the head; innervated by accessory nerve ($\text{cranial nerve XI}$) and branches of $C_2$ and $C_3$.

Scalenes

Lateral neck muscles (anterior, middle, posterior) originating on the transverse processes of cervical vertebrae and inserting on the first $2$ ribs; they elevate ribs $1$ and $2$ to aid inspiration and flex/rotate the neck; innervated by cervical spinal nerves.

Splenius Capitis

A superficial broad 'bandage muscle' of the posterior neck originating on the ligamentum nuchae and spinous processes of $C_7 - T_6$, inserting into the mastoid process and occipital bone; it extends or hyperextends the head and tilts/rotates the head to the same side; innervated by cervical spinal nerves (dorsal rami).

Semispinalis Capitis

A deep composite intrinsic back muscle originating on transverse processes of $C_7 - T_{12}$ and inserting on the occipital bone and cervical/thoracic spinous processes; it extends the vertebral column and head and rotates them to the opposite side; innervated by spinal nerves (dorsal rami).

Erector Spinae

The prime mover of back extension forming the intermediate layer of intrinsic back muscles; consists of three vertical columns (iliocostalis, longissimus, spinalis) all innervated by spinal nerves (dorsal rami).

Iliocostalis

The most lateral column of the erector spinae (comprising lumborum, thoracis, and cervicis parts); acting together, its fibers extend the vertebral column; acting on one side, it laterally flexes the spine toward that side.

Longissimus

The intermediate column of the erector spinae (comprising thoracis, cervicis, and capitis parts); extends and laterally flexes the vertebral column, with the capitis portion extending and rotating the head to the same side.

Spinalis

The most medial column of the erector spinae (comprising thoracis and cervicis parts); primarily acts to extend the vertebral column.

Quadratus Lumborum

A fleshy posterior abdominal wall muscle originating on the iliac crest and lumbar fascia and inserting onto the transverse processes of $L_1 - L_4$ and the lower margin of the 12th rib; laterally flexes the spine individually, extends the lumbar spine jointly, and aids forced inspiration; innervated by $T_{12}$ and upper lumbar ventral rami.

Rectus Abdominis

A medial superficial abdominal pair originating on the pubic crest and symphysis and inserting into the xiphoid process and costal cartilages of ribs $5 - 7$; segmented by three tendinous intersections, it flexes and rotates the lumbar spine, stabilizes the pelvis, and increases intra-abdominal pressure; innervated by intercostal nerves ($T_6$ or $T_7 - T_{12}$).

External Oblique

The largest and most superficial of the lateral abdominal wall muscles with fibers directed downward and medially ('hands in pockets'); its inferior aponeurosis forms the inguinal ligament; it flexes the vertebral column, rotates the trunk, and compresses the abdominal wall; innervated by intercostal nerves ($T_7 - T_{12}$).

Internal Oblique

A lateral abdominal muscle deep to the external oblique with fibers running predominantly upward and medially; flexes and rotates the vertebral column and compresses the abdominal wall; innervated by intercostal nerves ($T_7 - T_{12}$) and $L_1$.

Transversus Abdominis

The deepest muscle of the abdominal wall with horizontally arranged fibers; compresses abdominal contents; innervated by intercostal nerves ($T_7 - T_{12}$) and $L_1$.

External Intercostals

$11$ pairs of muscles lying between ribs whose fibers run downward and anteriorly; they pull the ribs toward each other and elevate the ribs to aid inspiration; innervated by intercostal nerves.

Internal Intercostals

$11$ pairs of muscles lying deep and at right angles to the external intercostals whose fibers run downward and posteriorly; they depress the ribs during forced expiration; innervated by intercostal nerves.

Diaphragm

The broad dome-shaped prime mover of inspiration pierced by the aorta, inferior vena cava, and esophagus; flattens on contraction to increase the vertical dimensions of the thorax; innervated by the phrenic nerves ($C_3 - C_5$).

Pectoralis Minor

A flat, thin muscle lying directly beneath the pectoralis major originating from the anterior surfaces of ribs $3 - 5$ (or $2 - 4$) and inserting on the coracoid process of the scapula; pulls the scapula forward and downward; innervated by medial and lateral pectoral nerves ($C_6 - C_8$).

Serratus Anterior

A fan-shaped 'boxer's muscle' originating by slips from ribs $1 - 8$ (or $9$) and inserting into the entire anterior medial border of the scapula; prime mover to protract and hold the scapula against the rib cage; paralysis results in 'winging' of the scapula; innervated by the long thoracic nerve ($C_5 - C_7$).

Subclavius

A small cylindrical anterior thorax muscle extending from the costal cartilage of rib $1$ to the inferior groove of the clavicle; stabilizes and depresses the pectoral girdle; innervated by the nerve to subclavius ($C_5, C_6$).

Trapezius

The most superficial muscle of the posterior thorax; superior fibers elevate the scapula, middle fibers retract (adduct) it, and inferior fibers depress it; innervated by accessory nerve ($\text{cranial nerve XI}$) and $C_3 - C_4$.

Levator Scapulae

A thick straplike muscle at the back and side of the neck originating on transverse processes of $C_1 - C_4$ and inserting onto the medial border of the scapula superior to the spine; elevates and adducts the scapula; innervated by cervical spinal nerves and dorsal scapular nerve ($C_3 - C_5$).

Rhomboids

Two roughly diamond-shaped posterior thoracic muscles (rhomboid minor and major) originating from spinous processes of $C_7 - T_5$ and inserting on the medial border of the scapula; they stabilize and retract the scapula ('squaring the shoulders'); innervated by the dorsal scapular nerve ($C_4, C_5$).

Pectoralis Major

A large fan-shaped muscle covering the superior chest; prime mover of arm flexion that adducts and medially rotates the arm against resistance; innervated by lateral and medial pectoral nerves ($C_5 - C_8, T_1$).

Deltoid

A thick, multipennate triangular muscle forming the shoulder mass; prime mover of arm abduction when all fibers contract simultaneously; innervated by the axillary nerve ($C_5, C_6$).

Latissimus Dorsi

A broad, flat triangular muscle of the lumbar and lower thoracic back; prime mover of arm extension and powerful adductor and medial rotator of the arm (active in hammering, swimming, and chin-ups); innervated by the thoracodorsal nerve ($C_6 - C_8$).

Teres Major

A thick, rounded muscle situated inferior to teres minor that extends, medially rotates, and adducts the arm as a synergist of latissimus dorsi; innervated by the lower subscapular nerve ($C_6, C_7$).

Coracobrachialis

A small cylindrical muscle originating on the coracoid process of the scapula and inserting onto the medial shaft of the humerus; flexes and adducts the arm; innervated by the musculocutaneous nerve ($C_5 - C_7$).

Subscapularis

A rotator cuff muscle filling the subscapular fossa and inserting into the lesser tubercle of the humerus; prime mover of medial arm rotation and stabilizer of the shoulder joint; innervated by subscapular nerves ($C_5 - C_7$).

Supraspinatus

A rotator cuff muscle located in the supraspinous fossa of the scapula that inserts into the superior greater tubercle of the humerus; initiates arm abduction and stabilizes the shoulder; innervated by the suprascapular nerve.

Infraspinatus

A rotator cuff muscle located in the infraspinous fossa of the scapula inserting into the greater tubercle of the humerus; laterally rotates the arm and holds the humeral head in the glenoid cavity; innervated by the suprascapular nerve.

Teres Minor

A small, elongated rotator cuff muscle lying inferior to the infraspinatus and inserting into the greater tubercle of the humerus; laterally rotates the arm and stabilizes the shoulder joint; innervated by the axillary nerve.

Biceps Brachii

A two-headed fusiform muscle of the anterior arm compartment inserting into the radial tuberosity; flexes and supinates the forearm; innervated by the musculocutaneous nerve ($C_5, C_6$).

Brachialis

A major flexor of the forearm lying immediately deep to the biceps brachii, inserting onto the coronoid process of the ulna; innervated by the musculocutaneous nerve.

Brachioradialis

A superficial muscle of the lateral forearm originating on the lateral supracondylar ridge of the humerus and inserting at the base of the radial styloid process; acts as a synergist in forearm flexion; innervated by the radial nerve.

Triceps Brachii

A large, three-headed muscle that is the sole muscle of the posterior arm compartment, inserting into the olecranon of the ulna; powerful forearm extensor; innervated by the radial nerve ($C_6 - C_8$).

Anconeus

A short triangular muscle at the posterior elbow blended with the distal triceps; synergist of triceps brachii in elbow extension; innervated by the radial nerve.

Pronator Teres

A two-headed superficial muscle of the anterior forearm compartment; pronates and weakly flexes the forearm; innervated by the median nerve.

Flexor Carpi Radialis

A superficial anterior forearm muscle running diagonally to insert at the bases of metacarpals $2$ and $3$; powerful flexor and abductor of the hand and a clinical guide to the radial artery at the wrist; innervated by the median nerve.

Palmaris Longus

A small fleshy muscle with a long insertion tendon inserting into the palmar aponeurosis; tenses the skin and fascia of the palm; often absent; innervated by the median nerve.

Flexor Carpi Ulnaris

The most medial superficial anterior forearm muscle inserting into the pisiform, hamate, and fifth metacarpal; flexes and adducts the hand; innervated by the ulnar nerve ($C_8, T_1$).

Flexor Digitorum Superficialis

An intermediate layer muscle of the anterior forearm inserting by four tendons into the middle phalanges of digits $\text{II} - \text{V}$; flexes the hand and middle phalanges for speed and against resistance; innervated by the median nerve ($C_7, C_8, T_1$).

Flexor Pollicis Longus

A deep anterior forearm muscle inserting into the distal phalanx of the thumb; flexes the distal phalanx of the pollex; innervated by a branch of the median nerve ($C_8, T_1$).

Flexor Digitorum Profundus

A deep anterior forearm muscle inserting by four tendons into the distal phalanges of digits $\text{II} - \text{V}$; flexes the distal interphalangeal joints; medial half innervated by the ulnar nerve and lateral half by the median nerve.

Pronator Quadratus

The deepest muscle of the distal anterior forearm running horizontally; it is the only muscle arising solely from the ulna and inserting solely into the radius; prime mover of forearm pronation; innervated by the median nerve ($C_7, C_8$).

Extensor Carpi Radialis Longus

A superficial posterior forearm muscle originating on the lateral supracondylar ridge and inserting at the base of the second metacarpal; extends and abducts the hand; innervated by the radial nerve ($C_6, C_7$).

Extensor Carpi Radialis Brevis

A superficial posterior forearm muscle lying deep to extensor carpi radialis longus and inserting at the base of the third metacarpal; extends and abducts the hand while steadying the wrist; innervated by the deep branch of the radial nerve.

Extensor Digitorum

The prime mover of finger extension in the superficial posterior forearm; inserts by four tendons into the extensor expansions and distal phalanges of digits $\text{II} - \text{V}$; innervated by the posterior interosseous nerve ($C_7, C_8$).

Extensor Carpi Ulnaris

The most medial superficial muscle of the posterior forearm, inserting into the base of the fifth metacarpal; extends and adducts the hand; innervated by the posterior interosseous nerve.

Supinator

A deep posterior muscle at the elbow that wraps around the proximal radius; assists biceps brachii to forcibly supinate the forearm and works alone in slow supination; innervated by the posterior interosseous nerve.

Abductor Pollicis Longus

A deep posterior forearm muscle located distal to the supinator, inserting into the base of the first metacarpal and trapezium; abducts and extends the thumb; innervated by the posterior interosseous nerve.

Extensor Pollicis Longus and Brevis

A deep posterior muscle pair originating from the dorsal radius/ulna and inserting into the distal and proximal phalanges of the thumb; extends the thumb; innervated by the posterior interosseous nerve.

Extensor Indicis

A tiny deep posterior forearm muscle arising close to the wrist and inserting into the extensor expansion of the index finger; extends digit $\text{II}$ and assists in extending the wrist; innervated by the posterior interosseous nerve.