chap 11 Muscular System: Axial and Appendicular Skeleton

Comprehensive practice flashcards defining the major muscle groups, functional classifications, structural arrangements, and individual axial and appendicular muscles covered in Chapter 11.

Axial Muscles

Skeletal muscles that have both their origins and insertions on the axial skeleton; they support and move the head and vertebral column, assist in facial expression, breathing, chewing, and swallowing, and protect abdominal and pelvic organs.

Appendicular Muscles

Skeletal muscles that control movements of the upper and lower limbs and the pectoral and pelvic girdles, organized into groups based on body location or the skeletal part they move.

Origin

The less movable attachment of a skeletal muscle, typically located more proximal to the body.

Insertion

The more movable attachment of a skeletal muscle that is pulled toward the origin during muscle contraction, typically located more distal.

Circular Muscles

Muscles composed of concentrically arranged fascicles that create a sphincter to close or open an orifice (e.g., orbicularis oris).

Parallel Muscles

Muscles with fascicles that run parallel to the muscle's long axis, known for high endurance and sometimes featuring an expanded central belly (e.g., rectus abdominis).

Convergent Muscles

Muscles whose fascicles merge toward a single common attachment site, such as a tendon or aponeurosis sheet (e.g., pectoralis major).

Pennate Muscles

Feather-like muscles whose fascicles pull at an angle relative to the tendon; divided into unipennate, bipennate, and multipennate subtypes.

Agonist (Prime Mover)

A muscle that contracts directly to produce a specific movement, such as the triceps brachii causing forearm extension.

Antagonist

A muscle whose contraction opposes the movement of the agonist, ensuring smooth movement and controlled speed (e.g., biceps brachii during forearm extension).

Synergist

A muscle that assists the agonist by contributing additional tension or stabilizing the point of origin as a fixator (e.g., biceps brachii and brachialis acting together in elbow flexion).

Orbicularis Oculi

A circular facial muscle surrounding the orbit that closes the eye.

Orbicularis Oris

A circular muscle of facial expression encircling the mouth that closes the mouth and puckers the lips ("kissing muscle").

Occipitofrontalis

A scalp muscle consisting of a frontal belly that raises the eyebrows and an occipital belly that retracts the scalp slightly.

Epicranius

The muscular and aponeurotic unit formed by the occipitofrontalis muscle connected to the epicranial aponeurosis (galea aponeurotica).

Mentalis

A facial muscle associated with the mouth that protrudes the lower lip into a pout.

Buccinator

A facial muscle located in the cheek that compresses the cheek against the teeth during chewing.

Temporalis

A broad, fan-shaped muscle of mastication that elevates and retracts (pulls posteriorly) the mandible at the temporomandibular joint.

Masseter

The most powerful and important muscle of mastication; elevates and protracts (pulls anteriorly) the mandible.

Sternocleidomastoid (SCM)

An anterolateral neck muscle originating on the sternum and clavicle and inserting on the mastoid process; bilateral contraction flexes the neck, while unilateral contraction causes lateral flexion to the contracting side and rotation of the head to the opposite side.

External Intercostals

Respiratory muscles occupying the intercostal spaces that elevate the ribs during inspiration, expanding the thoracic cavity.

Internal Intercostals

Respiratory muscles positioned deep to the external intercostals with fibers oriented at right angles; they depress the ribs during forced expiration.

Diaphragm

An internally placed, dome-shaped muscle partitioning the thoracic and abdominal cavities; the primary muscle of breathing whose contraction pulls the central tendon inferiorly to expand the thoracic cavity during inspiration.

External Oblique

The most superficial abdominal wall muscle with inferomedially oriented fibers; its aponeurosis forms the inguinal ligament inferiorly, and unilateral contraction laterally flexes and contralaterally rotates the vertebral column.

Internal Oblique

An abdominal muscle located deep to the external oblique with fibers running superomedially; compresses abdominal organs and assists in flexing the vertebral column.

Transversus Abdominis

The deepest muscle of the abdominal wall; compresses and holds abdominal organs in place, aiding in lateral flexion and contralateral rotation of the vertebral column.

Rectus Abdominis

An anterior abdominal wall muscle composed of straight vertical fibers partitioned by tendinous intersections ("six-pack"); flexes the vertebral column and compresses abdominal contents.

Linea Alba

A vertical fibrous band running down the anterior abdominal midline between the bilateral rectus abdominis muscles.

Pectoralis Minor

An anterior thoracic muscle positioned deep to the pectoralis major that depresses and protracts the scapula (hunches the shoulders).

Serratus Anterior

A fan-shaped anterior thoracic muscle between the ribs and scapula that protracts, stabilizes, and superiorly rotates the scapula.

Levator Scapulae

A posterior thoracic muscle attaching to the cervical vertebrae and scapula that elevates and inferiorly rotates the scapula.

Rhomboid Major and Minor

Posterior thoracic muscles running inferolaterally from the vertebrae to the scapula deep to the trapezius; they elevate, retract, and inferiorly rotate the scapula.

Trapezius

A large, diamond-shaped posterior thoracic muscle extending from the skull and vertebral column to the pectoral girdle; extends the neck and can elevate, depress, retract, or rotate the scapula.

Latissimus Dorsi

A broad triangular muscle of the back that acts as the prime arm extensor, while also adducting and medially rotating the arm.

Pectoralis Major

A thick, fan-shaped muscle on the superior, anterior thorax that acts as the prime arm flexor, while also adducting and medially rotating the arm.

Deltoid

The prime abductor of the arm; its anterior fibers flex and medially rotate the arm, lateral fibers abduct the arm, and posterior fibers extend and laterally rotate the arm.

Teres Major

A posterior muscle that extends, adducts, and medially rotates the arm at the glenohumeral joint.

Rotator Cuff (SITS)

A functional group of four scapular muscles—Supraspinatus, Infraspinatus, Teres minor, and Subscapularis—that stabilize the glenohumeral joint and execute shoulder movements.

Subscapularis

A rotator cuff muscle situated on the anterior surface of the scapula that medially rotates the arm (functions in the wind-up phase of a pitch).

Supraspinatus

A rotator cuff muscle situated superior to the scapular spine that abducts the arm (functions in executing pitch delivery).

Infraspinatus

A rotator cuff muscle situated inferior to the scapular spine that adducts and laterally rotates the arm (functions in slowing the arm at the end of a pitch).

Teres Minor

A rotator cuff muscle located inferior to the infraspinatus that adducts and laterally rotates the arm (assists in slowing the arm at the end of a pitch).

Biceps Brachii

A two-headed muscle on the anterior humerus that originates on the scapula and inserts on the radius; flexes and supinates the forearm and weakly assists in flexing the arm.

Brachialis

A muscle located deep to the biceps brachii on the anterior humerus that serves as the most powerful flexor of the forearm at the elbow joint.

Brachioradialis

A superficial muscle located on the anterolateral forearm that acts as a synergist in elbow flexion.

Triceps Brachii

A large, three-headed muscle on the posterior arm that serves as the major extensor of the forearm; its long head originates on the scapula and helps extend and adduct the arm.

Pronator Teres and Pronator Quadratus

Anterior compartment forearm muscles that rotate the radius across the ulna to pronate the forearm.

Supinator

A muscle situated in the posterior compartment of the forearm that acts to supinate the forearm.

Flexor Digitorum Superficialis

The intermediate layer muscle of the anterior forearm whose four tendons insert onto the middle phalanges of digits 2–5, flexing the wrist, metacarpophalangeal (MP), and proximal interphalangeal (PIP) joints of those digits.

Extensor Carpi Ulnaris

A muscle in the superficial layer of the posterior forearm compartment that inserts on the fifth metacarpal bone to extend the wrist and adduct the hand.

Fascia Lata

Deep fascia of the thigh that binds muscles together and partitions them into anterior, medial, lateral, and posterior compartments.

Iliopsoas

A composite muscle consisting of the psoas major and iliacus that extends from the lumbar vertebrae and ilium to the femur to flex the thigh.

Adductor Magnus

A medial compartment thigh muscle that adducts, extends, and laterally rotates the thigh.

Gluteus Maximus

The largest of the buttock muscles; acts as the chief extensor of the thigh and also laterally rotates the thigh.

Gluteus Medius

A gluteal muscle located deep to the gluteus maximus that abducts and medially rotates the thigh.

Hamstrings

A posterior thigh muscle composite—consisting of the biceps femoris, semimembranosus, and semitendinosus—that extends the thigh and flexes the knee.

Quadriceps Femoris

A composite muscle of the anterior thigh composed of four heads (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius) that acts as the prime mover of knee extension.

Sartorius

A strap-like anterior thigh muscle that flexes and laterally rotates the thigh, as well as flexing and medially rotating the leg.

Gracilis

A medial compartment thigh muscle that adducts the thigh and flexes the leg at the knee joint.

Fibularis Longus and Fibularis Brevis

Lateral leg compartment muscles that act as powerful foot evertors and weak plantar flexors.

Gastrocnemius

A two-bellied superficial posterior leg muscle forming the calf that flexes the leg and plantar flexes the foot.

Soleus

A broad muscle in the superficial posterior leg located deep to the gastrocnemius that plantar flexes the foot.