3.2 Major Muscles

Adductor brevis

Muscle that adducts and medially rotates the thigh

Adductor longus

Muscle that adducts, medially rotates, and flexes the thigh

Adductor magnus

Muscle with an anterior fascicle that adducts, medially rotates, and flexes the thigh, and a posterior fascicle that assists in thigh extension

Agonist (prime mover)

Muscle whose contraction is responsible for producing a particular motion

Antagonist

Muscle that opposes the action of an agonist

Atrophy

Loss of mass and function

Autorhythmicity

Heart's ability to control its own contractions

Belly

Bulky central body of a muscle

Bi

Two

Biceps brachii

Two-headed muscle that crosses the shoulder and elbow joints to flex the forearm, assist in supination, and flex the arm at the shoulder

Biceps femoris

Hamstring muscle

Brachialis

Muscle deep to the biceps brachii that provides power in flexing the forearm

Brachioradialis

Muscle that can flex the forearm quickly or help lift a load slowly

Deltoid

Shoulder muscle that abducts the arm, flexes and medially rotates it, and extends and laterally rotates it

Diaphragm

Dome-shaped skeletal muscle that separates the thoracic and abdominal cavities

Digastric

Muscle with anterior and posterior bellies that elevates the hyoid bone and larynx when swallowing; also depresses the mandible

Extensor

Muscle that increases the angle at a joint

Extensor digitorum

Muscle that extends the hand at the wrist and the phalanges

External oblique

Superficial abdominal muscle with fascicles that extend inferiorly and medially

Fascicle

Bundle of muscle fibers within a skeletal muscle, surrounded by perimysium

Flexion

Movement that decreases the angle of a joint

Flexor

Muscle that decreases the angle at a joint

Gastrocnemius

Most superficial muscle of the calf

Gluteal group

Muscle group that extends, flexes, rotates, adducts, and abducts the femur

Gluteus maximus

Largest gluteus muscle; extends the femur

Gluteus medius

Muscle deep to the gluteus maximus that abducts the femur at the hip

Gluteus minimus

Smallest gluteal muscle; deep to the gluteus medius

Gracilis

Muscle that adducts the thigh and flexes the leg at the knee

Hamstring group

Three long muscles on the back of the leg

Insertion

End of a skeletal muscle attached to the structure, usually a bone, that is moved when the muscle contracts

Internal oblique

Flat, intermediate abdominal muscle with fascicles that run perpendicular to those of the external oblique

Latissimus dorsi

Broad, triangular axial muscle located on the inferior part of the back

Masseter

Main muscle for chewing; elevates the mandible to close the mouth

Maximus

Largest

Medial compartment of the thigh

Region containing the adductor longus, adductor brevis, adductor magnus, pectineus, gracilis, and associated blood vessels and nerves

Medialis

To the inside

Medius

Medium

Minimus

Smallest

Oblique

At an angle

Origin

End of a skeletal muscle attached to another structure, usually a bone, in a fixed position

Pectoralis major

Thick, fan-shaped axial muscle covering much of the superior thorax

Pectoralis minor

Muscle that moves the scapula and assists in inhalation

Prime mover (agonist)

Principal muscle involved in an action

Quadratus femoris

Muscle deep to the gluteus maximus on the lateral thigh that laterally rotates the femur at the hip

Quadriceps femoris group

Four muscles that extend and stabilize the knee

Rectus

Straight

Rectus abdominis

Long, linear muscle extending along the middle of the trunk

Rectus femoris

Quadriceps muscle on the anterior aspect of the thigh

Sartorius

Band-like muscle that flexes, abducts, and laterally rotates the leg at the hip

Semimembranosus

Hamstring muscle

Semitendinosus

Hamstring muscle

Sternocleidomastoid

Major muscle that laterally flexes and rotates the head

Synergist

Muscle whose contraction helps a prime mover perform an action

Tensor fascia lata

Muscle that flexes and abducts the thigh

Transversus abdominis

Deep abdominal layer with fascicles arranged transversely around the abdomen

Trapezius

Muscle that stabilizes the upper part of the back

Tri

Three

Triceps brachii

Three-headed muscle that extends the forearm

Vastus intermedius

Quadriceps muscle between the vastus lateralis and vastus medialis; deep to the rectus femoris

Vastus lateralis

Quadriceps muscle on the lateral aspect of the thigh

Vastus medialis

Quadriceps muscle on the medial aspect of the thigh

Visceral muscle

Smooth muscle found in the walls of visceral organs