Muscles - Actions Flashcards
buccinator
draws corner of mouth laterally; compresses cheek (as in whistling); holds food between teeth during chewing
epicranius (frontal belly)
with aponeurosis fixed, raises eyebrows
epicranius (occipital belly)
fixes aponeurosis and pulls scalp posteriorly
orbicularis oris
closes lips; purses and protrudes lips (kissing and whistling muscle)
orbicularis oculi
closes eye, produces blinking, squinting, and draws eyebrows inferiorly
platysma
tenses skin of neck; depresses mandible; pulls lower lip back and down
epicranial aponeurosis (a tendinous sheet, not a muscle)
broad, tendon-like sheet beneath the scalp - lifts the eyebrow and the upper eyelid, thus producing horizontal wrinkles of the forehead
zygomaticus major & minor
raises lateral corners of mouth upward (smiling muscle)
masseter
prime mover of jaw closure, elevates mandible
temporalis
closes jaw; elevates and retracts mandible
digastric (with anterior & posterior bellies)
acting together, elevate hyoid bone; open mouth and depress mandible
sternocleidomastoid
simultaneous contraction of both muscles of pair causes flexion of neck, acting independently, rotate head toward shoulder on opposite side
deltoid
acting as a whole, prime mover of arm abduction; when only specific fibers are active, can act as a synergist in flexion, extension, and rotation of arm
pectoralis major
prime mover of arm flexion; adducts, medially rotates arm; with arm fixed, pulls chest upward (thus also acts in forced inspiration)
pectoralis minor
with ribs fixed, draws scapula forward and inferiorly; with scapula fixed, draws rib cage superiorly
serratus anterior
prime mover to protract and hold scapula against chest wall; rotates scapula, causing inferior angle to move laterally and upward; essential to raising arm; fixes scapula for arm abduction
external intercostals
pulls ribs toward one another to elevate rib cage; aid in inspiration
internal intercostals
draws ribs together to depress rib cage; aid in forced expiration; antagonistic to external intercostals
diaphragm
prime mover of inspiration flattens on contraction, increasing vertical dimensions of thorax; increases intra-abdominal pressure
rectus abdominis
flexes the vertebral column; increases abdominal pressure; fixes and depresses ribs; stabilizes pelvis during walking; used in sit-ups and curls
transversus abdominis
compresses abdominal contents
external oblique
as for internal oblique: above rectus abdominis; compresses abdominal wall; also aids muscles of back in trunk rotation and lateral flexion; used in oblique curls
internal oblique
as for external oblique: above rectus abdominis; compresses abdominal wall; also aids muscles of back in trunk rotation and lateral flexion; used in oblique curls
linea alba (a tendinous sheath, not a muscle)
a tendon-like band that runs along the midline - brings the two sides of the rectus abdominis together and helps hold and control the abdominal wall
erector spinae group (iliocostalis, longissimus, spinalis)
extend from the pelvis to the head - laterally flex the vertebral column and posture muscles; extends and rotates the neck
trapezius
extends head; raises, rotates, and retracts (adducts) scapula and stabilizes it; superior fibers elevate scapula (as in shrugging the shoulders); inferior fibers depress scapula
latissimus dorsi
prime mover of arm extension; adducts and medially rotates arm; brings arm down in power stroke, as in striking a blow
teres minor
same as for infraspinatus: lateral rotation arm; helps hold head of humerus in glenoid cavity; stabilizes shoulder
teres major
extends, medially rotates, and adducts arm; synergist of latissimus dorsi
supraspinatus
initiates abduction of arm; stabilizes shoulder joint
infraspinatus
same as for teres minor: lateral rotation arm; helps hold head of humerus in glenoid cavity; stabilizes shoulder
subscapularis
rotates humerus medially
rhomboid minor & major
pull scapulae medially (retraction); stabilize scapulae; rotate glenoid cavity downward
levator scapulae
elevates and adducts scapula; with fixed scapula, laterally flexes neck to the same side