Superficial skeletal muscles. let's review each muscle to see its location
and read about the action it performs. occipitalis draws back the scalp to
raise the eyebrows. trapezius upper elevates the scapula and extends the
head and neck. middle retracts scapula medially. and lower, elevates scapula,
upward rotation of the scapula, and downward rotation of the scapula. deltoid
abducts the arm, flexion and medial rotation, extension and lateral rotation
infraspinatus external rotation of the humerus, stabilizes the glenohumeral
joint, and part of the rotator cuff. teres major assists in adduction of the arm,
medial rotation of the arm, and extension from a flexed position. teres minor
laterally rotates the arm, assists in adduction of the arm, stabilizes the
glenohumeral joint, and is part of the rotator cuff.
rhomboid major and minor. retracts the scapula, and is located deep to the
trapezius where it cannot be seen. Latissimus dorsi: adduction of
humerus, medial rotation of the humerus, extension from flexed position, and
downward rotation of the scapula. triceps brachii: long, adducts the arm, extends at
the shoulder, and a little elbow flexion. lateral extends the forearm at the elbow.
and medial extends the floor arm at the elbow. brachial radialis: Acts as a synergist
in forearm flexion. extensor carpi radialis longus: extends the hand at the
wrist, radially deviates the hand at the wrist, weekly flexes the
forearm at the elbow, and weekly supinate the forearm. extensor carpi ulnaris:
extends and adducts the hand at the wrist. extensor digitorum: extends the
fore medial digits, extends the wrist if the fingers are flexed, abducts the
digits, and is the most medial muscle in the posterior forearm. gluteus medius
anterior and lateral fibers abduct and medially rotate the thigh. posterior
fibers may laterally rotate the thigh and it stabilizes the pelvis and
prevents free limb from sagging Deering gait. gluteus maximus: powerful extensors
of the hip, laterally rotates the thigh, upper fibers aid in abduction of the
thigh, fibers of IT band stabilize a fully extended knee.
adductor magnus: Aduucts the thigh.
posterior fibers also extend and laterally rotate the thigh.
hamstrings extended the thigh, flex the lower leg, and include the biceps femoris,
semitendinosus, and semimembranosus. biceps femoris: flexor at the knee,
laterally rotate the thigh if flexed at the knee, and extends the hip.
semitendinosus extends the hip. flexes the knee. medially rotates the tibia/
semimembranosus flexes the knee. extends the hip. medially rotates the tibia. pulls
medial meniscus posterior during flexion.
gastrocnemius plantar flexes the ankle, knee flexion, and stabilizes ankle and
knee when standing. soleus plantar flexes the foot. fibularis longus:
planter flexes and averts the foot. calcaneal tendon: insertion for the
gastrocnemius and soleus muscles. iliotibial tract insertion for the
tensor fasciae latae and gluteus maximus. deltoid abducts the arm, flexion and
medial rotation, extension and lateral rotation. biceps brachii: flexes the
forearm at the elbow, supa Nate's forum from neutral
stabilizes anterior aspect of the shoulder, flexes the shoulder. brachialis:
elbow flexion underneath the biceps brachii. pronator Teres: pronates the
forearm and weakly flexes the elbow. brachioradialis: flexes the forearm at
the elbow, permits the forearm when supinated,
supinate the forearm when pronated. flexor carpi radialis: flexes the hand at
the wrist, radially deviates the wrist and may assist to pronate the forearm.
palmaris longus: flexes the hand at the wrist. pectoralis minor: depresses and
downward Lee rotates the scapula , assists in scapular protraction from a retracted
position, stabilizes the scapula, and is deep and cannot be seen. pectoralis major
adducts humerus, medially rotates humerus flexion of the arm from
extension. serratus anterior: Protracts the scapula stabilizes scapula, and
assists in upward rotation. intercostals fix intercostal spaces during
respiration and aid force inspiration by elevating the ribs rectus abdominis
flexes trunk aids forced exploration raises intra-abdominal pressure external
oblique supports abdominal-wall assists forced
expiration assists in raising intra-abdominal pressure with muscles of
opposite side it abducts and rotates the trunk internal oblique supports
abdominal wall assists forced respiration assists in raising
intra-abdominal pressure with muscles of the other side abducts and rotates the
trunk fibers run medial to lateral underneath the external oblique
transversus abdominus supports abdominal wall aides forced expiration and raising
intra-abdominal pressure is deep and cannot be seen
aleosis flexes the torso and thigh with respect to each other
pectineus flexes hip adducts thigh medially rotates the thigh rectus
femoris extends the knee and flexes the hip vastus lateralis extends the knee
and can abnormally displace the patella
vastus medialis: extends the knee. tensor fasciae latae: abduction inflection at
the hip, week extension of knee joint, stabilizes the pelvis during walking,
counters the pull of gluteus maximus on the iliotibial tract. Sartorius: flexes
hip and knee, laterally rotates the thigh if flexed at the hip. adductor longus:
adducts thigh, flexes thigh, may laterally rotate thigh at the hip.
graceless: adducts thigh, flexes knee and medially rotates the tibia.
tibialis anterior:
strongest dorsiflexor and inverts and adducts the foot. temporalis:
elevates mandible, and post fibers retract. a cedar elevates mandible
enables forced closure of the mouth. sternocleidomastoid:
if contracted singularly, will rotate the head and neck to the opposite side.
if contracted together, will cause anterior flexion of the head and neck.
frontalis: raises the eyebrows and wrinkles the forehead skin horizontally.
orbicularis oculi: powerfully closes the eye. zygomaticus minor
elevates the upper lip and zygomaticus major lifts and draws back the angles of
the mouth as in smiling. orbicularis Oris: closes the lips and protrudes the lips.
mentalis: elevates and protrudes the lower lip, wrinkles the skin over the chin.
depressor labii inferiorus: draws the lower lip inferiorly and laterally
during mastication. used with mentalis for frowning. Buccinator: draws the
corners of the mouth laterally and compresses the cheek involved in the
sucking action. sternohyoid: depresses hyoid bone and
hence the Larnx. congratulations you have completed this learning activity on
the superficial skeletal muscles.