Action Axial Muscles (BIO 201, Practical 2)

Elevation of mandible, mastication

Temporalis, Masseter

Sphincter of eyelids, closes eyes, aids in flow of tears

Orbicularis occuli

Elevates upper eyelid, opens eye

Levator palpabrae superioris

Elevates corner of mouth when smiling or laughing

Zygomaticus major

Elevation of upper lip

Zygomaticus minor

Encircles mouth, closes lips, protrudes lips, speech

Orbicularis oris

Draws lower lip and angle of mouth downward with horror or surprise, may aid in opening mouth widely

Platysma

Contralateral rotation of head, flexion of neck

Sternocleidomastoid

Bilateral: neck flexion, if spine is fixed, elevation of ribs 1-2; aid in breathing. Unilateral: lateral flexion of neck

Scalenes

Depresses mandible when hyoid is fixed, elevates hyoid when mandible is fixed

Digastric

Elevates hyoid, retracts hyoid

Stylohyoid

Spands mandible from side to side and forms floor of mouth, elevates floor of mouth in initial stage of swallowing

Mylohyoid

Depresses hyoid after it has been elevated

Sternohyoid

Depresses larynx after it has been elevated in swallowing and vocalization

Sternothyroid

Depresses hyoid after it has been elevated

Omohyoid

Depresses hyoid

Thyrohyoid

Scalenes

Bilateral: neck flexion, if spine is fixed, elevation of ribs 1-2 aid in breathing. Unilateral: lateral flexion of neck

Digastric

Depresses mandible when hyoid is fixed. Elevates hyoid when mandible is fixed.

Stylohyoid

Elevates hyoid. Retracts hyoid

Mylohyoid

Spans mandible from side to side and forms floor of mouth. Elevates floor of mouth in initial stage of swallowing.

Sternohyoid

Depresses hyoid after it has been elevated

Sternothyroid

Depresses larynx after it has been elevated in swallowing and vocalization

Omohyoid

Depresses hyoid after it has been elevated

Thyrohyoid

Depresses hyoid

External Intercostals

When scalenes fix rib 1, elevation and protraction of ribs 2-12, expanding the thoracic cavity

Internal Intercostals

In forced expiration, the interosseous part depresses and retracts the ribs, compelling the thoracic cavity and expelling air

Diaphragm

Prime mover of inspiration, contraction compresses abdominal viscera and aids in childbirth and expulsion of urine and feces

Rectus abdominis

Flexion of trunk, stabilizes pelvic region during walking, compresses abdominal viscera

External Abdominal Oblique

Support viscera, stabilizes vertebral column, maintains posture, contralateral rotation of waist

Internal Abdominal Oblique

Support viscera, stabilizes vertebral column, maintains posture, ipsilateral rotation of waist

Transverse abdominis

Compresses abdominal contents

Semispinalis

Contralateral rotation of neck, extension of head and neck

Illiocostalis

Lateral flexion of vertebral column. Extension of vertebral column

Rhomboideus Major

Retracts scapula

Levator Scapulae

Elevates scapula if cervical vertebrae are fixed. Lateral flexion of neck if scapula are fixed

Trapezius

Stabilizes scapula and shoulder during arm movements, elevates and depresses shoulder, rotates and retracts scapula

Serratus Anterior

With pectoralis minor, protracts scapula. Prime mover in all forward reaching and pushing actions. Fixes scapula during abduction of arm

Pectoralis minor

With serratus anterior, protracts the scapula

Pectoralis major

Flexion of shoulder, adduction of shoulder, medial rotation of shoulder

Latissimus Dorsi

Adduction of shoulder, extension of shoulder, medial rotation of the shoulder

Erector Spinae Group

• iliocostalis

• longissimus

• spinalis

longissimus

unilateral: lateral flexion of vertebral column, ipsilateral rotation of the head. Bilateral: extension of vertebral column, extension of head

spinalis

Unilateral: lateral flexion of vertebral column. Bilateral: extension of vertebral column

serratus posterior

depression of ribs 9-12

Rhomboideus minor

retracts scapula and braces shoulder

teres major

extends the arm, medially rotates humerus

supraspinatus

aids deltoid in abduction of arm, supports humeral head when carrying weight

infraspinatus

modulates action of deltoid, prevents humeral head from sliding upward, rotates humerus laterally

teres minor

modulates action of deltoid, prevents humeral head from sliding upward as arm is abducted, rotates humerus laterally

subscapularis

modulates action of deltoid, prevents humeral head from sliding upward as arm is abducted, rotates humerus medially

deltoid

anterior fibers flex and medially rotate arm, lateral fibers abduct arm, posterior fibers extend and laterally rotate arm