Knes 191A Lab Exam #1 Muscle Actions

Orbicularis Oris

constricts the mouth

Orbicularis Oculi

closes the eye

Masseter

elevates mandible & closes the jaw

Buccinator

Compresses the cheeks (whistle or blow)

Temporalis

elevates the mandible

Platysma

1. tenses the skin of the neck

2. depresses mandible

3. draws outer part of lip downward

Sternocleidomastoid

1. cervical flexion

2. cervical rotation - opposite direction (contralateral rotator)

Scalenes (anterior, middle, posterior)

1. cervical flexion

2. elevates ribs (first two ribs)

Erector Spinae

spinal extension (all divisions) (allows to bend back w/out collapsing)

Trapezius

extension at the neck (looking up)

External intercostals

elevates ribs (inhalation)

Internal intercostals

depresses ribs (exhalation)

Quadratus Lumborum

lateral trunk flexion (ipsilateral)

Rectus abdominis

1. trunk flexion (both)

2. trunk lateral flexion (ipsilateral)

3. depression of ribs

4. compression of abdomen

External oblique abdominis

1. trunk flexion (both)

2. trunk rotation (contralateral)

3. trunk lateral flexion (ipsilateral)

Internal oblique abdominis

1. trunk flexion (both)

2. trunk rotation (ipsilateral)

3. trunk lateral flexion (ipsilateral)

Transversus abdominis

compress abdomen (assist in exhalation)

Splenius capitis & cervicis

1. cervical extension (both)

2. cervical lateral flexion (ipsilateral)

3. cervical rotation (ipsilateral)

Semispinalis Capitis & cervicis

1. cervical extension (both)

2. cervical lateral flexion (ipsilateral)