ISBN 10: 1-292-02645-6 ISBN 13: 978-1-292-02645-9

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ISBN 10: 1-292-02645-6 ISBN 13: 978-1-292-02645-9

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Printed in the United States of America Chapter 10: The Muscular System

Axial Muscles Appendicular Muscles

Trapezius Occipital belly of Deltoid occipitofrontalis Infraspinatus Sternocleidomastoid Teres minor Teres major Rhomboid major Triceps brachii (long head) External oblique Triceps brachii (lateral head) Latissimus dorsi Brachioradialis Extensor carpi radialis longus Anconeus Flexor carpi ulnaris Extensor digitorum Extensor carpi ulnaris Gluteus medius Tensor fasciae latae Gluteus maximus Adductor magnus Semitendinosus Iliotibial tract Semimembranosus Gracilis Biceps femoris Sartorius Plantaris 2 he appendicular muscles stabilize Gastrocnemius or move components of the appen- Soleus dicular skeleton and include the remaining 40 percent of all skeletal muscles. Medical & Scientii c Illustration Module 10.3 Review he modules that follow organize the muscles into functional groups. How- a. What is the function of the axial muscles? ever, the skeletal system, like the body Calcaneal b. Identify the division (axial or appendicular) to itself, functions as an integrated unit, tendon which each of the following muscles belongs: Calcaneus biceps brachii, external oblique, temporalis, and and more than one muscle group will vastus medialis. usually be seen in one view. Structures c. Which structures labeled in the i gures in this not part of the muscular system will be module are not muscles? shown in italics.

337 SECTION 1 Review

1. Short answer Label the pennate muscles in the following diagram, and for each indicate the type of pennate muscle based on the relationship between the tendon(s) and fascicle organization.

a

b

c

Medical & Scientii c Illustration

2. Labeling a Label each of the indicated superi cial muscles in the b diagram to the right. Medical & Scientii c Illustration m c

d

e n f g o

h p i q j r

k s l t

338 SECTION 2

The Axial Muscles h e axial musculature is involved in stabilizing and positioning the head, neck, and trunk. Based on location and/or function, we can divide the axial muscles into the four groups shown here. h e groups do not always have distinct anatomical boundaries. For example, a function such as the extension of the involves muscles along its entire length.

1 he first group contains 2 he second muscles of the head and group—the neck that are not associated muscles of the verte- with the vertebral column. bral column—includes hese muscles include the numerous muscles muscles of facial expression of varied size that (Module 10.4), the extrinsic eye stabilize, flex, extend, muscles (Module 10.5), and the or rotate the vertebral muscles of the , pharynx, column (Module 10.7). and neck (Module 10.6). Medical & Scientii c Illustration Medical & Scientii c Illustration

4 he fourth group—the muscles of the pelvic 3 he third group floor (Module 10.9)—spans the pelvic outlet consists of the and supports the organs of the pelvis. oblique and rectus Medical & Scientii c Illustration muscles of the trunk (Module 10.8). hese muscles form broad sheets or bands that form the muscular walls of the thoracic and abdomino- pelvic cavities. Medical & Scientii c Illustration

339 10.4 Chapter 10: The Muscular System

The muscles of facial expression are important in eating and useful for communication

h e muscles of facial expression originate on 1 his anterior view the surface of the . At their insertions, the shows superficial i bers of the epimysium are woven into those of Epicranial muscles on the right the superi cial and the dermis of the skin. side of the face and h us, when they contract, the skin moves. deeper muscles on the left side of the face.

Frontal belly of Temporalis occipitofrontalis Corrugator supercilii Orbicularis oculi Procerus

A corresponding lateral Nasalis 2 view shows the major Zygomaticus minor ; note the abun- Zygomaticus major dance of muscles involved in Orbicularis oris Masseter movements of the lips. Buccinator The , which Depressor anguli oris forms the , has two bellies that are Platysma Depressor labii inferioris connected by a collagenous sheet, the (cut) .

Occipital belly Frontal belly Thyroid cartilage of the larynx

Epicra Clavicle nial ap one uro sis Medical & Scientii c Illustration

Orbicularis oculi Nasalis

Muscles of the Mouth and Cheek

Levator labii superioris Zygomaticus minor Zygomaticus major Buccinator Orbicularis oris Risorius Mentalis (cut) Depressor labii inferioris Temporalis Depressor anguli oris Masseter

Medical & Scientii c Illustration

340 Chapter 10: The Muscular System

Muscles of Facial Expression

Group and Muscle(s) Origin Insertion Action

Mouth Buccinator Alveolar processes of maxillary bone and Blends into i bers of orbicularis oris Compresses cheeks mandible Depressor labii inferioris Mandible between the anterior midline and Skin of lower lip Depresses lower lip the mental foramen Levator labii superioris Inferior margin of orbit, superior to the Orbicularis oris Elevates upper lip infra-orbital foramen Levator anguli oris Maxillary bone below the infra-orbital Corner of mouth Elevates the corner of the mouth foramen Mentalis Incisive fossa of mandible Skin of chin Elevates and protrudes lower lip Orbicularis oris Maxillary bone and mandible Lips Compresses, purses lips Risorius Fascia surrounding parotid salivary gland Angle of mouth Draws corner of mouth to the side Depressor anguli oris Anterolateral surface of mandibular body Skin at angle of mouth Depresses corner of mouth Zygomaticus major Zygomatic bone near zygomaticomaxillary Angle of mouth Retracts and elevates corner of mouth suture Zygomaticus minor Zygomatic bone posterior to Upper lip Retracts and elevates upper lip zygomaticotemporal suture Eye Corrugator supercilii Orbital rim of near nasal suture Pulls skin inferiorly and anteriorly; wrinkles brow Levator palpebrae superioris Tendinous band around optic foramen Upper Elevates upper eyelid (see Module 10.5) Orbicularis oculi Medial margin of orbit Skin around Closes eye Nose Procerus Nasal bones and lateral nasal cartilages Aponeurosis at bridge of nose and Moves nose, changes position and skin of shape of nostrils Nasalis Maxillary bone and alar cartilage of nose Bridge of nose Compresses bridge, depresses tip of nose; elevates corners of nostrils Scalp (epicranium) Occipitofrontalis Frontal belly Epicranial aponeurosis Skin of eyebrow and bridge of nose Raises , wrinkles forehead Occipital belly Occipital and Epicranial aponeurosis Tenses and retracts scalp Neck Platysma Superior thorax between cartilage of 2nd Mandible and skin of cheek Tenses skin of neck; depresses rib and acromion of scapula mandible

Module 10.4 Review

a. Identify the muscles associated with the mouth. b. State whether the following muscles involve the mouth, eye, nose, , scalp, or neck: buccinator, corrugator supercilii, mentalis, nasalis, platysma, procerus, and risorius. c. Explain how an individual is able to consciously move the skin on the scalp but is not able to consciously move the skin of the thigh.

341