CHAPTER 6The Muscular System

Skeletal Muscles of the Head, Neck, Trunk, Arm and Leg

STUDY GUIDE FOR TEST ON FRIDAY FEB. 10, 2012

Head and Neck Muscles• Facial Muscles

Frontalis—raises eyebrowsOrbicularis oculi—closes eyes, squints, Orbicularis oris —closes mouth and protrudes the lipsBuccinator —flattens the cheek, chewsZygomaticus —raises corners of the mouth – smile

Occipitalis – stabilize the frontalis• Chewing Muscles

Masseter —closes the jaw and elevates mandibleTemporalis —synergist , of the masseter, closes jaw

• Neck muscles Platysma —pulls the corners of the mouth inferiorly, lower jaw Sternocleidomastoid —flexes the neck, rotates the head, turn ear to chest

Figure 6.16

Cranialaponeurosis

Orbicularisoris

Orbicularisoculi

Frontalis

Zygomaticus

Buccinator

Platysma

Temporalis

Occipitalis

Masseter

Sternocleidomastoid

Trapezius

Muscles of Trunk, Shoulder, Arm

• Anterior muscles of the chestPectoralis major—adducts and flexes the humerusIntercostal muscles – Aid in breathing – not shown

in picture – muscle in between the ribs• Muscles of the abdominal girdle– Rectus abdominis—flexes vertebral column– External oblique—flex vertebral column; rotate

trunk and bend it laterally

Figure 6.17a

Deltoid

Pectoralismajor

Bicepsbrachii

Brachialis

Brachio-radialis

(a)

Figure 6.17b

Pectoralismajor

Rectusabdominis

Externaloblique

(b)

Serratus Anterior

Linea Alba

Muscles of Trunk, Shoulder, Arm

• Posterior muscles of the back– Trapezius—elevates, depresses, adducts, and

stabilizes the scapula– Latissimus dorsi—extends and adducts the

humerus– Erector spinae—back extension – not seen in

picture– Serratus Anterior – rotates scapula

Figure 6.18a

TricepsbrachiiLatissimusdorsi

Trapezius

Deltoid

(a)

Muscles of the Arm• Biceps brachii - flexes elbow• Brachialis—elbow flexion• Brachioradialis—elbow flexion• Triceps brachii—elbow extension• Deltoid – abducts the arm

Figure 6.17a

Deltoid

Pectoralismajor

Bicepsbrachii

Brachialis

Brachio-radialis

(a)

Muscles of the Posterior Lower Limb• Muscles causing movement at the hip joint include:

Gluteus maximus—hip extensionGluteus medius—hip abduction, steadies pelvis when walking

• Muscles causing movement at the knee joint– Hamstring group—thigh extension and knee flexion• Biceps femoris• Semimembranosus• Semitendinosus

Figure 6.20a

Gluteus medius

Gluteus maximus

Iliotibial tract(IT Band)

Biceps femoris

SemitendinosusSemimembranosus

Gastrocnemius

(a)

Hamstring group

Muscles of the Anterior Lower Limb

• Muscles causing movement at the knee jointSartorius—flexes the thighQuadriceps group—extends the knee• Rectus femoris• Vastus Lateralis• Vastus Medialis• Vastus Intermedius (internal – not seen)

Gracilis – adducts the thigh

Figure 6.20c

Sartorius

Rectus femoris

Vastus lateralis

Vastus medialisQua

dric

eps

(c)

Gracilis

Muscles of the Lower Limb

ANTERIOR– Tibialis anterior—dorsiflexion– Soleus—plantar flexionPOSTERIOR– Gastrocnemius – plantar flexion

Tibialis anteriorSoleus

anterior

Gastrocnemius

Soleus

Calcaneal (Achilles)tendon

posterior

Figure 6.22

Facial• Temporalis

• Masseter

Shoulder• Trapezius

• Deltoid

Arm• Triceps brachii• Biceps brachii• Brachialis

Forearm• Brachioradialis

Pelvis/thigh

Thigh (Quadriceps)• Rectus femoris• Vastus lateralis• Vastus medialis

• Tibialis anterior

Facial• Frontalis

• Orbicularis oculi• Zygomaticus

• Orbicularis orisNeck• Platysma• SternocleidomastoidThorax

• Pectoralis major• Serratus anterior

• Intercostals

Abdomen• Rectus abdominis

• External oblique

Thigh• Sartorius

• Gracilis

• Gastrocnemius

• Soleus

Figure 6.23

Arm• Triceps brachii

• Brachialis

Forearm• Brachioradialis

lliotibial tract

Leg• Gastrocnemius

• Soleus

Calcaneal(Achilles)tendon

Neck• Occipitalis

• Sternocleidomastoid

• Trapezius

Shoulder/Back• Deltoid

• Latissimus dorsi

Hip• Gluteus medius

• Gluteus maximus

• Hamstrings:Biceps femorisSemitendinosus

Semimembranosus