Skeletal MusclesPart 2

A few review questions

• Muscles of the face originate in the skull. Where do they insert?

• The skin• What is the strongest muscle associated with

chewing? • Masseter• What muscle action allows you to whistle?• Buccinator• What muscle closes the eye?• Orbicularis oculi

Muscles of the spine

• Covered by superfical back muscles

• Erector spinae is chief extensor of vertebral column

• Opposed by quadratus lumborum and various abdominal muscles

Iliocostalis, spinalis, longissimus

Muscles of the trunk

• Protect abdominal viscera

• Move vertebral column

• Assist in breathing (expiration)

• Assist in urination and defection

• Assist in childbirth

Muscles of trunk, continued

• Muscles associated with breathing– Diaphragm– External and internal

intercostals– Other muscles

become involved with forced breathing

Diaphragm separates thorax and abdomen

• Important for breathing

• Returning venous blood to the heart

• Three major openings – Aortic hiatus– Esophageal hiatus– Caval opening

Perineum: floor of pelvic cavity

• Levator ani– Pubococcygeis, iliococcygeus

• Coccygeus

• Support organs in pelvic cavity

• Resist pressure from coughing, urination, etc.

• Sphincters

Female and male perimeum

Deep muscles are the same

Appendicular muscles

• Shoulders and upper limbs– Pectoral girdle: anterior and posterior thoracic

muscles

• Pelvic girdle and lower limbs

Muscles of the neck, shoulder, and back

Muscles that position the pectoral girdle

Muscles originate on axial skeleton and insert on clavicle or scapula

Muscles that move the arm

Anterior Posterior

Range of movement at shoulder

• Elevation of scapula- shrugging• Depression- pull-up• Abduction-push-up• Adduction- pulling something toward you• Upward rotation- lifting arm past horizontal• Downward rotation- supporting weight with

hands• Deep muscles (rotator cuff) stabilize shoulder

Muscles that move the arm

• Deltoid, supraspinatus-abduction

• Rotator cuff-subscapularis, teres major (medial); infraspinatus, teres minor (lateral)

• Latissimus dorsi-extension, adduction

• Pectoralis major- flexion, adduction

Muscles of the upper limb

• Most muscles that insert on the forearm and wrist originate on the humerus

• Biceps brachii and triceps brachii originate on scapula

• Brachoradialis is opposed on triceps brachii

• Flexors of wrist are on anterior and medial surfaces of forearm; extensors are on posterior and lateral surface

• Flexor digitorum and extensor digitorum muscles perform flexion and extension of fingers

Muscles that move arm and hand

Arm Forearm

Trunk and proximal limbs

Muscles of the hip and lower limb

• Muscles that move the thigh (p. 298)– Gluteal group– Lateral rotator group– Adductor group– Iliopsoas group

• Muscles that move the leg (p. 303)(flexors, extensors)• Muscles that affect the ankles and feet (p. 312) (flexors,

extensors, intrinsic)

Muscles that move the thigh

Gluteus maximus Extends hip

Gluteus minimus Abducts thigh

Adductors Adduct thigh and flex hip

Gracilis Adducts thigh and flexes knee

Iliopsoas Flexes hip

Muscles that move the leg (anterior)

Muscles that move the leg (posterior)

Muscles that move the leg (lateral)

lateral Major groups

• Flexors of knee– Biceps femoris,

semimembranosus, semitendinosus, sartorius, popliteus

• Extensors of knee– Quadriceps (rectus

femoris, vastus intermedius, vastus lateralis, vastus medialis)

Muscles that move the leg

Hamstring muscles (biceps femoris, semimembranosus, semitendinosus)

Flex knee

Sartorius Flexes hip and knee

Quadriceps muscles (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius)

Extensors of knee

Muscles that move the foot and toes

Organization of leg muscles

• Muscles are in compartments, superificial and deep

• Anterior- extension• Posterior- flexion• Medial- adductor• Lateral- eversion of

foot, flexion (ankle)

Compartments

Formed by fascia; allow independent movement

Review compartments of upper limb (p. 314, 315)

arm forearm

Review compartments of lower limb (p. 316)

Summary

• Extrinsic and intrinsic muscles in hand are important for fine motor skills

• Muscles that move spine are complex in organization

• Muscles that move femur and large and powerful• Compartments are associated with types of

movement• Intrinsic muscles of foot are limited to support

and movement