CHAPTER 10 THE MUSCULAR SYSTEM II Part II: Major Muscles of the Upper and Lower Limbs

MUSCLES THAT MOVE THE ARM AT THE SHOULDER

deltoid (shoulder), pectoralis major(anterior chest), latissimus dorsi(lower back), teres major (posterior shoulder)

deltoid primary action

abducts the arm

pectoralis major primary action

flexes, adducts, and medially rotates the arm (turns the arm inward)

latissimus dorsi primary action

extends, adducts and medially rotates the arm

teres major primary action

extends, adducts, and medially rotates the arm

what’s the rotator cuff

a group of four muscles that help keep the

shoulder joint stable.

Remember SITS: the first letters of the four muscle names of rotator cuff

Supraspinatus

Infraspinatus

Teres minor

Subscapularis

Supraspinatus

Initiates arm abduction

Infraspinatus

Laterally rotates the arm; turns the

arm outward

Teres minor

Laterally rotates the arm

Subscapularis

Medially rotates the arm

MUSCLES THAT MOVE THE FOREARM AT THE ELBOW

Biceps brachii.

Brachialis

Brachioradialis

Triceps brachii

Biceps brachii

Anterior arm.

Flexes the elbow

Supinates the forearm; turns

the palm forward or upward

Brachialis

Anterior arm

Primary elbow flexor

Brachioradialis

Lateral forearm

Flexes the elbow

Triceps brachii

Posterior arm

Primary elbow extensor

Forearm muscles form..

anterior and posterior compartments, groups separated by connective tissue

Anterior forearm muscles mainly..

flex the wrist and fingers

Posterior forearm muscles mainly ..

extend the wrist and fingers

FOREARM MUSCLE COMPARTMENTS

Flexor carpi radialis

Flexor carpi ulnaris

Palmaris longus

Pronator teres.

Extensor digitorum

Extensor carpi ulnaris

Flexor carpi radialis

Wrist, radius side,

Flexor carpi ulnaris

Wrist, ulna side,

Palmaris longus

Palm; longus = long

Anterior forearm Flex the wrist

Pronator teres

Pronation, rounded

Anterior forearm Pronates the forearm; turns the palm

backward or downward

Extensor digitorum

Fingers

Posterior forearm Extends the fingers

Extensor carpi ulnaris

Wrist, ulna side

Posterior forearm Extends the wrist and moves the hand toward

the little-finger side

MUSCLES THAT MOVE THE THIGH AT THE HIP

Iliopsoas group;

Iliacus + psoas major

Tensor fasciae latae (TFL).

Gluteus maximus

Gluteus medius.

Sartorius

Adductor group;

Adductor longus

Pectineus

Gracilis

Primary hip flexor

Iliopsoas group;

Iliacus + psoas major

Iliacus: ilium. Psoas: lower-back region

Flexes, abducts, and medially rotates the thigh. Helps

stabilize the pelvis and knee

Tensor fasciae latae (TFL)

Tightens the thigh fascia, a sheet of

connective tissue

Powerful hip extensor

Gluteus maximus

Largest buttock muscle

Abducts the thigh and stabilizes the pelvis during walking.

Gluteus medius

Middle buttock muscle

Flexes the hip and knee. Abducts and laterally rotates the

thigh

Sartorius

Sartorius = tailor; named for the cross-

legged sitting position

Adductor group;

Adductor longus — long

Pectineus — comb-like

Gracilis — slender

Adduct the thigh

Quadriceps femoris is..

a group of four muscles in the anterior thigh.

• Quadriceps means four heads, and femoris refers to the thigh.

extends across both the hip and knee joints

Rectus femoris

extend across only the knee joint

the three vastus muscles

QUADRICEPS FEMORIS: ANTERIOR THIGH MUSCLES

Rectus femoris

Vastus group;

Vastus lateralis

Vastus medialis

Vastus intermedius

Extends the knee and also flexes the hip

Rectus femoris

Straight, thigh

Extend the knee

Vastus group;

vastus = large

Vastus lateralis

outer side

Vastus medialis

inner side

Vastus intermedius

between

a group of three major muscles in the posterior thigh

hamstrings

HAMSTRINGS: POSTERIOR THIGH MUSCLES

Hamstring group;

Biceps femoris

Semitendinosus

Semimembranosus

Flex the knee.

Most also extend the hip

Biceps femoris

`Two heads

Semitendinosus

`Partly tendinous

Semimembranosus

`Partly membranous

MUSCLES THAT MOVE THE ANKLE AND FOOT

Tibialis anterior.

Extensor digitorum.

Gastrocnemius

Soleus

Fibularis longus

Tibialis anterior

Front of the tibia

anterior leg

Dorsiflexion: lifts the foot toward the shin (front

of the leg).

Inversion: turns the sole (bottom of the foot)

inward.

Extensor digitorum

longus

anterior leg

Dorsiflexion and toe extension.

Gastrocnemius

“Belly” of the leg

Soleus

Flat, sole-fish shape

posterior leg

Plantar flexion: points the foot downward

Fibularis longus

Fibularis = along the

fibula

lateral leg

Eversion: turns the sole outward.

Also assists plantar flexion.

form the calf, the muscular back of the leg.

Gastrocnemius and soleus

Their tendons join to form

calcaneal (Achilles) tendon, which attaches to the calcaneus (heel bone

Assists knee flexion

Gastrocnemius

Helps maintain posture during standing and

supports walking.

Soleus

1.What is the primary action of the deltoid?

The deltoid lifts the arm out to the side.

2.How does the rotator cuff stabilize the shoulder

The rotator cuff muscles hold the top of the arm bone snugly in the shoulder socket

3.Compare biceps brachii and triceps brachii

4.Compare anterior and posterior forearm compartments

5.Compare gluteus maximus and gluteus medius

6.Compare quadriceps and hamstrings

7. Which muscles produce dorsiflexion and plantar flexion

8.Which major muscle dorsiflexes and inverts the foot