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Muscle System
Ch. 10
Four functional groups of muscle:
1- prime movers (agonists): Muscle that
bears the prime responsibility for effecting
a movement
2- antagonist: Muscle that opposes the
action of another muscle.
3- synergists: these muscles act as
stabilizers to the prime movers. They may
also contribute extra force to the prime
mover as well.
4- fixator: muscle that immobilizes one or
more bones (scapula)

Muscle are classified according to their fascicular
arrangement or attachment.
Parallel - long axis of fascicle runs with
longitudinal axis of muscle: sartorius muscle
Pennate - fascicle branch form central tendon
diagonally
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Unipennate - extensor muscles
Bipennate - rectus femoris
Multipennate - deltoid
Convergent - fascicle converge toward a single
tendon: pectoralis major
Circular - fascicle are arranged in concentric rings
Orbicularis oris and oculi
Types of muscle attachments: direct and
indirect
Direct (tendon) - epimysium of muscle
fused to periosteum of bone or
perichondrium of cartilage.
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Indirect (aponeurosis) - muscle fascia
extends beyond the muscle to bone or
another muscle. Latissimus dorsi or galea
aponeurotica
Muscle have points of attachment on the
skeleton via tendons or aponeurosis
Origin and insertion
Origin: end of the muscle attaches to the
stationary bone (non-moveable)
Insertion: end of muscle attaches to the
moving bone
Biceps (two heads) have two origins on
the scapula
Biceps inserts on the radius (crosses
elbow joint)
Muscle list
1- Frontalis:
O: galea aponeurotica
I: skin of eyebrows
N: Facial nerve (CN VII)
A: raises eyebrows
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2- Orbicularis oculi:
O: frontal bone
I: tissues of eyelid
N: Facial nerve
A: closes eyes
3- Temporalis:
O: temporal fossa
I: coronoid process of mandible
N: Trigeminal nerve (CN V)
A: closes jaw (muscle of mastication)
4- Orbicularis oris
O: indirectly from maxilla and mandible
I: encircles mouth
N: Facial nerve
A: puckers lips (kissing and whistling)
5- Platysma:
O: subcutaneous skin over delto-pectoral
region
I: skin widely over the mandible
A: depress mandible and lower lip
tenses the skin over the lower neck
N: facial nerve
6- Scalenes: located deep in the neck
anterior
middle
posterior
7- Sternohyoid:
O: manubrium
I: hyoid bone
A: depresses hyoid and larynx
8- Digastric: consists of two bellies that are
connected by an intermediate
tendon
9- Sternocleidomastoid:
O: manubrium and medial portion of clavicle
I: mastoid process
A: together they flex head forward;
separately they rotate head opposite to muscle
contracting
N: Spinal accessory (CN XI)
10- Deltoid:
O: lateral 1/3 of clavicle, acromion and
spine of scapula
I: deltoid tuberosity
A: arm abduction
N: axillary nerve
11: Pectoralis minor: Thin muscle located
underneath pectoralis major
O: ribs 3-5
I: coracoid process
12- Pectoralis major
O: medial 1/3 of clavicle
I: lateral lip of bicipital groove to the crest of the
greater tubercle
A: arm flexion, rotates arm medially
N: lateral and median pectoral nerves
13- Serratus anterior
O: ribs 1-8
I: vertebral border of scapula
A: protract and hold scapula
N: long thoracic nerve
14- Intercostals: accessory muscle to respiration
15- Rectus abdominis:
O: pubic symphysis
I: xiphoid process and costal cartilage
A: flex lumbar spine
N: intercostal nerves
16- Diaphragm:
O: inferior surface of rib cage
I: central tendon
A: primary muscle of respiration
N: phrenic nerve (C3,4,5)
17- Triceps brachii:
O: long head: infraglenoid tubercle of scapula
medial head: posterior humeral shaft
lateral head: posterior humeral shaft
I: olecranon process of ulna
A: forearm extension
N: radial nerve
18- Biceps brachii :
O: short head: coracoid process
long head: supraglenoid tubercle
I: radial tuberosity
A: forearm flexor
N: musculocutaneous nerve
19- Brachialis:
Forearm flexor (lifts ulna)
20- Brachioradialis: “drinking muscle”
O: distal end of humerus
I: styloid process of radius
A: forearm flexor
N: radial nerve
21- Flexor carpi radialis:
A: wrist flexor
N: median nerve
22- Palmaris longus:
O: medial epicondyle of humerus
I: palmar aponeurosis
A: weak wrist flexor
N: median nerve
Absent in 15% of the population (More
females than males)
23- Lumbricals: 4 worm shaped muscles
A: flex fingers at MCP joint
24- Iliopsoas: combination iliacus and psoas
muscle
A: primary hip and trunk flexor
25- Pectineus:
Short flat muscle that adducts thigh
O: pubis
I: lesser trochanter
26- Tensor fasciae latae:
O: ASIS
I: Iliotibial tract (Gerdy’s tubercle)
A: thigh abduction
27- Sartorius: “tailor’s muscle”
O: anterior superior iliac spine (ASIS)
I: upper medial surface of body of tibia
A: Flexes, abducts and laterally rotates thigh
N: Obturator nerve
28: Adductor longus
Common thigh adductor
29: Gracilis:
O: pubis
I: tibia
A: adducts thigh
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Quadriceps:
30: Rectus femoris
O: ASIS
I: patella by way of quadriceps tendon and
tibial tuberosity by way of patellar ligament
 A: hip flexor and knee extension
 N: femoral nerve
31: Vastus lateralis
medius
knee extension
intermedius
32: Tibialis anterior:
O: lateral condyle of tibia
I: medial cuneiform and 1st MTP.
A: dorsiflexion of foot
N: deep fibular nerve
33: Flexor hallucis longus: flexes great toe
“push off” while taking a step
Posterior
1- Occipitalis:
O: occipital bone
I: galea aponeurotica
A: pulls scalp posteriorly
I: facial nerve
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2- Trapezius
O: Occipital bone, vertebra of cervical and thoracic
spinous processes
I: acromion, spine of scapula and lateral 1/3 of
clavicle
A: extends head and raises scapula. “shrugging
shoulders”
N: Spinal Accessory nerve (CNXI)
Rotator cuff of shoulder: Holds humerus tight to
glenoid fossa (S.I.T.S.)
3- Supraspinatus:
O: supraspinous fossa of scapula
I: greater tubercle of humerus
A: assists in abduction
4- Infraspinatus
O: infraspinous fossa of scapula
I: greater tubercle of humerus
A: rotates humerus laterally
5- Subscapularis
O: subscapular fossa
I: lesser tubercle of humerus
A: medial rotation of humerus
6- Teres minor:
A: Arm adductor
7- Teres major:
A: posteromedial extension of humerus
8- Rhomboid major and minor
O: spinous processes of C7-T1 (minor)
I: medial border of scapula
A: retract scapula “standing up straight”
N: dorsal scapular nerve
9- Erector Spinae:
Iliocostalis
Longissimus
Spinalis
A: prime muscles for back extension
10- Latissimus dorsi
O: Thoracolumbar fascia (aponeurosis)
- T6-T12 and L1-L5 and iliac crest
I: intertubercular groove of humerus
A: arm extension and adductor
N: thoracodorsal nerve
11- Extensor carpi ulnaris:
Extension of the wrist
12- Extensor carpi radialis
Extends and abducts wrist
13- Flexor carpi ulnaris
Powerful wrist flexor
N: ulnar nerve
14- Extensor digitorum
Prime mover of finger extension
15- Gluteus medius
A: abducts and medial rotates thigh
N: superior gluteal nerve
16- Gluteus maximus
O: dorsal ilium, sacrum and coccyx
I: gluteal tuberosity of femur
A: powerful thigh extender
N: inferior gluteal nerve
Hamstrings (crosses knee joint- popliteal)
17- Biceps femoris:
O: ischial tuberosity
I: head of fibula and lateral condyle of tibia
A: thigh extension and knee flexion
N: Sciatic nerve
18- Semitendinosus:
A: extends thigh and knee flexion
19- Semimembranosus
A: extends thigh and flexes knee
20- Gastrocnemius
O: medial and lateral condyles of femur
I: posterior calcaneus (achilles tendon)
A: plantar flexes foot (raise up on toes)
N: Tibial nerve
21- Soleus
A: plantar flexes foot and raise up on toes
while seated
N: Tibial nerve