Chapter 11
The Muscular System
• Skeletal muscle major groupings
• How movements occur at specific joints
• Learn the origin, insertion, function and
innervation of all major muscles
• Important to allied health care and physical
rehabilitation students
10-1
Muscle Attachment Sites:
Origin and Insertion
• Skeletal muscles shorten & pull on the bones they are attached to
• Origin is the bone that does not move when muscle shortens
(normally proximal)
• Insertion is the movable bone (some 2 joint muscles)
• Fleshy portion of the muscle in between attachment sites = belly
10-2
Muscular System 3
1
Tenosynovitis
• Inflammation of tendon and associated connective
tissues at certain joints
– wrist, elbows and shoulder commonly affected
• Pain associated with movement
• Causes
– trauma, strain or excessive exercise
10-4
Lever Systems and Leverage
• Muscle acts on rigid rod (bone)
that moves around a
fixed point called a fulcrum
• Resistance is weight of body
part & perhaps an object
• Effort or load is work done
by muscle contraction
• Mechanical advantage
– the muscle whose attachment is farther from the joint will
produce the most force
– the muscle attaching closer to the joint has the greater range
of motion and the faster the speed it can produce
10-5
First - Class Lever
• Can produce mechanical
advantage or not depending on
location of effort & resistance
– if effort is further from fulcrum
than resistance, then a strong
resistance can be moved
• Head resting on vertebral column
– weight of face is the resistance
– joint between skull & atlas is
fulcrum
– posterior neck muscles provide
effort
10-6
2
Second - Class Lever
• Similar to a wheelbarrow
• Always produce mechanical
advantage
– resistance is always closer to fulcrum
than the effort
• Sacrifice of speed for force
• Raising up on your toes
– resistance is body weight
– fulcrum is ball of foot
– effort is contraction of calf muscles
which pull heel up off of floor
10-7
Third - Class Lever
• Most common levers in the body
• Always produce a mechanical
disadvantage
– effort is always closer to fulcrum
than resistance
• Favors speed and range of
motion over force
• Flexor muscles at the elbow
– resistance is weight in hand
– fulcrum is elbow joint
– effort is contraction of biceps
brachii muscle
10-8
Types of levers (Fig. 11.2)
Copyright 2009, John
Wiley & Sons, Inc.
3
Fascicle Arrangements
• A contracting muscle shortens to about 70% of its length
• Fascicular arrangement represents a compromise between
force of contraction (power) and range of motion
– muscles with longer fibers have a greater range of motion
– a short fiber can contract as forcefully as a long one.
10-10
Parallel
Muscular System 11
Fan
Muscular System 12
4
Pennate
Muscular System 13
Bipennate
Muscular System 14
Fusiform
Muscular System 15
5
Muscular System 16
Muscular System 17
Muscular System 18
6
Muscular System 19
Muscular System 20
Muscular System 21
7
•
Sphincter =
Ring of muscle surrounding
tubular organ
Smooth or skeletal
Muscular System 22
Coordination Within Muscle Groups
• Most movement is the result of several muscle
working at the same time
• Most muscles are arranged in opposing pairs at
joints
– prime mover or agonist contracts to cause the desired
action
– antagonist stretches and yields to prime mover
– synergists contract to stabilize nearby joints
– fixators stabilize the origin of the prime mover
• scapula held steady so deltoid can raise arm
10-23
How Skeletal Muscle are Named
• Direction the muscle fibers run
• Size, shape, action, number of origins or locations
• Examples from Table 11.2
– triceps brachii -- 3 sites of origin
– quadratus femoris -- square shape
– serratus anterior -- saw-toothed edge
10-24
8
Muscles of Facial Expression
• Arise from skull &
insert onto skin
• Encircle eyes, nose &
mouth
• Express emotions
• Facial Nerve (VII)
• Bell’s palsy = facial
paralysis due
10-25
Muscles of Facial Expression
• Orbicularis oculi closes
the eye
• Levator palpebrae
superioris opens the eye
• Orbicularis oris puckers
the mouth
• Buccinator forms the
muscular portion of the
cheek & assists in
whistling, blowing,
sucking & chewing
10-26
Extrinsic Muscles of the Eyeballs
• Extrinsic muscles insert onto
white of eye
• Fastest contracting & most
precisely controlled
• Cranial nerves 3, 4 & 6
innervate the six muscles
– 4 Rectus muscles & 2 obliques
• Intrinsic muscles are found
within the eyeball
• Levator palpebrae superioris
raises eyelid
10-27
9
Muscles that Move the Mandible
• Masseter, temporalis &
pterygoids
• Arise from skull & insert
on mandible
• Cranial nerve V
(trigeminal nerve)
• Protracts, elevates or
retracts mandible
– Temporalis & Masseter
elevate the mandible
(biting)
– temporalis retracts
10-28
Jaw Muscles -- Deep Dissection
• Lateral pterygoid protracts mandible
– sphenoid bone to condyle of mandible
• Medial pterygoid elevates & protracts mandible
– sphenoid bone to angle of mandible
• Together move jaw side to side to grind food.
10-29
Muscles that Move the Tongue
• 4 extrinsic mm arise
elsewhere, but insert
into tongue
– Genioglossus
• from inside tip of mandible
– Styloglossus
• from styloid process
– Palatoglossus
• from hard palate
– Hyoglossus
• from hyoid bone
• Together move tongue in various directions
• Intubation is necessary during anesthesia since Genioglossus
relaxes & tongue falls posteriorly blocking airway
10-30
10
Muscles of the Floor of the Oral Cavity
• Suprahyoid muscles lie superior to hyoid bone.
– Digastric m. extends from mandible to mastoid process
• used to open the mouth
– Mylohyoid m. extends from hyoid to mandible
• supports floor of mouth & elevates hyoid bone during swallowing
– Stylohyoid & Geniohyoid elevate the hyoid during swallowing 10-31
Muscles that Move the Head
• Sternocleidomastoid muscle
–
–
–
–
arises from sternum & clavicle & inserts onto mastoid process of skull
innervated by cranial nerve XI (spinal accessory)
contraction of both flexes the cervical vertebrae & extends head
contraction of one, laterally flexes the neck and rotates face in opposite
direction
10-32
Muscles of Abdominal Wall
• Notice 4 layers of muscle in the abdominal wall
10-33
11
Muscles of Abdominal Wall
• 4 pairs of sheetlike muscles
– rectus abdominis = vertically oriented
– external & internal obliques and transverses abdominis
• wrap around body to form anterior body wall
• form rectus sheath and linea alba
• Inguinal ligament from anterior superior iliac spine to upper
surface of body of pubis
• Inguinal canal = passageway from pelvis through body wall
musculature opening seen as superficial inguinal ring
• Inguinal hernia = rupture or separation of abdominal wall
allowing protrusion of part of the small intestine (more
common in males)
10-34
Transverse Section of Body Wall
• Rectus sheath formed from connective tissue aponeuroses
of other abdominal muscles as they insert in the midline
connective tissue called the linea alba
10-35
Muscles Used in Breathing
• Breathing requires a change in
size of the thorax
• During inspiration, thoracic
cavity increases in size
– external intercostal lift the ribs
– diaphragm contracts & dome is
flattened
• During expiration, thoracic
cavity decreases in size
– internal intercostal mm used in
forced expiration
Quadratus lumborum fills in space
between 12th rib & iliac crest to
create posterior body wall
• Diaphragm is innervated by
phrenic nerve (C3-C5) but
intercostals innervated by
thoracic spinal nerves (T2-T12)
10-36
12
Female Pelvic Floor & Perineum
• Both the pelvic diaphragm ( coccygeus & levator ani) and the
muscles of the perineum fill in the gap between the hip bones
– supports pelvic viscera & resists increased abdominal pressure during
defecation, urination, coughing, vomiting, etc
– pierced by anal canal, vagina & urethra in females
– levator ani may be damaged during episiotomy during childbirth (urinary
incontinence during coughing
10-37
Muscles of Male Perineum
• Perineum contains more superficial layer of muscle
– urogenital triangle contains external genitals
• muscle arrangement forms urogenital diaphragm assists in urination
(external urethral sphincter) and ejaculation (ischiocavernosus,
bulbospongiosus)
– anal triangle contains anus
• external anal sphincter
10-38
Stabilizing the Pectoral Girdle
• Anterior thoracic muscles
– Subclavius extends from 1st rib
to clavicle
– Pectoralis minor extends from
ribs to coracoid process
– Serratus anterior extends from
ribs to inner surface of scapula
• Posterior thoracic muscle
– Trapezius extends from skull &
vertebrae to clavicle & scapula
– Levator scapulae extends from
cervical vertebrae to scapula
– Rhomboideus extends from
thoracic vertebrae to vertebral
border of scapula
10-39
13
Axial Muscles that Move the Arm
• Pectoralis major & Latissimus dorsi extend from body wall
to humerus.
10-40
Muscles that Move the Arm
• Deltoid arises from acromion & spine of scapula & inserts on arm
– abducts, flexes & extends arm
• Rotator cuff muscles extend from scapula posterior to shoulder
joint to attach to the humerus
– supraspinatus & infraspinatus : above & below spine of scapula
– subscapularis on inner surface of scapula
10-41
Flexors of the Forearm (elbow)
• Cross anterior surface of elbow
joint & form flexor muscle
compartment
• Biceps brachii
– scapula to radial tuberosity
– flexes shoulder and elbow & supinates
hand
• Brachialis
– humerus to ulna
– flexion of elbow
• Brachioradialis
– humerus to radius
– flexes elbow
10-42
14
Extensors of the Forearm (elbow)
• Cross posterior surface of elbow
joint & forms extensor muscle
compartment
• Triceps brachii
– long head arises scapula
– medial & lateral heads from
humerus
– inserts on ulna
– extends elbow & shoulder joints
• Anconeus
– assists triceps brachii in extending
the elbow
10-43
Cross-Section Through Forearm
• If I am looking down onto this section is it from right or left arm?
10-44
Muscle that Pronate & Flex
• Pronator teres
– medial epicondyle to radius
so contraction turns palm of
hand down towards floor
• Flexor carpi muscles
– radialis
– ulnaris
• Flexor digitorum muscles
– superficialis
– profundus
• Flexor pollicis
10-45
15
Muscles that Supinate & Extend
• Supinator
– lateral epicondyle of humerus to
radius
– supinates hand
• Extensors of wrist and fingers
– extensor carpi
– extensor digitorum
– extensor pollicis
– extensor indicis
10-46
Retinaculum
• Tough connective tissue band that helps hold tendons in place
• Extensor & Flexor retinaculum cross wrist region attaching from bone
to bone (carpal tunnel syndrome = painful compression of median
nerve due to narrowing passageway under flexor retinaculum
10-47
Intrinsic Muscles of the Hand
•
•
•
•
•
Origins & insertions are within the hand
Help move the digits
Thenar muscles move the thumb
Hypothenar muscles move the little finger
Opposition, flexion, extension, abduction & adduction
10-48
16
Muscles that Move the Vertebrae
• Quite complex due to overlap
• Erector spinae fibers run
longitudinally
– 3 groupings
• spinalis
• iliocostalis
• longissimus
– extend vertebral column
• Smaller, deeper muscles
– transversospinalis group
• semispinalis, multifidis &
rotatores
– run from transverse process to
dorsal spine of vertebrae above &
help rotate vertebrae
10-49
Scalene Muscle Group
• Attach cervical vertebrae to uppermost ribs
• Flex, laterally flex & rotate the head
10-50
Muscles Crossing the Hip Joint
• Iliopsoas flexes hip joint
– arises lumbar vertebrae & ilium
– inserts on lesser trochanter
• Quadriceps femoris has 4 heads
– Rectus femoris crosses hip
– 3 heads arise from femur
– all act to extend the knee
• Adductor muscles
– bring legs together
– cross hip joint medially
– see next picture
• Pulled groin muscle
– result of quick sprint activity
– stretching or tearing of iliopsoas or
adductor muscle
10-51
17
Adductor Muscles of the Thigh
• Adductor group of muscle
extends from pelvis to linea
aspera on posterior surface of
femur
–
–
–
–
–
pectineus
adductor longus
adductor brevis
gracilis
adductor magnus (hip extensor)
10-52
Muscles of the Butt & Thigh
• Gluteus muscles
– maximus, medius &
minimus
– maximus extends hip
– medius & minimus abduct
• Deeper muscles laterally
rotate femur
• Hamstring muscles
–
–
–
–
semimembranosus (medial)
semitendinosus (medial)
biceps femoris (lateral)
extend hip & flex knee
• Pulled hamstring
– tear of origin of muscles
10-53
from ischial tuberosity
Cross-Section through Thigh
• 3 compartments of muscle with unique innervation
– anterior compartment is quadriceps femoris innervated by femoral nerve
– medial compartment is adductors innervated by obturator nerve
– posterior compartment is hamstrings innervated by sciatic nerve
10-54
18
Muscles of the Calf (posterior leg)
• 3 muscles insert onto calcaneus
– gastrocnemius arises femur
• flexes knee and ankle
– plantaris & soleus arise from leg
• flexes ankle
• Deeper mm arise from tibia or
fibula
– cross ankle joint to insert into foot
• tibialis posterior
• flexor digitorum longus
• flexor hallucis longus
– flexing ankle joint & toes
10-55
Muscles of the Leg and Foot
• Anterior compartment of leg
– extensors of ankle & toes
• tibialis anterior
• extensor digitorum longus
• extensor hallucis longus
– tendons pass under retinaculum
• Shinsplits syndrome
– pain or soreness on anterior tibia
– running on hard surfaces
• Lateral compartment of leg
– peroneus mm plantarflex the foot
– tendons pass posteriorly to axis
of ankle joint and into plantar
foot
10-56
Muscles of the Plantar Foot
• Intrinsic muscles
– arise & insert in foot
• 4 layers of muscles
– get shorter as go into deeper
layers
• Flex, adduct & abduct toes
• Digiti minimi muscles move
little toe
• Hallucis muscles move big toe
• Plantar fasciitis (painful heel
syndrome) chronic irritation
of plantar aponeurosis at
calcaneus
– improper shoes & weight gain
10-57
19
• Running injuries
• Compartment syndrome
10-58
20