Transcript Ch 11
Chapter 11
The Muscular System
Lecture Outline
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INTRODUCTION
• The voluntarily controlled muscles of the body make up the
muscular system.
• The muscular system and muscle tissue contribute to
homeostasis by producing movement, stabilizing body
position, regulating organ volume, moving substances within
the body, and producing heat.
• This chapter discusses how skeletal muscles produce
movement and describes the principal skeletal muscles.
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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
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HOW SKELETAL MUSCLES PRODUCE
MOVEMENT
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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
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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
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Lever Systems and Leverage
• A lever is a rigid structure that moves around a fixed point,
the fulcrum (F)
• The lever is acted on by two different forces: (Figure 11.1b).
– resistance (load) (L), which opposes movement
– effort (E) which causes movement Bones serve as levers
and joints serve as fulcrums.
• Leverage, the mechanical advantage gained by a lever, is
largely responsible for a muscle’s strength and range of
motion (ROM), i.e., the maximum ability to move the bones
of a joint through an arc.
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Levers
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Levers are categorized into three types –
• First class levers (EFL) e.g. a seesaw – the head on the
vertebral column (Figure 11.2a)
• Second-class (FLE) eg. a wheelbarrow(Figure 11.2b)
• Third-class (FEL) (Figure 11.1b) e.g. forceps - the elbow
joint (Figure 11.2c).
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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
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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
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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
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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
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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.
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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
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HOW SKELETAL MUSCLES ARE NAMED
• The names of most of the nearly 700 skeletal muscles are
based on several types of characteristics.
• These characteristics may be reflected in the name of the
muscle.
• The most important characteristics include the direction in
which the muscle fibers run, the size, shape, action,
numbers of origins, and location of the muscle, and the sites
of origin and insertion of the muscle
• Examples from Table 11.2
– triceps brachii -- 3 sites of origin
– quadratus femoris -- square shape
– serratus anterior -- saw-toothed edge
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PRINCIPLE SKELETAL MUSCLES
• Exhibits 11.1 through 11.20 list the principle skeletal
muscles in various regions of the body.
• Figure 11.3 shows general anterior and posterior views of
the muscular system.
• The exhibits contain objectives, an overview which provides
a general orientation to the muscles, muscle names, origins,
insertions, and actions, “relating muscles to movements,”
innervation, and Figures (11.4-11.23) that show the muscles
under consideration.
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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
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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
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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
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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
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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.
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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
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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
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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
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Muscles of Abdominal Wall
• Notice 4 layers of muscle in the abdominal wall
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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)
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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
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Muscles Used in Breathing
Quadratus lumborum fills in space
between 12th rib & iliac crest to
create posterior body wall
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• 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
• Diaphragm is innervated by
phrenic nerve (C3-C5) but
intercostals innervated by
thoracic spinal nerves (T2-T12)
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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)
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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
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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
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Axial Muscles that Move the Arm
• Pectoralis major & Latissimus dorsi extend from body
wall to humerus.
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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
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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
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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
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Cross-Section Through Forearm
• If I am looking down onto this section is it from right or left
arm?
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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
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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
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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
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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
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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
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Scalene Muscle Group
• Attach cervical vertebrae to uppermost ribs
• Flex, laterally flex & rotate the head
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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
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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)
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Muscles of the Butt & Thigh
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• 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
from ischial tuberosity
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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
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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
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Muscles of the Leg and Foot
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• 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
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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
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Compartment Syndrome
• Skeletal muscles in the limbs are organized in units called
compartments.
• In compartment syndrome, some external or internal
pressure constricts the structures within a compartment,
resulting in damaged blood vessels and subsequent
reduction of the blood supply to the structures within the
compartment.
• Without intervention, nerves suffer damage, and muscle
develop scar tissue that results in permanent shortening of
the muscles, a condition called contracture.
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IM injection
• Intramuscular injection penetrates the skin, subcutaneous
tissue and enters the muscle.
• They are given when rapid absorption is necessary, for
large doses, or when a drug is irritating to subcutaneous
tissue.
• Common sites of injection are the gluteus medius, vastul
lateralis, and deltoid.
• Intramuscular injections are faster than oral medications, but
slower than IV.
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