MUSCULAR SYSTEM

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MUSCULAR SYSTEM
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• Muscles make up 50-60 of body wt.
• More than 650 muscles in the body.
• Each muscle is made of thousands of muscle fibers
  the size of a fiber optic filament.
• It takes 17 muscles to smile 42 to frown.
• The hardest working muscle is the heart.

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• The largest muscle is the Gluteus Maximus.
• The longest muscle is the Sartorius.
• The strongest muscle is the Masseter

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• The prefix myo- mys- means muscle the prefix
  sarco- means flesh so if you hear these prefixes
  youll know were talking about muscles.

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Muscle Functions

• 1. Create skeletal movement by contracting
  relaxing.
• 2. control of organ vessel size
• 3. maintain posture position
• 4. support soft tissue
• 5. guard entrances and exits
• 6. maintain body temperature (85)
• 7. Only body tissue that can shorten (contract)

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1. 3 Kinds of Muscle Tissue

• Skeletal
• Striated
• Voluntary
• Stacked in Sheets

AKA Somatic Tissue
-Multinucleated -Found attached to skeleton
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C. 3 Kinds of Muscle Tissue

• Cardiac aka heart muscle
• Branched cells w/Single nuclei per cell.
• Thick striations called Intercalated discs that
  Involuntary
• Cells are fused so when one cell contracts,
  they all contract, creating the heartbeat.

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1. 3 Kinds of Muscle Tissue

• Smooth aka Visceral
• Spindle shaped
• Nonstriated
• Involuntary

-Found around hollow organs such as arteries,
esophagus, stomach
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D. Muscle Characteristics

• Contractility
• Ability to shorten and exert tension or force
• Excitability
• Ability to respond to stimuli
• Extensibility
• Ability to contract after being stretched
• Elasticity
• Ability to regain initial length after
  contraction

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I. Overview
E. Each muscle is an organ comprised of

1. Muscle tissue (smooth, cardiac, or skeletal)
2. Connective tissues
3. Nervous tissue
4. Blood

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II. Anatomy of Skeletal Muscle

• Connective Tissue
• Superficial
• Fascia Fibrous connective tissue surrounding
  separating each muscle

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A. Connective Tissue

• Deep
• Epimysium a tough outer coat of connective
  tissue surrounding the entire muscle.
• b. Perimysium - several sheathed muslce fibers
  wraped in a coarse fibrous membrane.

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A. Connective Tissue

• Deep
• c. Fascicles a bundle of perimysium muscle
  fibers.
• d. Endomysium - a delicate connective sheath
  around a single muscle fiber

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A. Connective Tissue

• 3. Tendons cord like dense fibrous connective
  tissue.
• Formed from the union of all three deep fascia
• Connect muscle to muscle or muscle to bone

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A. Connective Tissue

• 4. Aponeurosis flat sheet of connective
  tissue that indirectly attaches muscles to bones,
  cartilage or other muscles.

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Aponeurosis
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B. Muscle Fibers

• Each muscle fiber
• is a single, long, cylindrical muscle cell.
• Sarcolemma is the plasma membrane of a muscle
  cell.
• Sarcoplasm is the cytoplasm of a muscle cell.
• Many mitochondria
• Nuclei
• Sarcoplasmic reticulum

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B. Muscle Fibers

• 1. Each muscle fiber
• is wrapped in endomysium

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1. Each muscle fiber

• c. is a bundle of myofibrils which is made of a
  budle of myofilaments

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B. Muscle Fibers

• 2. Fascicles
• a bundle of muscle fibers
• wrapped in perimysium

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B. Muscle Fibers

• 3. Myofibrils
• made of thin and thick filaments

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B. Muscle Fibers

• 3. Myofibrils
• Thick filaments made up of the protein myosin.
• c. Thin filaments are made up of the protein
  actin.

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• Thick filaments

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• Thin filaments

Tropomyosin and troponin are regulatory
proteins Actin and myosin are contractile
proteins.
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B. Muscle Fibers

• 3. Myofibril
• d. Together, the thick and thin filaments
  make up the striations

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B. Muscle Fibers

• 4. Sarcomeres- chains of tiny contractile
  myofibrils
• Contractile unit of a muscle
• Consists of overlapping thick and thin
  filaments

Sarcomere
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B. Muscle Fibers

• 4. Sarcomere
• c. Muscle contraction

results from thick and thin filaments sliding
past one another.
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C. Neuromuscular Junction

• 1. Where the neuron and muscle fiber meet

1. The neuron and muscle fibers it controls make up
   a motor unit (2-2000 fibers/unit)

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MOTOR UNIT
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C. Neuromuscular Junction

• 3. When stimulated, all of the muscle fibers of a
  motor unit

contract all at once.
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C. Neuromuscular Junction

• 4. Anatomy
• Axon terminal nerve end

• Produces a neurotransmitter - acetycholine
  (Ach)

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C. Neuromuscular Junction

• 4. Anatomy Motor end plate
• site on muscle
• with

Motor end plate
acetycholine receptors
Synaptic cleft - space between the nerve motor
end plate
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III. Skeletal Muscle Contraction

• A. Initiation events

1. nerve impulse
2. ACh released
3. Ach binds to receptor on muscle
4. Enzyme (Acetylcholine esterase removes ACh

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III. Skeletal Muscle Contraction

• B. Action Potential

• ACh causes to Na to diffuse into cell
• If threshold is reached, action potential occurs
• - impulse travels along membrane resulting in
  contraction

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III. Skeletal Muscle Contraction

• C. Sliding Filament Theory
• Action potential causes Ca release from S.R
• Ca binds to thin filament
• Thin filament rotates exposing binding site for
  myosin
• Myosin binds actin
• uses ATP to "rachet" once
• releases, "and binds to next actin

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Calcium is the "switch" that turns muscle "on and
off" (contracting and relaxing).
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III. Skeletal Muscle Contraction

• D. How Neurotoxins Work
• cobra toxin and curare
• block Ach receptors
• cause flaccid paralysis, potentially fatal
  respiratory arrest
• nerve gas and insecticides
• inhibit AchE
• cause potentially fatal paralytic convulsions

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How a Nerve Gas Works
Normal
Nerve Gas
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Effect of Atropine on the Transmission of
Acetylcholine in the presence of a nerve agent
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III. Skeletal Muscle Contraction

• D. How Neurotoxins Work
• Botulism toxin and curare
• block Ach release
• cause flaccid paralysis, potentially fatal
  respiratory arrest
• Tetanus toxin
• cause excessive Ach release from motor neurons
• causes potentially fatal paralytic convulsions
  (lock jaw)

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III. Skeletal Muscle Contraction

• E. Rigor Mortis
• Ca pumps run out of ATP
• Ca cannot be removed
• continuous contraction
• eventually tissues break down

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IV. Energy Metabolism in Sk.Ms.
A. Aerobic Respiration

• Most efficient use of glucose
• Sources of glucose include blood glucose and
  stored glycogen
• 36ATP/glucose
• requires oxygen
• occurs in mitochondria
• Muscle cells have more mitochondria than any
  other cell
• Require a steady supply of O2

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B. Creatine-phosphagen system

1. During rest, muscles store energy as creatine
   phosphokinase (CPK or CK)
2. During intense exercise, ATP is depleted first,
   then CK is used to convert ADP back to ATP

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C. Lactic Acid Pathway

• Anaerobic use of glucose
• 2 ATP/ glucose
• Lactic acid produced as waste product Oxygen
  Debt
• Is toxic to tissue
• Can be recycled in liver

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V. Muscle Twitch -cycle of contraction and
relaxation
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V. Muscle Twitch -cycle of contraction and
relaxation

• A. Reasons for varying degrees
• 1. The number of muscle fibers innervated by a
  single neuron varies
• 2. Some motor units have lower thresholds than
  others
• 3. Muscle fibers differ functionally fast
  twitch slow twitch fibers

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V. Muscle Twitch

• B. Fast vs Slow Twitch Fibers
• 1. Differ in
• How they make ATP
• Speed of ATP break down
• Mitochondria content
• How fast they fatigue

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B. Fast vs Slow Twitch Fibers

• 2. Slow Twitch Fibers
• Smallest fibers
• Fatigue resistant
• Aerobic ATP production
• Many mitochondria
• Slow contractions
• Example uroanal muscles

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B. Fast vs Slow Twitch Fibers

• 2. Oxidative Fast Twitch Fibers FOG
• Fatigue resistant
• Aerobic ATP production
• Many mitochondria
• Fast contractions
• Example arm muscles

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B. Fast vs Slow Twitch Fibers

• 3. Glycolytic Fast Twitch Fibers
• Largest fibers
• Fatigue easily
• Anaerobic ATP production
• Few mitochondria
• Strong fast contractions
• Example sprinters leg muscles

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B. Fast vs Slow Twitch Fibers

• 4. Muscles have combination of all three fibers
• The number of each type varies from individual to
  individual
• Endurance running - slow and fast oxidative
  fibers Sprints - fast oxidative fibers and some
  fast glycolytic fibers Powerlifting - fast
  glycolytic fibers some fast oxidative
• Old age - increase in slow oxidative fibers

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B. Fast vs Slow Twitch Fibers

• 4. Muscles have combination of all three fibers
• Training/conditioning can change the predominant
  fiber type in muscles

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Anabolic steroids

• similar to testosterone
• large doses required for good effect
• Side effects
• overall - kidney and heart damage, aggressiveness
• females - sterility, facial hair, breast
  uterine atrophy
• males - baldness, atrophy of testis

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Sports injuries - RICE therapy

• Rest
• Ice
• Compression
• Elevation

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V. Skeletal Muscle

• A. Muslce Attachments
• Origin attachment site of a muscle or tendon to
  a bone that doesnt move during contraction.
• Insertion is the attachment site of a muscle or
  tendon to a moving bone that moves during a
  contraction. (usually distal)

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V. Skeletal Muscle

• B. Lever Systems
• lever - rod that moves at the fulcrum (fixed
  point)
• fulcrum typically the joint moving
• Resistance - gravity pulling on body
• Effort - muscle contraction

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V. Skeletal Muscle

• B. Lever Systems
• 4. Movement occurs when E gt R
• First class levers - E F R

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V. Skeletal Muscle

• B. Lever Systems
• 4. Movement occurs when E gt R

• 2nd class levers F R E

Levers that operate _at_ a mechanical disadvantage
are fast levers that require the muscles to exert
more force than the resistance to be moved.
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V. Skeletal Muscle

• B. Lever Systems
• 4. Movement occurs when E gt R

• 3rd class levers F E R
• most common

Levers that operate _at_ a mechanical advantage
allow a large load to be moved over a relatively
small distance but require relatively little
effort
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Interactions of Skeletal Muscles

• Skeletal muscles work together or in opposition
• Muscles only pull (never push)
• As muscles shorten, the insertion generally moves
  toward the origin
• Whatever a muscle (or group of muscles) does,
  another muscle (or group) undoes

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V. Skeletal Muscle Interactions

• C. Muscle Groups

• Many muscles are required for any given movement
• 1 muscle moves arm up
• another muscle moves arm down

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• C. Muscle Groups

2. Muscles work together

• Agonist
• gt Prime move
• gt muscle that causes a movement
• Antagonist
• gt opposes the muscle that stretches regulates
  the muscle contraction

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Ex. Arm flexion
Biceps Agonist (prime mover) Triceps --
Antagonist Uncurl arm -- roles are reversed
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• C. Muscle Groups

2. Muscles work together

• Synergist
• gtAssists the prime mover
• Fixator
• gtauxiliary muscles that steady a movement
  (immobilizes a bone or muscles origin)
• The Belly of a muscle is called the Gaster!

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Muscle Naming

• 1. Location of the muscle ex. Anterior tibialis,
  ASIS, supraabove, infrabelow, subunderneath
• 2. Size of the muscle ex. Maximuslargest,
  minimissmallest, vastushuge, longuslong,
  brevisshort, majorlarge, minorsmall
• 3. Direction of muscle fibers ex. Oblique (slant)
  Rectus (straight)
• 4. Number of origins ex. Triceps3 origins or
  biceps2 origins.

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Muscle Naming

• 5. Location of origin insertion ex.
  Sternocleidomastoid sternosternum,
  cleiodoclavicle, mastoidlocation on the
  temporal bone (mastiod bone)
• 6. Action of the muscle ex. Flexor shortens
  angle b/w 2 bones, Extensor increases the angle
  b/w 2 bones, Depressor lowers, abductor moves
  away from the midline, levator lifts a
  structure
• 7. Shape of the muscle ex. Trapezius, Rhomboids,
  deltoidtriangular, Latissimuswide, teresround,
  trapeziustrapezoid, serratussaw-tooth,
  orbiculariscircular
• Remember there are always exceptions to every
  rule some muscle do not obey this naming rule.

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Types of Body Movements

• Flexion movement that decreases the angle b/w 2
  bones. Seen in hinge joints ball socket
  joints.
• Extension movement that increases the angle b/w
  2 bones. If extension is greater than 180o its
  called hyperextension.
• Abduction Movement away from the midline of the
  body.

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Types of Body Movements

• Adduction Movement toward the midline of the
  body.
• Rotation Movement where 1 bone moves around the
  longitudinal axis of another bone. Common
  movement in ball socket joints.
• Circumduction a combination movement of
  flexion, extension, abduction adduction. The
  proximal end of a bone is stationary while the
  distal end moves in a circle. Common in ball
  socket joints.

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Types of Body Movements

• Dorsiflexion movement of foot decreases the
  angle b/w the foot the tibia. (upward movement
  of the foot take your foot off the gas)
  Dorsiflexion in the foot is comparable to
  extension of the hand _at_ the wrist.
• Plantarflexion movement of the foot to increase
  the angle b/w the foot the tibia. (downward
  movement of the foot mash on the gas)
  Plantarflexion of the foot is comparable to
  flexion of the hand _at_ the wrist.

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Types of Body Movements

• Inversion movement of the foot/ankle causing
  the sole of the foot to turn inward, (internal
  rotation).
• Eversion movement of the foot/ankle causing the
  sole of the foot to turn outward, (external
  rotation)
• Pronation movement causing the palm of the hand
  to turn down.

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Types of Body Movements

• Supination movement causing the palm of the
  hand to turn upward. (your hands are in
  supination when standing in anatomical position)
• Opposition move the thumb to touch to tips of
  the opposite finger tips of the same hand.
• Protraction movement of a body part anteriorly.
  forward motion (jutting out) of a limb.
• Retraction movement of a body part posteriorly.
  backward motion of a limb.

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Types of Body Movements

• Elevation upward movement of a body part.
• Depression downward movement of a body part.

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Types of Body Movements
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Types of Body Movements
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Types of Body Movements
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Joint Motions
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Arrangement of Muscle Fibers

• Convergent fascicles converge from a broad
  origin to a single tendon insertion (e.g.,
  pectoralis major)
• Circular fascicles are arranged in concentric
  rings (e.g., orbicularis oris)

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Arrangement of Muscle Fibers

• Parallel fibers run parallel to the long axis
  of the muscle (e.g., sartorius)
• Pennate (uni, bi, or multi) short fascicles that
  attach obliquely to a central tendon running the
  length of the muscle (e.g., rectus femoris)

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Major Skeletal Muscles Anterior View
Figure 10.4b
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Major Skeletal Muscles Posterior View
Figure 10.5b
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Muscle Functions of the Head Neck

• Frontalis Elevates the eyebrow wrinkles
  forehead horizontally.
• Orbicularis Oculi Closes the eyelids causes
  squinting, winking blinking.
• Orbicularis Oris Draws lips together pucker
  kissing muscle.
• Zygomaticus Raises corner of mouth laterally as
  in smiling or laughing.
• Buccinator Compresses the cheek to hold food
  during chewing, sucking in cheeks allows to
  blow a horn.

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Muscle Functions of the Head Neck

• Platysma Depresses corner of mouth Frowning,
  pouting tightens neck muscles when shaving.
• Masseter Raises mandible draws it forward
  Chewing
• Occipitalis Draws scalp backward.
• Temporalis Raises mandible. Covers temporal
  bone in head.
• Mentalis wrinkles chin.
• Sternocleidomastoid Flexes head bends it
  laterally.

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Muscles of the Scalp, Face, and Neck
Figure 10.6
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Functions of Ventral Muscles of the Torso

• Pectoralis Major Adducts, flexes rotates the
  humerus medially. Moves arm forward across
  chest. (adduction)
• Pectoralis Minor Draws scapula forward
  downward.
• Serratus Anterior draws scapula forward
  (protraction), upward rotation of the shoulder
  girdle.
• External Intercostals chest muscles that
  elevate ribs enlarge thorax during breathing.

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Ventral Torso Muscles
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Muscles of Respiration
Figure 10.10a
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Functions of Ventral Muscles of the Torso

• Internal Intercostals Draw adjacent ribs
  together.
• Diaphragm Expands thorax compresses contents
  of abdominal cavity. (breathing)
• Rectus Abdominus The major muscles for spine
  /trunk flexion (aka your 6pack)
• External Oblique Slanted muscles of the abdomen
  that flex rotate the trunk (aka you love
  handles)
• Internal Oblique flexion of the trunk, lateral
  flexion (same side), rotation (same side) of the
  trunk.
• Transverse Abdominis compresses the
  abdominal/pelvic cavity.

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Muscles of the Abdominal Wall
Figure 10.11a
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Functions of Dorsal Muscles of the Torso

• Trapezius Hyperextension of head adducts
  scapula raises scapula. Allows you to shrug your
  shoulder look up.
• Rhomboids Major Minor (beneath the trap)
  Small rectangular muscles that square the
  shoulders iow Adducts downward rotation of the
  shoulder.
• Latissimus Dorsi A large muscle that adducts
  extends the shoulder. (muscle originates from the
  lumbodorsal fascia)
• Teres Major Minor External rotation
  horizontal abduction of the arm.

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Functions of Dorsal Muscles of the Torso

• Erector Spinae Primary back extensor, runs the
  length of the spine. Also causes lateral trunk
  flexion rotation of the head, neck, shoulder,
  chest, arm muscles. Made up of three columns on
  each side of the vertebrae iliocostalis,
  longissimus, and spinalis. Lateral bending of the
  back is accomplished by unilateral contraction of
  these muscles
• Lumbar Aponeurosis Sheet like tendinous
  expansion of a muscle.
• Levator Scapulae Extension of the neck,
  downward rotation elevation of the scapula.
  Synergist to the trapezius.

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Dorsal Muscles of the Torso
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Muscle Functions of the Upper Extremity

• Shoulder
• Anterior Deltoid Abducts, flexes, internally
  rotates horizontally adducts the arm. (deltoid
  is the antagonist to the trapezius)
• Medial Deltoid Abducts the arm
• Posterior Deltoid Abducts, extends, externally
  rotates horizontally abducts the arm.
• Coracobrachialis flexes horizontally adducts
  the arm

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Muscles Crossing the Shoulder
Posterior view
Figure 10.14a
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Muscle Functions of the Upper Extremity

• ROTATOR CUFF SITS
• Supraspinatus abducts the upper arm.
• Infraspinatus Externally rotations the upper
  arm
• Teres Minor Externally rotates the upper arm.
• Subscapularis Internally rotations the upper
  arm.

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Posterior view
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Muscle Functions of the Upper Extremity

• Muscles of the Arm
• Biceps brachii Flexion of the elbow shoulder
  supination of the forearm.
• Brachialis Flexes the elbow.
• Pronator teres Pronates the forearm.
• Triceps brachii Extends the elbow, adducts
  extends the shoulder. (antagonist to biceps
  brachii)
• Anconeus Elbow extension

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Muscles Crossing the Shoulder
Anterior view
Posterior view
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Muscle Functions of the Upper Extremity

• Muscles of the Arm
• Supinator supinates the forearm.
• Flexor carpi radialis Flexes abducts the
  wrist.
• Flexor carpi ulnaris Flexes adducts the
  wrist.
• Extensor carpi radialis longus Extends
  adducts the wrist.
• Extensor digitorum (longus brevis) Extends
  the wrist.

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Superficial Dorsal view
Deep Dorsal view
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Muscle Functions of the Hand

• There are three groups of intrinsic hand muscles
• The thenar eminence (ball of the thumb)
• The hypothenar eminence (ball of the little
  finger) both have a flexor, an abductor, and an
  opponens (opposer)muscle
• The midpalm muscles, the lumbricals and
  interossei, extend the fingers
• The interossei also abduct and adduct the fingers

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Superficial Dorsal view
Deep Dorsal view
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Muscle Functions of the Hand

• Flexor digitorum Longus brevis flexes the
  fingers.
• Extensor digitorum longus brevis extends the
  Fingers.
• Extensor Pollicus Longus Brevis extends the
  thumb.
• Abductor Pollicus Longus Brevis abducts the
  thumb.
• Adductor Pollicus Longus Brevis adducts the
  thumb.
• Flexor Pollicus Longus Brevis flexes the
  thumb.

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Muscle Functions of the Lower Extremity

• Muscles of the Quadriceps (primary knee
  extensors)
• Rectus femoris hip flexion knee extension
• Vastus Lateralis Medialis knee extension.
• Vastus Intermedius knee extension
• Other Muscles of the Thigh
• Sartorius flexion, external rotation
  abduction of the hip Flexion internal rotation
  of the knee
• Gracilis Abduction, flexion internal rotation
  of the hip Internal rotation of the knee.
• Adductor longus Adduction, flexion horizontal
  adduction of the hip. Allows you to grip a
  horses back w/your legs.
• Adductor magnus Adduction, flexion horizontal
  adduction of the hip.

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Muscles of the Pelvis Femur
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Muscle Functions of the Lower Extremity

• Muscles of the Posterior Thigh
• Semimembranosus Extension of the hip Flexion
  internal rotation of the knee.
• Semitendinosus Extension internal rotation of
  the hip Flexion internal rotation of the knee.
• Biceps Femoris Extension of the hip External
  rotation flexion of the knee.

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Muscle Functions of the Lower Extremity

• Muscles of the Posterior Thigh
• Gluteus Maximus Extension, external rotation,
  horizontal abduction adduction of the hip.
  Used to extend the hip when climbing stairs
  forms the buttox.
• Gluteus Medius Minimus abduction, horizontal
  abduction internal rotation of the hip.

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Muscle Functions of the Lower Extremity

• Muscles of the lower leg
• Tibialis Anterior Dorsiflexion inversion of
  the foot.
• Extensor Digitorum Longus Dorsiflexion
  eversion of the foot.
• Extensor Hallicus Longus inversion extension
  of the big toe.
• Peroneus (Fibularis) Longus Brevis
  Plantarflexion eversion of the foot.

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Muscle Functions of the Lower Extremity

• Muscles of the lower leg
• Soleus plantarflexion of the foot. (lower calf
  muscle)
• Gastrocnemius Plantarflexion of the foot
  flexion of the knee. (upper calf muscle)
• Triceps Surae is the combination of the Soleus
  the Gastronemius. Aka toe dancers muscle.
• Abductor Hallicus Longus Brevis abducts the
  big toe.
• Adductor Hallicus Longus Brevis adducts the
  big toe.
• Flexor Hallicus Longus Brevis flexes the big
  toe.

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Muscles of the Lower Leg
Figure 10.22a
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Muscle Functions of the Lower Extremity

• Muscles of the lower leg
• Flexor digitorum Longus brevis flexes the
  toes.
• Extensor digitorum longus brevis extends the
  toes.
• Extensor Hallicus Longus Brevis extends the
  big toe.

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Muscles of the Anterior Lower Leg
Figure 10.21a
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References
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