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Muscles as Levers. Bones and muscles interact as levers : A simple machine used to transmit force A lever has 4 parts: Rigid bar/ rod Fulcrum or pivot where the bar turns Object moved against resistance Force that supplies energy for the bar to move Types: 1 st class lever

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muscles as levers
Muscles as Levers
  • Bones and muscles interact as levers: A simple machine used to transmit force
    • A lever has 4 parts:
      • Rigid bar/ rod
      • Fulcrum or pivot where the bar turns
      • Object moved against resistance
      • Force that supplies energy for the bar to move
    • Types:
      • 1st class lever
      • 2nd class lever
      • 3rd class lever
first class lever
First Class Lever
  • Fulcrum is located between the resistance and the force (resistance – fulcrum - force)
    • Ie. Scissors, seesaw, and hemostats
    • Ie. Tilting the head
second class lever
Second Class Lever
  • Resistance is located between the fulcrum and the force (fulcrum- resistance- force)
    • Ie. Wheelbarrow
    • Ie. Standing of the your toes
third class lever
Third Class Lever
  • Force is located between the force and the resistance (fulcrum- force- resistance)
    • Ie. Tweezers
types of levers
Types of Levers
  • You will be rotating about the room to different stations.
  • At each station you will be given a different task.
  • After completing the task you must determine the type of lever each of the following actions requires.
origin insertion
Origin & Insertion
  • Origin – attachment to an immoveable bone
  • Insertion – attachment to a movable bone
  • ILIOCOSTALIS= attaches to the ilium & ribs (costal = ribs)
direction of muscle fibers
Direction of Muscle Fibers
  • Relative to the Midline
  • RECTUS = parallel to the midline
    • RectusAbdominus
  • TRANSVERSE = perpendicular to midline
    • TransverseAbdominus
  • OBLIQUE = diagonal to midline
    • External Oblique
  • Structure near which muscle is found
    • FRONTALIS = near FRONTAL bone
  • Relative Size of Muscle
  • MAXIMUS = largest
    • GluteusMaximus
  • MEDIUS = middle
    • Gluteus Medius
  • MINIMUS = smallest
    • Gluteus Minimus
  • LONGUS = longest
    • FibularisLongus
  • BREVIS = short
    • FibularisBrevis
  • TERTIUS = shortest
    • FibularisTertius
number of origins
Number of Origins
  • Number of tendons of origin
  • BICEPS = Two
    • Biceps Brachii
    • Biceps Femoris
  • TRICEPS = Three
    • Triceps Brachii
    • Quadriceps Femoris
  • Relative Shape of the Muscle
  • DELTOID = triangular shape Δ
  • TRAPEZIUS = trapezoid shape  SERRATUS = saw-toothed ♒
  • RHOMBOIDEUS = rhomboid shape 
  • TERES = round ○

Anatomy of the Muscular System

  • Origin
    • Muscle attachment that remains fixed
  • Insertion
    • Muscle attachment that moves
  • Action
    • What joint movement a muscle produces
    • i.e. flexion, extension, abduction, etc.

Movement of Muscle

  • Muscles can only pull to create movement
  • Muscles rarely work alone, & are usually arranged in groups surrounding a joint:
    • Agonist (Prime Mover)- muscle that contracts to create action (major responsibility for certain movement)
    • Synergist- muscle that helps the agonist (aids the agonist/ prevents rotation)
    • Antagonist-muscle that opposes the agonist(undoes the desired action)
types of muscle contraction
Types of Muscle Contraction
  • For each of the sporting examples, you must do the following:
    • Research the types of muscles that are used in the example
    • Determine the agonist and antagonist muscles
    • Determine the contraction type
muscles of facial expression
Muscles of Facial Expression
  • Epicranius: covers the upper cranium; consists of 2 parts:
    • Frontalis- covers frontal bone
    • Occipitalis- covers occipital bone

United by epicranialaponeurosis(tendinous muscle) that contracts to raise the eyebrows thus wrinkling the forehead

muscles of facial expression1
Muscles of Facial Expression
  • OrbicularisOculi- muscle encircling the eye; closes the eye & compresses the lacrimal gland
  • OrbicularisOris- encircles the mouth; helps close and pucker the lips
muscles of facial expression2
Muscles of Facial Expression
  • Buccinator- in the cheek wall, compresses the cheek inward which helps hold food in contact w/ teeth when chewing
head neck muscles
Frontalis: elevate eyebrows 

Orbicularis Oculi: close eyelid 

Zygomaticus: draw angle of lip upward 

Buccinator: draws cheeks against teeth

Orbicularis Oris: closes mouth 

Platysma: draws lower lip down & back 

Cranial Aponeurosis: connects frontalis to occipitalis

Temporalis: elevates mandible

Occipitalis: draws scalp back

Masseter: elevates mandible


Flexes head

Draws head toward shoulder

Head & Neck Muscles
key muscles of facial expression
Smiling Muscles

Orbicularis Oculi


Levator Labii Superioris

Levator Anguli Superioris



Frowning Muscles


Orbicularis Oris

Depressor Anguli Oris

Depressor Labii Inferioris



Key Muscles of Facial Expression
  • Head and Neck
    • Frontal (frontalis) – over the frontal skull bone raise your eyebrows.
    • Orbicularis oculi – closes the eye.
    • Orbicularis oris – around the mouth; kissing muscle.
    • Masseter – elevates mandible allowing use to close our mouth and chew food.
    • Temporal (temporalis) – assists the masseter in closing the jaw.
  • Head and neck
    • Sternocleidomastoid – flexes the head toward the chest.
    • Trapezius – helps elevate, lower, and adducts the shoulders (scapula) and extend the head backwards.
muscles of mastication
Muscles of Mastication
  • Masseter: elevates mandible
  • Temporalis: elevates mandible
  • Medial pterygoid: elevates mandible
  • Lateral pterygoid: depresses mandible
muscles of the axial skeleton
Intrinsic Muscles

Erector Spinae: maintain posture of back/extension




Oblique Muscles: rotation of the vertebrae




Muscles of Quiet Respiration


External Intercostals

Internal Intercostals—deep breaths

Abdominal Muscles

External Obliques

Internal Obliques

Transverse Abdominus

Rectus Abdominus

Quadratus Lumborum

Muscles of the Axial Skeleton
muscles of scapular stabilization
Muscles of Scapular Stabilization
  • Trapezius:
    • Retraction (M)
    • Elevation (S)
    • Depression (I)
    • Upward Rotation (S, M)
  • Rhomboid—retraction
  • Levator Scapular—Elevation
  • Pectoralis Major—Protraction
  • Serratus Anterior—Protraction
anterior muscles of shoulder
Anterior Muscles of Shoulder
  • Deltoid
    • Flexion (A, M)/Extension (P, M)
    • Abduction (M)/Adduction (A)
    • Internal (A) /External Rotation (P)
  • Pectoralis Major
    • Adduction
    • Flexion
    • Extension
    • Internal Rotation
  • Biceps Brachii—Flexion
posterior muscles of shoulder
Posterior Muscles of Shoulder
  • Teres Major
    • Adduction
    • Extension
    • Internal Rotation
  • Latissimus Dorsi
    • Adduction
    • Extension
    • Internal Rotation
  • Triceps Brachii
    • Adduction
    • Extension
rotator cuff muscles sits
Rotator Cuff Muscles (SITS)
  • Supraspinatus
    • Abduction
  • Infraspinatus
    • External Rotation
  • Teres Minor
    • External Rotation
  • Subscapularis
    • Internal Rotation
muscles of the elbow forearm
Muscles of the Elbow/Forearm
  • Triceps Brachii—Extension
  • Bicep Brachii—
    • Flexion
    • Supination
  • Brachialis—Flexion
  • Brachioradialis—
    • Flexion
    • Pronation
  • Pronator Teres
  • Pronator Quadratus
  • Supinator Longus
muscles of the wrist hand
Muscles of the Wrist & Hand
  • Flexor Carpi Ulnaris
  • Flexor Carpi Radialis
  • Flexor Digitorum
  • Extensor Carpi Ulnaris
  • Extensor Carpi Radialis
  • Extensor Digitorum

Anterior (Palmar) View

Posterior (Dorsal) View

muscles of hip anterior muscles
Medial/Adductor Muscles:

Adductor Magnus

Adductor Longus

Adductor Brevis


Anterior Muscles







Lateral Rotation

Muscles of Hip:Anterior Muscles
muscles of hip gluteal muscles
Muscles of Hip: Gluteal Muscles
  • Gluteus Maximus—Extension
  • Gluteus Medius—Abduction
  • Gluteus Minimus—Abduction
  • Tensor Fasciae Latae—
    • Flexion
    • Abduction

** Gluteus Minimus is under the Gluteus Medius

muscles of anterior thigh
Muscles of Anterior Thigh
  • “Quadriceps”
    • Rectus Femoris—
      • Hip flexion
      • Knee extension
    • Vastus Lateralis—knee extension
    • Vastus Medialis—knee extension
    • Vastus Intermedius—knee extension
    • Sartorius—
      • Hip & Knee Flexion
      • Lateral Hip Rotation

**Vastus Intermedius is beneath Rectus Femoris

muscles of posterior thigh
Muscles of Posterior Thigh
  • “Hamstrings”
    • Responsible for Knee Flexion & Hip Extension
    • Semimembranosus
    • Semitendinosus
    • Biceps Femoris
  • Gastrocnemius
    • Knee Flexion
muscles of the lower leg
Muscles of the Lower Leg
  • Anterior Compartment
    • Tibialis Anterior—Dorsiflexion & inversion
    • Extensor Digitorum Longus
    • Fibularis Tertius—dorsiflexion & eversion
  • Posterior Compartment
    • Gastrocnemius—plantarflexion, knee flexion
    • Soleus—plantarflexion
  • Lateral Compartment
    • Fibularis Longus—plantarflexion & eversion
    • Fibularis Brevis—plantarflexion & eversion
anatomy of the muscular system
Anatomy of the Muscular System
  • Muscles That Move the Foot and Toes

Figure 7-22(a)

anatomy of the muscular system1
Anatomy of the Muscular System
  • Muscles That Move the Foot and Toes

Figure 7-22(b)

anatomy of the muscular system2
Anatomy of the Muscular System
  • Muscles That Move the Foot and Toes

Figure 7-22(c)

anatomy of the muscular system3
Anatomy of the Muscular System
  • Muscles That Move the Foot and Toes

Figure 7-22(d)

movements produced by muscle contractions
Movements Produced by Muscle Contractions

Flexion – movement reduces the angle between two bones at their joint.

Extension – opposite of flexion – increases the angle at a joint.

Abduction – moving a body part away from the midline of the body.

Adduction – moving a body part toward the midline of the body.

Rotation – movement of a body part around an axis.

movements produced by muscle contractions1
Movements Produced by Muscle Contractions

Supination – refers to hand position – movement turns palm up to the anterior position (anatomical position).

Pronation – palm of hand turned posteriorly.

Dorsiflexion – top of foot is elevated with toes pointing upward.

Plantar flexion – foot directed downward (standing on your toes).

  • Upper extremities
    • Pectoralis major – upper anterior chest; flexor of the upper arm
    • Latissimus dorsi – extensor of the upper arm.
    • Deltoid – powerful abductor of the upper arm.
    • Biceps Brachii – 2-headed muscle that serves as the primary flexor of the forearm.
    • Triceps brachii – 3 headed muscle on the posterior surface of the upper arm; extensor of the elbow/forearm.
  • Trunk
    • Anterior abdomen – 3 layers of muscles whose fibers run in different directions – girdle effect.
      • External oblique – outermost layer
      • Internal oblique – middle layer
      • Transversus abdominis – innermost layer
    • Rectus abdominus runs down the midline of the abdomen from the thorax to the pubis. (6-pack)
    • Respiratory muscles
      • Intercostal muscles – between the ribs
      • Diaphragm – separates the thoracic and abdominal cavities.
  • Lower Extremities
    • Gluteus maximus – forms the buttock; extensor of the thigh, supports the torso.
    • Gluteus medius – abducts the femur; injection site.
    • Hamstring muscles – flexors of the lower leg
      • Semimembranosus
      • Semitendinosus
      • Biceps femoris
  • Lower extremities
    • Quadriceps femoris – covers the upper thigh, extends the leg.
      • Rectus femoris
      • Vastus lateralis – injection site
      • Vastus medialis
      • (Vastus intermedius)
    • Tibialis anterior – dorsiflexes the foot
    • Gastocnemius – primary calf muscle, plantar flexion of the foot.
intramusclular injection sites
Intramusclular Injection Sites


Gluteus medius

Vastus lateralis