Muscles of the Body - Amazon S3 of thighs and gluteus maximus muscles ... spasms following injury to back structures.” 31 ... Gluteus medius Gluteus minimus (under medius)

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  • Muscles of the Body

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    "Copyright 2003-2004 University of Washington. All rights reserved including all photographs and images. No re-use, re-distribution or commercial use without prior written permission of the authors and the University of Washington." "Musculoskeletal Images are from the University of Washington "Musculoskeletal Atlas: A Musculoskeletal Atlas of the Human Body" by Carol Teitz, M.D. and Dan Graney, Ph.D."

    Other copies materials from Marieb, 5th ed., Martini, 6th ed. or online with reference

  • Fascicles

    Bundles of fibers


  • Skeletal muscle

    Epimysium: surrounds whole muscle

    Perimysium is around fascicle

    Endomysium is around each muscle fiber

  • Different arrangements

    of fascicles

  • Arrangement of fascicles influences movement and power

    Skeletal muscles can shorten by about 1/3 of their resting length The more nearly parallel to the axis, the more

    they can shorten This results in a larger distance of movement

    The power depends on the total number of fibers Stocky muscles (like bipennate vs parallel)

    have more fibers, therefore more powerful even though shorten very little

  • Interactions of Skeletal Muscles

    Muscles can only pull, they cant push Actions must be undone by a different

    muscle Muscles that produce opposite movements

    usually lie on opposite sides of a given joint

  • Interactions, continued

    Agonist: prime mover, major responsibility for producing a specific movement

    Antagonist: oppose or reverse a particular movement Usually contract a little to prevent overshooting the

    mark or slow the agonists action near the end Are being stretched or can remain relaxed when

    agonist works Antagonists for one movement can be agonists

    for another

  • Synergists help prime movers Add a little extra force to the same movement

    Or reduce undesirable extra movements (e.g.

    making a fist without flexing at wrist)

    Fixators: hold a bone firmly so agonist has a stable base on which to move a body part (e.g. fixing scapula when arm moves)

  • Compartments Contain muscles of similar developmental origin and function Dense fibrous connective tissue


    Upper limb: 2 compartments Lower limb: 3 compartments

  • Naming skeletal muscles (examples)

    Location: brachialis is in arm (brachium = arm) Shape: deltoid is triangular (delta = triangle) Size: minimus (smallest), longus (long), brevis

    (short) Direction of fascicles and fibers: rectus (straight);

    transversus (right angle) and oblique (oblique) to midline

    Number of origins: biceps (two heads), triceps (three heads), quadriceps (four heads)

    Action: flexor, extensor, adductor or abductor appear in the name

    Combinations of the above, e.g. extensor carpi radialis longus

  • Axial muscles Lie anterior and posterior to body axis

    (vertebral column) Move trunk; maintain posture Skeletal muscles of thorax, abdomen, and

    pelvis Many muscles of neck A few muscles in head

  • Limb muscles

    Arise from ventral region as limb buds Muscles develop from lateral parts of myotomes In general: dorsal (posterior) muscles become

    extensors and ventral (anterior) become flexors Lower limb rotates during embryonic

    development: Extensors on anterior (ventral) side: extend leg at

    knee, dorsiflex foot at ankle and extend toes Flexors on posterior (dorsal) side: flex leg at knee,

    plantarflex foot at ankle, flex toes

  • anterior

    Text Text

    to use for studying...

  • posterior

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    Muscles of the Head and Neck Scalp Muscle: epicranius frontal belly occipital belly gala aponeurotica

    Muscles of Facial Expression: insert on skin or another muscle Muscles of Mastication (chewing): all have

    insertions on the mandible Anterior Neck Muscles Posterior Neck Muscles

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    glossus = tongue

    Mastication: Jaw closure: masseter and temporalis Side to side grinding: pterygoids Buccinator: compresses cheek

    Deep chewing muscles

    Extrinsic tongue muscles Pharyngeal constrictors

    Tongue itself (instrinsic muscles): digestive tract section

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    Muscles of the Anterior Neck

    Above hyoid (suprahyoid): form floor of oral cavity, anchor tongue, elevate hyoid, move larynx superiorly during swallowing Below hyoid (infrahyoid): depress hyoid and larynx during swallowing and speaking Right side (of

    slide) is deeper than left


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    Anterolateral neck Scalenes elevate first 2 ribs

    Posterior neck Splenius (capitis and cervicis) extend head

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    Deep muscles of back

    Erector spinae (extend back):

    Iliocostalis Longissimus Spinalis

    Quadratus lumborum (lateral flexion)

    Labeled cervicis, thoracics, lumborum depending on where they are

    Right side: deeper

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    Per Marieb (worthwhile to know) During full flexion (i.e. when touching fingertips

    to floor), erector spinae are relaxed and strain is borne entirely by ligaments of back; on reversal of the movement, these muscles are initially inactive, and extension is initiated by hamstring muscles of thighs and gluteus maximus muscles of buttocks. As a result of this peculiarity, lifting a load or moving suddenly from a bent over position is potentially injurious to muscles and ligaments of back and intervertebral discs; erector spinae muscles readily go into painful spasms following injury to back structures.

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    Deep muscles of the thorax: breathing

    Intercostals Short: rib to rib

    Diaphragm prime mover of inspiration

    Lift rib cage: inspiratory

    Depress rib cage: in forced expiration

    Floor of thoracic cavity: when flattens, air moves in

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    Anterior Chest Muscles

    Deeper: pectoralis minor serratus anterior subclavius

    Superficial: sternocleidomastoid pectoralis major

  • Muscles of the abdominal wall

    Note inguinal ligament- from anterior superior iliac spine to pubic symphysis: lower border of external oblique rolls up on itself to form it

    From more superficial to deep: External oblique Internal oblique Transversus abdominis Nearer midline: Rectus abdominis

    The rectus abdominis is the medial pair of muscles; it is ensheathed by the aponeurosis of the lateral muscles, which dont come to the midline

    * *

  • Muscles of the abdominal wall from the side

  • Muscles moving the scapula trapezius levator scapulae rhomboids


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    9 Muscles crossing shoulder joint: movement of arm (humerus)

    Three most powerful of the nine and prime movers: pectoralis major latissimus dorsi deltoid

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    Rotator cuff supraspinatus, infraspinatus, subscapularis, teres minor

    remaining 2muscles : teres major and coracobrachialis

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    Forearm extensors (posterior)

    Triceps brachii Anconeus helps

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    Forearm flexors (anterior) Brachioradialis

    Biceps brachii


    3 muscle on right from this site:

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    Retinaculae (retinaculum, singular)

    retainers, wrist bands, ankle bracelets

    Bands of fascia holding tendons of wrist and ankle in place (prevent bow-stringing)

    Tendons covered by slippery tendon sheets

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    Forearm muscles: movement of wrist, hand and fingers

    Many arise from distal humerus Cross elbow, wrist and finger joints Minimal action at elbow At wrist joint: flexion, extension, abduction and

    adduction of the hand At finger joints: mostly just flex and extend (other

    movements- by small muscles in the hand itself)

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    Forearm muscles, continued Two compartments (each with superficial and

    deep muscle layers) Anterior = flexor compartment ( except includes 2 pronators)

    Most originate from a common tendon on the medial epicondyle of humerus

    Posterior = extensor compartment (except includes supinator and brachioradialis)

    Many arise from a common tendon from lateral epicondyle of humerus

    Most muscles that move the palm and fingers are located in the forearm, not the hand itself They operate by tendons like strings with puppets There are some small muscles in the hand itself

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    Anterior wrist pronator and flexors Origin on medial epicondle of humerus: pronator teres, flexor carpi

    radialis, palmaris longus, flexor carpi ulnaris, flexor digitorum sup


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