priniciples of myology def: science deals with muscles dr: ahmed sabervet. anat. 1. 2008 skeletal...
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PRINICIPLES OF MYOLOGY
Def: science deals with muscles
Dr: Ahmed Saber Vet. Anat. 1. 2008
Skeletal muscles are the active part of locomotor systemSmooth muscles move the visceraCardiac muscle produces heart contraction
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The main characters of muscles are: Irritability or Excitability - responsive to chemical, electrical, or mechanical stimuliContractility - ability of muscle to contract (shorten)Extensibility - ability to be passively stretched Elasticity - ability to return to its original length
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Types of muscles
1- smooth muscles:• Structures: long spindle
shaped, uni-nucleate, and non-striated (smooth)
• Locations: wall of visceral organ
• The control: involuntary autonomic control or endocrine control (myo-epithelial cells)
• function: Involuntary contractions that move materials through the organs
Dr: Ahmed Saber Vet. Anat. 1. 2008
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2- Cardiac muscles• Structures:
cylindrical, mostly uninucleate striated, and Branching and joins forming myocardium network (syncytium).The fibers are connected end-to-end at sites called intercalated disks.
Dr: Ahmed Saber Vet. Anat. 1. 2008
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• Locations: wall of heart• The control: involuntary• function: Involuntary autonomic
control and special local conducting system cause contractions of heart
Dr: Ahmed Saber Vet. Anat. 1. 2008
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3- Skeletal musclesThey forming about 40-45 % of
body weightThe muscle cell = muscle fiber
= myofiber• structures:
– Elongated, multinucleated, with long and transverse striation.
– Each muscle is divided into bundles or fascicles
– Each fascicles is composed of numerous muscle fiber (cells)
• Locations: in all body & forming active part of locomotor system
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Skeletal muscles (cont.)• The control: voluntary controlfunction: • voluntary somatic movement of the body• Maintain body position• Stabilizing the joint• Heat production• Guarded body entrances and orifices
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Architecture of skeletal muscle
• Each single muscle is consists of numerous bundles (fascicles)
• Each fascicles is consists of numerous muscle fibers
• The muscle fiber is the structural unite of muscle
boneTendon
MuscleEpimysium
Fascicle Fiber
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Epimysium: CT layer ensheated the entire muscle
Perimysium: CT layer ensheated each muscle bundle (fascicle)
Endomysium: CT layer ensheated each muscle fiber
Architecture of skeletal muscle
Muscle fascicle
Blood vessels
Epimysium
Muscle fiber &endomysium
Perimysium
Epimysium, perimysium and endomysium extend at the muscle end forming tendon or aponeurosis
They protect the cells and provide passage for vessels and nerves Dr: Ahmed Saber Vet. Anat. 1. 2008
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Architecture of skeletal muscle
Muscle fiberPerimysium
Fascicle
Endomysium
Epimysium
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Microscopic structures
Myofiber Myofibril
Myofilaments
Actin Myosin
Dr: Ahmed Saber Vet. Anat. 1. 2008
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Gross anatomy of skeletal muscle
1- anatomical parts:A- origin: • usually the proximal attachment of
muscle• Less movable part• Somtime more that one head (biceps)B- insertion:• Usually distal attachment• More movableC- belly:• The main balk of muscle between
origin and insertionDr: Ahmed Saber Vet. Anat. 1. 2008
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2- skeletal muscle attachmenta) Boneb) Cartilagec) Deep fascia (indirectly to bone)d) Skin and superficial fasciae) Intermediate tendonf) No attachment (no origin & no insertion,
as orbicularis oris)
Gross anatomy of skeletal muscle
Also muscle attachment may beDirect attachment: the epimysium is fused to periosteum or perichondrium directlyIndirect attachment: epimysium extends as sheet like aponeurosis before attaching to bone, cartilage, fascia or other muscle
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3- arrangements of skeletal muscle fibersBased on the angle between fiber and the line of pull
Gross anatomy of skeletal muscle
A- Parallel fibers:
1.Strap (sartorius)
2.Quadrates (quadratus femoris)
3.Fusiform (biceps brachi
Strap
Fusiform
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B- oblique fibers (pennation)
The fibers attached to tendon at oblique angle (feather like)
1- unipennate: on one side of tendonex extensor digitorun longus M
2- bipennate : on opposite sides of tendon, ex rectus femoris M
3- multipennate: muscle fibers attached to several fibrous bands within the muscle, the bands join forming one tendon, ex deltoid M
4- Centripennate: one central tendon
Unipennate
Bipennate
Multipennate
Dr: Ahmed Saber Vet. Anat. 1. 2008
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C- circular fibers1- circular: no
attachment, around orifices, ex orbicularis oris (around mouth)
2- convergent: broad origin and pointed insertion, ex pectoralis major
Circular
Convergent
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Functional types of muscles
1. Prime mover (Agonist muscles)– muscles most involved– cause joint motion through a specified
plane of motion when contracting
2. Antagonist muscles– located on opposite side of joint– have the opposite action to agonist
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3. Synergist– assist in action of agonists– not necessarily prime movers for the action
4. Fixators (stabilozers)– Fix the joint
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Blood and nerve supply
• Vessels and nerves pass through the connective tissue sheaths
• Bell is more vascular • One neuron supply
variable number of muscle fibers
• Motor unites = neuron+ muscle fiber innervated by this nerun
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Accessory structures of skeletal muscle
1. Sesamoid bone– In course of some tendon – as superficial and deep flexor tendons– Protect the tendon– Decrease friction– Redirect the pull angle of the tendon
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2. Fascia• is sheath of CT found
all over the body• Divided into• Internal fascia
(endothoracic, abdominaland pelvic)
• External fascia ( superficial and deep fascia)
skinSuperficial fascia
Deep fascia
Body wallInternal fascia
Bodycavity
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3. Synovial sacIs sac filled with synoviaLocated between two structures to decrease
the friction between these structures1. Subtendinous2. Subcutaneous3. subligamentous
Bone
Tendon Synovial
sac
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4. Tendon synovial sheath• elongated sac under the tendon• The edges of the sac become reflected
around the tendon• Consists of
– Outer fibrous layer– Double inner synovial– Parietal and visceral layer in between
small cavity filled with synovia• At edges meeting, the mesotendon present
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tendon
Outer fibrous
Mesotendon
Parietal synoviallayer
Visceral synoviallayer
Synovial fluid
4. Tendon synovial sheath
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5. Retinaculum• Transverse band of deep fascia around
carpal and tarsal joints • It fix the tendon and ligaments in its
position• As, flexor and extensor retinaculum of
carpus
Dr: Ahmed Saber Vet. Anat. 1. 2008