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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
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
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
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
• 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
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
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
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
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
Architecture of skeletal muscle
Muscle fiberPerimysium
Fascicle
Endomysium
Epimysium
Dr: Ahmed Saber Vet. Anat. 1. 2008
Microscopic structures
Myofiber Myofibril
Myofilaments
Actin Myosin
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
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
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
3. Synergist– assist in action of agonists– not necessarily prime movers for the action
4. Fixators (stabilozers)– Fix the joint
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
3. Synovial sacIs sac filled with synoviaLocated between two structures to decrease
the friction between these structures1. Subtendinous2. Subcutaneous3. subligamentous
Bone
Tendon Synovial
sac
Dr: Ahmed Saber Vet. Anat. 1. 2008
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
Dr: Ahmed Saber Vet. Anat. 1. 2008
tendon
Outer fibrous
Mesotendon
Parietal synoviallayer
Visceral synoviallayer
Synovial fluid
4. Tendon synovial sheath
Dr: Ahmed Saber Vet. Anat. 1. 2008
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