PRINICIPLES OF MYOLOGY
Def: science deals with muscles
Skeletal muscles are the active part of
locomotor system
Smooth muscles move the viscera
Cardiac muscle produces heart contraction
Dr: Ahmed Saber
Vet. Anat. 1. 2008
The main characters of muscles are:
Irritability or Excitability -
responsive to chemical, electrical, or
mechanical stimuli
Contractility - 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 muscles
They forming about 40-45 % of
body weight
The 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 control
function:
• 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
Fiber
Fascicle
Epimysium
Muscle
Tendon
bone
Dr: Ahmed Saber
Vet. Anat. 1. 2008
Architecture of skeletal muscle
Epimysium: CT layer
ensheated the entire
muscle
Perimysium: CT layer
ensheated each muscle
bundle (fascicle)
Endomysium: CT layer
ensheated each muscle
fiber
Muscle fascicle
Blood vessels
Epimysium
Muscle fiber &
Perimysium
endomysium
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 fiber
Perimysium
Fascicle
Endomysium
Epimysium
Dr: Ahmed Saber
Vet. Anat. 1. 2008
Microscopic structures
Myofibril
Myofiber
Myofilaments
Actin
Dr: Ahmed Saber
Vet. Anat. 1. 2008
Myosin
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 movable
C- belly:
• The main balk of muscle between origin
and insertion
Dr: Ahmed Saber
Vet. Anat. 1. 2008
Gross anatomy of skeletal muscle
2- skeletal muscle attachment
a)
b)
c)
d)
e)
f)
Bone
Cartilage
Deep fascia (indirectly to bone)
Skin and superficial fascia
Intermediate tendon
No attachment (no origin & no insertion, as
orbicularis oris)
Also muscle attachment may be
Direct attachment: the epimysium is fused to periosteum or
perichondrium directly
Indirect attachment: epimysium extends as sheet like aponeurosis
before attaching to bone, cartilage, fascia or other muscle
Dr: Ahmed Saber
Vet. Anat. 1. 2008
Gross anatomy of skeletal muscle
3- arrangements of skeletal muscle fibers
Based on the angle between fiber and the line of pull
A- Parallel fibers:
1.Strap (sartorius)
Strap
2.Quadrates (quadratus
femoris)
3.Fusiform (biceps brachi
Dr: Ahmed Saber
Fusiform
Vet. Anat. 1. 2008
B- oblique fibers
(pennation)
Unipennate
The fibers attached to tendon at
oblique angle (feather like)
1- unipennate: on one side of
tendon
ex 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
Dr: Ahmed Saber
Bipennate
Multipennate
Vet. Anat. 1. 2008
C- circular fibers
1- 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
Body wall
• is sheath of CT found all
over the body
• Divided into
• Internal fascia
(endothoracic,
abdominaland pelvic)
• External fascia (
superficial and deep
fascia)
Internal fascia
Body
cavity
skin
Dr: Ahmed Saber
Deep fascia
Superficial fascia
Vet. Anat. 1. 2008
3. Synovial sac
Is sac filled with synovia
Located between two structures to decrease the
friction between these structures
1. Subtendinous
Synovial
sac
Tendon
2. Subcutaneous
3. subligamentous
Bone
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
4. Tendon synovial sheath
Mesotendon
Outer fibrous
tendon
Synovial fluid
Dr: Ahmed Saber
Parietal synovial
layer
Visceral synovial
layer
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