PRINICIPLES OF MYOLOGY Def: science deals with muscles Dr: Ahmed SaberVet. Anat  Skeletal muscles are the active part of locomotor system  Smooth muscles move the viscera  Cardiac muscle produces heart contraction

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 SaberVet. Anat

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 SaberVet. Anat

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 SaberVet. Anat

Locations: wall of heart The control: involuntary function: Involuntary autonomic control and special local conducting system cause contractions of heart Dr: Ahmed SaberVet. Anat

3- Skeletal muscles They forming about % 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 SaberVet. Anat

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 SaberVet. Anat

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 bone Tendon Muscle Epimysium Fascicle Fiber Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat

Architecture of skeletal muscle Muscle fiber Perimysium Fascicle Endomysium Epimysium Dr: Ahmed SaberVet. Anat

Microscopic structures Myofiber Myofibril Myofilaments Actin Myosin Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat

2- skeletal muscle attachment a)Bone b)Cartilage c)Deep fascia (indirectly to bone) d)Skin and superficial fascia e)Intermediate tendon f)No attachment (no origin & no insertion, as orbicularis oris) Gross anatomy of skeletal muscle 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 SaberVet. Anat

3- arrangements of skeletal muscle fibers Based 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 SaberVet. Anat

B- oblique fibers (pennation) 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 Unipennate Bipennate Multipennate Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat

3. Synergist –assist in action of agonists –not necessarily prime movers for the action 4. Fixators (stabilozers) –Fix the joint Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat

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 SaberVet. Anat

2. Fascia is sheath of CT found all over the body Divided into Internal fascia (endothoracic, abdominaland pelvic) External fascia ( superficial and deep fascia) skin Superficial fascia Deep fascia Body wallInternal fascia Body cavity Dr: Ahmed SaberVet. Anat

3. Synovial sac Is sac filled with synovia Located between two structures to decrease the friction between these structures 1.Subtendinous 2.Subcutaneous 3.subligamentous Bone Tendon Synovial sac Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat

tendon Outer fibrous Mesotendon Parietal synovial layer Visceral synovial layer Synovial fluid 4. Tendon synovial sheath Dr: Ahmed SaberVet. Anat

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 SaberVet. Anat