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muscles of body


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Amna inayat medical college …

Amna inayat medical college
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  • 1. Muscle
  • 2. Functions:  Producing Movement  Maintaining Posture  Stabilizing Joints  Generating Heat  Although not usually cited as a major muscle function, skeletal muscles also protect more fragile internal organs (the viscera) by enclosure. Also, smooth muscle, in particular, forms valves to regulate the passage of substances through internal body openings.
  • 3. Functional Characteristics of Muscle Tissue  Excitability is the ability to receive and respond to a stimulus, that is, any change in the environment whether inside or outside the body. In the case of muscle, the stimulus is usually a chemical.  Contractility is the ability to shorten forcibly when adequately stimulated. This property sets muscle apart from all other tissue types.  Extensibility is the ability to be stretched or extended. Muscle fibers shorten when contracting, but they can be stretched, even beyond their resting length, when relaxed.  Elasticity is the ability of a muscle fiber to recoil and resume its resting length after being stretched.
  • 4. Classifications of muscles  According to structure 1. Skeletal muscle  attach to and cover the bony skeleton.  Skeletal muscle fibers are the long, cylindrical and multi-nucleated and contractile.  Under microscope, shows alternating dark and light bands, these stripes are called striations.  A.k.a. voluntary muscle because it is the only type subject to conscious control, i.e. controled by Somatic NS  Skeletal muscle is responsible for overall body mobility.  It can contract rapidly, but it tires easily and must rest after short periods of activity.
  • 5. 2. Cardiac muscle tissue • occurs only in the heart • Cylinderical, branching and anastomosing cells • cardiac muscle cells are also striated, but cardiac muscle is not voluntary (involuntary). • Most of us have no conscious control over how fast our heart beats, controlled by autonomic NS. • Cardiac muscle usually contracts at a fairly steady rate set by the heart’s pacemaker, but neural controls allow the heart to “shift into high gear” for brief periods. 3. Smooth muscle tissue • Long, spindle shaped • is found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages. • Its role is to force fluids and other substances through internal body channels. • It has no striations (nonstriated), and like cardiac muscle, it is not subject to voluntary control, controlled by autonomic NS. • Contractions of smooth muscle fibers are slow and sustained.
  • 6. According to function Voluntary muscles  All skeletal muscles EXCEPT  Pharynx  Larynx  Upper part of esophagus (skeletal muscle but involuntary in nature)  Ciliary body of eye (smooth muscle)  Involuntary muscles  All smooth muscles  Skeletal muscles of  Pharynx  Larynx  Upper part of esophagus  Cardiac muscle  Control of contraction is myogenic, within the muscles  Autonomic NS only modifies it
  • 7. According to Development  Mesodermal muscles  Derived from mesodermal tissue.  Almost ALL skeletal, smooth and cardiac muscles.  Ectodermal muscles  Derived from embryonic ectoderm.  Examples:  Smooth muscles of Iris  Arrector pili muscle of skin  Myo Epithelial cells associated with sweat glands.
  • 8. According to Phylogenetic History Somatic muscles Characterization Universally striated Develop from myotomes Controlled by Somatic NS Subtypes Somatic Axial muscles Limited to central or axial skeleton e.g. trunk muscles, muscles of eye ball Somatic appendicular muscles Limited to appendicular muscles, muscles of upper and lower limb.
  • 9. Visceral muscles Characterization Concerned with primitive gut Derived from mesenchyme surrounding the endodermal gut and not myotomes controlled or modified by autonomic NS Subtypes Muscles of pharyngeal arch apparatus Associated with structures developing from pharyngeal arch apparatus Striated in appearance Visceral smooth muscles Associated with endodermal gut tube Non-striated
  • 10. Classification of Skeletal Muscles According to relative color of skeletal muscle cell Red muscle fiber White muscle fiber 1. Red Muscle Fiber  Large amounts of myoglobin (gives the red color appearance!)  Many mitochondria.  Many blood capillaries.  Generate ATP by the aerobic system.  Split ATP at a slow rate.  Slow contraction velocity.  Resistant to fatigue.  Found in large numbers in postural muscles.  Needed for aerobic activities like long distance running.
  • 11. 2. White Skeletal fibers  Low myoglobin content.  Few mitochondria.  Few blood capillaries.  Large amount of Creatine phosphate.  Split ATP very quickly.  Fatigue easily.  Needed for sports like sprinting. Individual muscles are a mixture of 2 types of muscle fibers but their proportions vary depending on the action of that muscle
  • 12. According to architecture or form (Fascicular Architecture) Muscles can be arranged either parallel or obliquely to the line of action of the muscle.  Parallelly arranged muscles  Quadrilateral muscles (flat quadrangle shape)  Hypoglossus muscle of tongue  Thyrohyoid muscle of larynx  Gluteus maximus muscle  Fusiform or Spindle shaped muscles  Biceps brachii muscle  Flexor Carpi radialis muscle  Palmaris Longus  Strap or ribbon like muscles  Sartorius  Infrahyoid  Rectus Abdominis
  • 13.  Convergent – origin of the muscle is broad;  fascicles converge toward the tendon of insertion Pectoralis major  Pennate:  Unipennate  fascicles insert into one side of the tendon  Flexor pollicis longus muscle  Bipennate  fascicles insert into the tendon from both sides  Dorsal intossei  Multipennate  fascicles insert into one large tendon from all sides  Subscapularis muscle  Circular – fascicles are arranged in concentric rings  Orbicularis oculi  Orbicularis oris
  • 14.  Fan shaped muscles  Temporalis muscles  Gluteus muscles  Triangular muscles  Subclavius muscles  Adductor magnus muscles  Cylindrical muscles  Tibialis anterior muscles  Cruciate muscles  Adductor magnus muscles
  • 15. According to action/role during movements  Prime movers  A muscle that provides the major force for producing a specific movement is a prime mover or agonist of that movement.  The biceps brachii muscle, which fleshes out the anterior arm (and inserts on the radius), is a prime mover of elbow flexion.  Antagonists  Muscles that oppose, or reverse, a particular movement are called antagonists.  When a prime mover is active, the antagonist muscles are often stretched and may be relaxed.  flexion of the forearm by the biceps brachii muscle of the arm is antagonized by the triceps brachii  Fixators  Increase the intra-articular compression and stabalize the joint  Provides the immovable base for prime movers to act upon.  Synergists  Synergists help prime movers by  adding a little extra force to the same movement  reducing undesirable or unnecessary movements that might occur as the prime mover contracts
  • 16. Parts of Skeletal Muscles  Origin (Proximal attachment)  Proximal attachment of muscle  Doesn’t move while contraction  Can be any of the following structures…  Bones  Fasciae  Tendions  Articular capsules  Intermuscular Septa  Belly  Highly specialised, excitable, contractile  Highly vascular  Resistant to infection
  • 17.  Tendon  Rounded fibrous end of a skeletal muscle  Aponeurosis  Fibrous and membranous part of muscle by which it is attached to distal parts.  Insertion  Distal attachment  Movable during contraction