Muscle

Muscle

1. Organization

   • approx 600 skeletal muscles
     • approx half our body weight
       • 3 kinds of muscle tissue; skeletal, cardiac, smooth
         • 3 kinds of tissue: skeletal, cardiac, smooth
         • Specialized for one major purpose: converting chemical energy in ATP into mechanical energy of motion
           • Myology= the study of the muscular system

2. Function of Muscle

   • Movement
     • Move from place to place, movement of body parts, contents, breathing, circulation, feeding and digestion, defecation, childbirht
     • Stability:
       • Maintain posture, prevents unwanted movements. Antigravity muscles-resist pull of gravity stabilize joints
       • Control of openings and passageway
         • Sphincters: internal muscular rings control movement of food, bile, blood, and other material
         • Heat Production
           • as much as 85% of body heat

3. Connective Tissue of Muscle

   • Endomysium
     • Perimysium
       • Epimysium
         • Fascia
           • sheet of connective tissue that separates neighboring muscles or groups from each other and subcutaneous tissue.
         • Fibrous sheath surrounding the entire muscle.
           • outer surface grades into the fascia.
             • Inner surface sends projections between fascicles to form perimysium.
       • Slightly thicker layer of connective tissue.
         • Fascicles: bundles of muscle fibers wrapped in perimysium.
           • Carry larger nerves and blood vessesls, and stretch receptors.
     • thin sleeve of loose connective tissue. Surroundes each muscle fiber
     • Allows room for capillaries and nerve fibers to reach each muscle fiber.

4. Shapes and classification according to fascicle orientation

   • Fusiform
     • Parallel
       • Triangular (convergent)
         • Pennate
           • Circular (sphincters)
             • ring around body opening
               • orbicularis oculi, urethral, anal sphincters.
           • fascicles insert obliquely on a tendon
             • unipennate, bipennate or multipennate
               • palmar interosseus, rectus femoris and deltoid
           • feather shaped
         • fan-shaped, broad at origin, tapering to a narrower insertion.
           • pectoralis major, temporalis
       • Has uniform width and parallel fascicles.
         • can span longer distances than other shapes.
           • rectus abdominis, zygomaticus major
     • thick in middle, tapered at ends
       • biceps brachii, gastrocnemius

5. Muscle Attachments

   • Indirect attachment to bone
     • Tendons
       • tendons bridge the gap between muscle ends and bony attachment.
         • Collagen fibers of endo-, peri-, and epimysium continue into the tendon
           • Very strong structural continuity from muscle to bone
             • biceps brachii, Achilles tendon
     • Direct (fleshy) attachment to bone
       • Epimysium continues as tendon merges into periosteum as perforating fibers.
         • muscle seems to immerge directly from bone
           • margins of brachialis, lateral head of triceps brachii
   • Attachment to dermis
     • some skeletal muscles do not insert on bone, but in dermis of skin
       • muscles of facial expressions

6. Muscle Origins and Insertions

   • Origin
     • Belly
       • Insertion
         • Mobile
           • bony attachment to mobile end of muscle
       • Middle
         • thicker, middle region of muscle between origin and insertion
     • bony attachment at stationary end of muscle
     • Stable