Muscles part 1 structure,location,function

• Three Types of Muscle Tissue


  • Skeletal muscle tissue
  • Cardiac muscle tissue
  • Smooth muscle tissue

  
• Skeletal muscle tissue


  • Attached to bones and skin
  • Striated
  • Multi-nucleated
  • Voluntary (i.e., conscious control)
  • Powerful
• Cardiac muscle tissue


  • Only in the heart
  • Striated
  • Single nucleated
  • Involuntary
  • Autorhythmic
• Smooth muscle tissue


  • In the walls of hollow organs, e.g., stomach, urinary bladder, and airways
  • Not striated
  • Involuntary
  • Single nucleated
• Special Characteristics of Muscle Tissue


  • Excitability (responsiveness or irritability): ability to receive and respond to stimuli
  • Contractility: ability to shorten when stimulated
  • Extensibility: ability to be stretched
  • Elasticity: ability to recoil to resting length
• Muscle Functions


  • Movement of bones or fluids (e.g., blood)
  • Maintaining posture and body position
  • Stabilizing joints
  • Heat generation (especially skeletal muscle)
• Skeletal Muscle


  • Each muscle is served by one artery, one nerve, and one or more veins
• Connective tissue sheaths of skeletal muscle


  • Epimysium: dense regular connective tissue surrounding entire muscle
  • Perimysium: fibrous connective tissue surrounding fascicles (groups of muscle fibers)
  • Endomysium: fine areolar connective tissue surrounding each muscle fiber
• Skeletal Muscle: Attachments


  • Directly — epimysium of muscle is fused to the periosteum of bone or perichondrium of cartilage
  • Indirectly — connective tissue wrappings extend beyond the muscle as a ropelike tendon or sheetlike aponeurosis
• Microscopic Anatomy of a Skeletal Muscle Fiber

  • Cylindrical cell, up to 30 cm long
  • Multiple peripheral nuclei
  • Many mitochondria
  • Glycosomes for glycogen storage
  • Myoglobin for O2 storage
  • Also contain myofibrils, sarcoplasmic reticulum, and T tubules
• Muscle fibers are long cylindrical cells with many nuclei located near the center of the fiber.
• The insertion is the attachment point that moves when the muscle contracts.
• The origin is the attachment point that remains stationary during muscle contraction.
• Flexors bend a joint; extensors straighten a joint.
• Myofibrils consist of repeating units called sarcomeres, which are the basic contractile unit of muscle.
• Adduction brings two bones closer together; abduction separates them.
• Adductors bring body parts toward midline; abductors move away from it.
• Muscle fibers also have specialized structures called myofibrils, which are responsible for contraction.
• A muscle's action can be described by its direction of pull, which determines whether it flexes, extends, adducts, abducts, rotates, or stabilizes a joint.
• Flexors bend joints; extensors straighten them.
• A muscle's action can be described by its direction of pull.
• The cytoplasm of muscle fibers contains numerous mitochondria that produce ATP through aerobic respiration.