Myology and Muscle Classification

Myology

• Myology studies muscles and accessory structures like fascia, tendon sheaths, and bursae.
• Muscles are contractile tissues made of muscle fiber bundles, responsible for movement.

Muscle Functions

• Movement production
• Heat generation in warm-blooded animals
• Body stabilization
• Substance transport within the body

Muscle Classification

• Skeletal muscle: Striated, voluntary control
• Smooth muscle: Non-striated, involuntary control
• Cardiac muscle: Striated, involuntary control

Skeletal Muscle

• Striated fibers
• Multinucleated
• Voluntary control
• Epimysium: Outermost connective tissue layer surrounding the muscle
• Perimysium: Middle layer, encases fascicles (bundles of muscle fibers)
• Endomysium: Innermost layer, surrounds individual muscle fibers

Skeletal Muscle Forms

• Long muscles: Found in limbs
• Flat muscles: Found in abdomen and chest
• Short muscles: Various locations
• Sphincter muscles: Ring-like muscles closing orifices, examples include:
  • Sphincter ani: Around the anus
  • Orbicularis oris: Around the mouth
  • Orbicularis oculi: Around the eye

Skeletal Muscle Attachment

• Origin: Fixed point of attachment, usually proximal
• Insertion: Movable point of attachment, usually distal
• Tendon: Cord-like, fibrous tissue connecting muscle to bone
• Aponeurosis: Thin, strong sheet of fibrous tissue, found in flat muscle attachments
• Raphae: Interdigitation of aponeuroses, examples:
  • Pharyngeal raphe: Short aponeurosis
  • Linea alba: Wide and long aponeurosis between abdominal muscles

Skeletal Muscle Fiber Organization

• Parallel: Fibers parallel to the long axis of the muscle, example: biceps brachii
• Convergent: Muscle fibers converge on a single attachment point, example: pectoralis muscles
• Pennate: Muscle fibers are obliquely arranged, with different subtypes:
  • Unipennate: Fibers on one side of the tendon, example: extensor digitorum
  • Bipennate: Fibers on both sides of the tendon, example: rectus femoris
  • Multipennate: Series of bipennate arrangements, example: deltoid
• Circular: Also called sphincters, guard body entrances, example: obicularis oris

Muscle Actions

• Movements generated by muscle contraction, classified as:
  • Flexors
  • Extensors
  • Adductors
  • Abductors
  • Cutaneous

Muscle Terminology

• Agonist (prime mover): Muscle responsible for the primary movement
• Antagonist: Muscle opposing the agonist's movement
• Synergist: Smaller muscle assisting the agonist, may help start motion or stabilize the origin
• Fixator: Synergist muscle stabilizing the origin of the agonist

Sarcomere

• Basic structural and functional unit of muscle

Contractile Proteins

• Actin: Thin myofilament
• Myosin: Thick filament
• Tropomyosin: Thin filament
• Troponin: Thin filament
• Actin and myosin constitute approximately 55% of total protein in skeletal muscle

Muscle Description

• Name:
  • Action: extensor, adductor
  • Shape: quadratus, triangularis
  • Direction: rectus, oblique
  • Position: subscapularis, iliacus
  • Division: biceps, triceps
  • Size: major, minor
  • Attachment: sterno-cephalicus
  • Structure: semitendinosus
• Shape: triangular, quadrilateral, fusiform
• Attachment: cartilage, bone, skin
• Action: movement produced
• Structure: including direction and arrangement of fibers
• Relations: relationship to surrounding structures

Naming Skeletal Muscles

• Location: Identifies body regions, example: temporalis muscle
• Origin and insertion: First part of name indicates origin, second part indicates insertion, example: genioglossus muscle
• Fascicle organization: Describes fiber orientation within the muscle, example: rectus (straight), transversus, oblique
• Relative position: Describes muscle depth and location within the body, example: externus (superficialis), interus (profundus), extrinsic, intrinsic
• Structural characteristics: Number of tendons, shape, size, example: bi = 2, tri = 3, trapezius, deltoid, rhomboid, major, minor
• Action: Movement produced, example: flexor, extensor, retractor

Muscle Fascia

• Superficial fascia: Loose connective tissue, may contain fat, also called subcutaneous fascia
• Deep fascia: Dense fibrous tissue, spreads over muscles, may fuse with epimysium, tendons, bones, and ligaments, forms fibrous sheaths around muscles, forms annular ligaments to create canals for tendons

Bursa and Synovial Sheath

• Bursa: Fluid-filled sac reducing friction between structures
• Synovial sheath: Encloses tendons to reduce friction during movement
• Peritendon: Outer layer of the synovial sheath
• Mesotendon: Attaches the peritendon to tendon
• Bone: Connective tissue with a rigid extracellular matrix
• Periosteum: Membrane covering bone, important for growth, repair, and attachment of tendons

Smooth Muscle

• Non-striated
• Spindle-shaped
• Single nucleus
• Autonomic control

Cardiac Muscle

• Striated
• Uninucleated
• Intercalated discs facilitate synchronized contraction
• Autonomic control

Explore the fascinating field of myology, which focuses on muscle structure and function, including the various types of muscles and their roles in the body. This quiz covers muscle classifications, functions, and the intricacies of skeletal muscle anatomy.