Lecture Notes: Skeletal Muscles in Oregon

Introduction to Skeletal Muscles

• Skeletal muscles consist of various tissue types:
  • Nerves
  • Blood vessels
  • Connective tissue
  • Skeletal muscle tissue
• Each muscle receives nerve, artery, and drainage.
• Controlled consciously by the brain.

Muscle Fiber and Nerve Connection

• Every muscle fiber is connected to a nerve fiber.
• Nerve fibers link to the nervous system and brain.

Necessity for Oxygen and Nutrients

• Contracting muscle fibers need high oxygen and nutrients.
• Arteries and veins supply blood flow, carrying nutrients and waste.
• Fast removal of waste is crucial for muscle function.

Connective Tissue Sheaths

• Muscles are covered by connective tissue sheaths:
  • Epimysium: Covers the entire muscle, made of dense irregular connective tissue that blends with fascia.
  • Perimysium: Surrounds fascicles (groups of muscle fibers).
  • Endomysium: Fine areolar tissue surrounding each muscle fiber.

Muscle Organization

• Entire muscle surrounded by epimysium.
• Fascicle: Bundle of muscle fibers, surrounded by perimysium.
• Individual muscle fiber surrounded by endomysium.
• Skeletal muscle cells are multinucleated and striated.

Muscle Attachments

• Muscles have points of origin and insertion:
  • Origin: Immovable or less movable, attaches to bone.
  • Insertion: Attaches to movable bone.
• Example: Brachialis muscle originates at humerus, inserts at ulna.

Direct vs. Indirect Attachments

• Direct Attachments:
  • Epimysium fuses with periosteum or perichondrium.
• Indirect Attachments:
  • Connective tissue extends beyond muscle as a tendon (rope-like) or aponeurosis (sheet-like).

Tendons and Connective Tissue

• All connective tissue sheaths (epimysium, perimysium, endomysium) converge to form tendons.
• Tendons help attach muscles to skin, bones, or other muscles.

Myofibrils

• Within muscle cells are myofibrils, cylindrical protein structures responsible for contraction.

Summary

• Connective tissue sheaths are crucial for muscle structure and function.
• Tendons are extensions of muscle connective tissue, essential for muscle attachments.