Skeletal Muscle Histology - Intro

Skeletal Muscle Histology - Intro

skeletal muscle hierarchy

• Skeletal muscles divide into fascicles.
• Fascicles are units of muscle cells (aka skeletal myocytes, skeletal muscle fibers).
• Skeletal muscle cells comprise myofibrils and other organelles (notably, mitochondria).
• Myofibrils comprise proteins, notably thick and thin myofilaments.
• Myofilaments arrange into functional contractile units, called sarcomeres.

connective tissue hierarchy

• Skeletal muscle is covered in epimysium.
• Fascicles are covered in perimysium.
• Muscle cells are covered in endomysium.

Muscle Organization

Epimysium

• Envelopes the muscle (epi = upon, my = muscle).
• Dense irregular connective tissue.

Perimysium

• Divides the muscle into multiple wedges (peri = around); it covers each fascicle.
• Each fascicle comprises skeletal muscle cells (aka skeletal myocytes or muscle fibers).

Endomysium

• Surrounds the muscle cells.
• Loose areolar connective tissue that maintains the extracellular environment for proper muscle cell functioning.