Muscular Tissue Overview

Muscular Tissue

• Muscle tissue is composed of elongated cells called muscle fibers.
• The cell membrane is called sarcolemma, and the cytoplasm is sarcoplasm.
• Myofibrils are contractile elements within the sarcoplasm.
• Three types of muscle tissue exist: skeletal, cardiac, and smooth.

Skeletal Muscle

• Skeletal muscles are attached to the skeleton, enabling body movement.
• They are striated (have transverse bands), and voluntary (under our conscious control).

Gross Structure of Muscle and Surrounding Connective Tissue

• Whole Muscle: Composed of multiple muscle fascicles enveloped by epimysium (a connective tissue sheath).

• Muscle Fascicle: Bundles of individual muscle fibers surrounded by perimysium (a thinner connective tissue sheath).

• Muscle Fibers: Individual muscle cells, typically long, enclosed by sarcolemma and surrounded by endomysium which contains capillaries and nerves to supply each fiber.

• Myofibrils are long functional units within a muscle fiber, containing myofilaments (actin and myosin).

Light Microscopic Structure of Skeletal Muscle

• Skeletal muscle fibers are elongated and vary in length.
• They are multinucleated, with nuclei oval-shaped and situated under the sarcolemma
• The sarcoplasm is deeply acidophilic (staining dark) and shows cross-striations.
• Myofibrils are longitudinal and cylindrical, parallel to each other within a muscle fiber.

Sarcomere

• The sarcomere is the structural and functional unit of the skeletal muscle fiber.
• It's the distance between two Z lines.
• It contains thin filaments (actin) and thick filaments (myosin).
• The A band contains both thick and thin filaments.
• The I band consists of thin filaments only.
• The H zone is the central part of the A band, where only thick filaments are present.

Electron Microscopic Structure (EM)

• The sarcoplasm contains longitudinal myofibrils, numerous mitochondria, and a well-developed sarcoplasmic reticulum.
• Myofibrils show alternating dark (A bands) and light (I bands) transverse bands, creating the striations.

Quizzes

Multiple Choice

• (1)* What zones form the sarcomere?
• A complete A band and two halves of an I band.
• (2)* Which connective tissue surrounds the whole skeletal muscle?
• Epimysium