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• • In the longitudinal view there will be parallel fibers and multiple peripheral nuclei.
  • In the cross-sectional view there will be peripheral nuclei and the appearance of "cylindrical bundles".
• • A specialized terminology is used to describe muscles or muscle tissue. "sarkos" which means "flesh".
  • The cell membrane is called the sarcolemma, the cytoplasm is called the sarcoplasm, the endoplasmic reticulum is called the sarcoplasmic reticulum, and the muscle cell itself is called a muscle fiber.
  • This terminology is specific to muscles and is derived from the Greek root "sarkos" which means "flesh".
• • Skeletal muscles can be described as "bundles within bundles within bundles".
  • Each individual skeletal muscle fiber consists of bundles of myofibrils and is encased in a connective tissue called the endomysium.
  • Groups of skeletal muscle fibers are in tum gathered into bundles which are wrapped in more connective tissue called the perimysium.
  • These bundles are in turn grouped together and enclosed in a layer of dense connective tissue called the epimysium which forms individual muscles.
• • Each individual muscle is wrapped in a tough layer of fibrous connective tissue called the fascia.
  • These are continuous with tendons and the periosteum of bones.
• Muscle Fibers (myocytes or muscle cells)

  • are the basic unit of the muscle itself.
  • smallest functional unit or cell that a muscle can be divided into.
  • are made up of smaller sub-units called myofibrils.
• • These are in turn composed of threadlike myofilaments which are composed of the proteins actin and myosin.
  • Actin filaments are thin and appear as light bands under the microscope, while myosin filaments are thick and appear dark.
• • These have an overlappingstructure and are held together by chemical cross bridges.
  • The overlapping structure gives skeletal muscle a banded or striped look under the microscope.
• These alternating light and dark bands are called striations and give skeletal muscle its alternate name, and more accurate name, voluntary, striated muscle.
• • A closer look at the striations reveals that the myofibrils are composed of repeating units of actin and myosin called sarcomeres.
  • sarcomere represents the smallest individual contractile unit of al muscle fiber.
  • It is measured from the point where actin myofilaments overlap to the next actin overlap.
  • The actin overlap is called the "Z" line, so a complete sarcomere extends from Z line to Z line.
• Sarcomere

  •  is flanked by 2 protein structures known as Z discs.
  • The portion of the sarcomere which contains the thick filament is known as the A band.
  • A stands for anisotropic which is a fancy way of saying that it appears dark under the microscope.
  • The A band contains a zone of overlap (btwn thick & thin filaments) and an H zone which contains only thick filaments
• Skeletal muscle fibers

  not all alike in composition and function. For example, muscle fibers vary in their content of myoglobin.

  Myoglobin - the red-colored protein that binds oxygen in musclefibers.
• Skeletal muscle fibers that have a high myoglobin content are termed red muscle fibers and appear darker (the dark meat in chicken legs and thighs); those that have a low content of myoglobin are called white muscle fibers and appear lighter (the white meat in chicken breasts).
• Myofilament

  Thin myofilaments

  • Composed of actin protein
  • Associated with troponin and tropomyosin proteins

  Thick myofilaments

  • Composed of myosin protein
  • Form the cross-bridges