Concept explainers
Concept introduction: The primary cells that form a skeletal muscle are the skeletal muscle fibers. The skeletal muscle fibers have several specialized features. Like other cells, skeletal muscle cells have typical cellular features with the cytoplasm. The cytoplasm of skeletal muscle is specially known as sarcoplasm.
Answer to Problem 1DYB
Correct answer: The unit of skeletal muscle structure that is composed of bundles of myofibrils enclosed within a sarcolemma and surrounded by a connective tissue covering called endomysium is a skeletal muscle fiber. Hence, the correct answer is option (d).
Explanation of Solution
Reason for the correct answer:
The skeletal muscle fiber is composed mostly of myofibrils that extend the muscle fiber length. It is enclosed within a sarcolemma that represents the plasma membrane of the skeletal muscle fiber and surrounded by the connective tissue covering known as endomysium. Voltage-gated channels are present within the membrane of sarcolemma. These channels include both voltage-gated K+ channels and voltage-gated Na+ channels that participate in conducting the electrical signal.
Option (d) is given as “skeletal muscle fiber”.
The unit of skeletal muscle structure that is composed of bundles of myofibrils enclosed within a sarcolemma and surrounded by a connective tissue covering called endomysium is a skeletal muscle fiber. Hence, the correct answer is option (d).
Reasons for incorrect answer:
Option (a) is given as “myofibril”.
The myofibril is composed of actin thin filaments and myosin thick filaments that are organized into the sarcomeres. Hence, option (a) is incorrect.
Option (b) is given as “fascicle”.
The skeletal muscle consists of multiple fascicles that are mainly composed of bundles of muscle fibers. Hence, option (b) is incorrect.
Option (c) is given as “myofilament”.
The myofilaments are the contractile proteins bundled within the myofibrils. Hence, option (c) is incorrect.
Hence, options (a), (b), and (c) are incorrect.
The unit of skeletal muscle structure that is composed of bundles of myofibrils enclosed within a sarcolemma and surrounded by a connective tissue covering called endomysium is known as skeletal muscle fiber.
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