Multiple Choice
In skeletal muscle fibers, which structure serves as the primary intracellular storage site for calcium ions (Ca) used during contraction?
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9. Muscle Tissue
Structure of a Skeletal Muscle
Multiple Choice
In the structure of skeletal muscle, what is a muscle fascicle?
A
A connective tissue sheath that surrounds the entire muscle (epimysium)
B
A bundle of muscle fibers (muscle cells) surrounded by perimysium
C
A contractile unit within a myofibril composed of actin and myosin (sarcomere)
D
A network of membranous tubules that stores calcium for contraction (sarcoplasmic reticulum)
Verified step by step guidance1
Step 1: Understand the hierarchical organization of skeletal muscle. Skeletal muscle is composed of multiple levels, starting from the whole muscle down to the smallest contractile units.
Step 2: Identify the connective tissue layers associated with each level. The epimysium surrounds the entire muscle, the perimysium surrounds bundles within the muscle, and the endomysium surrounds individual muscle fibers.
Step 3: Define a muscle fascicle. It is a bundle of muscle fibers (muscle cells) grouped together and surrounded by the perimysium connective tissue sheath.
Step 4: Differentiate the muscle fascicle from other structures. For example, the sarcomere is the contractile unit within myofibrils, and the sarcoplasmic reticulum is a membranous network involved in calcium storage.
Step 5: Conclude that the muscle fascicle is specifically the bundle of muscle fibers wrapped by perimysium, distinguishing it from the entire muscle (epimysium) and smaller units like sarcomeres.
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