Thin Filament is made up of

Correct Answer: D

Rationale: Thin filaments comprise actin (structural backbone), troponin (Ca²⁺-binding regulator), and tropomyosin (site-covering protein), interacting with myosin for contraction. Myosin forms thick filaments, excluded from thin ones. Listing only troponin or tropomyosin omits actin's essential role thin filaments need all three. Actin alone misses regulatory components. The combination minus myosin defines thin filaments, enabling controlled actin-myosin binding, distinguishing it from partial or thick filament compositions, critical for sarcomere function.

Correct Answer: A

Rationale: Muscle fibres contain hierarchical structures. Myofibrils, bundles of sarcomeres, span the fibre's length (tens to hundreds of micrometres), housing myofilaments actin and myosin arrays within sarcomeres. Myosin is a protein molecule, and myopic is unrelated (likely a typo). Myofibrils, as the largest organized unit within the cell, integrate sarcomeres for contraction, distinguishing them from shorter myofilaments or molecular components, critical for muscle's macroscopic force generation.

Correct Answer: A

Rationale: Gluteus maximus denotes size maximus means largest relative to gluteus medius and minimus, all on the buttocks. Shape (e.g., trapezius), action (e.g., adductor), and origin-insertion (e.g., sternocleidomastoid) aren't specified. Its large mass aids hip extension, but size defines the name, distinguishing it in gluteal anatomy, reflecting naming conventions prioritizing relative scale.

Correct Answer: D

Rationale: Skeletal muscle's multinucleate nature a syncytium from fused myoblasts contrasts with uninucleate cardiac and smooth muscles. Striations occur in skeletal and cardiac, branching and intercalated discs are cardiac-specific. Multiple nuclei support skeletal muscle's size and repair, distinguishing it in structure and voluntary function, key to its histological identity.

Correct Answer: B

Rationale: Gluteus medius indicates size intermediate between maximus and minimus among gluteal muscles. Sternocleidomastoid names origin-insertion, flexor digitorum profundus action-depth, and trapezius shape. Medius' size-based naming distinguishes it, reflecting relative scale in gluteal anatomy, useful for comparative identification.