The Z-disc (Z-line) of a sarcomere serves as the anchor for which protein filaments, and what proteins compose the Z-disc itself?

• A Thin (actin) filaments anchor at the Z-disc; alpha-actinin is the primary Z-disc protein cross-linking antiparallel actin filaments ✓
• B Thick (myosin) filaments anchor at the Z-disc; M-protein and creatine kinase compose the Z-disc
• C Titin filaments anchor at the Z-disc; nebulin and desmin are also located exclusively at the Z-disc
• D Troponin-tropomyosin complexes anchor at the M-line within the Z-disc

Explanation

The Z-disc (from German 'Zwischenscheibe', meaning intermediate disc) is the dense structure that delineates the boundaries of each sarcomere. It anchors the plus (+) ends of thin actin filaments from adjacent sarcomeres. Alpha-actinin is the principal structural protein of the Z-disc, cross-linking antiparallel actin filaments. Nebulin runs along the thin filament and anchors to the Z-disc; desmin intermediate filaments connect adjacent Z-discs laterally between myofibrils. Titin (connectin) spans from Z-disc to M-line, providing the elastic restoring force. Myosin is anchored at the M-line, not the Z-disc.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.