Which of the following is NOT a distinct feature of intercalated discs in cardiac muscle cells?

• A. Desmosomes that provide strong mechanical attachment between cells
• B. Fascia adherens that anchor actin filaments and transmit contractile force
• C. Gap junctions that allow for electrical coupling between cells
• D. Tight junctions that prevent passage of ions between cells

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the structure and function of intercalated discs in cardiac muscle cells. Intercalated discs are specialized connections between cardiac muscle cells that facilitate synchronized contraction and communication.
2. Step 2: Review the three distinct features of intercalated discs: (1) Desmosomes, which provide strong mechanical attachment between cells, preventing them from pulling apart during contraction; (2) Fascia adherens, which anchor actin filaments and transmit contractile force between cells; and (3) Gap junctions, which allow for electrical coupling and ion passage, enabling rapid communication between cells.
3. Step 3: Analyze the provided options. Tight junctions are not a feature of intercalated discs. Tight junctions are typically found in epithelial cells and serve to prevent the passage of ions and molecules between cells, which is not the function of intercalated discs in cardiac muscle.
4. Step 4: Compare the correct answer (Tight junctions) with the other options. Desmosomes, fascia adherens, and gap junctions are all essential components of intercalated discs, while tight junctions are unrelated to cardiac muscle cell communication or contraction.
5. Step 5: Conclude that the correct answer is Tight junctions, as they do not contribute to the structural or functional properties of intercalated discs in cardiac muscle cells.