Biology Support & Movement SZABMU 2024 Reconduct
PMDC Verified Question 9 of 75
Contractile unit between two Z lines is absent in:
A
Skeletal muscles
B
Skeletal and cardiac muscles
C
Smooth muscles
D
Skeletal and smooth muscles
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Smooth muscles
Concept:

The presence of sarcomeres in muscle types.

Formula:

N/A (Conceptual)

Solution:

  • The precise repeating contractile unit bounded by two Z-lines is scientifically defined as a sarcomere.


  • Sarcomeres naturally align to form visible light and dark bands (striations) under a microscope.


  • Because Smooth muscles completely lack this highly ordered, rigid sarcomere structure (their actin and myosin are arranged diagonally across the cell), they exhibit no striations and therefore lack Z-lines entirely.


Why other options are incorrect:

Both skeletal and cardiac muscles rely heavily on perfectly aligned sarcomeres (Z-line to Z-line) to generate force, which is why both appear heavily striated.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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