Good fixation is indicated on an electron micrograph of a section of a plasma cell if the mitochondria show no swelling or disruption. Which statement best describes this finding?

• A. Swollen mitochondria
• B. No swelling or disruption
• C. Fragmented mitochondria
• D. Dense mitochondria

Answer: (B)

The key idea is that good fixation preserves cellular ultrastructure, so mitochondria should appear with intact membranes and normal morphology without signs of damage. When fixation is performed well, the mitochondria maintain their proper structure—that means no swelling and no breaks or disruption of the membranes.

Mitochondrial swelling would indicate osmotic imbalance or processing artifacts from delayed or inadequate fixation, suggesting poor fixation or cellular injury during handling. If mitochondria were fragmented or disrupted, that would point to damage or artifact as well, not to good preservation. Dense mitochondria can occur for other fixation or staining reasons but does not specifically signal good preservation.

So, describing mitochondria as having no swelling or disruption aligns with well-fixed tissue and preserved ultrastructure.