6.3.3 Examining Skeletal Muscle Under a Microscope

Steps for Examining Skeletal Muscle:

1. Preparation of a Microscope Slide:

• Obtain a thin section of muscle tissue.
• Stain the tissue with a dye, such as haematoxylin and eosin, to enhance visibility of structures.

2. Viewing Under the Microscope:

• Use a light microscope to examine the tissue.
• Start at a low magnification to locate the muscle fibres, then increase to a higher magnification for detail.

3. Key Features to Identify:

• Striations: Alternating light (I-bands) and dark (A-bands) bands caused by the arrangement of actin and myosin.
• Nuclei: Muscle fibres are multinucleated, with nuclei located at the periphery of the fibres.
• Sarcomeres: Visible at higher magnifications as the repeating units along a myofibril, marked by Z-lines.

4. Interpreting the Bands:

• A-band: Dark band where actin and myosin overlap.
• I-band: Light band containing only actin filaments.
• Z-line: Marks the boundaries of each sarcomere.
• H-zone: Lighter region in the centre of the A-band where there is no overlap of actin and myosin.

Practical Tips for Exam Success:

• Be prepared to identify and label the above structures in a diagram or photomicrograph of skeletal muscle.
• Understand how the banding pattern changes during muscle contraction, e.g., I-bands shorten, H-zones disappear, A-bands remain constant.