Skeletal Muscle Under the Microscope

Skeletal Muscle (Transverse & Longitudinal Section), Homo sapiens

Skeletal Muscle (Transverse & Longitudinal Section), prepared microscope slide

This slide shows skeletal muscle cut two ways, across the fibers and along them, stained with iron hematoxylin. It is the standard slide for seeing muscle fibers, their many nuclei, and the stripes (striations) that make skeletal muscle unique.

This slide shows human skeletal muscle (Homo sapiens) cut two ways, stained with iron hematoxylin. In the top piece, a transverse section cut across the muscle, the fibers look like packed, many-sided shapes grouped into bundles called fascicles. In the bottom piece, a longitudinal section cut along the muscle, the fibers are long and run side by side, with small nuclei along their edges. Skeletal muscle is also called striated muscle because of the fine stripes across its fibers. Comparing the two cuts helps students picture muscle fibers as long cylinders bundled together.

Labeled skeletal muscle under the microscope

Labeled skeletal muscle cross section under the microscope showing muscle fibers, a fascicle, nuclei at the fiber edge, striations and a blood vessel — Human skeletal muscle cut across, about 530 micrometers wide, stained with iron hematoxylin. Each many-sided shape is one muscle fiber with its nuclei at the edge, and the fibers are grouped into bundles called fascicles.

Striations: Fine stripes across a fiber cut at a slant
Fascicle: A bundle of fibers. The lower half of this view is one fascicle, with a gap between it and the bundle above
Blood vessel: A small vessel in the connective tissue between bundles
Nucleus at fiber edge: Nuclei sit at the edge of each fiber, not in the center
Muscle fiber: One long muscle cell, cut across

What to look for

Muscle fibers (cross section): Many-sided shapes packed together, each one a single long muscle cell cut across.
Fascicles: Bundles of fibers grouped together and wrapped in connective tissue (perimysium).
Nuclei at the edge: Dark nuclei pressed against the outer edge of each fiber, not in the center.
Muscle fibers (longitudinal section): Long, parallel fibers lying side by side.
Striations: Fine alternating light and dark bands across the long fibers, stained dark by iron hematoxylin.

Questions and answers

What does skeletal muscle look like under a microscope?

Skeletal muscle is made of long, cylindrical fibers with many nuclei along their edges. Cut lengthwise, the fibers show fine light and dark stripes called striations. Cut across, they look like packed polygons grouped into bundles.

How do you tell skeletal, cardiac, and smooth muscle apart?

Skeletal muscle has long, striped fibers with many nuclei at the edge. Cardiac muscle is striped too but has branched cells with one central nucleus and dark lines between cells. Smooth muscle has no stripes and is made of spindle-shaped cells with one central nucleus.

Why does skeletal muscle have stripes?

The stripes come from repeating units of the proteins actin and myosin inside each fiber. These units, called sarcomeres, line up across the fiber and slide together when the muscle contracts.

Compare it

How to identify tissue types

Category: Histology and Tissue
Scan magnification: 20x
Stain: Iron hematoxylin

Viewing this slide in class

This is a scan of a real prepared slide, not a simulation or a drawing. On StudyScope you can pan from the whole slide down to individual structures, always in focus, and measure them in real micrometers with the calibrated ruler. Present it live and every student screen follows your view and annotations. Students join with a room code on Chromebooks, iPads, or any browser, with no accounts.