HISTOLOGY REVIEWHISTOLOGY REVIEWMuscle TissueMuscle Tissue

Dr. Tim BallardDr. Tim Ballard

Department of Biology and Marine BiologyDepartment of Biology and Marine Biology

Skeletal muscle – longitudinal section – H&E – 10x objective

Skeletal muscle fibers (individual cells) are long and cylindrical, with multiple nuclei that are placed on the perimeter of the fibers.

Skeletal muscleSkeletal muscle

individual muscle fibers

nucleus

Skeletal muscle – longitudinal section – H&E – 20x objective

By moving the fine-focus adjustment gently up and down, you can see the alternating light and dark bands that form the striations.

Skeletal muscleSkeletal muscle

multiple nuclei on the periphery of

the cell

connective tissue and blood vessels between muscle

fibers

Skeletal muscle – longitudinal section – H&E – 40x objective

The striations, peripheral nuclei, and parallel fibers are the selling points that this is skeletal muscle seen in longitudinal section.

Skeletal muscleSkeletal muscle

multiple nuclei on the periphery of

the cell

connective tissue and blood vessels between muscle

fibers

individual muscle

fiber

Human esophagus (upper) – section – H&E – 10x objective

The upper esophagus of the human has skeletal muscle in both cross and longitudinal section.

Skeletal muscleSkeletal muscle

multiple nuclei on the periphery of

the cell

longitudinal skeletal muscle

fibersSee the striations?

skeletal muscle fibers in cross

section

See the peripherally-

placed nuclei?

Skeletal muscle – cross section – H&E – 40x objective

Why can’t you see the striations in a cross-section of skeletal muscle?

Skeletal muscleSkeletal muscle

skeletal muscle fibers in cross

section

Cardiac muscle – section – H&E – 10x objective

Compare this section with skeletal muscle. Look at the lack of parallel organization of the fibers compared to that of skeletal muscle.

Cardiac muscleCardiac muscle

Cardiac muscle cells run parallel to one another, but unlike skeletal muscle cells, the individual fibers branch to meet other cells, forming a meshwork or network of cells.

In this view the branching nature of the cardiac muscle cells is more visible. In addition, look at the nuclei. How many are there and where are they?

Cardiac muscleCardiac muscle

Cardiac muscle – section – H&E – 20x objective

One distinguishes cardiac muscle from skeletal muscle by the branching fibers, presence of intercalated discs, and centrally-placed single nuclei/cell.

Cardiac muscleCardiac muscle

intercalated disc

Cardiac muscle – section – H&E – 40x objective

centrally-located nucleus

striations

Cardiac muscle –section – silver – 20x objective

This stain clearly shows the single central nucleus, branching fibers, intercalated discs, and striations.

Cardiac muscleCardiac muscle

branching

nucleus

intercalated disc

Smooth muscle – teased apart – H&E – 20x objective

Individual cells are long, thin, and tapered on the ends. There is a single nucleus per cell, usually at its longitudinal center. There are no striations.

Smooth muscleSmooth muscle

The tapered nature of these cells allows them to be fitted together into sheets of cells, perfect for forming the walls of hollow organs. In addition, the lack of sarcomeres means that the muscle sheets can stretch to accommodate the increased pressure within the organs.

Large intestine – longitudinal section – H&E – 10x objective

Circular smooth muscle cells cut longitudinally would look like Longitudinal smooth muscle cells cut longitudinally would look like

Smooth muscleSmooth muscle

mucosa submucosa muscularis externa

inner circul

ar

outer longitudin

al

Duodenum – cross section – H&E – 40x objective

Circular smooth muscle cells cut in cross section would look like

Smooth muscleSmooth muscle

inner circular smooth muscle

Large intestine – longitudinal section – H&E – 40x objective

Contrast the smooth muscle cells with the collagen fibers just above them.

Smooth muscleSmooth muscle

smooth muscle

collagen fibers

end