HISTOLOGY REVIEW Muscle Tissue Dr Tim Ballard Department

HISTOLOGY REVIEW Muscle Tissue Dr. Tim Ballard Department of Biology and Marine Biology

Skeletal muscle – longitudinal section – H&E – 10 x objective individual muscle fibers nucleus Skeletal muscle fibers (individual cells) are long and cylindrical, with multiple nuclei that are placed on the perimeter of the fibers.

Skeletal muscle – longitudinal section – H&E – 20 x objective connective tissue and blood vessels between muscle fibers multiple nuclei on the periphery of the cell By moving the fine-focus adjustment gently up and down, you can see the alternating light and dark bands that form the striations.

Skeletal muscle – longitudinal section – H&E – 40 x objective multiple nuclei on the periphery of the cell connective tissue and blood vessels between muscle fibers er uscle fib m l a u id indiv The striations, peripheral nuclei, and parallel fibers are the selling points that this is skeletal muscle seen in longitudinal section.

Skeletal muscle Human esophagus (upper) – section – H&E – 10 x objective longitudinal skeletal muscle fibers See the striations? multiple nuclei on the periphery of the cell See the peripherallyplaced nuclei? skeletal muscle fibers in cross section The upper esophagus of the human has skeletal muscle in both cross and longitudinal section.

Skeletal muscle – cross section – H&E – 40 x objective skeletal muscle fibers in cross section Why can’t you see the striations in a cross-section of skeletal muscle?

Cardiac muscle – section – H&E – 10 x objective 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. Compare this section with skeletal muscle. Look at the lack of parallel organization of the fibers compared to that of skeletal muscle.

Cardiac muscle – section – H&E – 20 x objective 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 muscle – section – H&E – 40 x objective striations intercalated disc centrally-located nucleus One distinguishes cardiac muscle from skeletal muscle by the branching fibers, presence of intercalated discs, and centrally-placed single nuclei/cell.

Cardiac muscle –section – silver – 20 x objective branching intercalated disc nucleus This stain clearly shows the single central nucleus, branching fibers, intercalated discs, and striations.

Smooth muscle – teased apart – H&E – 20 x objective The tapered nature of these cells allows them to be fitted together into sheets of cells, perfect 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. 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 muscle Large intestine – longitudinal section – H&E – 10 x objective mucosa submucosa muscularis externa inner circular outer longitudinal Circular smooth muscle cells cut longitudinally would look like Longitudinal smooth muscle cells cut longitudinally would look like

Smooth muscle Duodenum – cross section – H&E – 40 x objective inner circular smooth muscle Circular smooth muscle cells cut in cross section would look like

Smooth muscle Large intestine – longitudinal section – H&E – 40 x objective collagen fibers smooth muscle Contrast the smooth muscle cells with the collagen fibers just above them. end