EM 359 Basal Lamina

Basal Lamina

Scanning electron microscopy (SEM) of a tangential section of the plasma membrane of a skeletal muscle cell.

This specimen was prepared using a technique known as deep etching. Etching removes ice from the surface of the frozen section by exposing it to a vacuum, revealing deeper structures previously hidden by the ice.

The three-dimensional appearance of the connective tissue adjacent to the plasma membrane (brown) is seen. The basal lamina comprises a meshwork of filaments of type IV collagen fibrils (yellow). Outside of the basal lamina are the larger fibrils of type I collagen (orange).

Unlike the open network seen here, the network of type IV collagen forms a framework for binding several types of glycoproteins (such as laminin), proteases, and growth factors. This highly cross-linked matrix functions as a molecular filter with selective permeability to many molecules and proteins.

Courtesy of John E. Heuser, Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, MO.