In the intermediate stratified layers of the epidermis (HA15), where the cells are alive, they look spiny (HA16A). The spines (arrowheads) are spot desmosomes that are holding the cells together. In the high magnification LM in A, the nuclei (N) are prominent. Recall that spot desmosomes are one component of the junctional complex, but they are also found outside junctional complexes where they connect epithelial cells to each other, especially in epithelia exposed to mechanical stress. The high magnification EM in B shows a region of interaction between two cells similar to those in A. The darkly stained, thickened areas of cell membrane are the dense plaques of spot desmosomes (D). Keratin filaments insert into these plaques and provide structural support by connecting desmosomes in different parts of the cell membrane. They also connect to hemidesmosomes (not shown) on the basal cell membrane that attach the cell to the basement membrane (BM). A nucleus and nuclear envelope can be seen at the right in B.