Basale: it is the deepest stratum. It has one layer of cells called keratinocytes, which are stem cells for the epidermis.
Spinosum: The keratinocytes in this layer have spiny shapes. They synthesize cytokeratin and lipids. In this layer, we can also find macrophages.
Granulosum: The keratinocytes of the previous layer ascend and synthesize keratohyalin, which is in granules. The keratohyalin helps to join keratin filaments. Also, the cells release the lipids synthesized in the previous layer, and they form a barrier that stops dehydration.
Lucidum: it is only on thick skin, like the one in the sole of the feet. The keratinocytes in this layer have expelled the nucleus and now are dead cells. The keratinocytes have a flat shape and form a thin layer.
Corneum: it is the most superficial layer. It is made of dead keratinocytes filled with keratin in their cytoplasm. It is a thick layer that suffers desquamation when new dead cells filled with keratin ascend from the previous layer.
At neuromuscular junctions, a neurotransmitter called as acetylcholine if found. Botulinum toxin inhibits the transmission of acetylcholine at the synaptic junctions. Botulin toxin acts at presynaptic junctions and blocks the release of acetylcholine, leading to paralysis.
