In this video, we're going to talk about the key features of the 4th epidermal cell layer in our lesson, which is the stratum lucidum, also known as the clear layer. This is a protective epidermal layer that is only present in thick skin, such as the skin on the palms of our hands and the soles of our feet, which have to encounter a lot of friction since we're constantly grabbing things, and our feet are constantly walking on floors. Evolutionarily, the thick skin has evolved to have this extra layer, this stratum lucidum. However, the stratum lucidum, or the clear layer, is not present in thin skin, which makes up most of the skin on our body.
Most of the skin on our body does not have the stratum lucidum. The stratum lucidum, or the clear layer of thick skin, consists of these flattened, dead, densely packed, and transparent keratinocyte cells that actually lack organelles. Recall from our previous lesson video that the organelles are degraded in the previous epidermal cell layer, the stratum granulosum. Notice over here in this diagram, you can see the stratum lucidum, or the clear layer, as this relatively small layer of cells that are transparent. The lack of organelles in the cells of this layer contributes to its transparency, which is why it's also known as the clear layer.
Now, notice here we have an image from the analogy from our previous lesson videos. We know that the keratinocyte, unfortunately, is going to be dead here, and lifeless Kerrie is locked in this thick coffin that you can see here, which is going to remind us of the stratum lucidum. You can see that there are these photographs of the previous epidermal cell layers, including the stratum granulosum, stratum spinosum, and the stratum basale. This here concludes our brief lesson on the stratum lucidum, or the clear layer. As cells divide, these cells are going to continuously get pushed up into more superficial layers.
The final superficial layer is the stratum corneum, and we'll talk about that layer in our next video. So, I'll see you all there.