Why do Fingers prune?
Dermatologists give many reasons for skin wrinkles. According to them, the outer layer of the skin called as epidermis is made up of unique type of cells called as keratinocytes. This type of cells comprise of a protein called as keratin. The keratinocytes have the tendency to reproduce at the lower region of the epidermal layer and make the old cells to reach out. While protruding out of the skin layer, the old cells are mostly dead half way out. The dead cells will lose their nuclei and leave out only the cell membrane made of lipids and proteins along with the keratin inside the cell. The membranes made up of lipids avoid water retention while the keratin in the cell tends to absorb more water.
When our skin is more exposed to water, the keratin present in our skin absorbs water. This makes the outer layer of the epidermis to swell by water absorption while the inner layers will remain intact. The inner layer cells do not increase in size. As there is no detachment between outer and inner layers, the outer cells will tend to surround the inner layer which is the cause for the formation of wrinkles. This process can be easily understood by using a fabric. A cloth is tightly bound to the fist for some time and its position is changed by loosening it later. As the surface area of the fabric increases, the wrinkles are seen on it due to its loosening. Similarly, the outer skin also increases the surface area by absorbing water. Hence, wrinkles are seen on it as only the outer layer increases in size.
The wrinkles mostly are observed in the finger tips only because the epidermal layer is dense in that region. As the epidermal layer is thicker, the presence of keratin also will be more in that and in turn the absorption of water will also be more. While the other part of the body will not have thick epidermis and cannot produce more wrinkles.