A closeup of the skin near my knuckle.
Photo by Matthew T. Ross

The skin of animals is an incredibly complicated structure containing many layers of tissue. Skin contains hair follicles, sweat glands, sensory cells, and all sorts of other structures. The most important properties of skin is that it is tough and yet flexible. The stretchiness comes from collagen fibers in the dermis (the lower tissue layer of the skin). Alternating areas of thicker and thinner skin also help to make the skin flexible. 

Above you can see an image of my knuckle. The larger grooves help with flexibility and prevent too much skin from bunching up at joints (such as a knuckle). The lines on your hand are a great example of this. The lines on your hands show up at about week 12 of gestation.

Wrinkling due to aging seems to be largely caused by fragmentation of collagen proteins. Xia et al. published a paper this year (2015) looking at what causes collagen fragmentation in a mouse model of aging. You can find that paper here:

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Matthew is a neuroscientist investigating vocal motor processing, focusing on how the brain changes during development, but is passionate about all things science. He loves art and photography, producing his own digital artwork inspired by science and anatomy. Matthew also plays guitar and piano and has recorded several albums. You can find more of his projects at his website:

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