Dermis of young vs old skin

A graphic from my book Skintelligent: What you really need to know to get great skin:

How the dermis ages:
Collagen - Collagen makes up more than 90% of the dry weight of human skin. It plays a central role in virtually all anti-ageing and skin rejuvenation treatments touted by big skin care. But what actually is collagen and what does it do for the skin?

As we age, the collagen in our dermis becomes stiffer and more resistant to being broken down. This is a bit of an odd finding because we generally think of old skin as loose and saggy. So what is going on here?
In simple terms, healthy young collagen is arranged in a neat, tidy network in the dermis, but as we age this network becomes disorganised and messy - resulting in decreased skin tension and changes in the way the skin looks.

I hope this helps, albeit it is a brief explanation - I explain in more detail in my book, and have a whole section called ' How Skin Changes When We Age'.