Re: Horning in

["David Marjanovic" <david.marjanovic@gmx.at>]

> Technically, the skin of many (most?) creatures is covered in a thin
> layer of keratin to help prevent pathogens from entering the body.

Keratin is an important component of skin cells; in tetrapods or amniotes,
whose skin contains dead layers of cells at the outside, the cells produce
more and more keratin until they die. This keeps the skin somewhat
waterproof and resistant. -- If I've understood the lecture Introduction to
Cell Biology correctly, then keratin is a component of the cytoskeleton of
many or all eukaryotic cells. (That wasn't asked in the exam. :o) )

Interestingly, bacterial spores, too, are covered with a thick layer of
keratin.

> Perhaps nails and hair (and feathers?) are also decended ultimately from
> skin keratin?

Of course. :-)