Each of the following is a function of the integumentary system, except
a) synthesis of vitamin c.
b) excretion of salts and wastes.
c) maintenance of body temperature.
d) protection of underlying tissue.
e) storage of nutrients.

A. Synthesis of vitamin C

Explanation:

Humans cannot synthesize vitamin C due to a mutation in gulonolactone oxidase gene that codes for a protein or enzyme needed for production of vitamin C. Since we cannot produce vitamin C ourselves we have to consume it from our diet such as green pepper, tomatoes and spinach.

Some animals due produce their own vitamin C by converting glucose into ascorbate but this is not achieved by the integumentary system, it is done by the kidney and liver.