Why are some minerals, such as copper, only needed in small amounts in your diet? they can be found in so many different foods. they only with one body function. large amounts of the mineral can cause death. they are not used by the body on a daily basis.

Mineral elements have two general body functions - building and regulating. There are two groups of minerals in the human body: macrominerals and trace minerals.
Macrominerals are minerals that are present in relatively large amounts in the body and are required in fairly large amounts in the diet. trace minerals on the other hand are minerals needed in the body in small amounts (iron, manganese, copper, iodine, zinc, cobalt, flour-ine, selenium, and several others). Large amount of these minerals can cause death. 
Taking too much of one essential mineral may upset the balance and function of other minerals in the body

the glands which are associated with each description is given below:

pancreas - is an endocrine and exocrine gland that secretes juices with enzymes for digestion. salivary glands- with protection and digestion in the mouth. liver- secretes bile for digestion.   lachrymal glands - secrete tears to moisten eyes and protect them from particles and infection.   sweat gland -regulates water, salt, and temperature. oil glands - to form a protective barrier on the skin.   goblet cells - secrete mucus for protection.