The chemicals that are included in this sack of salt water (the body is two thirds water) are really few in the number as to the types that are needed to build and maintain this body. There are only four main chemicals; hydrogen, carbon, oxygen, and nitrogen.
Hydrogen is the most abundant element in the whole universe. It powers the stars, including our own sun some 93 million miles away. It is thought to be the very first element created, and our bodies seem to need it to operate. For that matter, all plant and animal matter is composed of compounds with oxygen, carbon, nitrogen, sulfur, and a few other elements. Our bodies are approximately 10% hydrogen by mass. This hydrogen is combined with oxygen to make up the very water that we carry around with us everyday. The hydrogen atom forms special bridges between its self and other atoms called a "hydrogen bond". These hydrogen bonds are important in biological systems providing a way for chemicals such as oxygen and nitrogen to share space and to organize themselves into useful molecules know as proteins. Thus the structure and hence the properties of proteins depend on the existence of hydrogen bonds.
Carbon is the second most abundant element in the human body. (oxygen is first) Like hydrogen, it occurs in all plant and animal tissues. The joining of one carbon atom to another carbon atom produces a strong chemical bond. The uniqueness of carbon stems from the fact that these carbon to carbon bonds remain strong when carbon is also combined with other chemicals. This is the bond that really holds us together.
Oxygen is the most abundant element. It forms compounds with all other elements except some rare gases. It is by far the most abundant element in the earth's crust on the basis of both mass and number of total atoms. On a number basis, oxygen atoms are more numerous than all other kinds of atoms combined. It is a good thing since the air we breath is 20% oxygen by volume. The most import compound is the water molecule which all the other chemicals that reside in our bodies swim around. The water molecule is held together by the hydrogen bond, imagine that.
Nitrogen is about one-third as abundant as carbon. In plants and animals nitrogen is found combined in the form of proteins, which average in composition 51% carbon, 25% oxygen, 16% nitrogen, and 7% hydrogen. It has the ability if needed to form triple bonds.
So there you have it, the chemical cocktail that when combined in the right way holds us together. The blueprint for this cocktail is held in DNA.