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The elemental composition of the human body can be looked at from the point of view of either mass composition, or atomic composition. To illustrate both views, the adult human body is ~53% water, and water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent. Thus, most of the mass of the human body is oxygen, but most of the atoms in the human body are hydrogen atoms. Both mass-composition and atomic composition figures are given below (see chart at right). Body composition may also be analyzed in terms of molecular type (e.g., water, protein, connective tissue, fats (or lipids) apatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, muscle, bone, etc. In terms of cell type, the body contains hundreds of different types of cells, but notably, the largest number of cells contained in a human body (though not the largest mass of cells) are not human cells, but consist of bacteria (bacterial cells) residing in the normal human gastrointestinal tract. Major, minor and trace elements Almost 99% of the mass of the human body is made up of the six elements oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about % is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium. All are necessary to life. The remaining elements are trace elements, of which more than a dozen are thought to be necessary for life, or play a role in good health (e.g., fluorine, which hardens dental enamel but seems to have no other function). An easy way to remember some elements is “CHONPS“ (carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.) Other elements and questionable human-required elements Not all elements which are found in the human body in trace quantities play a role in life. Some of these elements are thought to be simple bystander contaminants without function (examples: caesium, titanium), while many others are thought to be active toxins, depending on amount (cadmium, mercury, radioactives). The possible utility and toxicity of a few elements at levels normally found in the body (aluminum) is debated. Functions have been proposed for trace amounts of cadmium and lead, although these are almost certainly toxic in amounts very much larger than normally found in the body. There is evidence that arsenic, an element normally considered a toxin in higher amounts, is essential in ultratrace quantities, even in mammalian. Some elements that are clearly used in lower organisms and plants (arsenic, silicon, boron, nickel, vanadium) are probably needed by mammals also, but in far smaller doses. Two halogens used abundantly by some (though not all) lower organisms (fluorine and bromine) are presently known to be used by mammals only opportunistically (i.e. they are used actively when present, but when absent, do not cause diseases or severe health problems). Elemental composition list Main article: Dietary mineral The average 70 kg adult human body contains approximately 3 x 1027 atoms and contains at least detectable traces of 60 chemical elements. About 25 of these elements are thought to play an active positive role in life and health in humans. The relative amounts of each element vary by individual, with the largest contributor due to fat/muscle/bone body composition ratio differences from person to person. The numbers in the table are averages of different numbers reported by different references. The adult human body averages ~63% water. This varies substantially by age, sex, and adiposity. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ±6% for females and 58 ±8% water for males. Water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent, and these numbers along with the complementary % numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures. Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom-fraction than any element. #elementalCompositionOfTheHumanBody #phenotype #genomics #whatIsTheBodyMadeOf #majorElementsInTheHumanBody #traceElementsInTheHumanBody #tableOfElements #atomicNumber #atomicMass #whatAreIsotopes #percentageOfBodyWeightOfEachElement #majorAndTraceElementsInTheBody #majorElementsPresentInTheHumanBody #majorElementsFoundInTheHumanBody #whatIsTheHumanBodyMadeOf #whatIsTheBodyMadeOfInPercentages #humanBodyComposition
