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Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm. About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium ...
Most biomolecules are organic compounds, and just four elements—oxygen, carbon, hydrogen, and nitrogen—make up 96% of the human body's mass. But many other elements, such as the various biometals, are also present in small amounts.
Parts-per-million cube of relative abundance by mass of elements in an average adult human down to 1 ppm. By mass, human cells consist of 65–90% water (H 2 O), and a significant portion of the remainder is composed of carbon-containing organic molecules. Oxygen therefore contributes a majority of a human body's mass, followed by carbon.
For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element. Atoms are extremely small, typically around 100 picometers across. A human hair is about a million carbon atoms wide.
Biological organisation is the organisation of complex biological structures and systems that define life using a reductionistic approach. [1] The traditional hierarchy, as detailed below, extends from atoms to biospheres. The higher levels of this scheme are often referred to as an ecological organisation concept, or as the field, hierarchical ...
The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems . The external human body consists of a head , hair , neck , torso (which includes the thorax and abdomen ), genitals , arms , hands , legs , and feet .
Human biology also encompasses all those organisms that live on or in the human body. Such organisms range from parasitic insects such as fleas and ticks, parasitic helminths such as liver flukes through to bacterial and viral pathogens. Many of the organisms associated with human biology are the specialised biome in the large intestine and the ...
Phenomenal anatomical observations of the human body were made, which contributed to the understanding of the brain, eye, liver, reproductive organs, and nervous system. The Hellenistic Egyptian city of Alexandria was the stepping-stone for Greek anatomy and physiology.