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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 common contaminants without function (examples: caesium, titanium), while many others are thought to be active toxins, depending on amount (cadmium, mercury, lead, radioactives).
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 .
When arranged this way, each entity is three things at the same time: It is made up of parts from the previous level below. It is a whole in its own right. And it is a part of the whole that is on the next level above. Typical examples include life emerging from non-living substances, and consciousness emerging from nervous systems.
This article contains a list of organs in the human body. It is widely believed that there are 79 organs (this number goes up if you count each bone and muscle as an organ on their own, which is becoming a more common practice [1] [2]); however, there is no universal standard definition of what constitutes an organ, and some tissue groups' status as one is debated. [3]
Dunbar's number has become of interest in anthropology, evolutionary psychology, [12] statistics, and business management.For example, developers of social software are interested in it, as they need to know the size of social networks their software needs to take into account; and in the modern military, operational psychologists seek such data to support or refute policies related to ...
Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its beginnings in prehistoric times. [ 2 ] Anatomy is inherently tied to developmental biology , embryology , comparative anatomy , evolutionary biology , and phylogeny , [ 3 ] as these are the processes by which ...
The history of anatomy has been characterized, over a long period of time, by a continually developing understanding of the functions of organs and structures in the body. Methods have also advanced dramatically, advancing from examination of animals through dissection of fresh and preserved cadavers (dead human bodies) to technologically ...
Each level in the hierarchy represents an increase in organisational complexity, with each "object" being primarily composed of the previous level's basic unit. [2] The basic principle behind the organisation is the concept of emergence —the properties and functions found at a hierarchical level are not present and irrelevant at the lower levels.