title: An estimation of the number of cells in the human body.
abstract: BACKGROUND
  All living organisms are made of individual and identifiable cells, whose number, together with their size and type, ultimately defines the structure and functions of an organism. While the total cell number of lower organisms is often known, it has not yet been defined in higher organisms. In particular, the reported total cell number of a human being ranges between 10(12) and 10(16) and it is widely mentioned without a proper reference.
  
  
  OBJECTIVE
  To study and discuss the theoretical issue of the total number of cells that compose the standard human adult organism.
  
  
  METHODS
  A systematic calculation of the total cell number of the whole human body and of the single organs was carried out using bibliographical and/or mathematical approaches.
  
  
  RESULTS
  A current estimation of human total cell number calculated for a variety of organs and cell types is presented. These partial data correspond to a total number of 3.72 × 10(13).
  
  
  CONCLUSIONS
  Knowing the total cell number of the human body as well as of individual organs is important from a cultural, biological, medical and comparative modelling point of view. The presented cell count could be a starting point for a common effort to complete the total calculation.
authors.affiliation: Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna , Bologna , Italy .
authors.forename: Eva
authors.initials: E
authors.lastname: Bianconi
authors.forename: Allison
authors.initials: A
authors.lastname: Piovesan
authors.forename: Federica
authors.initials: F
authors.lastname: Facchin
authors.forename: Alina
authors.initials: A
authors.lastname: Beraudi
authors.forename: Raffaella
authors.initials: R
authors.lastname: Casadei
authors.forename: Flavia
authors.initials: F
authors.lastname: Frabetti
authors.forename: Lorenza
authors.initials: L
authors.lastname: Vitale
authors.forename: Maria Chiara
authors.initials: MC
authors.lastname: Pelleri
authors.forename: Simone
authors.initials: S
authors.lastname: Tassani
authors.forename: Francesco
authors.initials: F
authors.lastname: Piva
authors.forename: Soledad
authors.initials: S
authors.lastname: Perez-Amodio
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Strippoli
authors.forename: Silvia
authors.initials: S
authors.lastname: Canaider
mesh_terms: D000328:Adult; D002452:Cell Count; D048429:Cell Size; D006801:Humans; D008954:Models, Biological; D009928:Organ Specificity