This file is from Wikimedia Commons and may be used by other projects.
The description on its file description page there is shown below.
Summary
DescriptionCalcium balance 2.jpg
English: Calcium balance in the human body, showing the movement of calcium ions from the plasma (central square) in and out of the various body compartments. The red arrows are roughly in proportion to the quantities moved in and out of the plasma per day. The influence of the various hormones (indicated by means of narrow arrows with + and - signs near their target organs) indicate the effects of high plasma concentrations of these hormones. Low concentrations have the opposite effect.
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.