Calcium homeostasis ：骨中鈣與血液中鈣存在著平衡

盡管大多數鈣在骨頭中，但這個平衡仍然存在

Bone helps to buffer the ph level of the blood

calcium is release from bone and deposited into blood when the blood ph level falls

calcium is deposited into bone from blood when the blood ph level rises

如果缺，總是要想一下：鈣是不是被偷走了，跑到血液中了