The x-axis is 'Age in years' going from 10 to 90 in increments of 10. The y-axis is 'Bone mass in grams' going from 0 to 1500 in increments of 500.
In female, the bone mass increases from 500 to 1100 grams until 30 years and then gradually decreases with age. In male, the bone mass increases from 500 to 1400 grams until 30 years and then remains steady until 50 years and then starts decreasing with age.