Explain why a person who is wheelchair-bound or bed-bound often has very low bone mass, especially in his or her legs.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. Parathyroid hormone increases the blood calcium ion concentration by increasing the activity of osteoblasts.

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

f. Vitamin D is required for calcium ion absorption from the intestines and retention in the kidneys.

Which of the following influences bone remodeling?

a. Vitamins such as vitamins D, C, and K

b. Intake of calcium ions

c. Hormones such as estrogen and testosterone

d. All of the above

Correctly order the following steps of fracture repair, placing a 1 by the first step, a 2 by the second step, and so on.          

____Osteoblasts in the periosteum lay down a bone callus of primary bone.          

____Damaged blood vessels bleed and fill the gap between the bone fragments with a hematoma.          

____The bone callus is remodeled and replaced with secondary bone.          

____Fibroblasts, chondroblasts, and blood vessels enter the clot, and the soft callus begins to bridge the gap between bone fragments.

How could diseases of the kidney, skin, and/or intestines cause diseases of the bone?

How could a disease that affects primarily cartilage impact bone growth and bone formation?

Explain why young men who take anabolic steroids (which mimic the actions of testosterone) often display stunted growth and have an overall shorter stature.

Lucy Dupre is a 2-year-old girl living in northern Canada. You notice that her growth seems abnormally slow and she has exhibited signs of weakened bones, including fractures. Her parents admit they have not supplemented her diet with vitamin D, as they feel that any supplementation is 'unnatural' and 'not organic.' Explain why Lucy is having problems with her bones and bone growth.