What is the connection between the liver (organ), UV radiation (sunlight), and bone tissue

The answer to this question would be: vitamin D

The UV is needed by the skin to make previtamin D3. Previtamin D3 or cholecalciferol made from the skin will be changed in the liver into 25 - hydroxyvitamin D3 and then sent to the kidney to be changed into 1,25 - dihydroxyvitamin D3. The last change in the kidney will active the vitamin D. Vitamin D has a role in the calcium absorption which was will strengthen the bone tissue.