On the other hand, osteoclasts are those cells in the bone that resorb the bone. They break down the bone by breaking down the bone matrix and releasing the calcium and the phosphate ions into our blood. So what our parathyroid hormone does is it increases the activity of osteoclast, meaning it increases the rate of resorption of bone. So we break down more bone matrix and we release more calcium into our blood, thereby increasing the concentration of calcium in our blood. Now, the parathyroid hormone also actually affects our kidneys, so it increases the amount of calcium that is reabsorbed by our kidneys, and this increases the concentration of calcium in our blood and decreases the amount of calcium found in our urine. Now, it also affects our intestines.