Osteoclasts then become more active without estrogen, and your body breaks down more bone. Certain medical conditions and some medications can speed up the process of osteoporosis. This is called secondary osteoporosis.
The phylum Porifera ("pore-bearing") consists of approximately 5,000 species of sponges. These asymmetrical animals have sac-like bodies that lack tissues, and are usually interpreted as representing the cellular level of evolution