Milia are small, white cysts commonly seen around the cheeks. Overview. Milia are commonly found on the skin of people of all ages. They are formed when keratin (a substance produced by the skin) becomes entrapped beneath the outer layer of the skin, forming a tiny cyst. An individual milium (the singular of milia) is formed at the base of a hair follicle or sweat gland.
The basic first level structure of cortical bone are osteons. Trabecular bone is much more porous with porosity ranging anywhere from 50% to 90%. It is found in the end of long bones (see picture above), in vertebrae and in flat bones like the pelvis. Its basic first level structure is the trabeculae. III.
Microscope at 400X. The outlined area is a cross section of an osteon of compact bone. In three dimensions an osteon is cylindrical in shape. In the center of each osteon is the central canal, a space that houses blood vessels and nerves that supply bone. Concentric layers of bone cells (osteocytes) and bone matrix surround the central canal. Osteocytes occupy spaces (lacunae) in the bone matrix. Osteocytes maintain the bone matrix.