optic disc, the small blind spot on the surface of the retina, located about 3 mm to the nasal side of the macula. It is the point where the fibers of the retina leave the eye and become part of the optic nerve.
Adult stem cells are found in many organs and tissues, including the skin. In fact, human skin is the largest repository of adult stem cells in the body. Skin stem cells reside in the basal layer of the epidermis where they remain dormant until they are activated by tissue injury or disease. 1.
There are 3 main types of cells in the top layer of the skin (called the epidermis): 1  Squamous cells: These are flat cells in the outer part of the epidermis that are constantly shed as new ones form. 2  Basal cells: These cells are in the lower part of the epidermis, called the basal cell layer.