Dense granules (also known as dense bodies or delta granules) are specialized secretory organelles. Dense granules are found only in platelets and are smaller than alpha granules|. The origin of these dense granules is still unknown, however, it is thought that may come from the mechanism involving the endocytotic pathway. Dense granules are a sub group of lysosome-related organelles (LRO). There are about three to eight of these in a normal human platelet.