The prostate consists of glandular and connective tissue. Tall column-shaped cells form the lining (the epithelium) of the glands. These form one layer or may be pseudostratified. The epithelium is highly variable and areas of low cuboidal or flat cells can also be present, with transitional epithelium in the outer regions of the longer ducts. The glands are formed as many follicles, which in drain into canals and subsequently 12–20 main ducts, These in turn drain into the urethra as it passes through the prostate. There are also a small amount of flat cells, which sit next to the basement membranes of glands, and act as stem cells.