The endocervical mucosa is about thick and lined with a single layer of columnar mucous cells. It contains numerous tubular mucous glands, which empty viscous alkaline mucus into the lumen. In contrast, the ectocervix is covered with nonkeratinized stratified squamous epithelium, which resembles the squamous epithelium lining the vagina. The junction between these two types of epithelia is called the squamocolumnar junction. Underlying both types of epithelium is a tough layer of collagen. The mucosa of the endocervix is not shed during menstruation. The cervix has more fibrous tissue, including collagen and elastin, than the rest of the uterus.