Endometrium. Light micrograph of a section through a healthy human endometrium, the mucosal lining of the uterus. This is the secretory stage, from the 15th-28th day of the menstrual cycle that follows ovulation (14th day). If, as in this case, a fertilised ovum has not implanted in the endometrium, then menstruation will occur at about the 28th day. The endometrium consists of a ciliated epithelium supported by a highly cellular connective tissue stroma containing many tubular glands. Under hormonal influences the endometrium undergoes regular cyclical changes so as to offer a suitable environment for implantation of a fertilised ovum. magnification unknown.