Histology of the endometrium and its layers?

The endometrium, the inner lining of the uterus, consists of two main layers: the functional layer (stratum functionale) and the basal layer (stratum basale). The functional layer is composed of columnar epithelial cells, uterine glands, and a rich supply of blood vessels, and it undergoes cyclical changes during the menstrual cycle, thickening in preparation for potential implantation. The basal layer remains constant and serves as the regenerative layer during the menstrual cycle, providing the foundation for the functional layer. Histologically, the endometrium exhibits distinct phases, including the proliferative, secretory, and menstrual phases, characterized by changes in glandular structure and vascularization.