Internal wall of uterus. Coloured scanning electron micrograph of the mucosa, also known as endometrium, lining the body of the human uterus. The endometrium consists of simple columnar cells of two types: ciliated (not seen) and secretory (seen). Secretory cells are characterised by a great number of microvilli (tiny projections) on their surfaces. These cells secrete glyco-proteinic material, which is useful in protecting the uterine mucosa.