In post-ovulatory phase thickness of endometrium is because of

In mammals an endocrine gland that develops in the ovary at the site of the Graafian follicle after rupture of the follicle wall and discharge of the ovum (ovulation); it consists of altered follicular (so-called lutein) cells. If pregnancy does not follow ovulation, the corpus luteum degenerates within one or two weeks (periodic, or menstrual, corpus luteum) ; if, however, the ovum is feilized and pregnancy begins, the corpus luteum grows very rapidly (corpus luteum of pregnancy) and is retained throughout the greater pa of pregnancy, secreting the hormone progesterone, which is necessary for the maintenance and development of the pregnancy.Ref: Ganong&;s review of medical physiology; 24th edition; page no:-401