the yellow endocrine body, at least 1-1.5 cm in diameter, formed in the ovary at the site of a ruptured ovarian follicle immediately after ovulation; there is an early stage of proliferation and vascularization before full maturity; later, there is a festooned, bright-yellowish lutein zone traversed by trabeculae of theca interna containing numerous blood vessels; the corpus luteum secretes estrogen, as the follicle did, and also secretes progesterone. If pregnancy does not occur, the body is called a
corpus luteum spurium (corpus luteum of menstruation), which undergoes progressive retrogression to a corpus albicans. If pregnancy does occur, the body is called a
corpus luteum verum (corpus luteum of pregnancy), which increases in size, persisting to the fifth or sixth month of pregnancy before retrogression.