After ovulation, if pregnancy does not occur within 10 to 12 days, the corpus luteum degrades into the:

1. After ovulation, the luteinized remains of the follicle become the corpus luteum, secreting progesterone. 2. If no embryo implants and sends a survival signal, the corpus luteum has a limited lifespan. 3. Within 10 to 12 days without pregnancy, it stops secreting progesterone. 4. It then degrades into a nonfunctional structure named the corpus albicans (a 'whitish body'), not the corpus spongiosum, which is unrelated penile erectile tissue. 5. So corpus albicans is correct. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 27 "The Reproductive System", p.1299 §Hormonal Control of the Ovarian Cycle_