Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The menstrual cycle is the reproductive cycle in female primates (e.g., monkeys, apes, and human beings), starting at puberty (menarche) and ending at years of age (menopause).
Menstrual Phase: Lasts for days; occurs when fertilization does not take place, leading to the breakdown of the endometrial lining and its blood vessels.
Follicular (Proliferative) Phase: Under the influence of (Follicle Stimulating Hormone) and (Luteinizing Hormone), primary follicles grow into mature Graafian follicles, and the endometrium regenerates through proliferation.
Ovulatory Phase: Both and reach a peak level in the middle of the cycle (about day). Rapid secretion of leading to its maximum level during the mid-cycle is called surge, which induces the rupture of the Graafian follicle to release the ovum (secondary oocyte).
Luteal (Secretory) Phase: The remaining parts of the Graafian follicle transform into the . It secretes large amounts of Progesterone, which is essential for the maintenance of the endometrium for implantation.
In the absence of fertilization, the degenerates into , leading to the disintegration of the endometrium and the start of a new cycle.
📐Formulae
💡Examples
Problem 1:
If a healthy human female has a menstrual cycle consisting of days, on which day is ovulation expected to occur?
Solution:
The luteal phase is generally constant at days. Therefore, the ovulation day is calculated as .
Explanation:
Ovulation occurs days before the onset of the next menstruation, regardless of the total cycle length. In a -day cycle, the ovulation occurs on the day.
Problem 2:
Explain the hormonal status when fertilization does not occur.
Solution:
Explanation:
Without the stimulus of (Human Chorionic Gonadotropin) from a developing embryo, the cannot be maintained. As it degenerates, progesterone levels drop sharply, causing the endometrium to shed.