Problem 18 - Anatomy and Physiology of Animals

Question

18\. Progesterone secreted by the placenta suppresses _________ to prevent maturation of ovarian follicles. a. \(\mathrm{LH}\) and estrogen b. \(\quad \mathrm{hCG}\) and \(\mathrm{FSH}\) c. FSH and LH d. estrogen and hCG

Step-by-Step Solution

Answer

Progesterone suppresses FSH and LH.

Step 1: Understand the physiological role of progesterone

Progesterone is a hormone that plays a key role in maintaining pregnancy. It is secreted by the placenta to suppress the maturation of new ovarian follicles during pregnancy.

Step 2: Identify the hormones involved in follicle maturation

Follicle maturation in the ovaries is primarily stimulated by the hormones FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone). These hormones are responsible for the growth and development of ovarian follicles.

Step 3: Link hormone suppression to progesterone

Since progesterone is secreted to prevent new follicles from maturing, it suppresses the actions of the hormones responsible for stimulating follicle growth, which are FSH and LH.

Step 4: Select the correct answer

Given that progesterone suppresses FSH and LH to prevent follicle maturation, the correct answer from the provided options is c. FSH and LH.

Key Concepts

Follicle maturation

Follicle maturation is a crucial process in the female reproductive cycle. It begins within the ovaries, where immature follicles undergo several stages of growth until a mature egg is released during ovulation. This maturation is not only essential for fertility but is also key to regulating the menstrual cycle. Within the ovaries, several follicles begin to develop, but typically only one reaches full maturity in each cycle. The entire maturation process is tightly regulated by various hormones and ends with the dominant follicle releasing an egg, ready for fertilization. Follicle maturation is critical for a successful reproductive process as it sets the stage for possible conception.

FSH (Follicle Stimulating Hormone)

FSH, or Follicle Stimulating Hormone, is one of the primary hormones involved in the maturation of ovarian follicles. It is produced by the pituitary gland, a small but powerful gland located at the base of the brain. FSH stimulates the growth of ovarian follicles in the ovary before the release of an egg in the process of ovulation. This hormone plays a crucial role at the beginning of the menstrual cycle, signalling the ovaries to prepare follicles for maturation.

• FSH levels rise at the start of the menstrual cycle.
• It promotes the growth of one or more follicles within the ovaries.

As follicles develop, they also produce estrogen, which in turn influences the body to prepare for the possible fertilization of the mature egg. Balancing FSH within the body is key, as both low and excessively high levels can impact fertility.

LH (Luteinizing Hormone)

Luteinizing Hormone, often abbreviated as LH, is another critical hormone in the reproductive system. Like FSH, it is also produced by the pituitary gland and plays a vital role in the reproductive cycle. LH is particularly important in the latter stages of follicle maturation. After FSH has stimulated the growth and development of the ovarian follicles, LH works to trigger ovulation — the process where a mature egg is released from the dominant follicle. This hormone surge, known as the "LH surge," is what typically prompts ovulation.

• The LH surge usually occurs midway through the menstrual cycle.
• It causes the final maturation of the egg before ovulation.

Following ovulation, LH supports the transformation of the ruptured follicle into the corpus luteum, which then secretes hormones such as progesterone to support potential pregnancy. Therefore, LH is not just integral to ovulation but also to the subsequent phases if fertilization occurs.