Reproductive cycle graph - Luteal phase | NCLEX-RN | Khan Academy

Summary

This video explains the female reproductive cycle, focusing on the luteal phase and the role of hormones like progesterone and estrogen. After ovulation, the corpus luteum forms, producing progesterone to prepare the uterine lining for a potential pregnancy. If pregnancy occurs, the embryo's HCG hormone keeps the corpus luteum alive, preventing menstruation. However, if no pregnancy occurs, the corpus luteum deteriorates, leading to a drop in progesterone and estrogen, which triggers menstruation and restarts the cycle. The process is outlined with key hormonal interactions and the importance of the uterine environment for implantation.

Takeaways

• 😀 The follicular phase focuses on stimulating follicle growth in the ovaries, leading to ovulation.
• 😀 Hormones such as FSH, LH, and estrogen are crucial for the stimulation of follicular growth during the follicular phase.
• 😀 The luteal phase follows ovulation and is characterized by the development of the corpus luteum.
• 😀 The corpus luteum produces progesterone and a small amount of estrogen to support pregnancy if fertilization occurs.
• 😀 Progesterone plays a key role in preparing the uterine lining (endometrium) for potential implantation of a fertilized egg.
• 😀 The corpus luteum's progesterone also helps to maintain a hospitable environment by reducing uterine muscle contractions.
• 😀 If pregnancy does not occur, the corpus luteum withers away, leading to a drop in estrogen and progesterone levels.
• 😀 The drop in hormones triggers menstruation and the start of the next menstrual cycle.
• 😀 If pregnancy occurs, the embryo produces HCG, which keeps the corpus luteum alive, continuing the production of progesterone and estrogen.
• 😀 In pregnancy, the placenta eventually takes over progesterone production after 2-3 months, and menstruation does not occur.

Q & A

What is the follicular phase and what is its main purpose?

The follicular phase is the first part of the menstrual cycle, focused on stimulating the growth of follicles in the ovaries. The main purpose is to prepare the body for ovulation by increasing the levels of hormones like FSH, LH, and estrogen.

What happens during the luteal phase after ovulation?

The luteal phase begins after ovulation and is characterized by the formation of the corpus luteum, a yellow structure that forms from the remnants of the follicle. This structure produces progesterone to support potential pregnancy and prepare the endometrium for implantation.

What role does the corpus luteum play in the menstrual cycle?

The corpus luteum produces progesterone and a small amount of estrogen after ovulation. Progesterone supports the uterine lining for implantation and gestation. If no pregnancy occurs, the corpus luteum degenerates, leading to a drop in hormone levels, which triggers menstruation.

How does progesterone contribute to the menstrual cycle?

Progesterone is a pro-gestation hormone that helps prepare the endometrium for potential implantation by increasing blood flow, promoting secretion from endometrial glands, and reducing uterine muscle contractions to prevent premature expulsion of a fertilized egg.

What causes menstruation to occur?

Menstruation occurs when the corpus luteum degenerates, leading to a drop in progesterone and estrogen levels. This drop signals the end of the luteal phase and the beginning of a new follicular phase, causing the shedding of the endometrial lining.

Why is the hormone inhibin produced by the corpus luteum?

Inhibin is produced by the corpus luteum to suppress the production of FSH from the anterior pituitary. This negative feedback mechanism helps regulate the menstrual cycle and prevent the development of new follicles during the luteal phase.

What happens when pregnancy occurs in the menstrual cycle?

When pregnancy occurs, the embryo produces human chorionic gonadotropin (HCG), which keeps the corpus luteum alive. This allows the corpus luteum to continue producing progesterone, maintaining the endometrial lining to support the pregnancy.

How does HCG influence the corpus luteum during pregnancy?

HCG, produced by the embryo, is structurally similar to LH, and it acts to preserve the corpus luteum by preventing it from atrophying. This ensures continued production of progesterone, which is necessary to maintain the uterine lining for pregnancy.

How long does the corpus luteum continue producing progesterone during pregnancy?

The corpus luteum produces progesterone for the first two to three months of pregnancy. After this period, the placenta takes over as the main producer of progesterone to maintain the pregnancy.

What is the significance of the menstrual cycle being 'put on hold' during pregnancy?

During pregnancy, the menstrual cycle is effectively put on hold because menstruation does not occur. This is due to the continued maintenance of the uterine lining by progesterone and estrogen, produced by the corpus luteum (early in pregnancy) and then the placenta.