[#3] OVÁRIOS: CICLO MENSTRUAL (CICLO UTERINO) | MK Fisiologia

Summary

This video explains the hormonal regulation of the uterine cycle, focusing on the endometrium's cyclical changes. It details the three phases: menstrual, proliferative, and secretory. The menstrual phase begins with the shedding of the endometrial lining due to hormone level drops. In the proliferative phase, estrogen promotes cell proliferation to regenerate the endometrium. The secretory phase is marked by progesterone stimulating gland secretion, preparing the endometrium for potential embryo implantation. The video also explores the roles of estrogen and progesterone in other reproductive structures, helping to understand their broader impact on fertility and pregnancy.

Takeaways

• 😀 The menstrual cycle is regulated by hormonal changes in both the ovaries and the uterus.
• 😀 The uterine cycle involves three phases: menstrual, proliferative, and secretory, which are influenced by ovarian hormonal fluctuations.
• 😀 The menstrual phase begins with the shedding of the endometrium, triggered by a drop in progesterone and estrogen levels.
• 😀 During the proliferative phase, estrogen stimulates the regeneration of the endometrial lining, preparing it for potential implantation.
• 😀 Estrogen also increases the number of progesterone receptors in the endometrium, setting the stage for the secretory phase.
• 😀 The secretory phase is marked by high progesterone levels, which prepare the endometrium for embryo implantation by stimulating glandular secretion and vascular changes.
• 😀 If fertilization does not occur, progesterone levels drop, causing vasoconstriction, which leads to the shedding of the endometrium and the onset of menstruation.
• 😀 Menstruation typically lasts 3 to 5 days in a 28-day cycle and involves a small loss of blood (about 30 ml).
• 😀 Prostaglandins, which are produced during menstruation, cause uterine contractions and are responsible for menstrual cramps.
• 😀 Estrogen and progesterone also influence other parts of the reproductive system, including the fallopian tubes, uterine muscles, and cervix, to optimize conditions for fertilization and implantation.
• 😀 Estrogen dominates before ovulation, facilitating fertilization, while progesterone takes over after ovulation to support pregnancy or the preparation for the next cycle.

Q & A

What is the main focus of the video script?

The video script primarily focuses on explaining the hormonal regulation of the uterine cycle, specifically the changes that occur in the endometrium, as opposed to the ovarian cycle which was discussed in a previous video.

What are the three layers of the uterus and their functions?

The uterus is composed of three layers: the endometrium (the innermost layer, which undergoes cyclic changes and is where embryo implantation occurs), the myometrium (a muscular middle layer), and the perimetrium (the outer connective tissue layer).

How is the uterine cycle divided and what are its phases?

The uterine cycle is divided into three phases: the menstrual phase (marked by the shedding of the endometrium), the proliferative phase (characterized by the rebuilding of the endometrium), and the secretory phase (when the endometrium prepares for potential embryo implantation).

What hormonal changes trigger the start of the menstrual phase?

The menstrual phase begins when there is a sharp decline in progesterone, estrogen, and inhibin levels, which occurs when the corpus luteum regresses at the end of the ovarian luteal phase, leading to the shedding of the functional layer of the endometrium.

How does estrogen affect the endometrium during the proliferative phase?

During the proliferative phase, estrogen promotes the proliferation of stromal and epithelial cells in the basal zone of the endometrium, which restores the lost tissue from menstruation and prepares the endometrium for potential implantation.

What role does progesterone play in the secretory phase of the uterine cycle?

Progesterone is the dominant hormone during the secretory phase. It stimulates the secretion of nutrients like glycogen from the uterine glands, increases blood flow to the endometrium through spiral arteries, and prepares the endometrium for embryo implantation.

What happens if the egg is not fertilized during the secretory phase?

If the egg is not fertilized, the corpus luteum regresses, leading to a sharp decrease in progesterone levels. This triggers the release of enzymes and inflammatory substances, leading to the breakdown of the functional layer of the endometrium, causing menstruation.

Why do women experience menstrual cramps?

Menstrual cramps are caused by the contraction of the uterine muscles due to the action of prostaglandins, which are released in response to hormonal changes during menstruation. These contractions help expel the blood and tissue from the endometrium.

What is the role of the spiral arteries in the endometrium during the secretory phase?

During the secretory phase, progesterone induces the spiral arteries in the functional layer of the endometrium to become more tortuous, facilitating increased blood supply, which provides essential nutrients and oxygen to the potential embryo.

How do estrogen and progesterone affect the other organs of the female reproductive system?

Estrogen and progesterone influence various organs outside the uterus. Estrogen promotes actions that aid in fertilization, such as stimulating nutrient-rich mucus secretion in the fallopian tubes, whereas progesterone supports implantation and pregnancy maintenance by modifying the cervix and uterus.