Reproductive Physiology Part 3 Flashcards
(38 cards)
What is a primordial follicle composed of, and when is it formed?
• Composed of an oocyte arrested in prophase I of meiosis.
• Surrounded by a single layer of squamous granulosa cells.
• Formed before birth and remains dormant until recruited.
What characterizes the transition from a primordial to a primary follicle?
• Granulosa cells change from squamous to cuboidal.
• The zona pellucida, a glycoprotein layer, begins to form around the oocyte.
What are the key features of a secondary follicle?
• Multiple layers of granulosa cells.
• Theca cells begin to differentiate into:
• Theca interna (secretes androgens).
• Theca externa (connective tissue support).
• Increased vascular supply to support growth.
What defines a tertiary (antral) follicle?
• Presence of a fluid-filled antrum.
• Granulosa cells continue to proliferate and nourish the oocyte.
• Theca interna continues to produce androgens, which granulosa cells convert to estrogen via aromatase.
• Theca externa provides structural support.
What distinguishes a pre-ovulatory (Graafian) follicle?
• Contains a large antrum.
• Oocyte is surrounded by cumulus oophorus, a cluster of granulosa cells.
• This is the dominant follicle, selected from a cohort, and ready for ovulation.
What triggers ovulation, and what happens to the oocyte?
• A surge in luteinizing hormone (LH) from the pituitary triggers ovulation.
• The follicle ruptures, releasing the secondary oocyte, which is now arrested in metaphase II of meiosis.
What happens to follicles that are not selected as the dominant one?
• They undergo atresia, a process of programmed cell death.
• This ensures only the most viable follicle proceeds to ovulation.
What hormone initiates the follicular phase and what does it do?
• FSH (Follicle-Stimulating Hormone) promotes follicular growth by stimulating granulosa cells in developing follicles.
What hormone is secreted by granulosa cells during the follicular phase, and what is its role?
• Estrogen, secreted by granulosa cells, helps in proliferation of the endometrium and regulates the feedback on the hypothalamus and pituitary.
How does estrogen affect FSH and LH secretion during the follicular phase?
• Moderate estrogen exerts negative feedback on FSH.
• High estrogen near ovulation causes a positive feedback effect, triggering a surge in LH.
Q: What is the hormonal trigger for ovulation, and when does it occur?
• A surge in LH (luteinizing hormone) around day 14 causes ovulation — the release of the oocyte from the dominant follicle.
What happens to the oocyte during ovulation?
• The oocyte completes meiosis I and is released as a secondary oocyte, which enters meiosis II and arrests at metaphase II until fertilization.
What structure forms from the ruptured follicle after ovulation?
• The ruptured follicle becomes the corpus luteum during the luteal phase.
What hormones are secreted by the corpus luteum, and what is their function?
• Progesterone and estrogen are secreted to:
• Maintain the endometrial lining.
• Inhibit GnRH, FSH, and LH through negative feedback.
What happens if pregnancy does not occur during the luteal phase?
• The corpus luteum regresses, leading to a drop in progesterone and estrogen levels.
• This hormone decline triggers menstruation.
What gland produces cervical mucus, and what regulates its composition?
• Endocervical glands produce cervical mucus.
• Its composition is regulated by estrogen and progesterone levels throughout the menstrual cycle.
What are the characteristics of cervical mucus during the follicular phase under estrogen influence?
• Thin, watery, stretchy (Spinnbarkeit).
• High in volume and alkaline.
• Facilitates sperm transport and supports sperm viability.
Q: Why is estrogen-induced cervical mucus important for fertility?
• It creates a sperm-friendly environment, helping sperm survive and migrate through the cervix into the uterus and fallopian tubes.
How does cervical mucus change during the luteal phase under progesterone influence?
:
• Becomes thick, viscous, and scant.
• Less permeable to sperm, acting as a barrier.
• Also inhibits pathogens, helping prevent infection.
What is the physiological purpose of thick cervical mucus during the luteal phase?
• To protect the uterus from microbial invasion.
• To prevent additional sperm entry after ovulation when fertilization is no longer viable.
Where is the oocyte released during ovulation, and why is this significant?
• The oocyte is released into the peritoneal cavity, not directly into the fallopian tube.
• This means precise coordination by the fallopian tube is necessary for successful capture.
What role do the fimbriae of the fallopian tube play in ovum pickup?
• The fimbriae sweep over the ovary at ovulation to guide the oocyte into the infundibulum of the fallopian tube.
What mechanisms assist the movement of the oocyte into the fallopian tube?
• Ciliary beating of epithelial cells and smooth muscle contractions in the tube help draw the oocyte inward.
How is the oocyte transported through the fallopian tube?
• Ciliary movement and peristaltic muscular contractions propel the oocyte through the tube toward the uterus.
