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Questions and Answers
What is the primary role of the ovarian suspensory ligament in regard to the ovary?
What initiates milk production in the mammary glands?
Which hormone is primarily responsible for the development of secondary male characteristics during puberty?
Which phase of the ovarian cycle involves the maturation of follicles?
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How are estrogens synthesized in females?
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What anatomical feature forms the expanded chambers close to the nipple in the mammary glands?
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What is the primary effect of testosterone in male fetuses?
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Which hormone is the most abundant estrogen in females?
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What event occurs during the follicular phase of the ovarian cycle?
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Which hormone primarily promotes follicular development during puberty?
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What role does progesterone play during the luteal phase of the menstrual cycle?
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How does increased progesterone affect the secretion of hormones from the hypothalamus?
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During which phase does the endometrium thicken in preparation for implantation?
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Which cells in the ovaries are primarily affected by FSH and LH?
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What happens to estrogen levels during childhood?
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How does inhibin influence FSH release from the anterior pituitary gland?
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What triggers menstruation in the ovarian cycle?
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Which hormones are primarily responsible for stimulating the proliferation of Granulosa cells during the follicular phase?
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What is the role of thecal cells during the late follicular phase?
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What happens to the endometrial layer when the spiral arteries constrict?
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What initiates the release of GRF, FSH, and LH at the beginning of the follicular phase?
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During which phase does the corpus luteum secrete estradiol and progesterone?
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How does estradiol affect the endometrium?
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What is the effect of high levels of progesterone and estrogen on GRF and FSH release during the follicular phase?
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Study Notes
Ovaries
- Produce immature oocytes (ova) through oogenesis.
- Release one egg each month (ovulation), traveling through uterine tubes towards the uterus.
- Produce and secrete female sex hormones, including estrogens and progesterone.
- Synthesize and release inhibin to regulate FSH activity.
Estrogen
- Low levels in childhood, increase rapidly during puberty.
- Estradiol is the main estrogen.
- Causes follicular development.
- Promotes development of secondary female sex characteristics:
- Breast development,
- Fat distribution changes, and
- Widening of hips.
- Increases growth hormone secretion during puberty, leading to increased bone growth.
Progesterone
- Thickens the endometrial layer of the uterus, preparing for a fertilized ovum.
- Acts on the hypothalamus to decrease GRF release and the anterior pituitary to decrease the release of FSH and LH.
- Suppresses uterine contractile activity during pregnancy.
- Promotes mammary gland development but suppresses lactation.
Regulation of Female Sex Hormones
- Similar to males, regulated by GRF (Gonadotropin-releasing hormone) secretion from the hypothalamus.
- GRF increases the release of FSH (Follicle-stimulating hormone) and LH (Luteinizing hormone) from the anterior pituitary gland.
- FSH and LH act on cells within the ovaries to regulate estrogen and progesterone synthesis and secretion.
- These cells include Granulosa cells, Thecal cells of ovarian follicles, and the Corpus luteum.
- Increased progesterone causes negative feedback on the release of GRF from the hypothalamus and FSH/LH from the anterior pituitary.
- Estrogen can have both positive and negative feedback effects on GRF, FSH, and LH release.
- Increased inhibin levels have negative feedback on the anterior pituitary gland to decrease FSH release.
Uterus
- Suspensory ligament extends from the ovary's lateral surface, passing the uterine tube's open end, reaching the pelvic wall.
- Contains the ovarian artery and vein, entering the ovary at the ovarian hilum (site of attachment to mesovarium).
Mammary Glands (Breasts)
- Produce and secrete milk for infant nourishment during initial months (lactation).
- Located in the subcutaneous tissue of the pectoral fat pad, close to chest skin.
- Consist of separate lobes, each containing secretory lobules draining into ducts.
- Lobular ducts merge into the lactiferous duct of each lobe, forming expanded chambers called lactiferous sinus near the nipple (where ducts open onto the body surface).
- The nipple is surrounded by the areola (reddish-brown skin), which is grainy due to large underlying sebaceous glands.
- Activated during pregnancy to produce milk.
Synthesis of Steroid Hormones
- Male and female sex hormones are steroid hormones (lipid-soluble), meaning they can cross cell membranes.
- Synthesized from cholesterol.
Testosterone
- Main androgen hormone in males.
- Produced from androstenedione.
- Aids in functional development of the testes and penis in the male fetus.
- Promotes secondary male characteristics during puberty (body hair, increased muscle mass and body size, voice deepening).
Estrogen in Females
- Estrogen is produced from androstenedione to estrone and estriol by the enzyme aromatose or testosterone to estradiol by aromatose.
- Estradiol is the most abundant estrogen.
Menstruation
- Prompted by rapid decline in estrogen and progesterone levels due to the corpus luteum's degeneration.
- The outer layer of the endometrium degenerates as spiral arteries constrict, cutting off blood and nutrient supply.
- Weakened arteries rupture, and degenerated tissue and blood are lost through the vagina.
Corpus Luteum / Menstruation
- Secretes estradiol and progesterone.
- Rising levels alter the endometrium to allow for a fertilized ovum.
- If fertilization does not occur:
- The corpus luteum degenerates.
- Estradiol and progesterone levels rapidly decline.
- Menstruation occurs.
Hormonal Control of the Ovarian Cycle
-
Follicular Phase 1 (Early-Mid Follicular Phase)
- High progesterone/estrogen levels inhibit GRF release (hypothalamus) and FSH/LH release (anterior pituitary).
- Low progesterone/estrogen levels at the start of the follicular phase due to corpus luteum degeneration.
- Lack of suppression leads to increased levels of GRF, FSH, and LH.
- FSH:
- Granulosa cell proliferation in primary/secondary follicles, increasing follicle size.
- Outer connective tissue cell differentiation into Thecal cells.
- Thecal cells have LH receptors.
- LH:
- Stimulates ovulation.
-
Follicular Phase 2 (Late Phase)
- Thecal cells respond to increased LH by increasing androgen synthesis and release.
- Androgens diffuse to the granulosa cells, where they are converted to estrogens by aromatose.
- FSH stimulates granulosa cells to secrete estrogen and increases inhibin release.
- Estradiol stimulates uterine endometrium proliferation and growth.
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Description
Explore the functions of the ovaries and the roles of estrogen and progesterone in the female reproductive system. This quiz covers oogenesis, hormonal regulation, and the physiological changes during puberty and pregnancy. Test your knowledge on how these hormones influence both reproductive health and secondary sex characteristics.
