Reproductive System and Hormonal Control (3B) - MCAT Biological and Biochemical Foundations of Living Systems
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Which hormone mediates milk ejection (letdown), and from which pituitary lobe is it released?
Which hormone mediates milk ejection (letdown), and from which pituitary lobe is it released?
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Oxytocin from the posterior pituitary. Oxytocin induces contraction of myoepithelial cells around mammary alveoli, facilitating milk release in response to suckling.
Oxytocin from the posterior pituitary. Oxytocin induces contraction of myoepithelial cells around mammary alveoli, facilitating milk release in response to suckling.
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Which male reproductive structure is the site of sperm maturation and storage?
Which male reproductive structure is the site of sperm maturation and storage?
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Epididymis. The epididymis allows sperm to gain motility and fertilizing capacity while storing them until ejaculation.
Epididymis. The epididymis allows sperm to gain motility and fertilizing capacity while storing them until ejaculation.
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What is the primary function of gonadotropin-releasing hormone (GnRH) in reproduction?
What is the primary function of gonadotropin-releasing hormone (GnRH) in reproduction?
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Stimulates anterior pituitary release of FSH and LH. GnRH from the hypothalamus acts on the anterior pituitary to initiate the release of gonadotropins essential for gametogenesis and steroidogenesis in both sexes.
Stimulates anterior pituitary release of FSH and LH. GnRH from the hypothalamus acts on the anterior pituitary to initiate the release of gonadotropins essential for gametogenesis and steroidogenesis in both sexes.
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What are the two gonadotropins released by the anterior pituitary in response to GnRH?
What are the two gonadotropins released by the anterior pituitary in response to GnRH?
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Follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These gonadotropins are crucial for regulating gamete production and sex hormone synthesis in the gonads.
Follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These gonadotropins are crucial for regulating gamete production and sex hormone synthesis in the gonads.
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What is the main target cell of LH in the testes, and what does LH stimulate there?
What is the main target cell of LH in the testes, and what does LH stimulate there?
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Leydig cells; stimulates testosterone synthesis. LH binds to receptors on interstitial Leydig cells, activating pathways that increase cholesterol conversion to testosterone.
Leydig cells; stimulates testosterone synthesis. LH binds to receptors on interstitial Leydig cells, activating pathways that increase cholesterol conversion to testosterone.
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What is the main target cell of FSH in the testes, and what does FSH stimulate there?
What is the main target cell of FSH in the testes, and what does FSH stimulate there?
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Sertoli cells; supports spermatogenesis and ABP production. FSH acts on Sertoli cells to promote sperm development and produce androgen-binding protein for testosterone concentration.
Sertoli cells; supports spermatogenesis and ABP production. FSH acts on Sertoli cells to promote sperm development and produce androgen-binding protein for testosterone concentration.
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What is the primary role of Sertoli cell androgen-binding protein (ABP) in the testes?
What is the primary role of Sertoli cell androgen-binding protein (ABP) in the testes?
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Concentrates testosterone in seminiferous tubules. ABP binds testosterone, maintaining high local concentrations necessary for spermatogenesis within the seminiferous tubules.
Concentrates testosterone in seminiferous tubules. ABP binds testosterone, maintaining high local concentrations necessary for spermatogenesis within the seminiferous tubules.
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What hormone from Sertoli cells provides negative feedback specifically on FSH secretion?
What hormone from Sertoli cells provides negative feedback specifically on FSH secretion?
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Inhibin. Inhibin selectively suppresses FSH release from the anterior pituitary, providing negative feedback to regulate spermatogenesis.
Inhibin. Inhibin selectively suppresses FSH release from the anterior pituitary, providing negative feedback to regulate spermatogenesis.
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What is the correct order of sperm transport from testis to outside the body?
What is the correct order of sperm transport from testis to outside the body?
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Seminiferous tubules → epididymis → vas deferens → urethra. This pathway ensures sperm maturation, storage, and delivery during ejaculation through the male reproductive tract.
Seminiferous tubules → epididymis → vas deferens → urethra. This pathway ensures sperm maturation, storage, and delivery during ejaculation through the male reproductive tract.
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What is the primary contribution of seminal vesicles to semen?
What is the primary contribution of seminal vesicles to semen?
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Fructose-rich, alkaline fluid with prostaglandins. Seminal vesicles provide energy sources and pH buffering to support sperm viability and stimulate uterine contractions.
Fructose-rich, alkaline fluid with prostaglandins. Seminal vesicles provide energy sources and pH buffering to support sperm viability and stimulate uterine contractions.
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What is the primary function of the prostate gland secretion in semen?
What is the primary function of the prostate gland secretion in semen?
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Adds enzymes and citrate; helps sperm motility and liquefaction. Prostate secretions supply nutrients and enzymes that enhance sperm movement and dissolve the semen coagulum post-ejaculation.
Adds enzymes and citrate; helps sperm motility and liquefaction. Prostate secretions supply nutrients and enzymes that enhance sperm movement and dissolve the semen coagulum post-ejaculation.
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What is the primary function of bulbourethral (Cowper) gland secretions?
What is the primary function of bulbourethral (Cowper) gland secretions?
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Lubricates and neutralizes urethral acidity (pre-ejaculate). Bulbourethral glands secrete mucus that prepares the urethra for sperm passage by reducing acidity and friction.
Lubricates and neutralizes urethral acidity (pre-ejaculate). Bulbourethral glands secrete mucus that prepares the urethra for sperm passage by reducing acidity and friction.
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What is the main hormonal role of testosterone in male reproductive physiology?
What is the main hormonal role of testosterone in male reproductive physiology?
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Promotes spermatogenesis and male secondary sex characteristics. Testosterone supports germ cell proliferation in the testes and develops traits like muscle mass and voice deepening.
Promotes spermatogenesis and male secondary sex characteristics. Testosterone supports germ cell proliferation in the testes and develops traits like muscle mass and voice deepening.
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What enzyme converts testosterone to dihydrotestosterone (DHT), and where is DHT most important?
What enzyme converts testosterone to dihydrotestosterone (DHT), and where is DHT most important?
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5α-reductase; external genitalia and prostate development. 5α-reductase enhances androgen potency; DHT is key for masculinization of external structures and prostate growth.
5α-reductase; external genitalia and prostate development. 5α-reductase enhances androgen potency; DHT is key for masculinization of external structures and prostate growth.
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What is the main anatomical site of oogenesis and follicle development?
What is the main anatomical site of oogenesis and follicle development?
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Ovary (within ovarian follicles). Oogenesis occurs in ovarian follicles, where oocytes mature under hormonal influence during the menstrual cycle.
Ovary (within ovarian follicles). Oogenesis occurs in ovarian follicles, where oocytes mature under hormonal influence during the menstrual cycle.
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What is the primary role of FSH in the ovarian follicle?
What is the primary role of FSH in the ovarian follicle?
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Stimulates granulosa cells and follicular maturation. FSH promotes granulosa cell proliferation and estrogen production, driving follicle growth and selection.
Stimulates granulosa cells and follicular maturation. FSH promotes granulosa cell proliferation and estrogen production, driving follicle growth and selection.
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What is the primary role of LH in the ovary during the menstrual cycle?
What is the primary role of LH in the ovary during the menstrual cycle?
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Triggers ovulation and supports corpus luteum formation. LH surge induces oocyte release and transforms the ruptured follicle into the progesterone-secreting corpus luteum.
Triggers ovulation and supports corpus luteum formation. LH surge induces oocyte release and transforms the ruptured follicle into the progesterone-secreting corpus luteum.
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What event is directly triggered by the mid-cycle LH surge?
What event is directly triggered by the mid-cycle LH surge?
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Ovulation. The LH surge causes enzymatic breakdown of the follicular wall, releasing the mature oocyte from the ovary.
Ovulation. The LH surge causes enzymatic breakdown of the follicular wall, releasing the mature oocyte from the ovary.
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Which ovarian structure secretes progesterone after ovulation, and what is it called?
Which ovarian structure secretes progesterone after ovulation, and what is it called?
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Corpus luteum; secretes progesterone (and some estrogen). Post-ovulation, the corpus luteum forms from follicular remnants and produces hormones to maintain early pregnancy.
Corpus luteum; secretes progesterone (and some estrogen). Post-ovulation, the corpus luteum forms from follicular remnants and produces hormones to maintain early pregnancy.
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What is the primary effect of progesterone on the endometrium after ovulation?
What is the primary effect of progesterone on the endometrium after ovulation?
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Promotes secretory endometrium and implantation readiness. Progesterone induces glandular changes in the endometrium, preparing it for potential embryo implantation and support.
Promotes secretory endometrium and implantation readiness. Progesterone induces glandular changes in the endometrium, preparing it for potential embryo implantation and support.
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What is the dominant feedback effect of low-to-moderate estrogen on GnRH, FSH, and LH?
What is the dominant feedback effect of low-to-moderate estrogen on GnRH, FSH, and LH?
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Negative feedback on GnRH, FSH, and LH secretion. Moderate estrogen levels inhibit hypothalamic GnRH and pituitary gonadotropin release to prevent excessive follicular stimulation.
Negative feedback on GnRH, FSH, and LH secretion. Moderate estrogen levels inhibit hypothalamic GnRH and pituitary gonadotropin release to prevent excessive follicular stimulation.
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What is the feedback effect of sustained high estrogen just before ovulation on LH release?
What is the feedback effect of sustained high estrogen just before ovulation on LH release?
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Positive feedback causing the LH surge. High estrogen from the dominant follicle switches to positive feedback, amplifying LH release to trigger ovulation.
Positive feedback causing the LH surge. High estrogen from the dominant follicle switches to positive feedback, amplifying LH release to trigger ovulation.
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What hormone maintains the corpus luteum in early pregnancy, and what secretes it?
What hormone maintains the corpus luteum in early pregnancy, and what secretes it?
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hCG secreted by syncytiotrophoblast (early placenta). hCG mimics LH to sustain corpus luteum progesterone production until the placenta takes over.
hCG secreted by syncytiotrophoblast (early placenta). hCG mimics LH to sustain corpus luteum progesterone production until the placenta takes over.
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What is the primary physiological trigger for menstruation in the absence of pregnancy?
What is the primary physiological trigger for menstruation in the absence of pregnancy?
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Withdrawal of progesterone due to corpus luteum regression. Declining progesterone destabilizes the endometrial lining, leading to its shedding as menstrual flow.
Withdrawal of progesterone due to corpus luteum regression. Declining progesterone destabilizes the endometrial lining, leading to its shedding as menstrual flow.
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Which hormone is responsible for milk production, and from which pituitary lobe is it released?
Which hormone is responsible for milk production, and from which pituitary lobe is it released?
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Prolactin from the anterior pituitary. Prolactin stimulates alveolar cells in mammary glands to synthesize milk components during lactation.
Prolactin from the anterior pituitary. Prolactin stimulates alveolar cells in mammary glands to synthesize milk components during lactation.
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