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Questions and Answers
Which hormone is responsible for the growth of testes, scrotum, and penis in boys?
What causes the hypothalamus to secrete gonadotropin-releasing hormone (GnRH)?
What is the function of paracrine hormones like inhibin, activin, and follistatin in the HPG axis?
At what age does puberty typically start for boys?
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What is the significance of leptin levels in relation to puberty onset in girls?
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Which hormone stimulates the anterior pituitary gland to secrete FSH and LH?
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What hormone is responsible for increasing body temperature during the menstrual cycle?
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Which phase of the menstrual cycle is characterized by the development of blood vessels and secretory glands in the endometrium?
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What triggers ovulation in the menstrual cycle?
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When does menstruation begin if no implantation occurs?
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Which hormone is responsible for causing the endometrium to proliferate during the menstrual cycle?
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What marks the beginning of the luteal or secretory phase of the menstrual cycle?
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What is the primary role of FSH in the female puberty process?
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Which hormone is responsible for inducing the growth of the seminiferous tubules in males?
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What marks the completion of female puberty according to the text?
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In males, what effect does testosterone have on the development of the penis?
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Which hormone is responsible for the growth of testicular volume in males?
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What event marks the completion of male puberty according to the text?
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What is the role of Leydig cells in the testes?
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Which part of the male reproductive system is responsible for the temporary enlargement of breasts in men due to hormonal fluctuations?
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What is the function of the Glands of Montgomery located in the areola?
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Which structure in the male reproductive system is responsible for powerful peristalsis to transport sperm toward the urethra?
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In which part of the male reproductive system does sperm mature?
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Which structure in the male reproductive system enters the pelvic cavity through the spermatic cord?
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What is the primary function of vasectomy?
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Which cells secrete testosterone, the primary androgen in males?
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What is the role of inhibin in male gonads?
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Which cells provide nutrients and hormonal signals for the development of sperm?
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What is the main function of dihydrotestosterone in males?
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How do mature sperm acquire motility?
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Study Notes
Female Puberty
- FSH stimulates growth of ovarian follicles, and with LH, stimulates production of estradiol by ovaries
- Early estradiol stimulates breast development and growth of skeleton, leading to pubertal growth spurt
- Later, interaction between pituitary secretion of FSH and LH and secretion of estradiol by ovarian follicles leads to ovulation and menstrual cycles
- Estradiol induces maturation of skeleton and eventually fusion of growth plates, ceasing linear growth
- Female puberty is complete with the first ovulatory menstrual period
Male Puberty
- Testes begin to produce mature sperm
- LH stimulates Leydig cells of testes to produce testosterone, leading to growth of seminiferous tubules and increase in testicular volume
- FSH stimulates further growth of seminiferous tubules and increase in testicular volume
- Testosterone induces growth of penis, deepening of voice, growth of hair, and increase in muscularity
- Some testosterone is converted to estradiol, leading to effects on skeletal maturation and breast development in males
- Male puberty is complete with the first ejaculation containing mature sperm
Reproductive Physiology
- Puberty onset typically occurs:
- In girls: around 8-9 years old, with breast development (thelarche)
- In boys: around 11 years old
- Estradiol leads to:
- Breast development
- Maturation of vagina, uterus, and ovaries
- Fat deposit in the hips in girls
- Estrogen increases production of growth factors, leading to rapid skeletal growth in both boys and girls
- Testosterone induces growth of testes, scrotum, and penis
HPG Axis
- Positive feedback loop created to produce more sex hormone
- Extrahypothalamic factors cause the hypothalamus to secrete gonadotropin-releasing hormone (GnRH)
- GnRH stimulates the anterior pituitary gland to secrete gonadotropins: FSH and LH
- FSH and LH stimulate the gonads (ovaries or testes) to secrete female or male sex hormones
- Paracrine hormones (inhibin, activin, follistatin) influence positive and negative feedback loops for the HPG axis
Adrenarche and Gonadarche
- Adrenarche: increased production of adrenal androgens prior to puberty, exhibited by axillary and pubic hair growth
- Gonadarche: gonadal maturation
- In females, ovaries begin to release mature ova
Breast Structure and Function
- Breast tissue can extend into the axilla (tail of Spence)
- Glands of Montgomery: sebaceous glands located in the areola, aid in lubrication of the nipple during lactation
- Gynecomastia: temporary breast enlargement in men due to hormonal fluctuations
Testes Structure and Function
- Essential organs of reproduction, producing gametes (sperm) and sex hormones (androgens, testosterone)
- Tunica vaginalis: outer covering
- Tunica albuginea: inner covering
- Seminiferous tubules: bulk of testes, site of sperm production (spermatogenesis)
- Leydig cells: produce androgens, chiefly testosterone
- Epididymis: sperm matures here
- Vas Deferens: duct with muscular layers capable of powerful peristalsis, transports sperm toward the urethra
Spermatogenesis
- Continuous process
- Spermatogonia: primitive male gametes, undergo continuous mitosis within the seminiferous tubules of the testes
- Develop into primary spermatocytes, then secondary spermatocytes, and finally spermatids
- Spermatids develop into sperm with the help of nutrients and hormonal signals from the Sertoli cells
- Process takes about 70-80 days
- Mature sperm migrate to the epididymis, where their capacity for fertilization continues to develop
Male Sex Hormones
- Androgens: primary androgen is testosterone, produced mainly in the Leydig cells of the testes
- Testosterone:
- Necessary for sexual differentiation and urogenital system development
- Important for nervous and skeletal tissue development
- Maintains libido
- Dihydrotestosterone: necessary for external virilization
- Prolactin: maintains biosynthesis of testosterone
- LH: acts on Leydig cells to regulate testosterone secretion
- FSH: acts on Sertoli cells to promote spermatogenesis
- Inhibin: secreted by the Sertoli cells, inhibits FSH secretion and functions as an autocrine/paracrine regulator in the male gonad
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Description
Learn about the onset of sexual maturation during puberty in girls and boys, along with the physiological changes such as breast development, maturation of reproductive organs, and hormonal influences. Understand the factors influencing the timing of puberty onset and the role of hormones like estradiol and estrogen.
