Sex Determination and Development
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Questions and Answers

What is the primary role of pulsatile GnRH secretion?

  • To regulate testosterone levels
  • To control the secretion of FSH and LH (correct)
  • To initiate oocyte maturation
  • To directly stimulate sperm production

Which hormone inhibits FSH secretion?

  • Gonadotropin
  • Testosterone
  • Activin
  • Inhibin (correct)

What is the role of Leydig cells in the male reproductive system?

  • They produce testosterone (correct)
  • They store sperm
  • They produce inhibin
  • They conduct sperm

What triggers spermatogenesis?

<p>Both gonadotropins and testosterone (B)</p> Signup and view all the answers

Which of the following is NOT a function of Sertoli cells?

<p>Producing testosterone (A)</p> Signup and view all the answers

What is an effect of androgens on male development?

<p>Development of secondary sex characteristics (A)</p> Signup and view all the answers

Which male accessory gland is responsible for secreting a fluid that nourishes sperm?

<p>Seminal vesicles (A)</p> Signup and view all the answers

Which environmental factor does NOT influence reproductive physiology in women?

<p>Caffeine consumption (D)</p> Signup and view all the answers

What substance must spermatids develop into to participate in fertilization?

<p>Acrosome (B)</p> Signup and view all the answers

After puberty, how frequently does tonic GnRH release occur?

<p>Every 1-3 hours (C)</p> Signup and view all the answers

What is the primary reason male gametogenesis has a continuous production of sperm from puberty until death?

<p>Mitosis resumes at puberty, supported by a resting pool of spermatogonia (A)</p> Signup and view all the answers

What occurs to primary oocytes before puberty in female gametogenesis?

<p>They arrest development after the first stage of meiosis (B)</p> Signup and view all the answers

Which of the following describes the fate of the secondary oocyte after ovulation?

<p>It completes the second meiotic division only if fertilized (A)</p> Signup and view all the answers

What is the main function of the hormone aromatase in the reproductive system?

<p>To convert androgens to estrogens (B)</p> Signup and view all the answers

At birth, what is unique about female gametogenesis compared to male gametogenesis?

<p>All eggs are already produced (A)</p> Signup and view all the answers

Which of the following best describes the feedback mechanisms of reproductive hormones in both sexes?

<p>Positive feedback dominates in females during ovulation (A)</p> Signup and view all the answers

What role does inhibin play in the regulation of reproductive hormones?

<p>Inhibits the secretion of FSH (B)</p> Signup and view all the answers

What happens during the first meiotic division in female gametogenesis?

<p>One secondary oocyte and a first polar body are formed (D)</p> Signup and view all the answers

In male gametogenesis, what is the outcome of the first meiotic division?

<p>Two identical spermatocytes are produced (A)</p> Signup and view all the answers

What is the primary hormonal trigger for both male and female gametogenesis?

<p>LH release (D)</p> Signup and view all the answers

What is the primary role of anti-Müllerian hormone (AMH) during the early follicular phase?

<p>Inhibits the development of other follicles in the current cycle (A)</p> Signup and view all the answers

During which phase of the ovarian cycle does ovulation occur?

<p>Mid-late follicular phase (A)</p> Signup and view all the answers

Which hormones are primarily secreted by the luteal cells of the corpus luteum?

<p>Estrogen and progesterone (C)</p> Signup and view all the answers

What occurs in the late luteal phase if pregnancy does not happen?

<p>The corpus luteum degenerates into corpus albicans (D)</p> Signup and view all the answers

What is the significance of the surge in LH and FSH during the mid-late follicular phase?

<p>They stimulate the final maturation of the dominant follicle (A)</p> Signup and view all the answers

What is a primary characteristic of secondary follicles during follicular development?

<p>Massive multiplication of granulosa cells begins (A)</p> Signup and view all the answers

What initiates the proliferative phase of the uterine cycle?

<p>Elevated estrogen levels from the growing follicles (A)</p> Signup and view all the answers

Which structure forms from the ruptured follicle after ovulation?

<p>Corpus luteum (C)</p> Signup and view all the answers

What causes the endometrium to thicken during the menstrual cycle?

<p>Growing levels of estrogen from secondary follicles (D)</p> Signup and view all the answers

What happens to primary oocytes if they are not selected for maturation during follicular development?

<p>They undergo atresia (D)</p> Signup and view all the answers

What is the function of the SRY gene in sex determination?

<p>It encodes a protein that initiates male reproductive development. (B)</p> Signup and view all the answers

What is the significance of the presence of testosterone during male embryonic development?

<p>It leads to the formation of the epididymis, vas deferens, and seminal vesicle. (B)</p> Signup and view all the answers

Which structure develops in the absence of both testosterone and Anti-Mullerian hormone (AMH)?

<p>Ovary (A)</p> Signup and view all the answers

What happens to the Müllerian duct in male embryonic development?

<p>It regresses due to AMH produced by Sertoli cells. (D)</p> Signup and view all the answers

How many pairs of sex chromosomes are present in a typical diploid human cell?

<p>1 pair of sex chromosomes (D)</p> Signup and view all the answers

Which hormone is responsible for the regression of the gonadal medulla in female embryonic development?

<p>None, it regresses naturally (A)</p> Signup and view all the answers

What type of cells produce testosterone in the developing male fetus?

<p>Leydig cells (B)</p> Signup and view all the answers

The diploid number of chromosomes in humans is represented as which of the following?

<p>2n (C)</p> Signup and view all the answers

What role do gametes play in the context of human reproduction?

<p>They are haploid cells that combine to form a diploid zygote. (B)</p> Signup and view all the answers

What is the outcome if the SRY gene is absent in an embryo?

<p>The embryo develops into a female. (D)</p> Signup and view all the answers

Flashcards

Spermatogenesis

The process of sperm production in males, beginning at puberty and continuing throughout life.

Oogenesis

The process of egg production in females, completed before birth and resuming at puberty.

Spermatogonia

Immature germ cells in males that divide mitotically to produce sperm.

Oogonia

Immature germ cells in females that divide mitotically before birth, forming all the eggs a female will ever have.

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Primary Oocyte

A female germ cell arrested in the first meiotic division, present at birth and resuming division at puberty.

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Secondary Oocyte

A female germ cell resulting from the first meiotic division, released at ovulation.

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Polar Body

A small cell produced during oogenesis that receives little cytoplasm and eventually degenerates.

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Androgens

Sex hormones like testosterone, dominant in males, responsible for male characteristics.

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Estrogens

Sex hormones like estradiol, dominant in females, responsible for female characteristics.

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Aromatase

An enzyme that converts androgens into estrogens.

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GnRH

A hormone produced by the hypothalamus that regulates the release of FSH and LH from the anterior pituitary gland. It is released in a pulsatile manner.

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FSH

Follicle-Stimulating Hormone. A hormone secreted by the pituitary gland responsible for stimulating gametogenesis in the gonads (egg and sperm production).

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LH

Luteinizing Hormone. A hormone produced by the pituitary gland that controls the production of sex hormones (testosterone in men and estrogen and progesterone in women).

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Inhibin

A hormone produced by the gonads that inhibits the secretion of FSH from the pituitary gland.

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Activin

A hormone produced by the gonads that stimulates the secretion of FSH from the pituitary gland.

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Pulsatile GnRH Release

The release of GnRH from the hypothalamus in a series of bursts or pulses, usually every 1-3 hours. This pattern is essential for regulating the production of FSH and LH.

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Pulse Generator

A region in the hypothalamus responsible for generating the pulsatile release of GnRH.

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Seminal Vesicles

Two small glands located near the bladder that contribute to the production of semen, providing nutrients and fluids to sperm.

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Prostate Gland

A gland located near the base of the bladder that contributes to the production of semen, providing fluid and enzymes that help protect and nourish sperm.

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Bulbourethral Gland (Cowper's Gland)

Two small glands located beneath the prostate gland that produce a pre-ejaculatory fluid that helps lubricate the urethra.

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Sex Chromosomes

A pair of chromosomes that determine an individual's sex. In humans, these are either XX (female) or XY (male).

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Sperm's Role

The sperm contributes the sex chromosome that determines the offspring's sex. It can carry either an X or a Y chromosome.

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Y Chromosome's Power

Presence of the Y chromosome is crucial for the development of male reproductive structures. It carries the SRY gene.

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Bipotential Gonads

Early embryonic structures that have the potential to develop into either male or female reproductive organs depending on hormonal signals.

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What does SRY do?

The SRY gene on the Y chromosome produces a protein known as the 'testes determining factor' that directs the bipotential gonads to develop into testes.

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Testosterone's Role

A hormone produced by Leydig cells in the testes, it triggers the development of male secondary sexual characteristics and male reproductive organs.

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AMH's Role

Anti-Mullerian hormone (AMH) secreted by Sertoli cells in the testes causes the degeneration of Mullerian ducts, which would otherwise develop into female reproductive structures.

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Female Development

In the absence of testosterone and AMH, the gonads develop into ovaries, and Mullerian ducts develop into female reproductive structures.

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Wolffian Duct

The precursor of the male reproductive tract. In the presence of testosterone, it develops into the epididymis, vas deferens, and seminal vesicle.

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Mullerian Duct

The precursor of the female reproductive tract. In the absence of AMH, it develops into the fallopian tubes, uterus, cervix, and upper vagina.

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Ovarian Cycle

The process of follicle development, ovulation, and corpus luteum formation within the ovary. It is a series of hormonal events that prepare the body for potential pregnancy.

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Follicular Phase

The first phase of the ovarian cycle where a small follicle grows and matures into a dominant follicle ready for ovulation. It's characterized by the rise of estrogen levels, stimulating endometrial growth.

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Early Follicular Phase

The initial stage of the follicular phase where FSH stimulates the growth of tertiary follicles. Estrogen levels increase, preventing FSH and LH release.

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Mid-to-Late Follicular Phase

The later stage of the follicular phase where estrogen levels spike, triggering a surge in LH and FSH. This surge causes the dominant follicle to release an egg.

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Ovulation

The process where the mature follicle ruptures and releases an egg from the ovary, triggered by the LH surge.

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Luteal Phase

The phase immediately after ovulation where the ruptured follicle transforms into the corpus luteum, secreting progesterone and estrogen. It prepares the uterus for implantation.

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Early-to-Mid Luteal Phase

The initial stage of the luteal phase where the corpus luteum grows and secretes progesterone and estrogen. These hormones support the endometrium and inhibit FSH and LH release.

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Late Luteal Phase & Menstruation

The final stage of the luteal phase where the corpus luteum degenerates if pregnancy doesn't occur. This leads to a drop in progesterone and estrogen levels, triggering menstruation.

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Uterine Cycle

The cyclical changes in the lining of the uterus that prepare it for potential implantation of a fertilized egg.

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Menstruation

The shedding of the uterine lining when pregnancy doesn't occur, caused by the decline in progesterone and estrogen levels.

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Study Notes

Sex Determination

  • Sperm determines sex by carrying either an X or Y chromosome
  • One pair of sex chromosomes (XX or XY) determines gender
  • The Y chromosome is essential for male development

Sex Chromosome Development

  • Autosomal cells are somatic cells, having 22 pairs of non-sex chromosomes
  • Gametes (egg and sperm cells) are haploid, meaning they contain 23 chromosomes.
  • Diploid cells have two sets of chromosomes, one from each parent, resulting in a total of 46 chromosomes.
  • Autosomal cells exclude sex cells/gametes

Bipotential Reproductive Structures

  • Early embryos have bipotential reproductive structures that have the potential to become male or female structures.
  • Chemicals/hormones determine the structure's development to either male or female structures
  • The gene SRY, found on the Y chromosome, is crucial
    • Leads to the production of the testes-determining factor when the SRY gene is present.
    • Results in testes formation otherwise, female structures develop

Sexual Differentiation

  • Male Development (Testosterone & AMH Present):
    • Gonadal cortex regresses (shrinks and disappears)
    • Gonadal medulla develops into testes
    • Wolffian duct forms epididymis, vas deferens, and seminal vesicle; testosterone converts the Wolffian duct into male accessory structures
    • Leydig / interstitial cells secrete testosterone
  • Female Development (Testosterone & AMH Absent):
  • Gonadal cortex develops into ovaries
  • Gonadal medulla regresses
  • Wolffian duct regresses
  • Mullerian duct develops into fallopian tubes, uterus, cervix, and upper half of the vagina.

Gametogenesis

  • Male Gametogenesis:

    • Begins in the fetus but doesn't proceed past mitosis until puberty.
    • Germ cells are spermatogonia and do not divide until puberty.
    • Mitosis resumes during puberty
    • Continuous sperm production begins during puberty and continues until death.

  • Female Gametogenesis:

    • Oogonia complete mitotic stages before birth
    • Female meiosis begins before birth, and oocytes remain arrested in the primary oocyte phase until puberty.
    • Beginning meiosis 1 steps before birth.
    • Oocytes complete meiosis, eventually become eggs in the mature stage only if fertilized, one egg is produced per cycle.
    • Oocyte maturation only occurs when selected and triggered every month during puberty and continues until menopause.

Basic Patterns of Reproduction

  • Both sexes produce androgens and estrogens.
  • Androgens are dominant in males
    • Testosterone is produced in the testes.
  • Estrogens are dominant in females
    • Estrogens, Progestins, and androgens are produced in the ovaries
  • Aromatase converts androgens to estrogens.
  • Positive and negative feedback pathways control reproductive function. GnRH, FSH and LH (pituitary gonadotropins) are released by different areas in the brain to control gamete production.

Hormonal Control of Spermatogenesis

  • Feedback pathways govern spermatogenesis, with testosterone playing a crucial role.

Primary and Secondary Sex Characteristics

  • Androgens influence primary and secondary sex characteristics in males.
  • Primary characteristics refer to reproductive ducts and organs.
  • Secondary characteristics include traits like pubic/axillary hair and muscular development.

Female Reproduction

  • Organization of ovary tissues, development of follicles from primordial to mature to release egg to fertilization, and development of the corpus luteum for the next cycle.
  • The menstrual cycle has ovarian and uterine cycles that occur simultaneously but in different locations.
  • Follicle development begins with the primordial follicle and progresses to the formation of a mature follicle that releases an egg during ovulation.

Menstrual Cycle

  • Ovarian and uterine cycles are synchronized, with alternating phases of follicular and luteal development in the ovaries, and accompanying proliferative and secretory phases in the uterus.

Contraceptives

  • Various methods exist, including abstinence, sterilization, barrier methods, hormonal treatments, and intrauterine devices (IUDs).
  • Abstinence and sterilization are very effective, followed by barrier methods, intrauterine devices and lastly hormonal treatments ineffectiveness varies greatly.

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Description

Explore the fascinating mechanisms of sex determination through chromosomes and hormonal influences. This quiz covers key concepts such as sex chromosomes, gametes, and bipotential reproductive structures essential for understanding gender development. Test your knowledge on the fundamental genetic factors involved in sexual differentiation.

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