Repro Part 4 - Sex determination: fetal endocrine

Which gamete is responsible for the sex of the child?

2 sex chromosomes

The chromosomal complement of sperm determines sex.

• the chromosomes for oocytes

• the chromosomes for sperm

• explain how the fusion of the chromosome work

At 6 weeks: what two things does the fetus develop?

the fetus has a bipotential primordium and rudimentary reproductive tracts

Bipotential primordium

• ovary or tesis

Rudimentary reproductive tracts

• mullerian duct - female

  • fallopian tube

  • uterus

  • upper vagina

• Wolffian duct -male

  • Epididymis

  • vas deferens

  • seminal vesicle

• However the fetus will at both before fully develpping their spefic organs for their assigned brith

XX: Development of structures

• what breaks down

• what forms the ovaries

• what structure gets worse

• Gonadal cortex forms ovary.

• Gonadal medulla regresses.

• Wolffian duct regresses (testosterone absent).

• Mullerian duct becomes the

  • fallopian tube

  • uterus

  • upper vagina

What is so special about the Y chromosome?

• what gene does it have

  • what does that do

Has SRY gene that promotes testes development

• the genes has TDF (testes-determining factor)

What does the SRY gene code for?

Gene regulatory protein (transcription factor)

Function of SRY

• what three hormones do

  • SF1

  • SRY

  • AMH

• What three things results in

• SF1: Steroidogenic factor 1 (transcription factor) \

• SRY →Testes form (note testes DO not need testosterone to form)

• AMH: Anti-Müllerian hormone

Three things that happen

• Development of Sertoli cells (AMH) & testes

• Development of Leydig cells (testosterone)

• Repression of female structures (viaAMH)

The role of SOX9 in gonadal development

• for men

• Two things that happen and explain one process

SOX9 initiates Sertoli cell differentiation

• Proliferation of Sertoli precursors

• Sertoli precursors organize around clusters of germ cells

Cellular events downstream of SOX9 rapidly organize testis structure

XY: Development of Structures

• what is broken down

• what forms the tesis

• What duct makes what

• what duct is broken down

  • Therefore what hormone is present

Gonadal cortex regresses.

Gonadal medulla forms a testis.

Wolffian duct forms epididymis, vas deferens, and seminal vesicle (testosterone present).

Müllerian duct regresses

(AMH present).

What two hormones regulate se differentiation in men

• for each hormone, what cells secrete it

• Explain what triggers both hormone secretion

• SRY gene

• the SRY protein initates the production of the gonad mendulla to differentiate into the testis

  • Leydig secrete testosterone

  • Sertoli cel secret AMH

Localization of testosterone and DHT in common XY structures

• where is tesosterone commonly found

• where is DHT commonly found

• tesosterone

  • vas deferens (the tube)

  • Seminal vesicles (edge of the tube)

• DHT

  • scrotum (edge of the testis)

  • penis

Hormones in common XX structures

• one hormones

  • Function

• Two hormones not present

• B-catenin supresses SOX0 expression

• No AMH or testosterone

Variations in sex determination & development Atypical hormone levels or action

• level of hormone in adrogen and pattern of synthesis

XY – atypical androgen synthesis (e.g., 5-a-reductase) or action

XX – excessive exposure to androgens during early gestation

What is androgen insensitivity

• Explain what it is and why does it happen

• What other hormone is affected

• Three things/symptoms to expect (fill out the form)

  • Internal structure

  • external structure

  • hormone levels

• androgen insensitivity (androgen receptors not functional) → androgen receptor not working → no testosterone action

• Symptoms

  • internal structue

    • testes undescended

  • External structure

    • Vagina lower portion (the closed end) is made

  • Hormone levels

    • androgen levels high

    • LH high

    • but no FSH (no testosterone - which results in the less negative feedback = makes sense)

What is activated during puberty

• what happens during puberty

• Which (female or male) have a more obvious signs

• At the onset of puberty, the GnRH system is activated

• Puberty: rapid growth and development with earlier, more obvious signs in girls

Activation is complex