Physiology Unit 7 Sexual Development

Are the male and female gonads different or indifferent for the first 40 days?

indifferent

What does the SRY gene stand for?

sex-determing region Y

Is the transcription factor for the SRY gene encoded on the X or Y chromosome?

Y chromosome

The SRY gene codes for what which is necessary to develop what?

codes for testis-determining factor (TDF) and develops male testes

When are the male testes developmentally functional?

1st trimester

The testes secrete large amounts of testosterone from which range of weeks which does what?

weeks 8-12, masculinizes the external genitalia

What develops in the absence of the SRY gene?

ovaries

When do ovaries develop functionally?

2nd trimester, not mature until 3rd trimester

At the time of birth, what is the functionality of the gonads?

relatively inactive

What kind of cells secrete testosterone and mullerian inhibition factor?

sertoli cells in testes

If mullerian inhibition factor is present, what happens to the structure that would have become the uterus and uterine tubes?

it degenerates

If no mullerian inhibition factor (MIF) is present what develops?

uterus and uterine tubes

If testosterone is secreted by mesonephric (wolffiann) cells what structures are formed?

epididymides, vas deferens, ejaculatory ducts, seminal vesicles

If no testosterone is secreted from the mesonephric (wolffian) cells what happens?

the structures that would have become the epididymides, vas deferens, seminal vesicles, and ejaculatory ducts degenerate

What are the 4 male external genitalia?

prostate, scrotum, spongy urethra, penis

Female accessory sex organs develop in response to a lack of what?

testes, testosterone, and MIF

What are the female accessory sex organs?

uterus and uterine tubes

What are the female external genitalia?

vagina, labia minora and majora, clitoris

What are the three main sex steroids?

testosterone, estrogen, progesterone

What releases gonadotropin-releasing hormone (GnRH)?

hypothalamus

When GnRH is released from the hypothalamus what does it stimulate?

anterior pituitary to release follicle stimulating hormone (FSH) and luteinizing hormone (LH)

What do kisspeptins do?

induce cyclic GnRH secretion in females (menstrual cycle)

What are kisspeptins suppressed by in males?

androgen

What are the 3 functions of FSH and LH?

stimulate spermatogenesis or oogenesis, stimulate gonadal hormone secretion, maintain structure of gonads

What is the predominant male sex hormone?

androgen (testosterone is the primary androgen)

What are the predominant female sex hormones?

estrogen and progesterone

What is the primary estrogen in pre-menopausal, non-pregnant women?

17-beta estradiol (E2)

Which estrogen is secreted by the placenta?

estriol (E3)

What is the primary estrogen in post-menopausal women?

estrone (E1)

Where are sex steroids primary produced?

gonads

Weaker or less active versions of sex steroids can be produced by what?

adrenal cortex and adipose

All sex steroids are originally derived from what?

cholesterol

What is the order of cholesterol becoming a sex steroid?

cholesterol, progesterone, androstenedione, testosterone, 17beta-estradiol

What does ligand binding do to the receptor?

activates it, induces a conformational change to allow dimerization and DNA binding

What does the DNA-binding domain bind to?

hormone response element

Where is a hormone-response element found?

promoter region of the target gene

Why must both half sites of a hormone-response element be occupied?

to promote transcription

What is a homodimer?

when both receptors are the same, occurs much more often

What is a heterodimer?

when receptors are different

Are FSH and LH very low or very high throughout childhood?

very low

At the onset of puberty what increases?

GnRH levels, cause is unknown

Puberty stimulates increased secretion of what?

LH and FSH, increased testosterone from testes and 17-beta estradiol from ovaries

The increased amount of sex steroids stimulates what?

development of secondary sex characteristics

What is required to classify someone as true gonadal intersex?

develop at least part of one ovary and one testis

What causes true gonadal intersex?

not all embryonic cells contain the SRY gene on the Y chromosome, some cells are XY and some are XX so characteristics of both develop

What can be the cause of complex of undetermined intersex?

a result of chromosomal abnormalities, ex. 45 XO, 47 XXY, 47 XXX

What is 46 XX intersex (Congenital Adrenal Hyperplasia)?

female with excessive secretion of androgen from adrenal cortex

In congenital adrenal hyperplasia, a lack of testes means no secretion of what?

MIF

What is the result of congenital adrenal hyperplasia?

ovaries and female accessory sex organs are created but there is masculanized external genitalia

What is 46 XY intersex (Testicular feminization syndrome, aka Androgen insensitivity syndrome)?

normally functioning testes and testosterone levels but target cells do not express androgen receptor

What is the result of someone with Testicular Feminization Syndrome (androgen insensitivity syndrome)?

undescended testes, no accessory sex organs, feminized external genitalia