Sexual development and gonads Flashcards
What kind of glands are the gonads
Endocrine
What makes sperm and testosterone in males
Testes
What makes ova, estrogen, and progesterone in females
Ovaries
What is sexual differentiation
Development of specific gonads, internal and external genitalia
What is sexual differentiation a result of
Y-chromosome presence of absence
How is sex characterized
Genetic
Gonadal
Phenotypic
What is genetic sex differentiation
Presence of Y chromosome
What is gonadal differentiation
Testes vs ovaries
What is phenotypic sexual differentiation
Male or female appearance
XX
Female
XY
Male
What decides what sex you are
SRY region of Y chromosome
When is the transcription factor for the SRY region of Y chromosome activated
Week 7
What does the activation of SRY region of Y chromosome initiate
Development of testes
What happens if there is no Y or there is a mutation in SRY?
Ovary development begins at week 9
What is the default sex
Female
What is gonadal sex
What type of gonad develops in response to genetics
What chromosomes develop ovaries
XX
What do the germ cells of the ovaries do
Produce oogonia
What do the theca cells of the ovaries do
Produce progesterone and testosterone
What do the granulosa cells of the ovary do
Produce progesterone and estrogen from testosterone
What do the germ cells of the testes do
Produce sperm
What do the serotonin cells of the testes do
Produce anti-mullerian hormone
What do the leydig cells of the testes do
Produce testosterone
What is phenotypic sex
What phenotype develops in response to gonadal sex (hormones)
What is the usually phenotypic sex of someone with XX
- internal-uterus, Fallopian tubes, upper vagina
- external-clitoris, labia, lower vagina
What is the usually phenotypic sex of someone with XY
- internal- epididymis, vas deferens, seminal vesicles and ejaculatory ducts
- external-penis and scrotum
Consider a person with an XY genotype, internal testes and normal female genitalia, what is their gonadal sex
Male
What is the default setting for sex
Female
What do you need for activation into male development
SRY
What two sets of ducts are present during embryonic development
Wolffian and Mullerian
What do ovaries develop from at week 9
Undifferentiated gonads, wolffian ducts degenerate, Müllerian ducts develop into the internal genitalia
What hormones are needed for external genitalia development in females
Estrogen and progesterone
What does SRY cause
Development of testes from undifferentiated gonads around week 6
What ducts are present and what ducts are destroyed in male development (SRY)
Tastes secrete and-mullerian hormone that degrades the mullarian ducts
Wolffian ducts develop into the internal genitalia due to testosterone from developing testes
What causes the wolffian ducts to develop into the internal genitalia of males
Testosterone from developing testes
Select the answer that would best describe a person with an XY genotype with an SRY mutation that renders it non functional
Intact Müllerian ducts
How does hormonal regulation occur
Via the hypothalamic-pituitary-gonadal axis
What kind of feedback loop is the hypothalamic-pituitary-gonadal axis
Negative feedback
Where is GnRH from
Hypothalamus
Where is FSH and LH from
Anterior pituitary
What do the gonads secret
Sex steroids and inhibin/activin
How are levels of sex hormones regulated
Tightly
When is there a large spike of sex hormones
Developing fetus
What hormone starts in the developing fetus at week 4
GnRH
When do LH and FSH rise in the developing fetus
Week 10-12
When do hormonal levels drop
As brith approaches
-stays low levels until puberty
After birth when do hormone levels rise again
Puberty
After birth, which is higher, FSH or LH
FSH
When do GnRH levels become cyclic
As puberty approaches
- both sexes have multiple daily spikes
- increase in frequency until puberty
- then fairly regular
After puberty what ar the spikes like in females
Larger monthly spikes
After puberty what are the hormon spikes like in males
Fairly stable levels
After puberty, which is high, LH or FSH
LH
What happens to GnRH at old age
Increases
- FSH>LH
- sex steroids decrease
- menopause/andropause
What initiates the final development of the testes
Rise in daily GnRH pulses
What all happens when there is a daily GnRH pulse that initiates the final development of the testes
- increased number of Leydig cells
- testes increase in seize
- accessory organs grow
- linear growth spurt and development of male secondary sex characteristics
What do the leydig cells produce
Testosterone
When the testes increase in size, what else increases
-more seminiferous tubules for sperm production
What initiates the final development of the ovaries in female puberty
Rise in daily GnRH
What happens during female puberty (daily rise in GnRH pulses that initiate final development of the ovaries)
- increases production of estrogens (estradiol)
- menarche occurs
- linear growth spurt and development of female secondary sex characteristics
What are some problems with SRY
Swyer syndrome
46,XX male
What is swyer syndrome
- 46, XY but SRY is non functional
- female external genitalia
- non-functional, streak gonads
- intact Müllerian ducts
What is 46 XX male
- phenotypically male
- possible small testes
- possible gynecomastia
- no mullerian organs
- sterile with no functioning sperm
What is klinefelters syndrome
- 47, XXY
- feminization of the male phenotype
- breast growth
- tall, sterile, poor coordination and low muscle mass
- broad hips
- slight learning disability
What is tuner syndrome
- 45, XO
- female missing an X chromosome
- short, with webbed neck, low sexy ears, and are infertile
- some learning disabilities and visual disabilities as well
Steroid synthesis pathway in adrenal
Used inboth adrenals and the gonads
What pathway is primarily used in gonads
Aldosterone to estrogen/testosterone
Congenital adrenal hyperplasia (CAH)
- adrenal glands have all the machinery to make androgens
- leads to excessive androgen production
- XX female will have ovaries but have ambiguous genitalia
- any defect in aldosterone or cortisol production can cause this
17a dehydrogenase deficiency in XY
-46, XY with underdeveloped or female genitalia
17a deficincy in XX
-46, XX range from normal but infertile to no menarche and underdeveloped female characteristics at puberty
17B hydroxysteroid dehydrogenase deficiency in XY
May have ambiguous genitalia or female external genitalia, but internal testes
17B hydroxysteroid dehydrogenase deficiency in XX
Females will be masculinized
5a reductase deficiency
- XX genotype with pseudo intersexuality
- underdeveloped male genitalia due to lack of DHT
- still be fertile after puberty due to other sources of DHT
Can’t make final sex hormone
Androgen insensitivity syndrome
- mutation of testosterone receptors so that they cannot bind testosterone (normal/elevated levels of testosterone)
- genotypically XY, phenotypically female
What is androgen insensitivity syndrome
Mutation of testosterone receptors
What is the genotype and phenotype of androgen insensitivity syndrome
Genotypically XY Phenotypically female -normal female external genitalia and secondary sex characteristics -short vagina, no uterus -will have undescended testes
How is androgen insensitivity syndrome diagnosed
Failed menarche
A patient presents to the clinic complaining of loss of energy, irregular menstration and weight gain. She is diagnosed with Cushings disease due to a pituitary tumor. Which of the following physical findings might she present with
Excess body hair
What is the male gonad
Testes
What do testes do
Produce sperm and secretes testosterone
When do testes descend
Around birth
What temp does sperm develop best
1-2C below body temp
Why doesthe scrotum raise and lower testes
To keep temperature right for sperm production
What are the testes made of
- mostly seminiferous tubules (80%)
- connective tissue (20%)
What are the 3 cell types in the seminiferous tubules
- sertoli cells
- spermatogonia
- spermocytes
What do Sertoli cells do
- blood teste barrier
- secrete fluid into tubule to transport spermatozoa
- secretes androgen binding protein to concentrate testosterone in the testes
What do the leydig cells do
In connective tissue outside the seminiferous tubules and secrete testosterone
Process in seminiferous tubules where the diploid spermatagonia cells divide into 4 haploid spermatid
Spermatogensis
What are the phases of spermatogensis
Mitotic phase
Meiotic phase
Spermiogenesis
Mitotic phase of spermatogensis
Spermatogonia divide to populate the testes with spermatocytes
What is the meiotic phase of spermatogensis
Spermatocytes divide to form spermatids
What is the spermiogenesis phase of spermatogenesis
Spermatids mature by losing cytoplasm and develop a flagella
Where are maturing sperm held until ejaculation
Epididymis
When do sperm become motel
After 18 hours
How long can sperm stay in suspended animation
For months
What happens to the sperm during ejaculation
Accessory glands add fluid to the sperm to form semen
What do the seminal vesicles add to the sperm
Citrate, fructose, prostaglandins, and fibrinogen
What do prostate glands add to sperm
Alkaline fluid that contains citrate, calcium, clotting enzymes and fibrinolysis
What is seems propelled by in ejaculation
Smooth muscle contractions
What happens once season is in a female reproduction tract
Sperm undergo capacitation to become fully active (5 hours)
What happens during capacitation to sperm
- takes 5 hours
- inhibitory factors present in semen are washed away
- full motility is achieved due to calciu, influx
- acrosome becoems more fragile due to removal of cholesterol
What does erection result from
PNS
How does the PNS stimulate erection
Release of NO relaxes vascular smooth muscle to increase blood flow, arterial flow is increased and venous flow is restricted
What does blood fill for erection
Corpus cavernosa and spongiosum
How is erection achieved
Due to increased pressure in the erectile tissue
What is the lubrication in males from (which nervous system)
PNS
What secretes mucus for lubrication in males
Bulbourethral and urethral glands
-clears and lubricates urethra for semen
What part of the nervous system is responsible for emission and ejaculation
SNS
Male emission
Combines sperm and seminal fluid in the internal urethra
Male ejaculation
Expulsion of semen out of the penis by muscular contractions
Male resolution (loss of sexual excitement)
Occurs 1-2 minutes after ejaculation
Steroid hormones that have masculinization effects
Androgens
Where are androgens primarily produces
Leydig cells in testes
What do androgens produce in males
Testosterone, DHT, and androstenedione
Which are the most potent between testosterone, DHT, androstenedione
Testosterone and DHT
Testosterone production in fetus
Allow growth and differentiate of internal genitalia in response to hCG
Production of testosterone before puberty is in response to
GnRH
When does GnRH peak
In adulthood and slowly declines with age
What is testosterone responsible for
Secondary male sex characteristics
Produced in fetus to allow growth and differentiation of external genitalia
DHT