Puberty, Sex Development Flashcards
When do urogenital ridges form and why
They form between 6-8 weeks of gestation due to the migration of primordial germ cells from the dorsal endoderm
What stage do the urogenital ridges form
They form in the indifferent stage
If the SRY gene is present what happens
You will have a testes differentiation by week 9 of gestation
If the SRY gene is absent what will happen
You will have ovaries present by 11-12 weeks of gestation
Name the major events that happen during sex determination and sex differentiation
Urogenital ridge
Bipotential gonad
Either 46, XX or 46,XY
46, XX become ovaries
46, XY become testis
Testis = Sertoli cells and leydig cells
When does sex determination occur
Around 6 weeks gestation through the presence or absence of the SRY gene
What do Sertoli cells produce to cause sex differentiation
Anti-mullerian hormone which causes regression of female structures
If testis are present and leydig cells are producing testosterone what happens to the developing internal genitalia
The wolffian system develops into the epididymis, vas deferens, seminal vesicles and ejaculatory ducts
If there are no testis or leydig cells producing testosterone what happens to developing internal genitalia
The mullerian system will develop into Fallopian tubes, uterus and the upper third of the vagina
Explain the timeline for sex differentiation in a male fetus
Germ cell migration occurs between 4-6 weeks gestation to form urogenital ridge
Sertoli cells are present at week 7 causing anti-mullerian hormone to be produced which causes Müllerian duct regression
Leydig cells are present from week 8 causing wolfffian duct stabilisation
At week 9 male external genital differentiation begins
Week 11 is when testicular descent begins to occur
From week 13 external genital grow
Explain the timeline in sex differentiation in a female fetus
Week 4 germ cell migration is seen from the endoderm to form the urogenital ridges
Week 6 somatic cells are present
Week 7 Müllerian duct stabilisation
Week 8 wolfffian duct regression occured due to the absence of testosterone
Week 8 oogonia begins to change to oocytes
Week 9 the uterus, tubes and vaginal canalisation
Week 10 no ovarian descent
What does DSD stand for
Disorder of sex development
What causes androgen insensitivity syndrome
Caused by mutations in the androgen receptor so they do not respond to androgens
What is puberty
The developmental changes a child undergoes to become sexually mature and physiologically ready to reproduce
What controls puberty
It is controlled by the hormones release in the hypothalamic- pituitary- gonadal axis
What does the release of GnRH stimulate the production and secretion of
LH and FSH from the anterior pituitary gland
What does the rise in FSH stimulate
FSH stimulates a rise in levels of oestrogen and oogenesis in females and onset of sperm production in males
What does the rise in LH stimulate
LH level rise stimulates the increased production of progesterone in females and an increase in testosterone in males
What can influence the onset of puberty
Genetic factors
Body weight
What is the first sign of puberty in females
Thelarche = beginning of breast development
What are the signs of puberty in females
First sign = thelarche
Second sign = pubarche
Menarche = first menstrual period (1.5-3 years after thelarche)
What is the first sign of puberty in males
Increase in testicular size
What is pubarche
A sign of puberty in males and the growth of pubic hair at the base of the penis
Why do both males and females have a growth spurt during puberty
The pubertal growth spurt is due to the interaction between the gonadal sex steroids, the growth hormone and insulin-like growth factor
