Puberty, Sex Development

Question 1

When do urogenital ridges form and why

Answer 1

They form between 6-8 weeks of gestation due to the migration of primordial germ cells from the dorsal endoderm

Question 2

What stage do the urogenital ridges form

Answer 2

They form in the indifferent stage

Question 3

If the SRY gene is present what happens

Answer 3

You will have a testes differentiation by week 9 of gestation

Question 4

If the SRY gene is absent what will happen

Answer 4

You will have ovaries present by 11-12 weeks of gestation

Question 5

Name the major events that happen during sex determination and sex differentiation

Answer 5

Urogenital ridge
Bipotential gonad
Either 46, XX or 46,XY
46, XX become ovaries
46, XY become testis
Testis = Sertoli cells and leydig cells

Question 6

When does sex determination occur

Answer 6

Around 6 weeks gestation through the presence or absence of the SRY gene

Question 7

What do Sertoli cells produce to cause sex differentiation

Answer 7

Anti-mullerian hormone which causes regression of female structures

Question 8

If testis are present and leydig cells are producing testosterone what happens to the developing internal genitalia

Answer 8

The wolffian system develops into the epididymis, vas deferens, seminal vesicles and ejaculatory ducts

Question 9

If there are no testis or leydig cells producing testosterone what happens to developing internal genitalia

Answer 9

The mullerian system will develop into Fallopian tubes, uterus and the upper third of the vagina

Question 10

Explain the timeline for sex differentiation in a male fetus

Answer 10

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

Question 11

Explain the timeline in sex differentiation in a female fetus

Answer 11

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

Question 12

What does DSD stand for

Answer 12

Disorder of sex development

Question 13

What causes androgen insensitivity syndrome

Answer 13

Caused by mutations in the androgen receptor so they do not respond to androgens

Question 14

What is puberty

Answer 14

The developmental changes a child undergoes to become sexually mature and physiologically ready to reproduce

Question 15

What controls puberty

Answer 15

It is controlled by the hormones release in the hypothalamic- pituitary- gonadal axis

Question 16

What does the release of GnRH stimulate the production and secretion of

Answer 16

LH and FSH from the anterior pituitary gland

Question 17

What does the rise in FSH stimulate

Answer 17

FSH stimulates a rise in levels of oestrogen and oogenesis in females and onset of sperm production in males

Question 18

What does the rise in LH stimulate

Answer 18

LH level rise stimulates the increased production of progesterone in females and an increase in testosterone in males

Question 19

What can influence the onset of puberty

Answer 19

Genetic factors
Body weight

Question 20

What is the first sign of puberty in females

Answer 20

Thelarche = beginning of breast development

Question 21

What are the signs of puberty in females

Answer 21

First sign = thelarche
Second sign = pubarche
Menarche = first menstrual period (1.5-3 years after thelarche)

Question 22

What is the first sign of puberty in males

Answer 22

Increase in testicular size

Question 23

What is pubarche

Answer 23

A sign of puberty in males and the growth of pubic hair at the base of the penis

Question 24

Why do both males and females have a growth spurt during puberty

Answer 24

The pubertal growth spurt is due to the interaction between the gonadal sex steroids, the growth hormone and insulin-like growth factor

Question 25

What is precocious puberty

Answer 25

Appearance of secondary sexual characteristics before the age of 8 in females and 9 in males

Question 26

What are the different types of precocious puberty

Answer 26

Iatrogenic - exposure to exogenous oestrogen via cream/lotions

True/complete - early maturation of the HPG axis = high levels of GnRH, LH and FSH

Incomplete - increased levels of oestrogen in females and androgens in boys independent of GnRH

Question 27

Precocious puberty can either be isosexual or contra sexual what does this mean

Answer 27

Isosexual is early sexual development consistent with the genetic and gonadal sex of the child

Contra sexual is early sexual development associated writ feminisation of a male or virilisation of a female

Question 28

What is delayed or absent puberty

Answer 28

Delayed or absent puberty is the absence of secondary sexual characteristics by the age of 13 in females and 16 in males

Question 29

What could be the cause of delayed puberty

Answer 29

Hypogondaotropic hypogonadism - disorder of either hypothalamus or pituitary gland

Hypergonadotropic hypogonadism - disorder of the gonads