3 - SEXUAL DEVELOPMENT

Question 1

what is the early stage of sexual development?

Answer 1

undifferentiated gonads develop in the first few months

the chemicals from undifferentiated gonads flood surrounding tissue

can switch on TDF gene if present

Question 2

sequence:

the initial male development (in normal XY males)

Answer 2

TDF gene is present in all cells (on Y chromosome)

1 - gonadal signals trigger TDF protein production

2 - immature gonads respond to TDF and turn into testes

3 - sertoli cells secrete MIH

4 - müllerian duct degenerates

5 - leydig cells secrete androgens (testosterone)

Question 3

do gonads produce testosterone?

Answer 3

no, only once developed into testes

don’t need testosterone for the initial development (TDF is needed)

Question 4

sequence:

subsequent male development following hormonal instructions

Answer 4

• androgens masculinise all body tissue (except brain)
• müllerian duct = already gone
• wolffian duct = male internal sex organs
• urogenital groove = male external genitals but needs 5-alpha-reductase
• androgens make body ‘male shaped’

Question 5

what is 5-alpha-reductase?

Answer 5

an enzyme in urogenital tissue that converts testosterone into DHT (dihydrotestosterone)

Question 6

what does the urogenital groove (cloaca) need to develop in males?

Answer 6

DHT - dihydrotestosterone

a type of testosterone

Question 7

sequence:

initial female development starts by default

Answer 7

• gonads develop into ovaries
  (granulosa cells=supporting cells)
  (thecal cells=hormone producing)

Question 8

what are granulosa cells?

Answer 8

supporting cells in the ovaries

Question 9

what are thecal cells?

Answer 9

hormone producing cells in the ovaries

Question 10

when are hormones produced by the ovaries?

Answer 10

only in puberty (if gametes are present)

Question 11

what is the purpose of sertoli cells?

Answer 11

secretion of MIH (müllerian inhibiting hormone) in males

to cause the müllerian duct to degenerate

Question 12

what is the purpose of leydig cells?

Answer 12

to secrete androgens in the testes

Question 13

statement:

gamete-producing cells originate somewhere else (in the yolk sac) and migrate to the gonads (through the gut)

Answer 13

-

Question 14

what does the cloaca separate into?

Answer 14

the rectum and urogenital structures (external genitals)

it is an all purpose output (unitary tract and intestines)

Question 15

sequence:

subsequent female development

Answer 15

• müllerian duct = female internal sexual organs
• wolffian duct = degenerates
• urogenital groove = female external genitalia
• female body = happens in the absence of chemical shaping (some required, but in broad terms not needed like in males)

Question 16

which sexual development regions have bipotential?

Answer 16

urogenital groove (cloaca) and gonads

Question 17

is an embryo sexually indifferent/bi potential?

Answer 17

yes - could develop either sex

Question 18

what is the wolffian duct also known as?

Answer 18

vas deferens

Question 19

what is the müllerian duct also known as?

Answer 19

oviduct