Sexual differentiation

Question 1

What is the cowpers gland also known as?

Answer 1

Bulbourethral gland

Question 2

Define sex determination?

Answer 2

— Developmental decision that directs the
“bipotential” gonad to develop as a testis or ovary
— In mammals, it is genetically controlled
— In some species, it is an environmental process

Question 3

Define sexual differentiation?

Answer 3

• Induced by products of the gonad
• Phenotypic sex established
• Development of internal and external genitalia

Question 4

What part of the Y chromosomes determines sex determining region?

Answer 4

SRY = part of the Y chromosome sex
determining region
The “Master switch” regulating testis pathway

Question 5

What are the sex chromosomes in birds? And what is male and what is female?

Answer 5

• Sex chromosomes called Z and W
• ZZ is male and ZW is female [female heterogametic
  species]

Question 6

Incubation temperature of egg determines development

of gonad towards ovary or testis. In crocodiles and turtles what does a higher temp create?

Answer 6

Crocodiles: higher temp is male determining
Turtles: higher temp promotes female development

Question 7

How are the external appearance of male characteristics created?

Answer 7

XY: Testosterone causes unisex genitalia to develop into penis and scrotum. Testosterone is converted to dihydrotestosterone. Dihydrotestosterone causes external appearance of penis and scrotum

Question 8

How are the external appearance of female characteristics created?

Answer 8

XX: Absence of testosterone causes development of
clitoris, labia and vaginal opening.
. Cells without the SRY gene express female genes
and at the same time inhibit male genes

Question 9

What is the pregonadal phase?

Answer 9

— Germ cells start to migrate from yolk sac.

Question 10

What is the bipotential gonad?

Answer 10

. The bipotential gonad (not clear if will be
ovary or teste at this point)
— Development of gonadal precursor tissue near
kidneys (genital ridge)
— Germ cells migrate to genital ridge

Question 11

Primary sexual differentiation is?

Answer 11

— Differentiation of reproductive tissues

— Reflects nature of the gonads

Question 12

Secondary sexual differentiation is?

Answer 12

— Development of secondary sexual characteristics

— Marks sexes as phenotypically distinct

Question 13

What does the paramesonpheric duct become in the female?

Answer 13

It becomes the mullerian duct the the fallopian tubes.

Question 14

What does the mesonpheric duct become in the male?

Answer 14

The wolffian duct and then vas deferens.

Question 15

What is the process of male sexual differentiation?

Answer 15

SRY protein present on Y chromosome–> Testes develop–> sertoli cells secrete anti-mulleruan hormone (AMH)–> degeneration of paramesonephric duct–> AMH also causes cells to differentiate –> testosterone cause male duct system differentiation and dihydrotestosterone cause development of penis, scrotum and accessory glands.

Question 16

Mesonepheric tubules become?

Answer 16

Efferent ducts.

Question 17

Mesonephric ducts become?

Answer 17

Epididymus and ductus deferens.

Question 18

What does the gubernaculum do?

Answer 18

It is attached to the base of the testis and base of scrotum. The gubernaculum grows inside the scrotum pulling the testis into the inguinal canal. The gubernaculum then regresses pulling the testis into the scrotum and remains as the scrotal ligament.

Question 19

How is the male brain sexually differentiated?

Answer 19

— Testosterone secreted into blood crosses the blood brain barrier where it is converted to oestradiol and oestradiol masculinises brain.

Question 20

How is the female brain sexually differentiated?

Answer 20

— Alpha fetoprotein binds to estradiol this complex can not cross blood brain barrier which therefore protects the female brain from the masculinising effects of oestradiol.

Question 21

What is freemartinism?

Answer 21

— Heifer born twin to a bull
— Common blood supply between male and
female fetus
— Female exposed to AMH and testosterone from
male so ducts do not develop
.Ovaries do not develop complement of germ cells
. Gonad may produce testosterone and androstenedione
. Central nervous system programmed so that male
behaviour exhibited.

Question 22

Cryptorchidism, Inguinal herniation and Hypospadias are all types of what?

Answer 22

Testicular descent problems:
—Cryptorchidism: Failure of testes to descent into scrotum
— Inguinal herniation: Portion of intestine passes through inguinal canal into vaginal cavity
— Hypospadias: Urethral opening at base of penis