L4: development of the reproductive tracts

Question 1

Explain embryonic folding and the importance of the hindgut

Answer 1

Gives rise to a gut tube – can be separated into a foregut, midgut & hindgut
Hindgut – important in the creation of the reproductive and urinary tracts -> gives rise to a single opening called the cloaca
-this becomes the urogenital sinus = common opening for the reproductive and urinary systems

Question 2

What is the urogenital ridge?

Answer 2

Area of intermediate mesoderm in the posterior abdominal wall that gives rise to the embryonic kidney and the gonad

Question 3

Describe the differentiation of the gonad

Answer 3

Primordial germ cells (specialised population of cells that arise from the yolk sac) migrate along the retroperitoneum to the gonad -> which at this point is indifferent
Y chromosome contains a SRY gene – genes in this region cause differentiation of the gonad into a testis -> formation of seminiferous tubules (primordial germ cells that remain will begin gametogenesis at puberty)
Without this gene – gonad will differentiate into an ovary (primordial germ cells remain as primordial follicles, which will then develop into oocytes at puberty)

Question 4

Describe the duct systems in the male

Answer 4

Presence of testes will produce androgens (testosterone) -> drive development of the duct system in men, epididymis & vas deferens, by maintaining the mesonephric duct (WOLFFIAN DUCT)
Mesonephric ducts fuse with the gonad, therefore it is not continuous & not open in the peritoneum

Question 5

Describe the duct systems in the female

Answer 5

Absence of testes will cause formation of the female internal genitalia, uterus, fallopian tubes & part of the vagina, as the mesonephric duct regresses 
Paramesonephric duct (MULLERIAN DUCT) remains – needs no stimulation (testes produce Mullerian inhibitory substance to prevent the duct from developing in males) 
Mullerian duct is separate to the gonad – no direct connection, hence there is a gap in communication within the abdominal cavity

Question 6

Describe the development of the external genitalia in males

Answer 6

Presence of testes will cause development of male external genitalia
Penis – elongation and fusion of the genital folds
Scrotum – fusion of the genital swellings

Question 7

Describe the development of the external genitalia in females

Answer 7

Absence of testes will lead to development of female external genitalia = vulva
No fusion of the genital folds or swellings occur, leading to the development of the labia minora & majora

Question 8

Describe the descent of the testes

Answer 8

Area of peritoneum pinches off to descend first, then the gubernaculum & testis follow behind all the way to the scrotum = processus vaginalis – normally closes off
Testis is connected to the scrotum by the gubernaculum

Question 9

Describe the descent of the ovary

Answer 9

Same process as testes but it stays in the pelvis due to the physical barrier of the developing uterus
Gubernaculum remains in the women as the round ligament
-stretching this ligament can cause pain in the labia