Embryology

Question 1

What is gastrulation and how & where does this occur?

Answer 1

Formation of the trilaminar disc, cells from the epiblast (ectoderm) invaginate into the area inbetween itself and the hypoblast (endoderm) so third layer (mesoderm) is formed, the cells migrate through the primitive streak

Question 2

What are the 2 areas in which the mesoderm layer does not develop?

Answer 2

Cranially - oropharyngeal membrane

Caudally - cloacal membrane

Question 3

How are tubes within tubes created in development? e.g. gut tube inner tube and skin tube outer tube

Answer 3

lateral folding and cranial-caudal folding

Question 4

What does the urogenital ridge develop from and which part is medial and which lateral?

Answer 4

Intermediate mesoderm

-urinary system lateral and genital system medial

Question 5

Both excretory ducts of the urogenital fold enter a common cavity. What is this called?

Answer 5

Cloaca

Question 6

The primordial germs cells (PGC’s) migrate via the dorsal mesentery from yolk sac to where?

Answer 6

To intermediate mesoderm

Question 7

After the PGCs migrate to urogenital ridge (intermediate mesoderm), coelomic epithelium proliferates and thickens to form what? What will these structures go on to become?

Answer 7

Genital ridges that will go on to become the primitive gonads

Question 8

What is coelomic epithelium?

Answer 8

Mesothelium that lines the peritoneum

Question 9

The proliferating epithelial cells forming the genital ridges form continue to proliferate to form what?

Answer 9

Somatic support cells enveloping the PGCs that form the primitive sex cords

Question 10

What are the two identical pairs of genital ducts?

Answer 10

Mesonephric (Wollfian) duct - eventually form male

Paramesonephric (Mullerian) duct - eventually form female

Question 11

What marks the ambisexual/bipotential phase of development and what week does sexual differentiation occur?

Answer 11

Genital ducts and indifferent gonads, sexual differentiation occurs from week 7 onwards

Question 12

What do the primitive gonads form from?

Answer 12

Genital ridges

Question 13

Female development occurs in the absence of what transcription factor?

Answer 13

SRY - sex determining region of y

Question 14

The surface epithelium of the ovary gives rise to what?

Answer 14

Cortical cords

Question 15

PGC’s differentiate into oogonia and then primary oocytes. What develops around these to support them and together what do these form?

Answer 15

Granulosa cells develop around primary oocytes and together they form the primordial follicles in the ovary

Question 16

What type of cells are thecal cells and what do they produce?

Answer 16

Endocrine cells - produce androgen that will become oestrogen

Question 17

What do the paramesonephric (Mullerian) ducts become?

Answer 17

Uterus, uterine tubes and superior vagina

Question 18

What are the 3 parts of the paramesonephric duct (Mullerian)? Which is open into coelomic cavity, which crosses the mesonephric duct and which portion fuses with the paramesonephric duct on the opposite side?

Answer 18

Cranial - opens into coelomic cavity
Horizontal -crosses the mesonephric duct
Caudal - fuses with duct on opposite side

Question 19

What will happen to the mesonephric ducts in the female?

Answer 19

They will regress

Question 20

Which part of the paramesonephric duct will give rise to the uterovaginal canal?

Answer 20

Caudal part

Question 21

How is the vaginal lumen is created by what?

Answer 21

Vacuolisation of the paramesonephric portion of the vagina and the sinuvaginal bulbs

Question 22

What do the somatic support cells develop into in males?

Answer 22

Mostly into seminiferous tubules but some will differentiate into Sertoli cells

Question 23

What do the primary sex cords that engulf the PGCs form in the males?

Answer 23

Testis/medullary cords

Question 24

The tesicular cords anastomose together to form the rete testis. What do the rete testis connect?

Answer 24

Rete testis connect the mesonephric tubules to the testis cords

Question 25

What does the mesonephric (Wollfian) duct eventually become?

Answer 25

vas deferens (AKA ductus deferens)

Question 26

A thickened layer of connective tissue forms between the coelomic epithelium and testis cords. What is this called?

Answer 26

Tunica albuginea

Question 27

How does SRY protein lead to degeneration of paramesonephric duct?

Answer 27

SRY protein stimulates formation of Sertoli cells which secrete AMH (anti-Mullerian hormone) which degenerates paramesonephric duct

Question 28

What is the role of SRY protein in the formation of the male genitalia and sex organs?

Answer 28

SRY protein stimulates formation of Sertoli cells which stimulate gonadal ridge cells to form Leydig cells. Leydig cells secrete testosterone & dihydrotestosterone (DHT) which form male genitalia and sex organs

Question 29

Dihydrotestosterone induces formation of epididymis, vas deferens and seminal vesicles and testosterone induces male specific external genitalia development and prostate. True/false?

Answer 29

False - other way around Testosterone secondary sex organs DHT external genitalia and prostate

Question 30

What is Persistent Mullerian Duct Syndrome?

Answer 30

Paramesonephric ducts fail to regress so patients present with uterus, vagina and uterine tubes but will have testes in ovarian location and have male external genitalia

Question 31

List uterine congenital abnormalities.

Answer 31

- double vagina, double uterus - bicornate uterus (like two uterus but join at cervix) - septated uterus - unicornate uterus - cervical atresia

Question 32

Testes originate at ___th thoracic level and are pulled caudally by the ____. Failure to descend of one or both testis is _______.

Answer 32

10th thoracic level Gubernaculum Cryptorchidism

Question 33

Prostate and bulbourethral glands, seminal vesicle glands develop during week 10. What do each develop from?

Answer 33

Prostate and bulbourethral glands are endodermal invaginations from the urethra and the prostate is above the bulbourethral glands. Seminal vesicles develop from mesonephric duct

Question 34

``` What does each of these structures become in the female: Genital tubercle Urethral fold Genital swelling Urogenital groove ```

Answer 34

Genital tubercle - clitoris Urethral fold - labium minus Genital swelling - labium majus Urogenital groove - vagina and urethra

Question 35

What “zips up” the midline to form the male spongy urethra?

Answer 35

Urethral groove

Question 36

What tissue grows to form glans penis and prepuce (foreskin)?

Answer 36

Ectodermal ingrowth

Question 37

An incomplete fusion of the paramesonephric duct | can cause what?

Answer 37

two uteri

Question 38

THe superior part of the vagina develops from what structure?

Answer 38

paramesonephric duct