Embryology

Question 1

When does gastrulation happen?

Answer 1

week 3

Question 2

What is gastrulation?

Answer 2

formation of the trilminar disc - ectoderm, mesoderm and endoderm
invagination of the epiblast cells through the primitive streak to form the definitive endoderm and mesoderm

Question 3

What are the main groups that the mesoderm is divided into?

Answer 3

partial
intermediate - urogenital system is derived from here
lateral plate

Question 4

What is the Cloaca?

Answer 4

output that eventually forms the urethra

Question 5

What is the mesonephric system?

Answer 5

produces urine at a low level and goes alongside the mesonephric duct

Question 6

What does the metanephric system form?

Answer 6

the kidney

Question 7

When do the gonads differentiate into male or female?

Answer 7

week 7

Question 8

How do the genital ridges form?

Answer 8

coelamic epithelium proliferates and thickens

Question 9

How do the primitive sex cords form?

Answer 9

proliferating epithlium forms somatic support cells which envelope to primordial germ cells

Question 10

What is the bipotential phase?

Answer 10

occurs up to week 7

development of the genital ducts

Question 11

What are the two names of the genital ducts?

Answer 11

mesonephric duct (Wollfian)
paramesonephric duct (mullarian)

Question 12

Where do both genital ducts connect?

Answer 12

posterior wall of the urogenital sinus

Question 13

What is male developement triggered by?

Answer 13

presence of SRY - sex determining region Y

Question 14

Describe the process of male development?

Answer 14

somatic support cells develop into sertoli cells
primary sex cords form the testis/medullary cords
rete testis connect the mesonephric tubules to form the testis cord
tunica albuginea forms the thickened connective tissue between the coelomic epithelium and testis cord

Question 15

What is the role of the sertoli cells in male development?

Answer 15

secrete AMH (anti mullarian hormone) which causes degeneration of paramesonephric duct
stimulate the gonadal ridge cells to form Leydig cells

Question 16

What is the role of testosterone?

Answer 16

induces formation of the epididymis, vas deferens and seminal vesicles

Question 17

What is the role of dihydrotestosterone?

Answer 17

induces male specific external genitalia developement and prostate

Question 18

What is persistant mullarian syndrome?

Answer 18

due to mutations of AMH or AMH receptor genes
paramesonephric duct fails to regress leading to the formation of a uterus, vagina and uterine tubes, testis in ovary position and external male genitalia

Question 19

Which verterbal level do the testes originate?

Answer 19

T10

Question 20

How do the testes descend?

Answer 20

pulled caudally by the gubernoculum

Question 21

When do male accessory glands form?

Answer 21

week 10

Question 22

What does the seminal vesicle form from?

Answer 22

outpouching of the mesonephric duct

Question 23

What do the prostate and bulbourethral glands form from?

Answer 23

endodermal invaginations of the urethra

Question 24

At what week can you recognise the sex of a baby from a scan?

Answer 24

week 16

Question 25

What happens to the cloaca to differentiate males and females?

Answer 25

cloaca membrane ruptures and allows free communication | cloacal folds fuse crainally to form the. genital tubercle and caudally to form the urethral folds and anal folds

Question 26

How is the phallus formed?

Answer 26

elongation of the genital tubercle

Question 27

How is the penile urethra formed?

Answer 27

urethral folds are pulled to form the urethral groove, then they close to form the penile urethra

Question 28

How is the foreskin formed?

Answer 28

circular ingrowth of the ectoderm around the periphery of the glands

Question 29

What is hypospadias?

Answer 29

external urethral opening lies in an abnormal position along the urethral aspect of the penis

Question 30

How is the clitoris formed?

Answer 30

extension of the genital tubercle

Question 31

How is the labia minor and major formed?

Answer 31

genital swellings - labia major | urethral folds - labia minor

Question 32

How is the vestibule that the vagina and urethra open into formed?

Answer 32

urogenital groove

Question 33

Describe the basics of female development?

Answer 33

germ cells differentiate into oogla then into primary oocytes somatic support cells differentiate into granulosa cells and surround the primary oocyte, forming primordial follicles in the ovary

Question 34

What is the role of thecal cells?

Answer 34

stimulate oestrogen | stimulate formation of the female external genitalia and development of the paramesonephric ducts

Question 35

Where do the paramesonephric ducts open up into?

Answer 35

peritoneal cavity

Question 36

What do the paramesonephric ducts give rise to?

Answer 36

uterine tubes uterus superior vagina

Question 37

What is a Gartners cyst?

Answer 37

remnant of the mesonephric duct

Question 38

What are the 3 parts of the paramesonephric duct?

Answer 38

cranial horizontal caudal

Question 39

What does the cranial part of the paramesonephric duct become?

Answer 39

fallopian tube

Question 40

What does the horizontal part of the paramesonephric duct become?

Answer 40

Fallopian tube

Question 41

What does the caudal part of the paramesonephric duct become?

Answer 41

uterus cervis superior 1/3rd of vagina

Question 42

What forms the lower 2/3rds of the vagina?

Answer 42

sinovaginal bulbs