21 - Embryology

Question 1

what 3 things occur at week 3?

Answer 1

gastrulation

neurulation

somite formation

Question 2

what occurs between weeks 4-8?

Answer 2

organogenesis

Question 3

what occurs from week 9 to post-natal period?

Answer 3

maturation of organ systems

Question 4

which system forms the template for the reproductive system?

Answer 4

urinary system

Question 5

how many sets of kidneys develop during urinary system development and why?

Answer 5

3 - each acts as a template for the subsequent stage

Question 6

what is the first set of kidneys which develop?

Answer 6

Pronephros – cervical region – vestigial

Question 7

what is the second set of kidneys which develop?

Answer 7

Mesonephros – thoracolumbar region – briefly functional

Question 8

what is the third set of kidneys which develop?

Answer 8

Metanephros – pelvic region – functional

Question 9

when does genital (gonadal) ridge formation occur?

Answer 9

week 5-6

Question 10

how does gonadal ridge form?

Answer 10

@ ~ week6, Medial part of mesonephric ridge becomes thickened to form gonadal ridge

Question 11

what is formed when germ cells migrate into the gonadal ridge?

Answer 11

indifferent gonad

Question 12

how do germ cells migrate to gonadal ridge?

Answer 12

migrate from yolk sac, via dorsal mesentery, and embed into primitive sex cords

Question 13

how is paramesonephric duct formed?

Answer 13

Epithelium of the mesonephros invaginates to form a tube

Question 14

describe urinary and reproductive formations in males (4)?

Answer 14

1 - gonad forms testis

2 - Mesonephric duct develops into epididymis, vas deferens, seminal vesicle

3 - Paramesonephric duct degenerates

4 - Urogenital sinus forms bladder, urethra; and prostate

Question 15

describe urinary and reproductive formations in females (4)?

Answer 15

1 - Gonad forms the ovary

2 - Mesonephric duct degenerates

3 - Paramesonephric duct forms fallopian tube, uterus, cervix part of vagina

4 - Urogenital sinus forms bladder and lower part of vagina

Question 16

describe the origin of seminal vesicles?

Answer 16

Outgrowth from caudal end of mesonephric duct

Question 17

describe the origin of prostate?

Answer 17

Outgrowth(s) from urethra (from urogenital sinus)

Question 18

which hormone influences the formation of male external genitalia?

Answer 18

testosterone

Question 19

how does indifferent gonad develop into testis?

Answer 19

presence of TDF

Question 20

how does indifferent gonad develop into ovaries?

Answer 20

by default - no TDF or SRY region

Question 21

what is the result of absence of testosterone in females?

Answer 21

degeneration of mesonephros and mesonephric duct

Question 22

what gives rise to the female genital tract?

Answer 22

Paramesonephric ducts

Question 23

Cranial (open funnel) end of paramesonephric duct becomes associated with what in females?

Answer 23

ovary

Question 24

what does the Caudal end of paramesonephric duct (uterovaginal primordium) become in females?

Answer 24

uterus and superior part of vagina

Question 25

what develops into the inferior part of the vagina?

Answer 25

urogenital sinus

Question 26

in males, what occurs at week 7?

Answer 26

descent of testis to level of T10

Question 27

in males, what occurs at week 12?

Answer 27

descent of testis to level of deep inguinal ring

Question 28

when do the testis enter the scrotum?

Answer 28

week 39 - just prior to birth

Question 29

in females, what occurs at week 7?

Answer 29

descent of ovaries to level of T10

Question 30

in females, what occurs at week 12?

Answer 30

descent of ovaries to level of broad ligament

Question 31

once ovaries have descended, what does the round ligament do?

Answer 31

Round ligament drawn through inguinal canal to attach to labrum majorum

Question 32

what is associated with descent of testis?

Answer 32

Formation of the larger inguinal canal

Question 33

what is associated with descent of ovaries?

Answer 33

the presence of the round ligament and its passage through the inguinal canal

Question 34

define Cryptorchidism?

Answer 34

a condition in which one or both of the testes fail to descend from the abdomen into the scrotum

Question 35

4 reasons for absence of testes in scrotum?

Answer 35

Undescended Ectopic Retractile testes Absent testes

Question 36

3 complications associated with Cryptorchidism?

Answer 36

Infertility Malignant transformation (germ cell tumours) Testicular torsion

Question 37

how to manage Cryptorchidism?

Answer 37

Orchiopexy

Question 38

give an example of a condition which arises due to remnants of mesonephric duct?

Answer 38

gartner's cysts

Question 39

give 4 examples of anomalies of the paramesonephric duct?

Answer 39

Complete duplication Bicornuate uterus Septate uterus Arcuate uterus

Question 40

what does mesonephric duct become?

Answer 40

vas deferens

Question 41

what ultimately determines the differentiation of gonads?

Answer 41

presence of SRY region

Question 42

what does mesoderm become?

Answer 42

indifferent gonad