21 - Embryology Flashcards
what 3 things occur at week 3?
gastrulation
neurulation
somite formation
what occurs between weeks 4-8?
organogenesis
what occurs from week 9 to post-natal period?
maturation of organ systems
which system forms the template for the reproductive system?
urinary system
how many sets of kidneys develop during urinary system development and why?
3 - each acts as a template for the subsequent stage
what is the first set of kidneys which develop?
Pronephros – cervical region – vestigial
what is the second set of kidneys which develop?
Mesonephros – thoracolumbar region – briefly functional
what is the third set of kidneys which develop?
Metanephros – pelvic region – functional
when does genital (gonadal) ridge formation occur?
week 5-6
how does gonadal ridge form?
@ ~ week6, Medial part of mesonephric ridge becomes thickened to form gonadal ridge
what is formed when germ cells migrate into the gonadal ridge?
indifferent gonad
how do germ cells migrate to gonadal ridge?
migrate from yolk sac, via dorsal mesentery, and embed into primitive sex cords
how is paramesonephric duct formed?
Epithelium of the mesonephros invaginates to form a tube
describe urinary and reproductive formations in males (4)?
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
describe urinary and reproductive formations in females (4)?
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
describe the origin of seminal vesicles?
Outgrowth from caudal end of mesonephric duct
describe the origin of prostate?
Outgrowth(s) from urethra (from urogenital sinus)
which hormone influences the formation of male external genitalia?
testosterone
how does indifferent gonad develop into testis?
presence of TDF
how does indifferent gonad develop into ovaries?
by default - no TDF or SRY region
what is the result of absence of testosterone in females?
degeneration of mesonephros and mesonephric duct
what gives rise to the female genital tract?
Paramesonephric ducts
Cranial (open funnel) end of paramesonephric duct becomes associated with what in females?
ovary
what does the Caudal end of paramesonephric duct (uterovaginal primordium) become in females?
uterus and superior part of vagina
what develops into the inferior part of the vagina?
urogenital sinus
in males, what occurs at week 7?
descent of testis to level of T10
in males, what occurs at week 12?
descent of testis to level of deep inguinal ring
when do the testis enter the scrotum?
week 39 - just prior to birth
in females, what occurs at week 7?
descent of ovaries to level of T10
in females, what occurs at week 12?
descent of ovaries to level of broad ligament
once ovaries have descended, what does the round ligament do?
Round ligament drawn through inguinal canal to attach to labrum majorum
what is associated with descent of testis?
Formation of the larger inguinal canal
what is associated with descent of ovaries?
the presence of the round ligament and its passage through the inguinal canal
define Cryptorchidism?
a condition in which one or both of the testes fail to descend from the abdomen into the scrotum
4 reasons for absence of testes in scrotum?
Undescended
Ectopic
Retractile testes
Absent testes
3 complications associated with Cryptorchidism?
Infertility
Malignant transformation (germ cell tumours)
Testicular torsion
how to manage Cryptorchidism?
Orchiopexy
give an example of a condition which arises due to remnants of mesonephric duct?
gartner’s cysts
give 4 examples of anomalies of the paramesonephric duct?
Complete duplication
Bicornuate uterus
Septate uterus
Arcuate uterus
what does mesonephric duct become?
vas deferens
what ultimately determines the differentiation of gonads?
presence of SRY region
what does mesoderm become?
indifferent gonad
