10 – Fetal Development of Genital System II

Question 1

X chromosome does not have SRY gene and cells without SRY express:

Answer 1

-genes important for female gonad development
*inhibit genes associated with male gonad development

Question 2

Sequence of ovary development:

Answer 2

1. Primary sex cords degenerate
2. Epithelial cells break away from surface and surround primitive germ cells (PGCs)=form ovigerous cords
3. PGCs in developing ovary undergo mitosis (oogonia to enter meiosis)
4. Ovigerous cords differentiate into primitive follicular cells=primordial follicles

Question 3

Primitive follicular cells from ovigerous cords differentiating:

Answer 3

-future granulosa cells
>granulosa cells=Sertoli cells in male
*primordial follicles formed

Question 4

Mesonephric duct and ovary development:

Answer 4

-still intact early on
*regresses while rete tubules degenerate
>no duct outlet for the gametes like in male
*paramesonephric duct develops further and enlarges

Question 5

Primordial follicles:

Answer 5

-stay as primordial follicles in the PERIPHERY that will become the CORTEX
>don’t penetrate deeply

Question 6

Ovigerous cords will disappear completely:

Answer 6

-defined cortical and non-germinal medullary region forms

Question 7

Paramesonephric duct enlarges with an opening=

Answer 7

-future infundibulum
>no direct connection, but very close

Question 8

When do follicles start to grow in large domestic animals?

Answer 8

-second half of fetal life

Question 9

Follicle development/arrangement in cattle, sheep, and pigs:

Answer 9

-RANDOMLY distributed in the cortex

Question 10

Follicle development/arrangement in dogs and cats:

Answer 10

-CLUSTERS in cortex

Question 11

Follicular development/arrangement in horses:

Answer 11

-confined to a more central region
-non-follicular region is in the PERIPHERY
*’inside out’=ovulation fossa

Question 12

Ovulation fossa (horses):

Answer 12

-portion of the ovary that becomes concave and retains the coelomic epithelial covering
>where more centrally located oocytes can be released

Question 13

Descent of ovaries:

Answer 13

-under POSTERIOR DISOLOCATION
*varies among species
-final position if maintained by ligaments

Question 14

Development of female reproductive tract ducts:

Answer 14

1. Caudal end of paramesonephric duct interacts with urogenital sinus
2. Paramesonephric ducts will fuse together near attachment
3. Small bud evaginates form caudal part of urogenital sinus to fuse with caudal tip of fused paramesonephric ducts and elongates

Question 15

Fused paramesonephric ducts are the future:

Answer 15

-cervix
-uterine body

Question 16

Bicornuate uterus:

Answer 16

-mare: stunted horns and larger uterine body
-pigs: have very long/developed uterine horns and a small uterine body

Question 17

Cranial portion of vagina, cervix, and uterus originate from:

Answer 17

-paramesonephric ducts=mesoderm

Question 18

Caudal portion of vagina and vestibule originate from:

Answer 18

-urogenital sinuse=ectoderm

Question 19

Accessory glands:

Answer 19

-epithelial buds from primitive urethra and urogenital sinus will give rise to URETHRAL and VESTIBULAR GLANDS
>homologous to male prostate and bulbourethral glands

Question 20

Broad ligament:

Answer 20

-in the fusion process of paramesonephric ducts, the reproductive tract is sandwiched between 2 layers of peritoneum=genital fold=future broad ligament

Question 21

Cloacal folds: (external genitalia)

Answer 21

-fuse ventrally to form genital tubercule
-become sub-divided into anal and urogenital folds with anal and urogenital membranes

Question 22

Mesoderm lateral to each urogenital fold will: (external genitalia)

Answer 22

-proliferate and elevate to create the labio-scrotal (genital) swellings

Question 23

Urogenital folds in females (external genitalia):

Answer 23

-will NOT fuse during development
*develop into LABIA

Question 24

Genital tubercule gives rise to:

Answer 24

-clitoris

Question 25

Estrogens (external genitalia):

Answer 25

-primary inducer of the development of female external genitalia

Question 26

Bipotential gonad: male vs. female structures

Answer 26

-male: interstitial cells
-female: thecal cells (mesonephric cells)

Question 27

Coelomic epithelium: male vs female structures

Answer 27

-male: Sertoli cells
-female: granulosa cells

Question 28

Mammary glands arise in developing embryo along the:

Answer 28

-ventral epidermal (ectoderm) thickenings=MAMMARY RIDGES (mammary lines)
>number that develop is species dependent

Question 29

Thick mammary ridges development: ‘stages”

Answer 29

1. Primary mammary bud: not branched
2. Secondary mammary bud: penetrates dermis more, branched, no ducts

Question 30

Secondary mammary buds undergo:

Answer 30

-canalization so that at birth each mammary gland has a lactiferous duct opening into larger ducts that empty to the exterior via a teat or nipple

Question 31

Puberty and pregnancy period: (mammary glands)

Answer 31

-only period where a proper duct and Alveolar system is being constructed
Ex. during repeated estrous cycles

Question 32

Final alveolar development in the dam takes place:

Answer 32

-during last trimester of pregnancy

Question 33

4 processes/levels where anomalies of sexual development can occur:

Answer 33

-chromosomal level
-gonadal differentiation
-duct system differentiation
-development of external genitalia

Question 34

Turner’s syndrome:

Answer 34

-chromosomal abnormality
*only one X is present (XO)
-primordial germ cells reach gonad, but many degenerate shortly after arrival
-most prevalent in horses, but also humans, pigs, dogs and cats

Question 35

Turner’s syndrome: primordial germ cells reach gonad, but many degenerate shortly after arrival leading to:

Answer 35

-hypoplastic ovary
-small uterus
-underdeveloped external genitalia
*due to lack of gonadal hormones

Question 36

Klinefelter’s syndrome:

Answer 36

-results from non-disjunction during meiosis giving XXY
-presence of Y results in MALE determining genes INFLUENCING development
-sometimes see an ovotestes: mixture of ovarian and testicular tissue
-humans, dogs, cats, swine, sheep, cattle

Question 37

Klinefelter’s syndrome: male determining genes influence development

Answer 37

-male gonads form, produce male related hormones=individual develops PHENOTYPICALLY as a male
-presence of female chromosomes drives production of female related genes=hypoplastic testes and prevention of spermatogenesis

Question 38

What are some abnormalities of uterus and vagina?

Answer 38

-fusion of uterus gives different types
>duplication of uterus with separate vaginas
>unicornuate uterus
>very narrow cervix (atretic cervix)