Female- Genitalia Development

Question 1

Female sex determination

Answer 1

-Sex chromosomes determine whether embryo becomes male and female. Y has SRY, X does not.
>cells without SRY express genes important for female gonad development and inhibit genes associated with male gonad development
**key female genes: Dax-1, FOXL2 which suppress testes, promote ovaries

Question 2

Sequence of Ovary development

Answer 2

1.Primary sex cords degenerate without SRY present
2.Epithelial cells break away from surface and surround PGCs to form ovigerous cords
3. Ovigerous cords differentiate into primitive follicular cells (future granulosa cells), later develop into primordial follicles
4. Primitive follicular cells surrounding the primitive germ cells do not penetrate into the developing ovary and instead stay as primordial follicles in the periphery that will be cortex.
5.Ovigerous cords disappear, and a defined cortical and non-germinal medullary region form

Question 3

Development of oocytes

Answer 3

Primitive germ cells in developing ovary undergo mitosis to form oogonia
>Oogonia will enter meiosis and eventually form oocytes

Question 4

Mesonephric and Paramesonephric ducts in females

Answer 4

-Mesonephric duct is intact initially, but will regress with rete tubules making no duct outlet for the gametes like in male
-Paramesonephric duct develops further and enlarges to eventually become future infundibulum

Question 5

Timing of oogonial mitosis

Answer 5

-species differences
>begins during varying times of gestation, and ends either during end of gestation of after birth

Question 6

Follicle development during fetal life

Answer 6

-in large domestic animals, follicles start to grow during second half of fetal life
-developing dominant follicles do not ovulate till puberty

Question 7

Calf follicle development

Answer 7

follicular waves start to develop as early as 2 weeks of age

Question 8

Equine follicle development

Answer 8

-development of follicles is confined to a more central region while non-follicular region is in periphery of ovary

-ovulation fossa: concave, retained coelomic epithelial covering that allows central oocytes to release

Question 9

Follicle confines

Answer 9

-Cattle, sheep, pig: follicles are randomly distributed in cortex

-Dogs and cats: occur in clusters in cortex

Question 10

Descent of ovaries

Answer 10

-ovaries undergo posterior dislocation that varies among the species

-final position maintained by ligaments: suspensory ligaments and proper ligaments

Question 11

Dog and cat ovary descent

Answer 11

-ovaries move only slightly and occupy the area in the sub-lumbar region caudal to kidneys

Question 12

Mare ovary descent

Answer 12

ovaries occupy region between kidney and pelvic inlet

Question 13

Pigs and cattle ovary descent

Answer 13

descent is pronounced
>ovaries take a position much closer to the pelvic inlet

Question 14

Development of female reproductive tract ducts

Answer 14

1.Paramesonephric duct
-Cranial part of paramesonephric duct remains open (infundibulum) to the abdominal cavity
- caudal part interacts with urogenital sinus and fuse together near attachment

2. A small bud evaginates from the caudal part of the urogenital sinus to fuse with the caudal tip of the fused paramesonephric ducts. Defined cervix and cranial portion of vagina forms. Bud elongates. and continuous duct system is formed.
3. Vestibule originates from urogenital sinus by invagination.

Question 15

What originates from endoderm and mesoderm?

Answer 15

-Endoderm: caudal part of vagina and vestibule

-Mesoderm: cranial portion of vagina, cervix, uterus from paramesonephric ducts

Question 16

Uterine types

Answer 16

1.duplex
2.Bicornuate
3.simplex

Question 17

Duplex uterus

Answer 17

-occurs in marsupials and rabbits
-two cervices, forked penis

Question 18

Bicornuate uterus

Answer 18

-occurs in mares (poorly developed horns) and cows (moderately developed horns)
and dogs and cats (highly developed uterine horns)

Question 19

Simplex uterus

Answer 19

-occurs in primates
-no uterine horns, large uterine body

Question 20

Accessory glands

Answer 20

Epithelial buds from primitive urethra and urogenital sinus give rise to urethral and vestibular glands

Question 21

Homologues Accessory glands for males vs females

Answer 21

Males: prostate and bulbourethral glands

Females: urethral and vestibular glands

Question 22

Where do the gonad and duct systems originate from in both males and females?

Answer 22

from behind the peritoneum (retroperitoneal)

Question 23

supportive structures of female

Answer 23

Broad ligament that surrounds uterus to support it from the dorsal and lateral aspects

Question 24

Formation/development of the supportive structures

Answer 24

-Caudally, gonadal ridges and paramesonephric ducts continue to move ventrally but still do not fuse. Gonadal ridge even rotates to a degree.
-in the fusion process, the reproductive tract is now sandwiched between 2 layers of peritoneum called the genital fold which will eventually become the broad ligament

Question 25

Development of the female external genitalia

Answer 25

1.Mesenchymal cells will move around cloacal membrane and form 2 folds called cloacal folds

2. Folds fuse ventrally to form genital tubercle. Folds also become subdivided into anal and urogenital folds with anal and urogenital membranes

3.mesoderm lateral to each urogenital fold will proliferate and elevate to create the labio-scrotal or genital swellings

4.Urogenital folds will not fuse during development and will develop into the labia

5. Genital tubercle gives rise to the clitoris

Question 26

What hormone is the primary inducer of the development of female external genitalia?

Answer 26

estrogens

Question 27

Mammary gland development

Answer 27

1.arise in developing embryo along two ventral epidermal thickenings called mammary ridges.

2.thick ridges develop primary mammary buds when the epidermal tissue begins to move inward and penetrate into the mesenchyme.

3. primary buds then elaborate into branches to further penetrate the dermis forming the secondary buds

4.Secondary buds continue to increase in length and budding. Then canalization occurs to ensure that each gland has a lactiferous duct opening into larger ducts that empty to exterior via a teat or nipple

Question 28

Mammary ridges

Answer 28

-extend from axillary region to the inguinal region of embryo

-number of mammary glands that develop on the ridges is very species dependent

Question 29

Final changes that occur in mammary glands

Answer 29

-changes occur at birth and puberty, puberty and pregnancy, during pregnancy, lactation and involution

**only during period between puberty and pregnancy is a proper duct and alveolar system being created (ie. during repeated estrous cycle)

Question 30

Alveolar development in a dam

Answer 30

final alveolar development will take place in last trimester of pregnancy.
>alveoli will group lobules that empty into a common duct or lobe

Question 31

At what level do anomalies of sexual development occur?

Answer 31

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

Question 32

cause of Turner’s syndrome

Answer 32

-due to chromosomal abnormalities. When only one X chromosome is present (never occurs with only one Y, so must always have X for viable pregnancy)

-primordial germ cells reach the gonad but many degenerate shortly after arrival.
>lack of gonadal hormones

-most prevalent in horses, also found in humans, pigs, dogs, cats

Question 33

Turner’s syndrome clinical signs

Answer 33

-hypoplastic ovary
-small uterus
-underdeveloped external genitalia

Question 34

Klinefelter’s syndrome

Answer 34

-results from non-disjunction during meiosis giving XXY

> presence of Y chromosome results in male-determining genes influencing development resulting in male gonads and male related hormones being produced resulting in individual developing male phenotypes

> presence of female chromosomes drives production of female realted genes resulting in hypoplastic testes which can prevent spermatogenesis

-found in humans, dogs, cats, sheep, swine, cattle

Question 35

Abnormalities of uterus and vagina

Answer 35

-fusion of uterus can vary
>uterus is split in two
>malfusion resulting in only one uterus
>incomplete exit out of uterus