Female- Genitalia Development Flashcards
Female sex determination
-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
Sequence of Ovary development
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
Development of oocytes
Primitive germ cells in developing ovary undergo mitosis to form oogonia
>Oogonia will enter meiosis and eventually form oocytes
Mesonephric and Paramesonephric ducts in females
-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
Timing of oogonial mitosis
-species differences
>begins during varying times of gestation, and ends either during end of gestation of after birth
Follicle development during fetal life
-in large domestic animals, follicles start to grow during second half of fetal life
-developing dominant follicles do not ovulate till puberty
Calf follicle development
follicular waves start to develop as early as 2 weeks of age
Equine follicle development
-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
Follicle confines
-Cattle, sheep, pig: follicles are randomly distributed in cortex
-Dogs and cats: occur in clusters in cortex
Descent of ovaries
-ovaries undergo posterior dislocation that varies among the species
-final position maintained by ligaments: suspensory ligaments and proper ligaments
Dog and cat ovary descent
-ovaries move only slightly and occupy the area in the sub-lumbar region caudal to kidneys
Mare ovary descent
ovaries occupy region between kidney and pelvic inlet
Pigs and cattle ovary descent
descent is pronounced
>ovaries take a position much closer to the pelvic inlet
Development of female reproductive tract ducts
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
- 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.
- Vestibule originates from urogenital sinus by invagination.
What originates from endoderm and mesoderm?
-Endoderm: caudal part of vagina and vestibule
-Mesoderm: cranial portion of vagina, cervix, uterus from paramesonephric ducts