4 - Female Embryogenesis Flashcards
Three embryonic germ layers
Endoderm, mesoderm, ectoderm
What is developed from the endoderm?
Digestive system, lungs, endocrine system
What is developed from the mesoderm
Muscle, skeleton, cardiovascular, reproductive system
What is developed from the ectoderm
Nervous system, skin, hair
What is the ICM?
Inner cell mass
Mesoderm
What part of the reproductive tract is developed by the ectoderm? What other system?
External vagina or penile sheath
Clitoris or penis
Nervous system: hypothalamus, anterior & posterior pituitary
Oral and nasal cavities
What part of the reproductive tract develops from the mesoderm? What other systems?
Gonads, uterus, cervix, internal vagina
Epididymus, ductus deferens, accessory sex glands in males
Urinary, skeletal systems
Blood vessels, muscle
What systems develop from the endoderm?
Digestive, respiratory, glandular
Six steps of female embryonic development
- Development of hypothalamic-hypophyseal systems
- Migration of primordial germ cells from the yolk sac
- Sex cords develop in the gonad & mesonephric renal system transformation
- Sexual differentiation (Sex from structure)
- Development of female tract & ovaries
- Formation of broad ligament
Average gestation period for cattle, sheep, swine, dogs and cats
Cattle = ~280-290 days
Sheep = ~145-150 days
Swine = 3 months, 3 weeks, 3 days
Dog = 60-65 days
Cat = 63-67 days
How does the development of the hypothalamic-hypophyseal system occur?
Infundibulum hooks around Rathke’s pouch to become the pituitary gland
Infundibulum becomes posterior, Rathke’s pouch is anterior
= diff embryonic origins
What is migration of primordial germ cells?
Primordial germ cells are gametes that become oocytes during puberty
Migrate from yolk sac into genital region (gonadal ridge that eventually becomes the ovary)
Three stages of the embryonic renal system
- Pronephros
- Mesonephros
- Metanephros
What is the pronephros
Most primitive form of the kidney found in developing embryo
Limited function, eventually degenerates
What is the mesonephros
Early kidneys of mammalian embryo; regresses to give way to Metanephros
The remnants of the mesonephros become what?
Portions of the reproductive tract:
Mesonephric ducts (Wolffian ducts) = male repro tract
Paramesonephric ducts (Mullerian ducts) = female repro tract
What is the metanephros
Final renal system that eventually becomes the functioning kidneys in adult animal
Male sex determination is dependent on…
Testis determining factor (TDF) which develops testes
Testes sertoli cells secrete anti-mullerian hormone which degenerates the paramesonephric duct and causes leydig cells to differentiate, leading to testosterone production and development of repro syste
How does female sex determination work?
No testis determine factor -> ovaries develop -> no anti-mullerian hormone -> paramesonephric ducts become the oviducts, uterus, cervix and vagina
The paramesonephric ducts become what parts of the female repro tract? Why are there different tissues in the cranial and caudal vaginas?
Para form oviducts, uterine horn, cervix and cranial vagina
Caudal vagina develops from the urogenital sinus
Gonad in male vs female
Male = testis
Female = ovary
What does the mesonephros duct become in males?
Epididymis, ductus deferens
What does the urogenital sinus become in males vs females?
Male = urethra, male accessory sex glands
Female = urethra, caudal vagina - vestibule
Slide 24**
Important
Describe broad ligament formation
Repro tract begins to drop into the body cavity as BL (mesometrium) forms
Tract is then suspended in the abdominal cavity
Two kinds of anomalies during sexual differentiation in females and give example
Gonadal dysgenesis: incomplete development of gonads
e.g. Turner syndrome (only one X chromosome, one ovary does not fully develop)
Hermaphrodites: both ovarian and testicular tissues
e.g. Freemartin
Three causes of Hermaphrodism
Sex chromosome translocation
Mutation of sex linked genes
Hormonal exposure in utero (Freemartin)
What is freemartinism? In calves?
In female calves of heterosexual twins, embryonic membranes fuse prior to organ development so both calves share the same cotyledons & blood supply mixes
Female is exposed to testes determining factor (TDF) and anti-mullerian hormone (AMH) from male and development of fem repro tract from paramesonephros is inhibited
Occurs 90% of the time in hetero twins
Characteristics of a freemartin calf
- Incomplete development of female tract
- vestigial ovarian formation
- no estradiol production
- abnormally high testosterone
- bull-like behaviour and appearance
- infertile
