Embryogenesis of Pituitary Gland and Reproductive Tract Flashcards
What is the stomodeum?
Part of the embryonic mouth.
What is Rathke’s Pouch?
Part of the stomodeum.
What is the infundibulum in the case of pituitary gland development?
A funnel-shaped structure at the base of the brain.
In what direction does the infundibulum grow during pituitary gland development?
Down towards the mouth.
In what direction does Rathke’s pouch grow during pituitary gland development?
Up towards the brain.
What connects Rathke’s pouch to the stomodeum?
A stalk that regresses when Rathke’s pouch fuses with the infundibulum.
What structure becomes the posterior pituitary gland?
The infundibulum.
What structure becomes the anterior pituitary gland?
Rathke’s Pouch.
What is the sella turcica?
The cavity in the sphenoid bone that houses the pituitary gland.
What is the alternate name for the genital ridge?
The gonadal ridge.
Where do primordial germ cells come from in mammals?
The gut, specifically the endoderm.
How are primordial germ cells transported in birds?
The bloodstream.
Where do primordial germ cells end up in mammals?
The gonadal/genital ridge.
What does the genital/gonadal ridge become?
An ovary or a testis.
What did the Jost (Yahst) experiment discover?
Removing the Mullerian ducts still leads to the embryo being female (in the absence of T and AMH stimulation).
What are the two types of ducts found in the embryo?
- Mullerian (paramesonephric) duct.
- Wolffian (mesonephric) duct.
What are the steps of sex determination in mammals?
- Chromosomal sex.
- Gonadal sex.
- Hormonal sex.
- Phenotypic sex.
- Behavioral and/or Brain sex.
How chromosomes are in one pair in mammals?
Two chromosomes.
What determines sex in seaworms, fish, and reptiles?
The environment.
What animals have multiple sex chromosomes?
Invertebrates, reptiles, insects.
What animals are haplodiploid?
Bees and spiders.
What does haplodiploid mean?
When either the male or female does not possess all of the chromosomes required to produce offspring.
What are the sex chromosome combinations that result in males?
- XY.
- XXY.
- XXYY.
- XXXY.
*2-4 results in males with impaired sperm production.
What are the sex chromosome combinations that result in females?
- XX.
- XXX.
What sex chromosome combination results in a female with incomplete ovarian development?
XO.
*Turner’s Syndrome.
On which sex chromosome is the gene controlling testicular differentiation found on in mammals?
The Y-Chromosome.
What does the SRY gene code for the production of?
Testis Determining Factor (TDF).
What is the function of testis determining factor?
To act as a DNA-binding protein and a transcription factor.
What does (TDF) cause to occur?
- Development of Sertoli cells.
- Anti-Mullerian Hormone to be produced by the Sertoli cells.
- Primary sex chord/seminiferous tubule development.
What occurs if the SRY gene is absent?
The secondary sex chords (egg nests) develop.
What does Anti-Mullerian Hormone (AMH) do?
It prevents Mullerian ducts from forming.
What are three other functions that the Y-chromosome codes for?
- Long bone growth.
- Androgen production.
- Spermatogenesis.
What are the male and female sex chromosomes in birds?
- Males: ZZ*.
- Female: ZW**.
*The SRY gene is found on the Z chromosome.
**The W chromosome determines sex.
What does the testosterone secreted from the Leydig cells cause the formation of?
- Epididymis.
- Seminal vesicles.
- Vas deferens.
What are the steps of female tract development?
1a. No Testosterone.
1b. Wolffian ducts regress.
2a. No AMH.
2b. Mullerian ducts become the uterus, oviducts, cervix, and anterior vagina.
What causes the differences in the uterine body between species?
The differences in the degree of fusion of the Mullerian ducts.
What does the synthesis of DHT cause to form?
- Penis.
- Accessory sex glands (Prostate and Cowper’s gland).
- Scrotum.
How do males and females differ in behavior?
- Males are more aggressive when playing.
- Males are better at spatial recognition and organizing things into a space.
What happens if a female rat is given a dose of testosterone shortly after birth?
The female will fail to copualte or cycle as an adult.
What part of the hypothalamus must be deactivated or removed for the hypothalamus to be defeminized?
The surge center.
What are the steps of hypothalamus defeminization?
- Testosterone crosses the blood-brain barrier.
- Testosterone is converted into estradiol.
- Estradiol deactivates the surge center.
If estradiol is the hormone that causes defeminization, then why is the hypothalamus in females unaffected?
Females have a higher level of alpha-fetoprotein, which binds to estradiol and prevents it from crossing the blood-brain barrier.
Where is alpha-fetoprotein produced?
- Fetal liver.
- Embryonic yolk sac.
What is the biochemical classification of alpha-fetoprotein?
Glycoprotein.
What tissue are undescended testis bound to?
The peritoneum.
Are the testes full size when testicular descent occurs?
No.
What is the heritability of cryptorchidism?
Highly heritable.
What are the two types of cryptorchidism?
- Unilateral: One testis fails to descend. Still fertile.
- Bilateral: Both testes fail to descend. Sterile.
What does cryptorchidism cause the germ cells to do?
Fail to multiply and then die. This leaves only sertoli cells in the seminiferous tubules.
What type of cancer are cryptorchid individuals more likely to develop?
Testicular cancer.
What is an inguinal hernia?
When a loop of the intestine is pulled down with the testis.
*If not corrected, the loop may become necrotic and will kill the animal.
How is an inguinal hernia detected?
Finding an abnormal bulge in the scrotum.
What is a Freemartin?
A female who was exposed to T and AMH due to having a fused placenta with her male twin.
When does the placental fusion occur, leading to a shared blood supply in Freemartins?
At the time of testis formation, but before ovarian formation.
What is special about the blood of a freemartin and its twin?
Their blood is chimeric because they possess some WBCs that have XX sex chromosomes and some white blood cells that possess XY sex chromosomes.
What is the frequency of Freemartinism?
93%+.
What are the reproductive characteristics of Freemartins?
- Ovatestis.
- Adult male behavior.
- No Mullerian ducts.
- No anterior vagina.
- Clitoral enlargement and protrusion.
- No uterus, cervix, or oviducts.
What are the characteristics of complete androgen insensitivity in an XY individual look-like?
- No androgen receptors.
- Have testes instead of ovaries.
- No T response —> No Wolffian duct development.
- Mullerian duct regression due to AMH.
- External genitalia is female.
What are the characteristics of 5alpha reductase deficiency in an XY individual look-like?
- Testis.
- Mullerian duct regression due to AMH.
- Wolffian duct development.
- Pseudovagina and female external genitalia until puberty (become more phenotypically male).
- No DHT.
