Embryogenesis of Pituitary Gland and Reproductive Tract Flashcards
1
Q
what 3 features does the primitive embyro brain have?
A
- infundibulum
- Rathke’s pouch
- stomodeum
2
Q
is the infundibulum in the primitive brain the same as the one in the oviduct?
A
no
3
Q
what is the stomodeum?
A
embryonic mouth
4
Q
in the first stage of development of the pituitary gland, what is happening?
A
- infundibulum starts to grow down to Rathke’s puch
2. Rathke’s pouch grows up towards infundibulum
5
Q
what happens in the second stage pf pituitary gland development?
A
- infundibulum keeps growing down
2. Rathke’s stalk regresses to separate it from embyronic mouth
6
Q
what happens in the 3rd stage of pituitary gland development?
A
sphenoid bone develops around Rathke-infundibulum structure
7
Q
what happens in the final stage of embryonic pituitary gland development?
A
the sella turcica is formed, which is a pocket that contains what is now called the pituitary gland
8
Q
where does the posterior pituitary come from?
A
infundibulum of brain
9
Q
where does the anterior pituitary come from?
A
Rathke’s pouch
10
Q
what happens to the primordial germ cells of the yolk sac during embyonic development?
A
they migrate to the genintal/gonadal ridge (in the midgut)
11
Q
what do the primordial germ cells become once they settle at the genital/gonadal ridge?
A
primitive sex chords
12
Q
list the order of kidneys in embryonic development and their fates
A
- pronephros: regresses
- mesonephros: becomes portions of the repro tract
- metenephros: will become adult kidney and urinary ducts
13
Q
what was done in the Jost experiments?
A
embyros were castrated prior to fetal development
14
Q
what was found about the paramesonephric/mullerian ducts in the Jost experiments?
A
they became structures of female tract
15
Q
what was found about the mesonephric/wolffian ducts in the Jost experiments?
A
they became structures of the male tract
16
Q
when both ducts were castrated in the Jost experiments, what was the default setting of an embryo?
A
female
17
Q
list the order of sex determination (5)
A
- chromosomal sex
- gonadal sex
- hormonal sex
- phenotypic sex
- brain and/or behavioral sex
18
Q
what animals have a single pair of sex chromosomes?
A
mammals and avians
19
Q
for what animals is sex environmentally determined? (temp affects sex)
A
sea worms, fish, reptiles
20
Q
what animals have multiple sex chromosomes?
A
invertebrates, insects, reptiles
21
Q
what does haplodiploidy mean?
A
only females have sex chromosomes
22
Q
what animals are haplodiploidy?
A
bees, spiders
23
Q
what chromosome determines sex in mammals?
A
Y, only need one Y to be a male
24
Q
what is the important gene on the Y chromosome that codes for testis determining factor?
A
SRY gene
25
what does testis determining factor cause? (3)
1. primary sex chord (seminiferous tubule) development
2. sertoli cell development
3. anti-mullerian hormone production by sertoli cells
26
what does testis determining factor do? (2)
1. codes for a DNA binding protein
| 2. acts as a transcription factor
27
what happens in the absence of SRY?
secondary sex chords (egg nests) develop
28
name 3 things that other genes on the Y chromosome are responsible for
1. spermatogenesis
2. androgen production
3. long bone growth
29
why are males taller on average than females?
because the SRY gene codes for long bone growth
30
what is different about the sex chromosomes of birds?
the female is the heterozygote (ZW) and the male is the homozygote (ZZ)
31
where is the SRY gene found in birds (on which chromosome)?
on the Z chromosome
32
is SRY the only sex determining gene in birds? why or why not?
it is not, because it is found on the Z chromosome, which both males and females have
33
in testicular development, what is found in/develops from the primary, epithelial, or medullary sex chords? (2)
1. primordial germ cells (gonocytes)
| 2. pre-sertoli cells
34
what do gonocytes (primordial germ cells) become?
spermatogonia
35
what is AMH?
anti-mullerian hormone
36
what are the 2 functions of AMH?
1. leydig cell differentiation
| 2. degeneration of Mullerian duct
37
from which germ layer does the prostate derive?
the ectoderm
38
list the flow of development of an XY male (6)
1. testis determining factor (SRY gene product)
2. testes develop
3. sertoli cells secrete anti-mullerian hormone (AMH)
4. AMH causes leydig cell differentiation and mullerian duct degeneration
5. leydig cells produce testosterone
6. testosterone causes development of the male duct system
7. testosterone is combine with 5a reductase to form dihydrotestosterone, which causes development of penis, scrotum, and accessory sex glands (prostate, cowper's)
39
what are the 3 components of the male duct system?
1. epididymis
2. vas deferens
3. seminal vesicles
40
list the flow of development of an XX female (4)
1. no TDF, bc no SRY gene
2. ovaries develop in absence of TDF
3. lack of testosterone causes wolffian duct to regress
4. no AMH leads to Mullerian ducts becoming female repro organs
41
what female organs develop from the mullerian ducts? (4)
1. oviducts
2. uterus
3. cervix
4. anterior region of vagina
42
what happens to the Mullerian ducts as they develop in females?
originally two ducts, one on each side of repro tract, will either form uterine horns or fuse depending on species
43
where does the female repro tract develop?
outside the peritoneum
44
how does the broad ligament form?
the peritoneal cavity, with the membrane, pulls together, and fuses into broad ligament
45
when does external genitalia become distinctly male or female?
around week 7-8 of gestation
46
what allows for the female phenotype?
absence of dihydrotestosterone
47
what big thing needs to form in the brain to distinguish male from female?
female hypothalamus needs surge center
48
what happened to female rats when they were given testosterone shortly after birth?
they failed to copulate or cycle normally like females as adults
49
what type of nucleus was found in female rats given testosterone shortly after birth? what does this mean?
sexually dimorphic nucleus, some male and some female traits in hypothalamus
50
list three differences in behavior between males and females
1. aggression
2. childhood play
3. 3D visual rotation- males usually better
51
what gender is the hypothalamus inherently?
inherently female
52
what must males do to their surge centers?
must "defeminize" surge center to make it inoperative
53
how do males defeminize their surge centers?
1. testosterone crosses the blood-brain barrier, is converted to estradiol and defeminizes the surge center
2. androgens (produced postnatally) polish off the process
54
what is Alpha-fetoprotein (AFP)?
a protein that binds estradiol and prevents it from crossing the blood-brain barrier
55
where is AFP produced? (2)
in the embryonic yolk sac and fetal liver
56
what type of protein is AFP?
a glycoprotein
57
do males produce AFP? how does that affect them?
they do, it just doesn't do much in males
58
why does AFP not do much in males?
AFP is not interested in testosterone, so testosterone can cross the blood brain barrier and defeminize surge center once converted to estradiol
59
sum up brain differentiation is males (6)
1. testis produces testosterone (T)
2. T crosses blood brain barrier
3. T is converted to estradiol by aromatase
4. estradiol defeminizes hypothalamus
5. androgen exposure is necessary postnatally
6. hypothalamus now has tonic center only
60
sum up brain differentiation in females (5)
1. ovary produces estradiol
2. AFP binds estradiol
3. binding prevents estradiol from crossing blood-brain barrier
4. surge center forms bc hypothalamus not defeminized
5. hypothalamus now has tonic and surge center
61
how does testicular descent begin?
with fusion of peritoneum and gubernaculum
62
what happens to the gubernaculum once fused with peritoneum?
rapid, visceral growth of testis in the scrotal cavity
63
what does regression of the gubernaculum cause?
causes testis to pull down from bottom, testis pulled onto scrotum
64
when the gubernaculum is fully regressed, describe the space between the visceral and parietal tunica vaginalis?
continuous with peritoneum
65
give 2 problems that can occur with testicular descent
1. cryptorchid
| 2. inguinal hernia
66
describe heritability of cryptorchidism
highly heritable
67
give the 2 type of cryptorchidism
1. unilateral
| 2. bilateral
68
what is the fertility of a unilateral cryptorchid?
one testis fails to descend, but one is still fertile
69
what is the fertility of a bilateral cryptorchid?
when both testes fail to descend, never fertile if not corrected before puberty
70
what risk comes with cryptorchidism?
higher percentage develop testicular cancer
71
what does surgical correction of cryptorchidism do? what does it not do?
can fix fertility, but does not decrease cancer risk
72
describe an inguinal hernia
part of intestine gets pulled into scrotum with testes during testicular descent
73
what causes cryptorchidism?
germ cells fail to multiply and then die, leaving sertoli cells only in seminiferous tubules
74
what can happen as a result of an inguinal hernia?
blood supply to intestine is cut off, resulting in necrosis and an incomplete digestive system
75
when does a freemartin happen?
female born twin to a bull
76
what happens placentally with a freemartin?
placenta membranes fuse and share a common blood supply
77
what does the shared blood supply of a freemartin and her bull twin cause and why?
since testes develop first, female will be exposed to testosterone and anti-mullerian hormone before her own ovarian formation
78
what happens to the twins when a freemartin is rpesent?
animals are chimeric (WBC from other twin), and TDF (SRY) is expressed in both individuals
79
describe the ovaries of a freemartin
ovaries do not grow but are chimeric, are ovotestis!
80
what is the result of ovotestes, hormonally and genetically?
SRY and therefore AMH and testosterone are produced, causing further changes and adult male behavior
81
what does the AMH from the bull twin do to a freemartin?
blocks mullerian ducts, resulting in formation of a posterior vagina only, but on anterior vagina, no cervix, no uterus, etc.
82
what does the testosterone from the bull twin do to a freemartin?
1. clitoral enlargement
| 2. brain changes like that of a male
83
what can freemartins be used for due to their adult male behavior?
estrus detectors!
84
are all freemartin abnormalities the same?
no, they exist on a continuum
85
what causes complete androgen sensitivity in an XY individual?
no androgen receptor
86
will testes still produce testosterone in an XY individual with no androgen receptor? what is the result?
yes, but no testosterone response so no Wolffian duct development
87
is AMH still present in an XY individual with an no androgen receptor? what is the result?
yes, will cause Mullerian ducts to regress, meaning external genitalia will be female due to lack of androgen
88
what is a 5a reductase deficiency in an XY individual called?
guevodoces
89
describe what happens in guevodoces
1. testis produce T
2. AMH is present so Mullerian ducts regresses
3. Wolffian ducts develop normally
4. pseudovagina and female external genitalia
5. at puberty may differentiate into more of a phenotypic male
