Embryogenesis of pituitary gland

Question 1

Germ cell migration

Answer 1

-germ cells originate in ectoderm of inner embryo
-maturation occurs and the endoderm differentiates into the yolk sac
-primordial cells from yolk sac wall migrate through mesoderm, around gut and down through the developing genital ridge
-birds - germ cells move through
blood
-migration occurs around 4th week of gestation

Question 2

Fetal kidneys

Answer 2

• pronephros
• mesonephros
• paramesonephritic duct
• metenephros

Question 3

Pronephros

Answer 3

Develops into part of reproductive tract

Question 4

Endoderm (germ layer)

Answer 4

• Digestive system
• lungs
• endocrine system

Question 5

Mesoderm (germ later)

Answer 5

• muscle
• skeleton
• cardiovascular
• reproductive system

Question 6

Ectoderm (germ layer)

Answer 6

• nervous system
• skin
• hair

Question 7

Anterior pituitary

Answer 7

-develops from rathke’s pouch

Question 8

Rathke’s pouch

Answer 8

Outgrowth of the embryonic mouth

-forms from evagination of the oral cavity

Question 9

Posterior pituitary

Answer 9

Forms from infindonulum

Question 10

Infindibulum

Answer 10

• Base of the embryonic brain

- grows down to meet Rathke’s pouch

Question 11

Sella turcia

Answer 11

• back of roof of mouth

- depression in sphenoid bone which surround the anterior and posterior pituitary

Question 12

Mesonephric kidney

Answer 12

Gonad

Question 13

Mesonephric duct

Answer 13

Wolffian duct in male

Question 14

Paramesonephric duct

Answer 14

Mullerian duct in female

Question 15

Jost paradigm

Answer 15

Chromosomal sex–>gonadal sex–>hormonal sex–>phenotypic sex–>and/or behavioral sex

Question 16

Removal of gonads

Answer 16

• formation of female parts

- default

Question 17

Y chromosome

Answer 17

Gene on this chromosome determines testicular differentiation

Question 18

SRY

Answer 18

• sex reversal gene Y
• gene that encodes TDF (testes determining factor)
• DNA binding protein that enhances transcription of RNA that codes for proteins that cause development of seminiferous tubules, androgen production and AMH an sertoli cells
• absence: medullary chords regress and secondary sex chords form that will become the egg nests
• problem: good repro tract formation but no sperm production

Question 19

Drosophila sex

Answer 19

• depends on number of X chromosomes
• X or Xy or XO: male
• XX or XXX or XXY: female

Question 20

Human sex chromosomes

Answer 20

XX, -male, normal
XXY,XXXY,XXXXY -male w impaired sperm production
XX, XXX-female
XO: turners syndrome

Question 21

SRY and birds

Answer 21

-females: ZW
-males: ZZ
W determines sex
SRY found on Z chromosome
-problem: sex determined by Z but SRY is on the W

Question 22

Sertoli cells

Answer 22

-secrete anti mullerian hormone

Question 23

Anti mullerian hormone

Answer 23

• causes differentiation of leydig cells

- causes mullerian ducts to regress

Question 24

leydig cells

Answer 24

• secrete testosterone
• binds to testosterone receptors in nucleus of target cells, developmental changes via transcription
• differentiation of wolffian ducts into vas effereitia, vas deferens, epididymis and seminal vesicles

Question 25

Differentiation of accessory glands in males

Answer 25

- testosterone converts to dihydrotestosterone | - dht goes into nucleus and changes transcription ( catalyzed by 5alpha reductase)

Question 26

Cryptorchid, unilateral or bi lateral

Answer 26

Problem with descent of testes; very heritable - germ cells fail to multiply so only sertoli cells remain - testicular cancer

Question 27

Inguinal hernia

Answer 27

- Inguinal ring doesn't completely close - part of intestines gets stuck and pinched off - death

Question 28

Brain or behavioral sex

Answer 28

-exposure of brain to sex steroids during fetal development determines responses as an adult

Question 29

5alpha reductase deficiency

Answer 29

- can't make dihydrotestosterone - testis, AMH and some wolffian ducts - infertile - psedovagina that may differentiate into male during puberty

Question 30

Testicular feminization

Answer 30

- no androgen receptors - testis and AMH - no testosterone response - no wolffian or mullerian duct - external genitalia-female

Question 31

Freemartin

Answer 31

- twins share hormones from shared blood supply - female twin is masculinization - tested develop earlier, clitoral enlargement bc of testosterone exposure - AMH causes regression of mullerian ducts and no vagina