Endocrine Reg of Differentiation

Question 1

What is reproduction?

Answer 1

Transfer of genetic material and formation of a new entity

Question 2

What is the first type of sexual reproduction?

Answer 2

Asexual:
Single parent
Via Mitosis
Results in creation of diploid cells from diploid cells (offspring have same genotypes/phenotypes)

Question 3

What is the second type of reproduction?

Answer 3

Sexual:
2 parents
Gametes produced via meiosis
Results in production of haploid gametes 
Offspring have different phenotypes

Question 4

What is the female hypothalamic gonadal axis?

Answer 4

Ovaries

Question 5

What is the male hypothalamic gonadal axis?

Answer 5

Testes

Question 6

How does one distinguish male meiosis vs female meiosis?

Answer 6

# of haploid daughter cells:
Male- 4 haploid daughter cells which yields 4 gametes
Female- 1 haploid daughter cell which yields 1 mature gamete (+ 2 polar bodies)

Question 7

What is the difference between true and pseudo hermaphrodites?

Answer 7

True hermaphrodites have both male and female genitalia whereas psuedo-hermaphrodites have the internal genitalia of on sex but the external genitalia of the opposite or both sexes.

Question 8

What is the SRY and who contributes it?

Answer 8

Sex-determining region of Y chromosome (so it has to come from the male) responsible for initiating the development of testes. If not activated (by testosterone?) then offspring is female by default.

Question 9

Which gene is found on the X chromosome and why is it so important?

Answer 9

The x chromosome contains the gene that codes for androgen (hormone) receptors. This is important because in order for a hormone to be able to act on the target tissue, there must be the hormone (androgen) receptor.

Question 10

At what point during gestation are the gonadal ridges invaded by migratory germ cells?

Answer 10

Approximately 6 weeks

Question 11

An early embryo has what two ducts? What does each one eventually lead to?

Answer 11

Wolffian duct and Mullerian duct: The wolffian duct becomes the future internal male reproductive tract while the mullerian duct becomes the future internal female reproductive tract.

Question 12

In addition to the SRY gene on the short arm of the Y chromosome there is also the (?) gene which leads to the development of (?)

Answer 12

TDF: Testis-determining factor –>Testes

In order to actively stimulate the wolffian duct into the male reproductive tract there must be the development of testes.

Question 13

What 2 hormones does the development of the male INTERNAL genitalia depend on and by cells are they produced? What happens if one of the hormones is not present? Which hormone is it?

Answer 13

Testosterone and Mullerian-inhibiting hormone:
Testosterone is produced by leydig cells while MIH is produced by sertoli cells

In the absence of testosterone, the wolffian ducts regress and the mullerian ducts become fallopian tubes, uterus, cervix, and upper 1/3 of the vagina

Question 14

What are the 2 types of cells present in the fetus within the first 5 weeks? What cell lines does each type differentiate into?

Answer 14

Coelomic epithelial cells and Mesenchymal stromal cells:

Coelomic cells are the precursors to granulosa and sertoli cells

Mesenchymal cells are the precursors to theca and leydig cells

Sertoli & Leydig = male

Granulosa and Theca = female

Question 15

Seminiferous tubules and sertoli cells form as a result of?

Answer 15

Primordial germ cells that migrate from the cortex into primitive sex cord of the medulla

Question 16

How does female gonadal differentiation vary from that of male?

Answer 16

• medulla regresses
• germ cells undergo mitosis => OOGONIA
• From stroma, theca cells develop and are then arrested in late PROPHASE

Question 17

How do sex steroids navigate circulation? Progesterone?

Answer 17

Sex Steroid Binding Globulin (SSBG) or albumin

- Progesterone travels attached to Corticosteroid Binding Globulin (CBG)

Question 18

Where in the body are sex steroids metabolized and about how long is their half life?

Answer 18

Liver

-> 30-60 minutes

Question 19

What is the common feature of the almost all androgens? Which one is the odd one out? Which enzyme is required to get to this androgen?

Answer 19

Cholesterol->Pregnenolone-> a-hydroxypregnenolone-> DHEA-> Androstenediol-> Testosterone

They all have 19 carbons

(Estrogens have 18 tho)

Also… conversion into estrogens requires the enzyme AROMATASE

Question 20

What hormone is not able to be produced in the case of a 17,20-desmolase deficiency?

Answer 20

Testosterone

Question 21

How should one go about distinguishing primary sex characteristics from secondary sex characteristics?

Answer 21

The primary are responsible for the storing and transporting of gametes (gonads and accessory sex organs) whereas the secondary are not.

-> 2ary: “external specialization”

Question 22

In males, Testosterone is responsible for the development of (1) whereas the prostate, penis, and scrotum develop as a result of (2)

Answer 22

1. Epididymus, vas deferens, seminal vesicle, ejaculatory duct
2. DHT

(Testosterone–>5a-reductase=DHT)

Question 23

At what point during gestation does external genital differentiation begin for both males and females?

Answer 23

9-10 weeks

Question 24

In females, DHT or the lack thereof, is responsible for the development of what? What is the common tissue between male and female genitalia?

Answer 24

Clitoris, Labia majora, labia minora, and lower vagina

genital tubercle, genital swelling, urethral folds, urogenital sinuses

(Glans penis, scrotum, penile shaft, prostate gland)

Question 25

What is the mode of inheritance of Androgen insensitivity syndrome? What is the predominant genotypic/phenotypic presentation?

Answer 25

1. x-linked recessive (results in absence of androgen receptors on target tissue)
2. Genotype = XY
3. Phenotype = female, undescended testes (can still produce testosterone), no internal tract, blind ending vagina, infertile, little to no pubic hair, and greater than avg. height