Sexual Differentiation

Question 1

Name the four levels in which sex can be defined.

Answer 1

1. Chromosomal
2. Gonadal
3. Somatic (physical appearance) - external and internal
4. Psychic

Question 2

What is 45, X? This is characterized by _____ dysgenesis.

Answer 2

Turner syndrome - gonadal dysgenesis

Question 3

What is 47, XXY? This is characterized by _____ _______ dysgenesis.

Answer 3

Klinefelter syndrome - seminiferous tubule dysgenesis

Question 4

Gonads are initially ________ and develop from the primitive gonadal streak on the genital ______.

Answer 4

initially indifferent and develop from the primitive gonadal streak on the genital ridge.

Question 5

Ovaries develop from the ________ of the indifferent gonad and testis develop from the _______ of the indifferent gonad in week ___ of embryonic development.

Answer 5

ovaries from the cortex, testis from the medulla in week 6

Question 6

Embryonic ovaries produce no estrogens, while testis produce ________ and _____ to control further masculinization.

Answer 6

testis produce testosterone and MIS

Question 7

The first thing that happens in differentiation from indifferent –> male is the SRY gene activates a transcription factor called _____ that activates transcription of testis-forming genes.

Answer 7

Testis-determining factor (TDF)

Question 8

Which two testicular cell types are involved in generating products that aid in further sexual differentiation?

Answer 8

Leydig cells and sertoli cells.

Question 9

What hormone do leydig cells primarily make that plays a role in early sexual differentiation? What does this hormone do?

Answer 9

Leydig cells make testosterone which acts on the Wolffian duct system to form the epididymis, seminal vesicles, and vas defrens.

Testosterone is also converted to DHT, which acts to form the penis, prostate, and urethra.

Question 10

What important substance do sertoli cells primarily release that plays a role in early sexual differentiation? What does this substance do?

Answer 10

Sertoli cells make Mullerian Inhibiting Substance/Factor which acts on the Mullerian duct, resulting in inhibition of the formation of the uterus and fallopian tubes.

Question 11

What is the most common enzyme deficiency that results in formation of ambiguous genitalia? Describe what happens.

Answer 11

21-hydroxylase deficiency blocks downstream formation of cortisol and aldosterone and results in the build up of products that are shunted to an androgen (testosterone, DHT) forming pathway. This results in masculinization of external structures (but not internal structures, that is done with MIS).

Question 12

Name a specific example of congenital adrenal hyperplasia.

Answer 12

21-hydroxylase deficiency

Question 13

Name a specific example of congenital adrenal hyperplasia that can result in incomplete masculinization of genetic males.

Answer 13

3-beta hydroxysteroid dehydrogenase deficiency results in the ability to make only DHEA which is a very weak androgen

Question 14

The age of puberty has been _________ in the U.S. over the past 175 years.

Answer 14

decreasing

Question 15

Average puberty onset age for males in the U.S. is _____ and for female African Americans it is ______ and ______ for female caucasians.

Answer 15

Males: 9-10 years old
AA females: 7-8
Caucasian females: 8-9

Question 16

Delayed puberty workups are indicated if females have not had menses by age _____ and if males have absent testicular development by age _____.

Answer 16

females by age 13, males by age 14

Question 17

What are the five steps of male puberty?

Answer 17

1. Pre-adolescence
2. Beginning of testicular enlargement
3. Penile enlargement
4. Growth of the glans penis
5. Completion into the appearance of adult genitalia

Question 18

What is the method of pubertal developmental staging called?

Answer 18

Tanner Staging

Question 19

The hypothalamus releases _____, which acts on the anterior pituitary, causing release of _____ and ____ that acts on the gonads.

Answer 19

hypothalamus releases GnRH and AP releases LH, FSH

Question 20

In males, LH acts on ______ cells, which make _______ that help sustain ______ cells.

Answer 20

LH acts on Leydig cells, which make androgens that help sustain Sertoli cells.

Question 21

In males, FSH acts on ______ cells, which help sperm grow. These cells also make _____ and _____.

Answer 21

FSH acts on Sertoli cells and they make ABP and inhibin

Question 22

Androgens in males are produced primarily by the testis but also by ______, ______, and _____.

Answer 22

adrenal, adipose, and skin

Question 23

List the potency of the male androgens from most to least potent.

Answer 23

DHT > testosterone&raquo_space; androstendione > DHEA

Question 24

Androgens have the negative effect of ______ enlargement in males 50 years and older and also contribute to male-pattern baldness.

Answer 24

prostate

Question 25

What can exogenous anabolic steroids do to testicles?

Answer 25

Induce atrophy by altering androgen synthesis.

Question 26

What are the female stages of puberty?

Answer 26

1. Telarche (breast development)
2. Pubarche (pubic hair)
3. Menarche (menstruation)

Question 27

Initially, menstrual periods are _____ in length. They are also usually _______ and the cycles are _______.

Answer 27

variable in length, anovulatory, and irregular in cycle.

Question 28

In females, LH acts on _____ cells. FSH acts on _____ cells.

Answer 28

LH acts on theca cells, FSH acts on granulosa cells.

Question 29

What do theca cells make and what do those things do?

Answer 29

Theca cells make androgens and progestins. Androgens promote the health of granulosa cells. Progestins act on the uterus to regulate the uterine cycle.

Question 30

What do granulosa cells make and what do those things do?

Answer 30

Granulosa cells make inhibins, activins, progestins, and estrogens. Inhibins feedback on the AP (negative) and activins positively feedback on the AP. Progestins and estrogens act on the reproductive tract and both also feedback on the AP, hypothalamus, and CNS.

Question 31

GnRH release is ______.

Answer 31

pulsatile

Question 32

At around age 50, FSH and LH levels ______ in females.

Answer 32

increase

Question 33

Describe the three categories of abnormal puberty development.

Answer 33

1. Precocious pseudopuberty is when there is early development of secondary sex characteristics due to abnormal exposure of androgen to immature males or estrogen to immature females. NO gametogenesis occurs!
2. True precocious puberty is early but otherwise normal early puberty due to normal physiologic processes.
3. Constitutional precocious puberty: no underlying cause. More common in females.

Question 34

Proteases are released during the acrosome reaction to facilitate penetration of the ovum. Shortly after, _____ is released which mediates fusion to the ovum membrane.

Answer 34

fertilin

Question 35

The blastocyst secretes hCG, which acts as an ___________ agent, has growth-promoting activity and acts as an _______ growth factor that promotes placental development.

Answer 35

hCG is an immunosuppressive agent and acts as an autocrine growth factor

Question 36

Name five things that the placenta synthesizes.

Answer 36

1. hCG
2. Human chorionic somatomammotrophins
3. Peptide hormones
4. Neuropeptides
5. Placental variants of hypothalamic hormones

Question 37

Can insulin, IGF, and T3 cross the placenta?

Answer 37

Nope

Question 38

Describe the maternal-placental-fetal unit.

Answer 38

The mother supplies cholesterol to the placenta.

The placenta turns cholesterol into pregnenolone and progesterone, both of which are transferred to the fetus.

The fetal adrenals turn pregnenolone into DHEAS and progesterone into cortisol and cortisone. DHEAS is converted to 16-OHDHEAS. Some of the DHEAS and 16-OHDHEAS is also transferred back to the placenta.

In the placenta DHEAS is converted to estradiol, 16-OHDHEAS is converted to estriol. These are estrogens and these also transfer to the mother.