Week 1: Sexual differentiation

Question 1

gonadal sex development

Answer 1

• XX: primitive gonad with cortex and medulla. The medulla atrophies and cortex becomes ovary
• XY: medulla expands and cortex atrophies. Medulla becomes testis. SRY gene on Y chromosome governs development of the testis

Question 2

Development of internal duct system in reproductive tract

Answer 2

• early development: have Wolffian ducts and Mullein ducts
• males: testis produces testosterone which stimulates Wolffian ducts (masculinization) and anti-Mullerian hormone which inhibits and leads to degeneration of Mulleran ducts (defeminization).
• Wolffian ducts develop into epididymis, vas deferens, seminal vesicles, and prostate gland. Testosterone converted to DHT to induce prostatic outgrowth.
• females: no hormones. degeneration of Wolffian ducts and continuation of Mullerian ducts. Mullein ducts become oviducts, uterus, and upper 1/3 of the vagina.

Question 3

Development of external genitalia

Answer 3

1. males
   - DHT dependent: testosterone converted by 5a-reductase to DHT
   - glans gives rise to glands of penis
   - genital tubercle: shaft of penis
   - urethral folds: median raphe
   - labio-scrotal folds: scrotum
2. female: no hormones present
   - glans give rise to clitoris
   - genital tubercle: shaft of clitoris
   - urethral folds: labia minora
   - labio scrotal folds: labia majoria

Question 4

Neural differentiation: sex differences in the brain

Answer 4

• sexually dimorphic nucleus of bulbocavernosus in spinal cord: large in male. Controls musculature of penis
• SDN-POA: masculinized by estrogen. many brain sex differences due to estrogen metabolized from testosterone. cluster of neurons much greater in males.
• some sex differences due to hormones, some due to genetics

Question 5

Gender and sexual orientation

Answer 5

• size of INAH3 varies with sexual orientation in men

- fiber tracts may also vary with gender and sexual orientation

Question 6

Turner’s syndrome

Answer 6

• XO only one X chromosome due to nondisjunction in either oocyte or sperm
• ovaries degenerate during development
• won’t go through puberty. webbing in neck. Short stature because gene in X chromosome involved in height

Question 7

Klinefelter’s syndrome

Answer 7

XXY

• tall, eunuchoid proportions (long arms long legs)
• not much evidence of secondary development, female body habitus. limited gonadal development.

Question 8

Congenital adrenal hyperplasia (CAH)

Answer 8

• results from mutations in steroidogenic enzymes synthesizing cortisol in adrenals
• lacks ability to generate cortisol or aldosterone, and synthesize excess androgens
• begins start of 2nd trimester.
• variable virilization of females
• XX genotype, variable phenotype.
• with partial virilization, raised as females, capable of fertility

Question 9

Androgen insensitivity syndrome (AIS)

Answer 9

-XY individuals with AIS have defect in androgen receptor, they are insensitive to own testicular androgens
-intraabdominal testes, short blind ended vagina, female phenotype
-often unrecognized at birth, raised as girls, and at puberty show breast growth due to estrogens aromatized from androgens. Little pubic or axillary hair.
-amenorrheic.
Rx: surgical removal of testes. replacement with OCPs

Question 10

5a reductase deficiency

Answer 10

• lack ability to convert testosterone to DHT
• external genitalia in XY males are feminized at birth. Testes descend into labia majora.
• During puberty: elevated levels of testosterone induce virilization, and male secondary sex characteristics
• genotype XY, phenotype: female in childhood, male at puberty