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Flashcards in Reproduction 1 Deck (58):

describe the determinants of sexual differation

The type of sex: genetic, genotypic, or chromosomal

gonadal sex: ovaries+/-female fetal tract or testis+/-male fetal tract

genital or phenotypic sex with external sexual characteristics - most importantly external genitalia from lower fetal tract development

gender identification


What are the characteristics of genetic/genotypic/chromosomal sex and how is it identified?

determined by sex chromosome endowment: XX, XY (especially the Y determined at fertilization)



What are the characteristics of gonadal sex and how is it identified?

determined by normal differentiation and especially the activation of SRY/TDF to yield male at about 7 weeks and female at 11 weeks

histology of gonads


What are the characteristics of genital/phenotypic sex and how is it identified?

determined by the activation and integration of
1. neuroendocrine axes
2. paracrine, endocrine control of genital tract development

physical exam


What are the characteristics of gender identity?

independent of genotype, unknown


discuss the general male genetic identity

Y chromosome required for testicular development with rare exceptions

Sry - sex determining gene on Y chromosome
XY with no Sry develop ovaries
XX with added Sry develop testis
X chromosome encodes androgen receptor


discuss the general female genetic identity

Ovary development depends on XX and no Y

Loss of one X results in ovarian dysgenesis but no loss of female ducts or genitalia


When do primordial germ cells migrate to the gonadal ridge?

5-6 weeks of gestation


is the gonadal ridge male or female specific?

neither - it is indifferent


What are the gene factors that determine maleness?

Sry is a transcription factor for Sox9, which induces proliferation of the primitive sex cords


What are the gene factors that determine femaleness?

Rspo1 and Wnt4 drive developmental progression, but ovary development will occur regardless due to lack of Sry


What do female internal genitalia develop from?

the cortex of the gonadal ridge


What do male internal genitalia develop from?

the medulla of the gonadal ridge


What are the three structures of the indifferent duct system?

mullerian duct
wolffian duct


What is the function of the mesenephros

produces urine during 6-10 weeks gestation and acts as a transient kidney for the developing fetus


What induces the regression of the mullerian duct in males?

AMH and inhibin B made by sertoli cellls


What stimulates the formation of internal genitalia in males?

Testosterone and DHT - androgens formed by Leydig cells


What induces the regression of the wolffian duct in females?

absence of testis, not the presence of ovaries!


What does the mullerian duct differentiate into in females?

top: fallopian tubes
middle: uterus
bottom: cervix and upper third of vagina


What does the genital tubercle develop into?

males: glans penis

females: clitoris


what doe the urogenital folds develop into?

males: ventral penis

females: labia minora


What does the urogenital sinus develop into?

males: prostate

females: lower vagina


What do the labioscrotal folds develop into?

males: scrotum

females: labia majora


What do the penis, scrotum, and prostate require?

The conversion of testosterone into DHT


What causes developmental defects in male external genitalia?

inhibition or mutation in converting enzyme 5-alpha-reductase


What are some general features of mitosis?

somatic cells only. daughter cells are genetically identical


What are some general features of meiosis I?

germ cells, duplication of DNA, recombination of chromes = genetic diversity. Chromosomes split in meiosis I


What are some general features of meiosis II?

no duplication, chromatids split, 4 daughter cells


What are the three main cell types in the testes?

gametes: sperm
sertoli cells: secrete AMH and inhibin B
Leydig cells: synthesize and secrete testosterone/DHT


What are the cell types of the ovaries?

Gametes (ova) and follicular cells are the follicles


What does follicular maturation result in?

Granulosa cells – secrete and synthesize estrogens and progesterone

Thecal cells – make androgens


What does DHT stimulate development of?

prostate and external genitalia


What does testosterone stimulate development of?

male internal genitalia


What does the wolffian duct differentiate into in males?

top: epididymus
middle: ductus deferens
bottom: seminal gland, ejaculatory duct


What is unique about Meiosis I in females?

arrested at diplotene of prophase until activation (puberty to 45+ years)


What causes meiosis arrest, and what produces it?

Oocyte maturation inhibitor (OMI), secreted by follicular cells in ovary


what is unique about meiosis II in females?

arrested at metaphase II until fertilized by sperm


discuss spermatogenesis in males

ongoing process from puberty through old age


discuss some structural errors that can result in chromosome abnormalities?

translocations: equal or unequal exchange of chromosomal material

inversions: piece of chromosome gets inserted upside down

deletions/duplications: loss or addition of part of a chromosome

rings: two ends of chromosomes attached to form a ring


what can happen if part of the Y chromosome containing the Sry gene gets translocated to the X?

XX female with male phenotype due to presence of Sry gene - this happens because X is inactivated

XY with female phenotype due to lack of Sry gene


What is the genotype of Turner's Syndrome?



What is the genotype of Klinefelter's Syndrome?



What is Klinefelter's Syndrome usually a result of?

meitotic non-disjunction


What is Turner's Syndrome characterized by?

Gonadal dysgenesis - ovaries do not develop and become a streak of fibrous tissue

Although one X becomes inactivated later in life, and thus only one is necessary for life, at this stage you must have both Xs for ovary development


Discuss some physical presentations of a person with Turner Syndrome

Short statue, shield chest, webbed neck, upper torso deformities. Most do not go through puberty or have menstrual cycles


Discuss some physical and hormonal traits of someone with Klinefelter's Syndrome

Patients have a Y chromosome - testes are present but are small and hyalinated, and they are infertile

Testosterone is low due to testicular dysfunction

Gynecomastia: elevated estradiol

micropenis, eunuchoid body: lower body > than upper body by at least 2" with short arms


What is the genetic etiology of hermaphroditism?

60% XX
20% XY
20% mosaicism/chimerism


What is the phenotype of hermaphroditism?

male/female designation is based on which gonad is present (internal or external for males)


What is male pseudohermaphroditism?

Testes present, but some or all female internal/external genitalia also present


What is an example of male pseudohermaphroditism?

Androgen resistance due to loss (complete) or mutation (partial) in X-linked androgen receptor gene (karyotype 46, XY)


discuss the hormonal and phenotypic traits of male pseudohermaphroditism due to complete androgen resistance

Y chromosome induces mullerian duct regression and testes (undescended)

lack of androgen effects (no Wolffian duct development, no external genitalia)

hormones: androgen levels are high due to lack of feedback, high estrogens lead to development of female body characteristics

phenotype: female with blind vaginal pouch


discuss the hormonal and phenotypic traits of male pseudohermaphroditism due to partial androgen resistance

Y chromosome induces mullerian duct regression and testes (undescended)

Wolffian duct develops, gynecomastia

hormones: Androgen levels are high due to lack of feedback, estrogen levels high (for male)

phenotype: ambiguous with blind vaginal pouch (under masculinized)


What is female pseudohermaphroditism?

Ovaries present, but some or all male internal/external
genitalia also present


female pseudohermaphroditism is a result of what?

Developmental defect – not due to chromosomal abnormality


What is the phenotype of female pseudohermaphroditism?

Virilization due to increased androgens. Ambiguous genitalia, advanced skeletal age


What are some examples of female pseudohermaphroditism?

Fetal congenital adrenal hyperplasia ** most common

Maternal androgen excess due to adrenal or ovarian tumors, possibly also due to progestational drugs (birth control)


what is "true" hermaphroditism?

Both testes and ovaries present “gonadal” sex, but phenotypic sex ambiguous (XX hermaphrodites typically raised as females)

Cryptorchidism (undescended testes) and hypospadias are common

No spermatogenesis because other Y genes not present


what might be a cause of true hermaphroditism?

Possible SRY translocation or loss of RSPO1 gene (testes repressor)