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FHB IV- Endocrinology > Reproduction 1 > Flashcards

Reproduction 1 Flashcards

1
Q

Describe the hierarchy of determinants of sexual differentiation.

A

Slide 6

Chromosome
gonads
genitalia
gender identity

Genetic are chromosome and gonads

Hormones, internal structures, external structures, social behavior - genitalia and gender identity

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2
Q

Define sex vs gender.

A

Sex – biologically determined
chromosomal complement

“sex differences” – refer to biologically inherent differences

Gender – socially determined
usually related to appearance: genitalia and secondary sex characteristics

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3
Q

Describe sexual determination.

Female vs male? How is gonadal sex determined?

Describe the sex determining gene/transcription factor. Major target?

A

Genotype (chromosomal sex):

46, XX = female sex

46, XY – male sex

Gonadal sex (determined by chromosome):

Y chromosome determines male gonads (testes)

SRY gene = sex determining region Y
(also called TDF – testis determining factor)

SRY is a transcription factor – major target is SOX9

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4
Q

How do you characterize and identify genetic, genotypic or chromosomal sex?

A

Determined by sex chromosomal
endowment: XX, XY – especially the
Y determined at
fertilization

Karyotype
analysis

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5
Q

How do you characterize and identify gonadal sex
ovary/female fetal tract
testis/male fetal tract?

A

Determined by normal differentiation
and especially activation of SRY/TDF to yield male at about 7 weeks (female
about 11 weeks)

Histology of
gonad

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6
Q

How do you characterize and identify genital or phenotypic or body sex with external sexual characteristics – most importantly external
genitalia from lower
fetal tract development?

A

Determined by activation and
integration of
1) neuroendocrine axes
2) paracrine, endocrine control of genital tract development

Physical exam

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7
Q

How do you characterize and identify gender identification or
“behavioral sex”?

A

Seems independent of genotype, phenotype and hormones – may
involve rearing cues or psycho social factors or is unknown

Observation
And psychological
tests

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8
Q

Describe genetic sex for male. What is required for testicular development?

What happens to XY mice with no functional Sry?

XX mice with added Sry?

X chromosome encodes?

A

Y Chromosome: [Y defines the guy]. Required for testicular development (rare exceptions). Sry
= sex determining gene located on the Y chromosome

XY mice with no functional Sry develop ovaries
XX mice with added Sry develop testis
X Chromosome: X Chromosome – encodes the androgen receptor

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9
Q

What does ovary development depend on?

A

Ovary development depends on the presence of 2X and no Y chromosome

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10
Q

What does loss of one X chromosome result in?

A

Loss of one X chromosome results in ovarian dysgenesis but not loss of female ducts or genitalia

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11
Q

Explain dichotomous development of gonad, internal ducts, and external genitalia.

A

…

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12
Q

Describe primordial germ cells. When do they migrate to gonadal ridge?

A

Primordial germ cells (PGC) – migrate to gonadal ridge (5-6 weeks gestation)

Primordial (indifferent) gonad bipotential for testis or ovary

Primordial gonad is indifferent – not male or female specific. Bipotential development into either
testes or ovaries depending on specific gene factors.

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13
Q

What direct the specific development of gonad?

What gene expression patterns lead to gonad differentiation in male/female?

A

Germ cells direct the specific development of the gonad
Specific gene expression patterns lead to gonad differentiation

Male: Sry + Sox9
Female: Rspo1 + Wnt4

Male = SRY is gene that determines testis formation. Transcription factor for Sox9.
Sox9 = induces proliferation of the primitive sex cords.

Female = Rspo1 and Wnt4 drive developmental progression, but ovary will develop regardless of
these factors due to absence of SRY gene.

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14
Q

Where do male and female internal genitalia develop from?

A

CORTEX – develops into female internal genitalia

MEDULLA – develops into male internal genitalia

Female internal genitalia develop from cortex of
gonadal ridge.

Male internal genitalia develop from medulla of
gonadal ridge.

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15
Q

Describe the embyronic development of the male gonad.

A

indifferent gonad= primitive sex cords

proliferation of sex cords (SRY, SOX9)

Penetration of medulla by sex cords

Differentiation of medullary cords- becomes testes

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16
Q

Describe embryonic development of female gonad.

A

indifferent gonad= primitive sex cords

sex cords disorganize-cortical epithelial cells proliferate
(due to absence of SRY)

cortical cords develop from cortical epithelium

Cells form clusters around germ cells - epithelial cells become follicular cells -ovary develops

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17
Q

Describe 3 main cell types in testes.

A

TESTES: 3 main cell types
Gametes (sperm)

Sertoli cells – secrete antimullerian hormone (AMH)

Leydig cells – synthesize and secrete testosterone/DHT

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18
Q

Describe the composition of ovaries.

A

OVARIES:
Gametes (ova)
Follicular cells

gametes and follicular cells = follicle

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19
Q

What does follicular maturation result in the formation of?

A

Granulosa cells – secrete and synthesize estrogens and progesterone

Thecal cells – make androgens

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20
Q

Depending on its chromosomal complement, an undifferentiated cell can be destined to proceed
in the male or female developmental pattern.

Describe the indifferent duct system.

A

Mesoneprhos – produces urine during 6-10
weeks gestation and acts as a transient kidney for
the developing fetus. (degenerates in both sexes)

Mullerian Duct – undergoes further development
in females. Also called “paramesonephric duct”

Wolffian Duct – undergoes further development
in males. Also called “mesonephric duct”

21
Q

Describe the male internal genitalia.

Describe testes. What do sertoli cells make? What are effects?

What do Leydig cells make?

What effect does Wolffian duct have?

What is DHT?

A

TESTES –
Sertoli cells make AMH and Inhibin B – AMH induces regression of the Mullerian duct

Leydig cells make androgens: testosterone and DHT stimulate formation of internal genitalia from Wolffian duct:
Testosterone: 
top = epidiymis, 
middle = ductus deferens, 
base = seminal vesicle, ejaculatory duct

DHT: prostate, external genitalia

22
Q

Describe the female internal genitalia.

What induces the regression of Wolffian ducts?

A

Absence of Testes (not presence of ovary) induces regression of Wolffian ducts

23
Q

Describe female internal genitalia:

How do mullerian ducts differentiate (top, middle, bottom)

A

Mullerian Ducts differentiate:
Top – fallopian tubes
Middle – fuses to become uterus
Bottom – cervix and upper 1/3 of vagina

24
Q

Describe contrasting patterns of male and female differentiation of the internal genital ducts. Experiments of Alfred Jost (1953) → important determinants of these patterns.

A

Slide 21

25
Q

What do penis, scrotum, prostate require?

What is effect of “propecia”?

A

-DHT
Penis, scrotum, and prostate require conversion of testosterone into DHT.

”Propecia” inhibits 5alpha-reductase

Inhibition or mutation of converting enzyme (5alpha-reductase) will cause developmental
defects in external male genitalia.

26
Q

Describe the following as pertains to male:

genital tubercle
urogenital folds
urogenital sinus
labioscrotal folds

A

genital tubercle- glans penis

urogenital folds- ventral penis

urogenital sinus- prostate

labioscrotal folds- scrotum

27
Q

Describe the following as pertains to female:

genital tubercle
urogenital folds
urogenital sinus
labioscrotal folds

A

genital tubercle- clitorus

urogenital folds- labia minora

urogenital sinus- lower vagina

labioscrotal folds- labia majora

28
Q

Contrast mitosis and meiosis as it relates to the process of gametogenesis.

Define mitosis, meiosis I, and meiosis II.

A

Mitosis – somatic cells only. Daughter cells are genetically identical

Meiosis I – germ cells
Duplication of DNA. Recombination of chromosomes = genetic diversity.
Chromosomes split in meiosis I

Meiosis II
No duplication
Chromatids split
4 daughter cells

29
Q

Define the following:

Gametogeneis
Spermatogenesis
Oogenesis

A

GAMETOGENESIS: process of forming a haploid gamete (spermatozoa or ovum)

SPERMATOGENESIS: specific to male

OOGENESIS: specific to female

Spermatogenesis =
4 daughter cells/germ cell
See diagram slide 26

30
Q

When do chromosomes split?

A

Meiosis I

31
Q

When do chromatids split?

A

Meiosis II

32
Q

When is genetic diversity established in meiosis?

A

through recombination of chromosomes in meiosis I

33
Q

Describe oogenesis.

When is meiosis I arrested?
Where is OMI secreted from and what effect does it have?

When is meiosis II arrested?

A

oogenesis =
1 daughter cell/germ cell plus polar bodies

Meiosis I is arrested at diplotene of prophase until activation (puberty to 45+ years).

 Oocyte
maturation inhibitor (OMI) is secreted from follicular cells in ovary and causes meiosis arrest.

Meiosis II is arrested at metaphase II until fertilized by sperm

34
Q

Describe male spermatogenesis duration.

A

Ongoing process from puberty through old age

35
Q

What composes a primordial follicle?

A

Primordial follicle = primary oocyte + follicular cells

36
Q

Are there oogonia present at birth? Explain.

A

No oogonia are present at birth – all converted to primary oocytes or subject to atresia

37
Q

List examples of chromosomal abnormalities.

A

Structural Errors =
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 chromosome join to form a ring

Chimerism = genetically distinct cells (arising from different zygotes)

Mosaicism = cell specific chromosome differences (i.e. X inactivation) “calico cats”

Aneuploidy = abnormal numbers of chromosomes
“down syndrome = trisomy 21”

38
Q

Describe a structural chromosomal abnormality.

A

Structural –

Part of the Y chromosome gets translocated to the X

XX female with male phenotype due to presence of SRY gene

XY phenotype with female phenotype due to lack of SRY gene – this happens because the X chromosome is inactivated

39
Q

Explain the following chromosomal abnormalities:

XO
XXY
XY (2 possibilities)

A

XO – Turner’s Syndrome

XXY – Klinefelter’s syndrome (1:500 to 1:1000, most common chromosomal disorder in boys) – usually due to meiotic nondisjunction

XY – loss of X-linked androgen receptor (recessive) - pseudohermaphroditism

XY – loss of 5alpha-reductase gene

40
Q

Describe Turner’s syndrome.

What karyotype?

Describe gonads.

Describe the phenotype.

A

45, XO KARYOTYPE “gonadal dysgenesis”
Both X chromosomes are required during development for oogonia. Ovary becomes a “streak” = fibrous tissue
Systemic phenotypic issues due to aneuploidy

Turner syndrome is characterized by gonadal dysgenesis – ovaries do not develop and becomes a
“streak” of fibrous tissue. Both XX chromosomes are required during early differentiation of the
ovary, although one X chromosome becomes deactivated later in life, so 2 copies are no longer
required. Chromosomal aneuploidy often results in multiple other systemic phenotypes, of which
the pathology is not completely understood. Turner syndrome patients have very short stature,
“shield” chest, webbed neck, and upper torso deformities. Most do not go through puberty or
have menstrual cycles.

41
Q

Describe Klinefelter Syndrome 47.

A

XXY

Y chromosome: testes present (small, hyalinated); infertile

Testosterone is low (due to testicular dysfunction), micropenis

Eunuchoid body: lower segment greater than upper segment by more than 2”; short arms

Gynecomastia – elevated estradiol

Systemic phenotypic issues due to aneuploidy

42
Q

Describe the etiology of hermaphroditism.

A

Etiology – Chromosomal (genetic); Hormonal (development) Hermaphrodite karyotype diversity:
60% are XX
20% are XY
20% mosaicism/chimerism.

43
Q

Describe the following hermaphroditism phenotypes.

Male Pseudohermaphroditism
Female Pseudohermaphroditism
“True” hermaphroditism

A

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

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

“True” hermaphroditism – Both testes and ovaries present “gonadal” sex. Phenotypic sex ambiguous.

44
Q

Describe Male Pseudohermaphroditism.

Complete:
What is present?
Describe phenotype for complete androgen resistance (hormones and phenotype)

A

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

Complete: loss of X-linked AR gene

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

Phenotype for complete androgen resistance:

Hormones: Androgen levels are high (lack of feedback, estrogen levels high (for male). Gonadotropins?

Phenotype: female with blind vaginal pouch

Y chromosome – induces mullerian duct regression, testes (undescended); lack of androgen effects (no Wolffian duct development, no external genitalia)
High estrogens induce development of female body characteristics

45
Q

Describe Female Pseudohermaphroditism. What is present? What causes it?

Describe the most common type.
Describe cause and phenotype.

A

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

Developmental defect – not due to chromosomal abnormality.

1) Fetal congenital adrenal hyperplasia ** most common
2) Maternal androgen excess due to adrenal or ovarian tumors, possibly also due to
progestational drugs (drugs with progesterone-like action).
Phenotype: virilization due to increased androgens. Ambiguous genitalia, advanced skeletal age

46
Q

Describe “true” hermaphroditism.

What is present?
Phenotypic sex?
Spermatogenesis?
External genitalia?

A

Both testes and ovaries present “gonadal” sex.

Phenotypic sex
ambiguous. XX hermaphrodites generally raised as females. Possible SRY translocation or loss of RSPO1 gene (testes repressor).

No spermatogenesis because other Y genes not present.

Differentiation of external genitalia is highly variable – ambiguous

Cryptorchidism (undescended testes) and hypospadias are common.

47
Q

Describe Male Pseudohermaphroditism.

Phenotype for partial androgen resistance. What type of mutation? (hormones and phenotype)

What does Y chromosome do? High estrogens?

A

Phenotype for partial androgen resistance:
Partial: AR mutation – partially functional

Hormones: Androgen levels are high (lack of feedback, estrogen levels high (for
male). Gonadotropins?

Phenotype: ambiguous with blind vaginal pouch (under masculinized)

Y chromosome – induces mullerian duct regression, testes (undescended);
Wolffian duct develops, gynecomastia

48
Q

Describe virilization by androgens?

What results?

A

Virilization by androgens- advanced skeletal “age”, clitoromegaly and other ambiguities of genital anatomy.

FHB IV- Endocrinology (17 decks)

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