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SFIV Test 3 > Sexual Differentiation > Flashcards

Sexual Differentiation Flashcards

1
Q

What is the SRY gene?

A

Sex determining gene on the Y chromosome

Encodes for a DNA-binding protein that functions as a transcription factor for male testis differentiation

Located close to the pseudoautosomal region on the Y

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2
Q

What are indifferent gonads?

A

Gonads prior to 7th week of gestation are identical

Composed of external cortex and internal medulla

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3
Q

What are primordial germ cells?

A

Originate outside of the gonad

Begin migrating from the yolk sac endoderm to the indifferent gonad early in 5th week

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4
Q

What occurs after the PGCs enter the developing genital ridge?

A

They are rapidly surrounded by cords of somatic cells

The sex chromosomes in these somatic cells determine the type of gonad the genital ridge will become

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5
Q

What is the gene product of the SRY gene and what is its function?

A

SOX9 transcription factor that is the principal regulator of Sertoli cell differentiation

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6
Q

How are the testis cords formed?

A

The primitive sex cords penetrate deep into the medulla and form the testis cords

Subsequently, they become separated from the genital ridge by a mesenchymal layer that later becomes the tunica albuginea

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7
Q

What is the first histologically discernable event of testis differentiation?

A

Appearance of Sertoli Cells in the medulla between weeks 6-7

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8
Q

What are gonocytes?

A

PGCs transition to gonocytes within the testis cords and enter mitotic arrest at 10-12 weeks

By this time the gonocytes will have differentiated into prespermatogonia

Male germ cells are prevented from entering meiosis until puberty

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9
Q

What are the testis cords?

A

Precursors to seminiferous tubules

Remain as solid structures until puberty, when the develop a lumen and mature into fully functional seminiferous tubules

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10
Q

What is the role of paracrine factors released by sertoli cells?

A

Recruiting mesenchymal cells to differentiate into:

Peritbuluar myoid cells

Male-specific vasculature endothelial cells

Leydig cells

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11
Q

What do Leydig cells produce?

A

Testosterone

Insulin-like 3 (INSL3)

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12
Q

What is the relationship between seminiferous tubules and germ cells?

A

Presence of germ cells is not a requirement for seminiferous tubule development

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13
Q

What is Klinefelter syndrome?

A

Males with XXY karyotype caused by nondisjunction

Small, firm testes with hyalinized seminiferous tubules

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14
Q

What three things does the differentiation of an ovary require?

A

Invasion of the cortex by PGCs

Reactivation of the inactivated X chromosome in germ cells

Absence of the SRY gene

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15
Q

What is Turner Syndrome?

A

Ovarian disgenesis associated with a 45, X karyotype

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16
Q

What do the PGCs do in ovarian differentiation?

A

Migrate to presumptive ovary and differentiate into oogonia

At week 11, some of the oogonia will leave the pool of proliferating cells and enter into meiosis (primary oocytes)

17
Q

When is meiosis arrested in primary oocytes?

A

Prophase I

18
Q

What is atresia?

A

Form of programmed cell death

Occurs to some oogonia when with the onset of oogonial meiosis

19
Q

What occurs in the ovary after week 13?

A

Primordial follicles arise as pregranulosa cells affregate to form a single layer of cells around the primary oocyte

20
Q

What are the three reasons for decline of germ cells in the ovary post-20 weeks?

A

Decrease in the rate of oogonial mitosis

Atresia of oogonia that are not incorporated into follicles

Atresia of follicles that start to mature

21
Q

What are cortical cords?

A

Represent a second wave of cord formation that occurs at week 7

Extend into underlying mesenchyme

PGCs are incorporated into cortical cords and during month three, the cortical cords break up into distinct cell clusters (primordial follicles)

22
Q

What are primordial follicles?

A

Primary oocyte surrounded by a single layer of pregranulosa cells

23
Q

What is the pathway responsible for ovarian differentiation in the absence of SRY?

A

B-catenin/WNT4

24
Q

What are the two sets of genital ducts in the undifferentiated reproductive tract of both sexes?

A

Mesonephric/wolffian ducts

Paramesonephric/mullerian ducts

25
Q

What do the wolffian ducts differentiate into if they persist?

A

Epididymis

Vas deferens

Seminal vesicles

Ejaculatory ducts

26
Q

What do the Mullerian ducts differentiate into if they persist?

A

Fallopian tubes

Uterus

Cervix

Upper third of the vagina

27
Q

What hormones are required for male genital tract differentiation and where are they produced?

A

Anti-mullerian hormone (AMH) - Sertoli cells

Testosterone - fetal Leydig Cells

28
Q

How does the female genital tract differentiate?

A

The differentiation of the genital ducts along gemale lines occurs in the absence of hormone stimulation

Most frequently occur uterine anomalies are the result of varying degrees of fusion of the Mullerian ducts

29
Q

What is syndrome of persistent Mullerian ducts?

A

Rare condition that can occur when a normal genotypic/phenotypic male cannot synthesize AMH or has a defective receptor

Muellerian duct derivatives are present in inguinal hernias

Testes often fail to descend

30
Q

What are the common primordial structures that give rise to the external genitalia?

A

Genital Tubercle -clitoris/glans penis

Genital Fold - ventral folds of penis/labia minora

Labioscrotal Swelling - Labia majora/scrotum

31
Q

How do indifferent external genital structures undergo differentiation in males?

A

Requires dihydrotestosterone

Formed from testosterone by 5a-reductase

32
Q

What is hypospadias?

A

External genitals of males in the absence of androgen stimulation

Results in ambiguous external genitals or micropenis with an urethral opening located on the ventral surface

33
Q

How does the urogenital sinus differentiate in males and females?

A

Males -Prostatic buds develop from the urogenital sinus

Females - lower part of the vagina forms from the walls of the urogenital sinus

34
Q

What is symptom of complete androgen resistance?

A

Testes capable of secreting androgens will be present in abdomen

Male and female internal genital tracts are absent

External sexual characteristics are female

35
Q

What is 5a-reductase deficiency?

A

Internal genitalia will develop along male lines and external genitalia will be ambiguous

Further masculinization of external genitalia will occur at puberty

36
Q

What factors promote testes descent?

A

Insulin-like peptide3

Testosterone

Both produced by Leydig cells

SFIV Test 3 (14 decks)

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