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Physiology 2 > Reproduction: Sexual Differentiation & Disorders > Flashcards

Reproduction: Sexual Differentiation & Disorders Flashcards

1
Q

What is sexual determination?

A

Genetically controlled process dependent on the ‘switch’ on the Y chromosome which determines whether someone will be a male or female.

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2
Q

What is sexual differentiation?

A

The process by which internal and external genitalia develop as male or female

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3
Q

What are the different types of sex?

A
  • Genotypic sex - Whether a person’s genome contains two X chromosomes (female) or an X and a Y chromosome (Male)
  • Gonadal sex - Whether a person’s gonads become testes or ovaries
  • Phenotypic sex - Development of particular external genitalia e.g. Vulva or penis
  • Legal sex - Sex that is on a persons birth certificate
  • Gender identity - What gender a person identifies as
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4
Q

What gene present on the Y chromosome is responsible for determining gonadal sex?

A

SRY gene

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5
Q

Briefly describe how the SRY gene determines gonadal sex

A
  • SRY gene switches on briefly during embryo development which causes it to induce its own transcription to produce the SRY protein
  • SRY protein then causes the production of lots of other proteins that results in the gonad differentitating into the testis
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6
Q

If there’s no SRY gene present what do the gonads differentiate into?

A

Ovaries

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7
Q

Why are gonads said to have bipotential?

A

Because they have the ability to develop into either male or female internal genitalia and the chances of them developing into either one are equal

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8
Q

What is the name of the structure that is a precursor to the gonads?

A

Genital ridge

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9
Q

Where do the genital ridges develop within an embryo and after how many weeks do they develop?

A
  • They develop at the posterior wall of lower thoracic lumbar region.
  • They develop after 3½ - 4½ weeks
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10
Q

There are 3 cell types that will invade the genital ridges during their development, what are the names of these 3 cell types?

A
  • Primordial germ cells
  • Primitive sex cords
  • Mesonephric cells
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11
Q

Each of the cell types that invade the genital ridges also have bipotential. Give the names of the cells that each of these cell types can differentiate into

A
  • Primoridial germ cells: Differentiate into Sperm (male) or Oocyte (female)
  • Primitive sex cords: Differentiate into Sertoli cells (male) or Granulosa cells (female)
  • Mesonephric cells: Differentiate into Blood vessels and Leydig cells (male) or Theca cells (female)
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12
Q

Where to the primordial germ cells initially develop and by what process do they develop?

A
  • Primordial germ cells start off as small cluster of cells in the epithelium of the yolk sac of the embryo
  • They begin to develop/expand via mitosis
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13
Q

What pathway do the primordial germ cells take to migrate to the genital ridges?

A

They migrate from the yolk sac, through the connective tissue of the hind gut, to the region of the developing kidney and on to the genital ridge

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14
Q

Once the primordial germ cells have migrated to the genital ridges what occurs to the primitive sex cords?

A

The primitive sex cords migrate from epithelium that overlies the genital ridge to the genital ridge itself and associates with the primordial germ cells already present

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15
Q

Describe what happens to the primitive sex cords specifically in males

A
  • In males the primitive sex cords penetrate deeply into the genital ridges and completely surrond the primordial germ cells to form a tube-like structure
  • In males the primitive sex cords do have the SRY gene and so they express it
  • This eventually causes the primitive sex cords to differentiate into Sertoli cells
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16
Q

In males, what causes the primordial germ cells to differentiate into Spermatozoa?

A
  • When the Sertoli cells that differentiated from the primitive sex cords that surronded the primoridal germ cells come into contact with one another
  • Primordial germ cells get exposed to the expressed SRY from the Sertoli cells which is specifically what causes them to differentiate
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17
Q

What hormone do the Sertoli cells secrete?

A

They secrete the Anti-mullerian hormone (AMH)

18
Q

Describe what happens to the primitive sex cords specifically in females

A
  • In females the primitive sex cords don’t penetrate that deeply into the genital ridges and instead of completely surronding the primordial germ cells they form small clusters around them
  • In females the primordial germ cells don’t express the SRY gene and so they differentiate into Granulosa cells
19
Q

In females, what causes the primordial germ cells to differentiate Oocytes?

A
  • When the Granulosa cells that differentiated from the primitive sex cords that surronded the primordial germ cells in clusters come into contact
  • Granulosa cells don’t express SRY so without this primordial germ cells differentiate into Oocytes
20
Q

Once the primitive sex cords reach the genital ridges in males, what happens to the mesonephric cells?

A
  • They migrate from the mesonephric primordium, which is just lateral to the genital ridges, to the genital ridges.
  • Then under the influence of the SRY produced by the developing Sertoli cells the mesonephric cells differentiate to form:
    • Vascular tissue
    • Leydig cells (mainly differentitate into these)
    • Basement membrane – Later contributes to formation of seminiferous tubules
21
Q

What hormone do the Leydig cells secrete?

A

Testosterone

22
Q

Once the primitive sex cords reach the genital ridges in females, what happens to the mesonephric cells?

A
  • They also migrate from mesonephric primordium to the genital ridges and because they aren’t under the influence of SRY they differentiate to form:
    • Vascular tissue
    • Theca cells
23
Q

Explain how the internal sexual organs develop in males

A
  • Before internal sex organ development males contain both the Mullerian and Wolffian ducts
  • The developing testis contain both Sertoli and Leydig cells
  • The sertoli cells secrete Anti-Mullerian hormone which will result in the regression of the Mullerian duct
  • The leydig cells secrete Testosterone which causes the growth of the Wolffian duct which will develop into the Epididymis, Vas deferens and the Seminal vesicle.
24
Q

Explain how the internal sexual organs develop in females

A
  • Before sexual organ development females also contain both Mullerian and Wolffian ducts
  • Because the developing ovaries don’t secrete Anti-Mullerian hormone it means the Mullerian duct is able to grow and develop into the uterus, uterine tubes and upper 1/3rd of the vagina
  • Because the developing ovaries also don’t secrete Testosterone it means that the Wolffian duct regresses
25
Q

In males what changes occur during the development of the external genitalia?

A
  • Genital tubercule forms the glans penis (head of penis)
  • Genital swellings fold in themselves to form the scrotum
  • Scrotal skin becomes ruggated
  • Prostate forms
26
Q

What substrate induces the development of the male external genitalia and how is this substrate produced?

A
  • Dihydrotestosterone induces development of male external genitalia
  • Produced via reaction that converts testerone into dihydrotestosterone
  • Reaction catalysed by 5-α-reductase found in genital skin
27
Q

In females what changes occur during the development of the external genitalia?

A
  • Genital tubercule develops into clitoris
  • Urethral fold becomes opening to the vagina and the Labia minora
  • Genital swelling becomes Labia majora
28
Q

What are some disorders of sexual differentiation?

A
  • Gonadal dysgenesis - Disorder in which sexual differentiation is incomplete
  • Sexual reversal - Disorder in which a person’s phenotype does not match their genotype
  • Intersex - Disorder in which a person has some components of both genitalia
29
Q

Gonadal dysgenesis can occur due to Androgen insensitivity syndrome, what is androgen insensitivity syndrome?

A

Androgen insensitivity syndrome is when a person who is genetically male (XY) is resistant to androgens (male hormones) such as testosterone

30
Q

What changes in sexual differentiation occur due to Androgen insensitivity syndrome?

A
  • Testosterone doesn’t have any effect so the Wolffian duct isn’t able to grow.
  • This means it isn;t able to develop into the vas deferens, Epididymis etc.
  • Anti-Mullerian hormone is still produced so the Mullerian duct regresses - this means no internal genitalia develop
  • Testosterone still coverted into dihydrotestosterone but this won’t have an effect because testosterone receptors are faulty
  • This means female external genitalia will develop instead
31
Q

What are the 2 different types of Androgen insensitivity syndrome?

A
  • Complete androgen insensitivity syndrome - Appear completely female at birth and assigned female gender despite being XY.
  • Incomplete androgen insensitivity syndrome - Present with varying degrees of male/female external genitalia
32
Q

Gonadal dysgeneis can also be caused by 5-α-reductase deficiency. What changes in sexual differentiation occur due to 5-α-reductase deficiency?

A
  • 5-α-reductase deficiency means testosterone isn’t converted into dihydrotestosterone
  • Without dihydrotestosterone male external genitalia development isn’t able to be induced
  • This means female external genitalia will develop
  • Male internal genitalia will develop as normal
33
Q

Why does the incidence of 5-α-reductase deficiency vary?

A

Varies because it’s autosomal recessive which means a person can be a carrier or have 2 copies of a variant that causes 5-α-reductase deficiency

34
Q

Gonadal dysgenesis can also be caused by turner syndrome. What is turner syndrome?

A

Syndrome that results in a person only having one X chromosome rather than having two X’s and an X and a Y.

35
Q

What changes in sexual differentiation will occur as a result of turner’s syndrome?

A
  • Person only has one X so genetic sex is female
  • Female internal and external differentiation will occur as normal
36
Q

If Turner’s syndrome doesn’t cause a problem with female genitalia development then what problems do occur?

A
  • Failure of ovarian function
  • Uterus and uterine tubes are present but small, other defects in growth and development.
37
Q

If females only ever express one X chromosome in all their cells why do females with Turner syndrome exhibit symptoms?

A
  • It’s beleived that not every single gene on the other X chromosome is inactivated due to X-inactivation
  • Also believed that these genes are important for particular functions
38
Q

Gonadal dysgenesis can also be caused by Congenital adrenal hyperplasia. What is Congenital adrenal hyperplasia?

A
  • A group of disorders which reuslts in a deficiency of one of the enzymes needed to cause the adrenal glands to secrete cortisol
39
Q

21-Hyrooxylase is one of the enzymes that can be affected by Congenital adrenal hyperplasia. What reaction does 21-Hyrooxylase catalyse?

A

Catalyses the conversion of Progestagens, e.g. progesterone into Glucocorticoids, e.g. Cortisol, and Mineralocorticoids

40
Q

21-Hyrooxylase deficiency can lead to failure to synthesise cortisol. What effects can this cause?

A
  • No cortisol leads to production of Corticotropin releasing hormone (CRH) and Adrenocorticotropic hormone (ACTH) by hypothalamus and pituitary gland
  • ACTH causes cholesterol uptake into the adrenal glands
  • In the adrenal glands cholesterol is converted into progestagens which would normally be converted into aldosterone and cortisol
  • However, due to 21-Hyrooxylase deficiency the cholesterol can’t be converted into cortisol s it leads to a build up of aldosterone.
41
Q

What changes to sexual differentiation are caused by Congenital adrenal hyperplasia?

A
  • Results in a female being exposed to high levels of androgens, e.g. testosterone
  • Still growth in Mullerian ducts due to no anti-mullerian hormone as they’re aren’t any Sertoli cells - Females have ovaries not testis
  • This means you get development of female internal genitalia
  • Incomplete Wolffian duct regression due to presecence of testosterone
  • Male extrnal genitalia development due to prescence of testosterone (gest converted into dihydrotestosterone).

Physiology 2 (29 decks)

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