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Yr2: Reproduction > Sex Differentiation and Gametogenesis > Flashcards

Sex Differentiation and Gametogenesis Flashcards

1
Q

what determines if a foetus is male or female

A

whether they have an XX or XY chromosome

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2
Q

When is genotypic Sex established in mammals

A

At fertilisation

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3
Q

what is Turner Syndrome and what does it result in

A
  • when someone has an XO chromosome
  • results in a female that:
    > is sterile
    > has poorly developed breasts
    > has very small sexual organs
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4
Q

sexual differentiation

what is sexual differentiation

A

the development of any male- or female-specific physical or behavioral characteristic, to equip organisms with the necessary anatomy and physiology to allow sexual reproduction to occur.

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5
Q

genotypic sex

what is Klinefelter syndrome and what 3 thinks does this result in

for second part think height, testes and breasts

A
  • someone who possesses XXY chromosomes

results in a male that:

  • is above average height
  • has Underdeveloped testes
  • has Occasional breast development
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6
Q

Grastrulation

what is Gastrulation?

A
  • the process by which agastrulaforms from ablastula.
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7
Q

PGCs

How can primordial germ cells (PGCs) be characterized

think density, outline and diameter

A
  • high electron cytoplasm density
  • irregular outline
  • diameter of 10 -20 µm (depending on species, stage, shape)
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8
Q

PGCs

What in PGCs are used as an indicator enzyme and why

for second part think of activity in cytoplasm of PGC

A

alkaline phosphatase as there is high activity of it in PGCs peripheral cytoplasm

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9
Q

PGCs

Outline how the testis develop from PGCs if male leaning

think medulla of something and then something else regressing

A
  • develops from the medulla of the primordial (undifferentiated) gonad causing the cortex to regress
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10
Q

PGCs

Outline how the ovary develop from PGCs if female leaning

think cortex of something causing the regression of something else

A
  • develops form the cortex of the primordial (undifferentiated) gonad causing the medulla to regress
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11
Q

sex determining region on Y chromosome

Outline how male development occurs in the developing goand in the presence of the SRY gene (Sex determining Region on the Y chromosome)

for step 1, think SRY directing cells to differentiate

for step 2, think about 3 things what these differentiated cells

A
  1. SRY directs somatic cells in developing goand to differentiate into Sertoli cells instead of follicle cells
  2. Sertoli Cells then:
    - induce primordial germ cells to commit to sperm development
  • secrete anti-Mullerian hormone, causing the Mullerian duct to regress
  • Help induce other somatic cells to differentiate into Leydig cells, which secrete testosterone
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12
Q

SRY

Outline how female development occurs in the developing gonad in the absence of SRY gene (SEX determining Region on Y chromosome)

A
  1. In absence of SRY, Primordial germ cells commit to egg development, so somatic cells develop into:
  • follicle cells (to support egg development)
  • theca cells (which secrete oestrogen)
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13
Q

SRY

When do theca cells begin secreting oestrogen?

A

puberty

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14
Q

gonadal differentiation

Why does an indifferent gonad develop into a testis and when does an ovary develop instead of a testis

think TDF for first part

for second part think TDF and critical window

A
  • develops into testis in response to Testis Differentiation Factor (TDF) before WEEK 9 of development

An ovary will develop instead of a testis if:
- TDF is not present

  • TDF is only present after the Week 9 critical window has passed.
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15
Q

gonadal differentiation

what 3 hormones does further male pattern sexual differentiation depend on and which of these hormones is produced by the testis and which of these is converted into by peripheral tissues?

A

3 hormones:
- Testosterone
- Dihydrotestosterone (DHT)
- Anti-mullarian hormone (AMH)

  • testosterone and AMH produced by testis

peripheral tissues convert testosterone to DHT

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16
Q

testicular differentiation

What 3 cell types make up the testicular cords?

A
  • Peritubular myoid cells
  • Sertoli cells
  • Primordial germ cells
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17
Q

What is the rete testis?

think interconnected tubules and sex cords and what this creates

A

a system of interconnected tubules formed by the primitive sex cords creating an outlet for sperm

18
Q

ovarian differentiation

Outline the 5 stages of ovarian differentiation in female embryos

stage 1, think what regresses and what thickens in pGCs and what this gives rise to

for stage 2 think about how many oogonia in ovaries in week 8 and then what that number is in week 20

for stage 3 think what happens to a large number of oogonia and what the remainder are surrounded by

for stage 4 think what stage all oocytes are locked in by week 20 and until what point it is like this

for stage 5 think how many primordial follicles will be available for reproduction at birth

A
  • medulla of gonad regresses while cortex thickens due to mitotically dividing PGCs, giving rise to oogonia
  • by week 8 developing ovaries contain 600,000 oogonia, increasing to 6-7 million by week 20
  • large number of oogonia die and are resorbed, and remainder are surrounded by single layer of Granulosa cells, forming primordial follicles
  • by week 20 all oocytes are locked at prophase I of meiosis and remain that state until the follicle is selected for maturation or death later in life
  • At birth, each ovary holds around 1 million primordial follicles that will be available for reproduction for the rest of the female’s life
19
Q

oogenesis and primordial follicle formation

Define primordial follicle

think oocyte in a specific stage and what surrounds it

A

Oocyte locked in Prophase I (of meiosis I) that is surrounded by a single layer of flat granulosa cells

20
Q

external genitalia

What week does the genital tubercle begin to enlarge to form the phallus in both sexes

A

week 4

21
Q

external genitalia

outline how external genitalia develops in males

think genital tubercle, urogenital folds and laboscrotal swellings and what they become

A
  1. genital tubercle becomes the glans penis (tip of penis)
  2. urogenital folds fuse to form the shaft of penis
  3. labioscrotal swellings become the scrotum
22
Q

external genitalia

Outline how external genitalia develops in females

think about genital tubercle, urogenital folds, labioscrotal swellings and the ventral (anterior) labioscrotal swellings and what they become

A
  1. genital tubercle becomes clitoris
  2. urogenital folds remain separate as the labia minora
  3. labioscrotal swellings become labia majora and remain unfused
  4. ventrally, the labioscrotal swellings fuse to form the mons pubis
23
Q

puberty and gametogenesis

what 2 physiological processes does puberty involve?

A
  • gonadarche
  • adrenarche
24
Q

puberty and gametogenesis

what is gonadarche and what is it induced by?

for first part think maturation of gonads and what they produce as a result

for second part think about hormones released by anterior pituitary

A
  • physical and functional maturation of the gonads, such that they produce gametes and sex steroids
  • induced by increased production of FSH and LH by anterior pituitary
25
Q

puberty and gametogenesis

What is adrenarche

think steroidal production by cortex

A

the increased production of the androgenic steroids by the adrenal cortex

26
Q

puberty and gametogenesis

What does gonadarche lead to in males and what does it lead to in females

for males think sperm

for females think follicles and first menstruation

A
  • in MALES, leads to initiation of sperm production by testes
  • in Females, leads to folliculogenesis and menarche
27
Q

spermatogenesis

What are the 4 key stages of spermatogenesis and define them

for first one think generation of a type of spermatocyte and via what process

for second stage think meiosis of spermatocytes to produce something

for third stage think maturation of spermatid to something else

for fourth stage think release of something from a specific cell to a tubule lumen

A
  • Spermatocytogenesis: generation of primary spermatocytes via mitotic division of spermatogonia
  • spermatogenesis: meitotic generation of round spermatids from spermatocytes
  • spermiogenesis: Maturation of spermatid to spermatozoon
  • Spermiation: release of spermatozoon from Sertoli cell to tubule lumen
28
Q

the seminiferous tubule

what does the seminiferous tubule contain and what are the 4 examples of spermatogeic cells

think sperm cells and another type of cell for frst part

for second part think different stages of sperm cell

A
  • contain spermatogeic cells and Sertoli (sustentacular) cells

4 examples of spermatogeic cells are:

  • Spermatogonia (stem cell)
  • Spermatocytes
  • Spermatids
  • Spermatozoa (mature sperm)
29
Q

sertoli cell

What do Sertoli cells support

A

the development of the spermatids

30
Q

sertoli cell

how do sertoli cells complete their function

A
  • provide structural and metabolic support
  • promote cell division
31
Q

sertoli cell

What are Sertoli cells stimulated by?

think a sex steroid and a gonadotrophin

A

FSH
Testosterone

32
Q

sertoli cell

Where do Sertoli cells extend from?

A

from basement membrane to lumen

33
Q

leydig (interstitial) cells

What is the principal role of Leydig cells?

think testosterone and LH

A

Synthesis and secretion of testosterone in response to stimulation by LH (steroidogenesis)

34
Q

leydig cells

What other than testosterone production and secretion does LH control in Leydig cells?

think receptors and growth and differentiation

A
  • LH receptor availability (-ve feedback)
  • Leydig cell growth and differentiation
35
Q

leydig cells

How can testosterone produced by Leydig cells act?

think paracrine for first way it can act

for second way think endocrine

A
  • locally on the seminiferous tubules to promote spermatogenesis
  • Diffuse into general circulation
36
Q

spermiogenesis - cellular reorganisation

Outline the 6 steps of the process of spermiogenesis

A
  • Spermatid becomes spermatozoon by:
  1. Sperm lose vast majority of cytoplasm which is taken up by Sertoli cells
  2. Centriole then produces flagellum
  3. Golgi apparatus forms acrosome vesicle
  4. Gene expression machinery is now shut down and becomes quiescent
  5. Finally, mitochondria migrate to flagellum
37
Q

spermatogenesis (meiosis)

Outline Meiosis I – primary spermatocyte in Spermatogenesis

A
  1. Chomosomes replicate (2n –> 4n)
  2. Chromosomes condense and pair homologously
  3. Chromosomes crossover and form a chiasmata where genetic info is exchanged
  4. homologous chromosomes separate
38
Q

spermatogenesis (meiosis)

Outline Meiosis II – secondary spermatocyte in spermatogenesis

A
  1. Chromosomes don’t replicate (remain condensed)
  2. Centromeres divide and separate chromatids, generating haploid cells (1n)
39
Q

hormonal control of spermatogenesis

What does FSH act on to enhance spermatogenesis

think cells that facilitate development of spermatids

A
  • acts on Sertoli cells of the seminiferous tubules
40
Q

hormonal control of spermatogenesis

how does feedback control regulate testicular function

A

Sertoli cells secrete inhibin (growth factor) which negatively regulates pituitary function

Yr2: Reproduction (24 decks)

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