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Embryology > Gametogenesis > Flashcards

Gametogenesis Flashcards

1
Q

What does meiosis and cyto differentiation do

A
  • reduce the number of chromosomes

- compete maturation

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2
Q

What are primordial germ cells , how formed and their functions

A

-cells that diff into gametes

  • formed form epiblast during 2nd week of development
  • move through primitive streak during gastrulation and migrate to wall of yolk sac towards gonads
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3
Q

How do PGC’s increase in number

A

-mitotic division during migration to gonads and in the gonads

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4
Q

What are linked genes

A

/genes on same chromosome which are inherited together

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5
Q

What is synapsis and cross over

A
  • coming together and condensing of homologous chromosomes during meiosis
  • interchange of homologous chromosome segments as they break up during meiosis
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6
Q

What is a chiasma

A

-X like structure formed during cross over of homologs as points of interchange attach

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7
Q

Effects of meiosis

A
  • genetic variability due to synapsis

- random distribution of chromosomes into daughter cells

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8
Q

What are polar bodies , how formed and fate

A
  • of the 4 daughter cells from 1• oocyte only 1 is mature oocyte and the other 3 are polar bodies ; less cyto and smaller
  • degenerate during development
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9
Q

What is oogenesis and where does it occur and when does it begin

A
  • formation of ooctyes from oogenia in the ovaries

- before birth

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10
Q

What happens to PGC when it arrives at gonad during oogenesis

And what happens to its product

A
  • it divides ( mitosis )and differentiates into oogenia
  • divides mitotically around end of 1st trimester and becomes 1• oocyte surrounded by cluster of epi cells. Have arrested division at prophase 1
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11
Q

Where are follicular cells derived from

And oogenia In a cluster

A
  • surface of epi covering ovaries

- single cell ( PGC )

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12
Q

What happens during 5th and 7th month of prenatal oogenesis

A
  • max number of oogenia reached and cell death begins as cells become atretric
  • most cells have degenerated except for a few near surface. No more oogenia and surviving oocytes have entered prophase of meiosis 1 individually surrounded by single squamous ( primordial follicule )
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13
Q

What happens at birth of oogenesisi

A

-primordial follicules enter resting stage of prophase known as diplotene stage

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14
Q

What stimulates diplotene stage and where does it come from

What is primordial follicle

A
  • oocyte maturation inhibitor , small peptide secreted by follicules
  • 1• oocyte arrested at prophase and its simple squamous epi
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15
Q

What happens to pool of primordial follicules

A
  • they are recruited ( 15-20 ) each month and simple is now cuboidal and they secrete glycoprotein zona pellucida
  • also proliferate into stratified granulosa layer

-growing follicule

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16
Q

What happens to growing follicule

A
  • epi secrete zona
  • proliferate into stratified granulosa layer
  • now a 1• follicule
  • some die but other accumulate fluid in space called antrum
17
Q

Describe the Antrum stage

A
  • 1• follicule accumulate fluid in between cells and the fluid filled spaces join and form antrum
  • longest stage
18
Q

Describe graafian / mature follicule stage

A
  • antrum increases in size from a small crescent shape
  • has cumulus oorphus
  • has theca externa and interna
19
Q

What separates granulosa from theca CT

A

-granulosa originated from basement membrane

20
Q

Function of processes from follicular into zona and how connection formed !?

A

-finger like processes from follicular interdiginate with plasm of oocyte
/transport materia between the 2

21
Q

What is cumulus oorphus

A

-intact granulosa around oocyte

22
Q

Describe the theca interna and externa structure and functions

A

-more fibrous , cells secrete steroid , rich in blood vessels
Outer layer

-cellular inner layer , more diffuse

23
Q

How many oocytes mature during ovarian cycle and what happens to the rest

A
  • usually 1

- degenerate and become atretic

24
Q

What happens to graafian follicule

Where is polar body located

A
  • undergoes 1st meiotic division to reduce chromosomes # and form 2• oocyte
  • polar body present now between zona and membrane of cell
25
Q

What happens to 2• oocyte

A
  • undergoes 2nd meiotic division to form 4 daughter cells

- polar body may also undergo division

26
Q

What influences 1st and 2nd meiotic Division

A

-LH hormone ( luteinizing hormone ) which induces preovulatory growth phase

27
Q

What is spermatogenesis and when and where does it occur

A
  • begins at puberty

- process by which spermatogonium are converted into spermatozoa in the testis

28
Q

Appearance of germ cells in testis and where are the support cells derived from

A
  • pale appearance
  • surface epi of testis
  • sertoli or sustentacular
29
Q

Function of support cells in testis and what happens to sex cords after puberty

A
  • assist in release of spermatozoa
  • protect, support
  • participate in nutrition

-acquire lumen and become seminiferous tubes

30
Q

Describe process of spermatogenesis

A

-PGS diff into spermatogonium - diff into type A dark spermatogonium - few mitotic divisions give type A pale spermatogonium - last division gives type B - diff’s into 1• spermatocyte which goes into prolonged prophase - 1st meiotic to form 2• spermatocytes - 2nd meiosis to form spermatids

31
Q

What are cells connected throughout spermatogenesis

And where are cells found throughout development

A
  • incomplete cytokinesis

- in sertoli

32
Q

Function and MOD of LH in spermatogenesis

A

-LH produced by pituitary binds to receptors on Leydig cells , stimulate testosterone production wc binds to Sertoli cells stimulating testicular fluid prod and synthesis of intercellular androgen receptor proteins

33
Q

What is spermiogenesis

A

-series of changes resulting in transformation of spermatids into spermatozoa

34
Q

Describe the process of spermiogenesis

A

1 Formation of acrosome from Golgi which covers half of nucleus
2 nucleus condenses
3 formation of neck, middle and tail piece
4 shedding of most of cyto which is phagocytized as residual body by sertoli
5 spermatozoa enter lumen of seminiferous tubes

35
Q

How are spermatozoa pushed into lumen

A

-by contractile elements in wall of seminiferous tubes

Embryology (5 decks)

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