gametogenesis Flashcards

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1
Q

where do gonocytes originate from

A

yolk endoderm

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2
Q

what do the gonocytes do at the genital ridges

A

differnetiate to oogonia or spermatagonia

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3
Q

what happens to cells surrounding the gonocytes

A

differentiates to follicle or sertoli cells

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4
Q

what day does gonadal development occur

A

38-40th day of embryogenesis

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5
Q

oogenesis vs spermatogenesis

A

> occurs mostly in ovaries * occurs all in testes
unequal div cytoplasm * Equal div cytoplasm
only 1 made, rest polar bods *4 made
begins in foetus * begins at puberty
monthly release after pub * continuous release
stops after menopause * lifetime

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6
Q

primary oocytes start meiosis. what day are oogonia differnetiated to this

A

10-12th week of human embryogenesis

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7
Q

where is meiotic division stopped at before puberty

A

diplotene

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8
Q

at what stage is it considered oocyte maturation

A

completion of 1st meiotic div and progression to metaphase 2

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9
Q

what develops during oocyte maturation

A

granulosa + theca cells
zona pellucida (glycoprotein covering)

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10
Q

Explain follilce stages in ovary

A
  1. primordial follicle (around primary oocyte)
  2. primary follicle
  3. gonatrophic hormones (FSH) stimulates follicle growth
  4. secondary follicle ( multiple cell layers around oocyte)
  5. tertiary follicle (with antrum)
  6. Graafian follicle
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11
Q

what stage is ovulated oocyte arrested at. and what happens after ovulation

A

metaphase 2, it has polar body and meiotic spindle.
after ovulation, follicle cells (cumulus cells) still connected to oocyte

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12
Q

briefly explain CORTICAL reaction

A
  1. signal sent to ER when sperm head penetrates ZP + touches oocyte membrane
  2. Calcium ions relased from ER + triggers exocytosis of CGs
  3. Cgs change Zona reaction? + doesnt allow other spermatozoa to pass
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13
Q

what are Cgs?

A

cortical granules - oocyte specific secretory vesicles
released during fertilization to prevent polyspermy

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14
Q

role of somatic cells in spermatogenesis

A

starts at puberty. spermatogonia close to basment mem of seminiferous tubules.
LH goes to LEYDIG cells.
SERTOLI cells support and nourish spermatogenic cells
leydig cells make testosterone

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15
Q

how long is meiotic period of spermatogenesis and differentiation

A

24 days
differentiation spermatids to spermatozoa = 5 weeks more

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16
Q

spermatozoa mature in synctium. why?

A
  1. to compensate possible recessive mutations by gene products of normal allele
  2. share sex chromosome products.
17
Q

Structure mature spermatozoa

A

head - acrosome, nucleus, receptors on membrane (for egg recognition + attachment)
neck - has centriole
midpiece/body - has mitochondria
tail - axial filament

18
Q

spermiogenesis = differentiation of spermatozoa from spermatids. explain 4 main stages of it

A
  1. nuclear condensation
  2. acrosome formation (contains hyaluronidase + acrosin that break down ovum membrane)
  3. cytoplasmic reduction (cytoplasmic components not needed are phagocyted by Sertoli cells)
  4. flagellum development
19
Q

Nuclear condensation

A

majority of histones replaced by protamine’s
sperm chromatin = nucleoprotamines coiled into toroids

20
Q

structure of sperm tail

A

axoneme = flexible axis of tail
9 double outer microtubules + 2 single in centre

21
Q

what are Nexin + Dynein

A

nexin = connects adjacent microtubule doublets
dynein = btw microtubules + responsible for movement

movement is when microtubules doublet slide one another, helped by dynein