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IMS > ORIGIN + DEVELOPMENT OF GERM CELLS > Flashcards

ORIGIN + DEVELOPMENT OF GERM CELLS Flashcards

1
Q

what are primordial germ cells?

A

Earliest germ cells

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2
Q

where do primordial germ cells arise from?

A

‘Migrate’ from yolk sac, through hind-gut to genital ridge

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3
Q

where do primordial germ cells enter?

A

Enter presumptive seminiferous tubes (hoops) with pro-Sertoli cells

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4
Q

where do primordial germ cells settle?

A

on the tubule wall first

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5
Q

what is spermatogonia?

A

is an undifferentiated male germ cell

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6
Q

where does spermatogonia take place?

A

outside the blood-testis barrier

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7
Q

what do spermatogonia undergo?

A

spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testis

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8
Q

how to primordial germ cells proliferate?

A

by mitosis

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9
Q

what do primordial germ cells develop into?

A

into gonocytes

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10
Q

how do gonocytes proliferate?

A

by mitosis

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11
Q

what do gonocytes develop into?

A

Pro-spermatogonia

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12
Q

what do Pro-spermatogonia develop into?

A

Spermatogonia by the end of the foetal stage

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13
Q

what is the prepubertal phase?

A

Earliest spermatogonia become stem cells and acquire self-renewal capacity

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14
Q

what is the process of spermatogonia in rodents?

A

A0 considered to be stem cells

Give rise to a succession of generations of A s’gonia

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15
Q

what does spermatogonia in rodents allow?

A

allows dramatic expansion of a small stem cell pool

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16
Q

what is the process of spermatogonia in humans?

A

Adark considered to be stem cells. Apale are proliferative.

form intermediate which form new cells.

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17
Q

what is a difference in process between spermatogonia in humans compared to rodents?

A

in humans

Large reserve of stem cells & relatively few proliferative divisions

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18
Q

what happens to spermatogonia in the prepubertal phase?

A

become stem cells and acquire self-renewal capacity

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19
Q

what does the peri-natal spermatogonial division produce?

A

spermatocytes

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20
Q

what is all post-stem cell development?

A

syncitia until just before sperm release

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21
Q

when does spermatocytes arrest occur?

A

in prophase of 1st meiotic division

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22
Q

what do B spermatogonia give rise to?

A

Preleptotene spermatocytes

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23
Q

what do Preleptotene spermatocytes give rise to?

A

Leptotene s’cytes

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24
Q

what do Leptotene s’cytes give rise to?

A

Zygotene s’cytes

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25
Q

what do Zygotene s’cytes give rise to?

A

Pachytene s’cytes

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26
Q

what do Pachytene s’cytes give rise to?

A

Diplotene s’cytes

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27
Q

what does Diplotene s’cytes lead to?

A

1st meiotic division

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28
Q

what happens after 1st meiotic division?

A

Secondary s’cytes produced

cells now haploid

29
Q

what does Secondary s’cytes lead to?

A

2nd meiotic division

30
Q

what is the role of Preleptotene spermatocytes?

A

S-phase

31
Q

what is the role of Leptotene s’cytes?

A

chromatin remodelling

32
Q

what is the role of Zygotene s’cytes?

A

chromatin remodelling

33
Q

what is the role of Pachytene s’cytes?

A

transcription, translation increase in size

34
Q

what do Diplotene s’cytes do?

A

enter meiosis

35
Q

what is spermatogenesis?

A

Development of spermatids

36
Q

what are the 3 types of spermatids?

A

round, elongating, maturation phase

37
Q

what are the round spermatids a product of?

A

the 2nd meiotic division

38
Q

what happens in round spermatids?

A

Nucleus still capable of transcription, DNA repair etc but activity diminishes. Nuclear histones are replaced by transition proteins

39
Q

what happens at the opposite pole?

A

Onset of flagellum development and acrosome dev.

40
Q

what are elongating spermatids?

A

transcriptionally inactive

41
Q

what are transition proteins replaced by in elongated spermatids?

A

protamines, much higher order of packing, dramatic reduction in nuclear size - essential for motility

42
Q

what happens to elongating spermatids?

A

Flagellum develops fully. Cytoplasm shrinks away to form droplet

43
Q

what are Maturation phase spermatids?

A

have morphology of mature spermatozoa

44
Q

what happens to Maturation phase spermatids?

A

Shed into lumen of tubule at spermiation. Cytoplasmic droplet phagocytosed by Sertoli cell

45
Q

what is a oogonium?

A

Primordial germ cell

46
Q

what does oogonium develop into?

A

primary oocyte arrested in prophase of meiosis I (diplotene)

47
Q

what happens at ovulation?

A

expulsion of 1st polar body (metaphase II)

48
Q

what happens after ovulation?

A

2nd period of arrest

49
Q

what happens at fertilisation?

A

expulsion of 2nd polar body

50
Q

in females where do all germ cell, mitotic activity occur?

A

during foetal life

51
Q

what is the final number of cells in the egg fixed?

A

in utero

52
Q

what happens at completion of mitoses?

A

cells enter meiosis but are arrested at diplotene

53
Q

what happens once the cells enter mitosis?

A

form germinal vesicle

54
Q

what happens at the dictyate stage?

A

Large numbers of dictyate germ cells die (by apoptosis) in last trimester

55
Q

what is an oogonium bounded by?

A

by basement membrane & surrounded by spindle-shaped cells
forms germinal vesicle

56
Q

what happens following arrest in gametogenesis?

A

1º oocyte surrounded by granulosa cells: primordial follicle

57
Q

what happens at puberty?

A

a few primordial follicle’s recruited to re-commence development

58
Q

what is Folliculogenesis?

A

-> 1º, 2º pre-ovulatory follicles

59
Q

what is the Pre-Antral follicle?

A

Secretion of glycoproteins forms zona pellucida

60
Q

what happens with Pre-Antral follicle?

A

Division of granular cells: cytoplasmic processes to oocyte; gap junctions; avascular

61
Q

what do Ovarian stromal cells form?

A

theca around follicle (interna +externa)

62
Q

what happens with the Antral (Graafian) follicle?

A

Granular cell proliferation increase in follicle size

63
Q

what does the secretion of follicular fluid do?

A

mucopolysaccharides + serum forms antrum

64
Q

what is the oocyte connected to?

A

to thick gran. cell layer (cumulus oophorous) by stalk

65
Q

what does the oocyte continue to store?

A

mRNA

66
Q

what is gonadotrophin?

A

hormone stimulates activity of the gonads

Synthesis of steroids

67
Q

what is the Pre-ovulatory follicle?

A

Transient peak of LH stim’s ovulation.

Breakdown of nuclear memb, separation of chrom’s + unequal division of cytoplasm, extrusion of 1st polar body

68
Q

what develops after the separation of chromatids?

A

metaphase plate 2nd meiotic arrest

IMS (52 decks)

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