ORIGIN + DEVELOPMENT OF GERM CELLS Flashcards Preview

IMS > ORIGIN + DEVELOPMENT OF GERM CELLS > Flashcards

Flashcards in ORIGIN + DEVELOPMENT OF GERM CELLS Deck (68):
1

what are primordial germ cells?

Earliest germ cells

2

where do primordial germ cells arise from?

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

3

where do primordial germ cells enter?

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

4

where do primordial germ cells settle?

on the tubule wall first

5

what is spermatogonia?

is an undifferentiated male germ cell

6

where does spermatogonia take place?

outside the blood-testis barrier

7

what do spermatogonia undergo?

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

8

how to primordial germ cells proliferate?

by mitosis

9

what do primordial germ cells develop into?

into gonocytes

10

how do gonocytes proliferate?

by mitosis

11

what do gonocytes develop into?

Pro-spermatogonia

12

what do Pro-spermatogonia develop into?

Spermatogonia by the end of the foetal stage

13

what is the prepubertal phase?

Earliest spermatogonia become stem cells and acquire self-renewal capacity

14

what is the process of spermatogonia in rodents?

A0 considered to be stem cells
Give rise to a succession of generations of A s'gonia

15

what does spermatogonia in rodents allow?

allows dramatic expansion of a small stem cell pool

16

what is the process of spermatogonia in humans?

Adark considered to be stem cells. Apale are proliferative.
form intermediate which form new cells.

17

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

in humans
Large reserve of stem cells & relatively few proliferative divisions

18

what happens to spermatogonia in the prepubertal phase?

become stem cells and acquire self-renewal capacity

19

what does the peri-natal spermatogonial division produce?

spermatocytes

20

what is all post-stem cell development?

syncitia until just before sperm release

21

when does spermatocytes arrest occur?

in prophase of 1st meiotic division

22

what do B spermatogonia give rise to?

Preleptotene spermatocytes

23

what do Preleptotene spermatocytes give rise to?

Leptotene s'cytes

24

what do Leptotene s'cytes give rise to?

Zygotene s'cytes

25

what do Zygotene s'cytes give rise to?

Pachytene s'cytes

26

what do Pachytene s'cytes give rise to?

Diplotene s'cytes

27

what does Diplotene s'cytes lead to?

1st meiotic division

28

what happens after 1st meiotic division?

Secondary s'cytes produced
cells now haploid

29

what does Secondary s'cytes lead to?

2nd meiotic division

30

what is the role of Preleptotene spermatocytes?

S-phase

31

what is the role of Leptotene s'cytes?

chromatin remodelling

32

what is the role of Zygotene s'cytes?

chromatin remodelling

33

what is the role of Pachytene s'cytes?

transcription, translation increase in size

34

what do Diplotene s'cytes do?

enter meiosis

35

what is spermatogenesis?

Development of spermatids

36

what are the 3 types of spermatids?

round, elongating, maturation phase

37

what are the round spermatids a product of?

the 2nd meiotic division

38

what happens in round spermatids?

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

39

what happens at the opposite pole?

Onset of flagellum development and acrosome dev.

40

what are elongating spermatids?

transcriptionally inactive

41

what are transition proteins replaced by in elongated spermatids?

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

42

what happens to elongating spermatids?

Flagellum develops fully. Cytoplasm shrinks away to form droplet

43

what are Maturation phase spermatids?

have morphology of mature spermatozoa

44

what happens to Maturation phase spermatids?

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

45

what is a oogonium?

Primordial germ cell

46

what does oogonium develop into?

primary oocyte arrested in prophase of meiosis I (diplotene)

47

what happens at ovulation?

expulsion of 1st polar body (metaphase II)

48

what happens after ovulation?

2nd period of arrest

49

what happens at fertilisation?

expulsion of 2nd polar body

50

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

during foetal life

51

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

in utero

52

what happens at completion of mitoses?

cells enter meiosis but are arrested at diplotene

53

what happens once the cells enter mitosis?

form germinal vesicle

54

what happens at the dictyate stage?

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

55

what is an oogonium bounded by?

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

56

what happens following arrest in gametogenesis?

1º oocyte surrounded by granulosa cells: primordial follicle

57

what happens at puberty?

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

58

what is Folliculogenesis?

-> 1º, 2º pre-ovulatory follicles

59

what is the Pre-Antral follicle?

Secretion of glycoproteins forms zona pellucida

60

what happens with Pre-Antral follicle?

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

61

what do Ovarian stromal cells form?

theca around follicle (interna +externa)

62

what happens with the Antral (Graafian) follicle?

Granular cell proliferation increase in follicle size

63

what does the secretion of follicular fluid do?

mucopolysaccharides + serum forms antrum

64

what is the oocyte connected to?

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

65

what does the oocyte continue to store?

mRNA

66

what is gonadotrophin?

hormone stimulates activity of the gonads
Synthesis of steroids

67

what is the Pre-ovulatory follicle?

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

what develops after the separation of chromatids?

metaphase plate 2nd meiotic arrest