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Reproductive System > Gametogenesis > Flashcards

Gametogenesis Flashcards

1
Q

What is spermatogenesis?

A

Production of sperm cells from germ cells

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2
Q

What is spermiogenesis?

A

Maturation of spermatids

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3
Q

What process produces gametes?

A

Meiosis

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4
Q

How is genetic variation produced in gametogenesis?

A

Crossing-over - exchange of DNA between homologous chromosones
Independent assortment - random orientation during metaphase
Random segregation - random distribution of alleles

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5
Q

Where does spermatogenesis take place?

A

Sertoli cells in seminiferous tubules

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6
Q

Describe the phases of spermatogenesis

A

Spermatogonium - undergoes mitosis

  • Ad spermatogonium
  • Ap spermatogonium

Ap spermatogonium (primary spermatocyte) - undergoes meiosis 1

Secondary spermatocyte - undergoes meiosis 2

Spermatid - undergoes spermiogenesis

Mature sperm

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7
Q

What is an Ad spermatogonium?

A

‘Resting’ spermatogonium - reserve stock

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8
Q

What is an Ap spermatogonium?

A

‘Active’ spermatogonium - maintains stock + after puberty produces type B spermatogonia which are primary spermatocytes

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9
Q

What is a spermatogenic cycle?

A

Time taken for reappearance of the same stage within a given segment of tubule

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10
Q

How long is a spermatogenic cycle?

A

~16 days

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11
Q

What is a spermatic wave?

A

Distance between each stage

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12
Q

How does spermatogenesis occur in the tubules?

A

Occurs in waves migrating through tubule

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13
Q

What is spermiation?

A

Spermatids released into the lumen of seminiferous tubules

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14
Q

What happens during spermiogenesis?

A

Spermatids released into lumen

Remodel as they pass through into epididymis

  • non motile until they reach the epididymis
  • moved by peristaltic contraction
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15
Q

What is sperm capacitation?

A

Final maturation step required for sperm to become fertile - occurs in female genital tract

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16
Q

What happens in sperm capacitation?

A

Removal of glycoproteins and cholesterol from sperm membrane

Activation of sperm signalling pathways

Allow sperm to bind to zona pellucida

17
Q

What is oogenesis?

A

Production of oocytes

18
Q

What happens to the oocytes before birth?

A 
Germ cells colonise gonadal cortex
Differentiate into oogonia
Proliferate
End of 3rd month = arranged in clusters
Some enter meiosis - stop in prophase 1 = primary oocytes
Majority degenerate
All surviving enter meiosis 1 
Surrounded by follicular cells
19
Q

What happens every month post puberty?

A

15-20 oocytes start to mature each month

20
Q

What are the stages of oocyte maturation?

A

Preantral
Antral
Preovulatory

21
Q

What happens in the preantral stage?

A

Primordial follicles grow

Follicular cells change from flat to cuboidal to produce stratified epithelium of granulosa cells

22
Q

What happens in the antral stage?

A

Fluid filled spaces appear between granulosa cells

Spaces form the antrum

23
Q

What happens in the preovulatory stage?

A

Induced by LH surge

Cell enters meiosis 2 - arrests in metaphase 2

24
Q

How is ovulation stimulated?

A

FSH + LH stimulate rapid growth of the follicle

LH surge increase collagenase activity
Prostaglandins increase in response to LH - cause muscular contractions in ovarian wall

Oocyte released

25
Q

What is the corpus luteum?

A

The remaining granulosa and theca cells

26
Q

What happens to the corpus luteum?

A

Cells become vascularised and change into lutein cells

Secrete oestrogens and progesterone - stimulate uterine mucosa to enter secretory stage

Dies after 14 days if no fertilisation

27
Q

How is the oocyte transported from the ovary?

A

Swept up by fimbriae

Propelled along fallopian tube by peristaltic contractions + cilia

28
Q

What happens to the corpus luteum if no fertilisation occurs?

A

Corpus luteum degenerates into corpus albicans

Progesterone production decreases - menstrual bleeding

29
Q

What happens to the corpus luteum if fertilisation occurs?

A

Degeneration prevented by HCG produced by embryo

Corpus luteum continues to grow and form the corpus luteum graviditatis

Continues to produce progesterone until 4th month

Reproductive System (22 decks)

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