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Reproductive System > Gametogenesis > Flashcards

Gametogenesis Flashcards

1
Q

What happens to germ cells after colonising the gonad?

A
  • proliferate by mitosis
  • reshuffle genetically + reduce to haploid by meoisis
  • cytodifferentiate into mature gametes
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2
Q

What are the two main functions of meiosis?

A
  • reduce the chromosome number in gamete to 23
  • genetic variation in each gamete
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3
Q

What allows for genetic variation in meiosis?

A
  • crossing over
  • independent assortment
  • random segregation
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4
Q

What is crossing over?
When does this occur?

A

Exchange of regions of DNA between 2 homologous chromosomes at chiasma

Prophase 1

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5
Q

What is independent assortment?

A

Random organisation of bivalents along metaphase plate

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6
Q

What is random segregation?

A

Random distribution of alleles among the 4 gametes

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7
Q

Outline spermatogenesis

A
  • spermatogonia divide by mitosis > Ad spermatogonium + Ap spermatogonium
  • Ap spermatogonium produce type B spermatogonia > primary spermatocytes
  • primary spermatocytes divide by meiosis > secondary spermatocytes > 4 spermatids
  • spermatids differentiate into spermatozoa (spermiogenesis)
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8
Q

What do spermatogonia divide into and how?

A
  • mitosis
  • Ad spermatogonium: resting
  • Ap spermatogonium: active > maintain stock + continue along spermatogenesis pathway
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9
Q

What do primary spermatocytes divide into and how?

A
  • meiosis
  • secondary spermatocytes > 4 spermatids
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10
Q

What is spermiogenesis?

A
  • spermatids differentiate into spermatozoa
  • when spermatids are released into lumen of seminiferous tubules + ends when they reach epididymis
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11
Q

Where does spermatogenesis occur?

A

Seminiferous tubules (Sertoli cells)

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12
Q

What is the spermatogenic cycle?

A

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

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13
Q

What is the spermatogenic wave?

A

Distance between spermatids groups at the same level of maturation

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14
Q

Describe the structure of sperm

A
  • head: contains nucleus (haploid genetic information to fuse with oocyte) | acrosome layer allows his to happen at contact with ovum
  • tail: motility for sperm
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15
Q

Why is zinc an important component of semen?
Where is it released from?

A

Needed for motility of sperm
Prostate

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16
Q

What is sperm capacitation?

A
  • occurs in female reproductive tract
  • final maturation step > fertile
  • removal of glycoproteins + cholesterol from sperm membrane
  • activation of sperm signalling pathways
  • allow sperm to bind to zona pellucida of oocyte + initiate acrosome reaction
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17
Q

Where does sperm capacitation occur?

A

Female reproductive tract

18
Q

What step is needed to make sperm fertile in IVF?

A

Incubated in capacitation media

19
Q

Outline maturation of oocyte before birth

A
  • germ cells in ovary differentiate into oogonia
  • oogonia proliferate by mitosis + enter meiosis but stop at prophase 1 > primary oocyte
  • primary oocyte are surrounded by follicular cells > primordial follicle
  • cells degenerate (atresia)
20
Q

What are the maturation stages of oocyte during puberty?

A

Preantral
Antral
Preovulatory

21
Q

Outline the preantral stage of oocyte maturation

A
  • primordial follicle from before birth
  • follicular cells change from flat > cuboidal > stratified cuboidal epithelium of granulosa cells
  • granolas cells secrete glycoproteins > forms zona pellucida
  • primary follicle formed
22
Q

Outline the antral stage of oocyte maturation

A
  • fluid filled spaces appear between granulosa cells > forms the antrum
  • follicle is called the secondary follicle
  • outer fibrous layer develops into theca externa + interna
23
Q

Outline the preovulatory stage in oocyte maturation

A
  • induced by surge in LH
  • follicle completes meiosis I > 2 haploid cells
  • secondary oocyte receives most of cytoplasm + polar body receives little
  • cell enters meiosis II > only completed if fertilisation occurs
24
Q

Outline what occurs during ovulation

A
  • FSH + LH stimulate rapid growth of follicles > graafian follicle to 2.5cm
  • LH surge increases collagenase activity
  • prostaglandins increase response to LH > contractions in ovarian wall
  • oocyte breaks from ovary
25
Q

What forms the corpus luteum?

A
  • Remaining granulosa + theca interna become vascularised
  • develop yellow pigment + change to lutein cells
26
Q

What does the corpus luteum do?

A
  • secrete oestrogens + progesterone
  • this stimulates uterine mucosa to enter secretory stage in prep for embryo implantation
  • dies after 14 days if no fertilisation occurs > corpus albicans
27
Q

What happens to corpus luteum if fertilisation doesn’t occur?

A
  • CL degenerates
  • forms fibrotic scar tissue - corpus albicans
  • decrease in progesterone > menstrual bleeding
28
Q

What happens to corpus luteum if fertilisation occurs?

A
  • degeneration of CL prevented by human chorionic gonadotropin
  • CL grows > corpus luteum graviditatis
  • progesterone secreted until 4th month (then placenta takes over)
29
Q

What prevents the degernation of corpus luteum if fertilisation occurs?

A

Human chorionic gonadotropin hCG
Secreted by embryo

30
Q

Outline oocyte transport

A
  • frimbriae ‘catch’ oocyte using sweeping movements
  • uterine tubes contract rhymtically
  • oocyte moved by peristaltic muscular contractions + cillia
31
Q

Compare spermatogenesis + oogenesis:
- amount produced
- when does it start?
- when does it end?
- motile gametes?
- where do stages occur?

A

Spermatogenesis:
- 200 million sperm a day
- 4 spermatids formed: no polar bodies + even cytoplasm division
- starts in puberty
- continues during adult life
-motile gametes
- all stages in testes

Oogenesis:
- 1 ovum per 28 day
- 1 ovum formed: 3 polar bodies + uneven division of cytoplasm
- starts in fetus
- ends at menopause
- non motile gametes
- last stage of meoisis II in oviduct

32
Q

What is spermiation?

A

Release of spermatid into lumen of seminiferous tubules

33
Q

Where do sperm become mobile?
How are they transported before this point?

A
  • epididymis
  • Sertoli cell secretions + peristalsis
34
Q

How many sperm are produced each day?

A

200 million

35
Q

When does oogenesis start, continue + complete in women?

A
  • Starts: in utero
  • Continues: at ovulation (puberty)
  • Completes: at fertilisation
36
Q

What replenishes the stock of spermatogonia avaliable for the production of sperm?

A

Type A spermatogonia

37
Q

Are germ cells diploid or haploid?

A

Diploid

38
Q

Karyotype of androgen insensitivity syndrome

A

46 XY

39
Q

Karyotype of klinefelters syndrome

A

47 XXY

40
Q

Karyotype of Turner’s syndrome

A

45, XO

41
Q

Function for rete testis

A

Helps move sperm from testicle to epididymis

Reproductive System (20 decks)

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