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Reproductive System > 2) Origins of the Gametes > Flashcards

2) Origins of the Gametes Flashcards

1
Q

Describe the process by which germ cells form gametes:

A

Proliferate by mitosis, genetic reshuffling and reduction to haploid in meiosis

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2
Q

What are the functions of meiosis?

A

Reduce chromosome number to 23

Ensure every gamete is unique

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3
Q

By what processes does genetic variation arise?

A

Crossing over
Random segregation
Independent assortment

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4
Q

Which part of the gonad do male germ cells colonise?

A

Seminiferous cords in medulla

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5
Q

Describe the route sperm take in the testis:

A

Seminiferous tubules -> rete testis -> ductili efferentes -> epididymis

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6
Q

Where do spermatozoa develop?

A

Seminiferous tubules in association with Sertoli cells

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7
Q

What does the blood testis barrier separate?

And what is its other function?

A

Surrounding interstitial tissues and germ cells from seminiferous tubules
Stops sperm being recognised as foreign

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8
Q

What cells secrete testosterone and where are they found?

A

Leydig cells in interstitial tissue

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9
Q

What is the name of the cells that are the ‘raw material’ for spermatogenesis?

A

Spermatogonia

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10
Q

What two cells do spermatogonium divide into?

A 
Ad spermatogonium (maintain stock)
Ap spermatogonium (primary spermatocytes)
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11
Q

Describe the formation of sperm from primary spermatocytes:

A

Primary spermatocytes become secondary spermatocytes and then spermatids by meiosis. Spermatids differentiate into sperm

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12
Q

What is the spermatogenic cycle?

A

Time taken for re-appearance of same stage within a given segment of tubule (16 days)

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13
Q

What is a spermatogenic wave?

A

Distance between same stage in a tubule

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14
Q

What is spermiogenesis?

A

Remodelling of spermatids and gaining of motility as they pass to epididymis

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15
Q

What allows spermatids to travel to the epididymis?

A

Sertoli cell secretions and peristaltic contractions

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16
Q

What secretions make up semen?

A

Seminal vesicle
Prostate gland
Sperm (via vas deferens)
Bulbourethral gland

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17
Q

What are the seminal vesicle secretions for?

A

AA, citrate, fructose and prostaglandins

Energy source

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18
Q

What are the bulbourethral gland secretions for?

A

Mucoproteins help lubricate and neutralise acidic urine in distal urethra

19
Q

What is the final maturation step for sperm?

A

Sperm capacitation

20
Q

What occurs in sperm capacitation?

A

Conditions in female genital tract stimulate:
Removal of glycoproteins and cholesterol from sperm membrane
Activation of sperm signalling pathways

21
Q

What does sperm capacitation allow?

A

Allows sperm to bind to zona pellucida of oocyte and initiate acrosome reaction

22
Q

Describe the colonisation by female germ cells:

A

Colonise gonadal cortex and differentiate into oogonia

23
Q

What stage are primary oocytes in?

A

Prophase I

24
Q

How are primary oocytes arranged?

A

Surrounded by flat epithelia cells called follicular cells forming primordial follicle

25
Q

What could be a reason that there is increasing risk of fetal chromosomal abnormalities in older pregnant women?

A

Primary oocytes remain in resting stage for many years, increasing chance of cell damage

26
Q

Why are there so few oocytes when puberty is reached?

A

Undergo atresia in late gestation and childhood

27
Q

In what stages do oocytes mature?

A

Pre-antral, antral and pre-ovulatory

28
Q

What changes occur to follicular cells in the pre-antral stage?

A

Change from flat to cuboidal before proliferating to produce stratified epithelium of granulosa cells

29
Q

What layers form around the oocyte in the pre-antral stage?

A

Zona pellucida, granulosa cells, inner and outer theca folliculi

30
Q

What are the granulosa cells surrounding the oocyte called?

A

Cumulus oophorus

31
Q

What occurs in the antral stage?

What does this development depend upon?

A

Fluid filled spaces appear in between granulosa cells to from an antrum
Development depends upon FSH binding to granulosa cells and LH binding to theca cells

32
Q

What occurs in the pre-ovulatory stage?

A

Oocyte completes meiosis I forming secondary oocyte (most of cytoplasm) and polar body. Cells enters meiosis II but arrests at metaphase

33
Q

When is meiosis II completed?

A

If oocyte is fertilised

34
Q

What causes oocyte release?

A

LH surge increasing collagenase activity and prostaglandins amplifying response and causing local contractions in ovarian wall

35
Q

Describe the formation of the corpus luteum:

A

Remaining granulosa and theca interna cells become vascularised, develop yellow pigment and change to lutein cells

36
Q

What does the corpus luteum secrete and what effect does this have?

A

Progesterone and oestrogen under influence of LH

Stimulates uterine mucosa to enter secretory stage in preparation for embryo implantation

37
Q

What causes the oocyte to move into the fallopian tube?

A

Fimbriae, uterine tube contracting and cilia

38
Q

What happens if there is no fertilisation?

A

After 14 days, corpus luteum degenerate forming corpus albicans
Decreased progesterone = menstrual bleeding

39
Q

What happens to corpus luteum if fertilisation occurs?

A

Degeneration prevented by human chorionic gonadotropin secreted by embryo
Forms corpus luteum graviditatis

40
Q

What happens to progesterone secretion if fertilisation occurs?

A

Cells of CL secrete progesterone until 4th month where placental secretion becomes adequate

41
Q

What is the effect of FSH in women?

A

Stimulate follicle growth and maturation

42
Q

What is the effect of LH in women?

A

Stimulate follicle maturation, ovulation due to surge and promotes corpus luteum development

43
Q

When is the follicular stage of the ovarian cycle?

A

0-14 days

44
Q

What is the luteal stage of the ovarian cycle?

A

14-28 days

Reproductive System (24 decks)

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