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Respiratory > Session 3 - gametes REPRO > Flashcards

Session 3 - gametes REPRO Flashcards

1
Q

where do germ cells originate from

A

in yolk sac wall near allantois

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2
Q

where do they migrate

A

gonadal ridge

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3
Q

how do they move

A

ameoboid manner , tilting and moving

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4
Q

what determines gender and as a result what develops and from where

A

if germ cell has 2 X chromosomes then will colonise the cortex of gonad (ovary formed) if it has Y chromosome medulla of gonad is colonized (testes)

default an ovary, prescience of Y chromosome precedes male development

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5
Q

what is SRY

A

gene on Y chromosome (sex determining region on y chromosome) codes for transcription factor and activates differentiation events and develop testes

testes determining factor

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6
Q

what happens once germ cells arrive at gonad

A

proliferate by mitosis (germ cells from spermatogonia –> will give rise to sperm (gametes))

genetic reshuffling and reduce to haploid by meiosis (in gonads–> Fallopian tube?)

cytodifferentiate into mature gametes

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7
Q

why is genetic reshuffling important

A

to ensure genetic diversity in offspring

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8
Q

what germ cell determines the sex of the embryo

A

sperm since it has either x or Y chromosome

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9
Q

what are the 2 main functions of meiosis

A

introduce genetic diversity

reduce chromosome number in gamete to 23

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10
Q

what is a bivalent and the role of meiosis one

A

one chromosome from mum and one from dad duplicate to form bivalent

role of meiosis one is to split bivalent into 2 daughter cells

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11
Q

what is the role of meiosis 2

A

split bivalent into 4 daughter cells

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12
Q

how many daughter cells are produced from male and female germ cells

define what polar bodies are

A

4 daughter cells, 1 daughter cells other 3 lost in structures called polar bodies (waste basket for genetic material)

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13
Q

how does genetic variation occur

A

crossing over (swap regions of DNA between 2 non sister) —> create diversity

independent assortment (each bivalent can align on metaphase plate independently)

random segregation (random distribution of alleles among the 4 gametes)

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14
Q

where does spermatogenesis occur

A

semineforus tubules

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15
Q

what do retes testis do

A

concentration leaving sperm

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16
Q

what do Sertoli cells do

A

nurture developing spermatids from spermatogonia (made between sertoli cells)

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17
Q

what are the 2 barriers of Sertoli cells and why are they important

A

basal and lumen compartments (due to tight junctions) form blood testis barrier (Sertoli cell barrier) important cuz of different cell environment (making vs developing spermatids in sertoli gaps)

due to diversity could have immune response against sperm cuz recognised as non self (Dif genetic complement) so it prevents this

18
Q

what is spermatogonia

A

(male germ cells) are raw material for spermatogenesis

generate 4 mature spermatids

19
Q

describe sperm production

A

germ cell divide by mitosis to make ad spermatogonium and ap spermatogonium which are primary spermocytes

primary divide by meiosis to make secondary spermatocytes and then spermatids

remember each primary spermatocyte forms 4 haploid spermatids which turn into spermatozoa (normal sperm)

20
Q

what are ad and ap spermatogonium

A

ad is resting stock and only used when called upon

ap is active and maintains stocks from puberty onwards , produce type B spermatogonia which give rise to spermatocytes

21
Q

what is the spermatogenic cycle

A

time taken for reappearance of same stage within given segment of tube

16 days

22
Q

what is the spermatogenic wave

A

distance between same stage (same as cycle but this measures distance not time)

23
Q

what is permeation

A

spermatids released into lumen of ST

24
Q

describe what happens as they make their way into epididymis

A

remodel as they pass down ST, through rate testies into ductile efferent and into epid to finally form spermatozoa

however, non motile and only move due to peristaltic contraction and Sertoli cell secretion until they reach epid

25
Q

where are spermatids turned to spermatozoa

A

epi d y d imis

26
Q

describe how sperm is delivered and what assists it on the way

A

seminal vesicles mostly responsible for semen secretion ( 70% )

prostate secretion ( 25 % )

bulbourethral gland secretions (Cowper gland) to help lubricate and neutralise acidic urine in distal urethra

27
Q

what is the final step called before sperm become fertile

A

sperm capacitation

28
Q

what stimulates sperm capacitation

A

conditions in female genital tract

  • removal of glycoproteins and cholesterol from membrane
  • activate sperm signalling pathways
  • allow sperm to bind to zone pellucid of oocyte and start acrosome reaction
29
Q

what is the acrosome reaction

A

across allow sperm to digest membrane and zone pellucida of secondary oocyte for penetration

30
Q

what is the main difference between gonade production in male and female

A

female have limited number and produced all before birth whereas male continuously producing and have millions

reduces with age due to atresia

31
Q

describe the process of oocyte maturation before birth

A

germ cells from yolk sac colonise gonadal cortex and turn into oogonia

proliferate via mitosis

arrange in clusters (at end of 3 month)

most continue to divide by mitosis but some enter meiosis (stop in prophase 1 and are called primary oocytes)

cell death of many oogenia via atresia

surviving primary oocytes enter meiosis 1 and are each surrounded by follicular cells (flat eps cells)

now called primordial follicle

32
Q

what happens to primary oocytes after puberty and list the stages

A

arrested in prophase 1 of meiosis until puberty

after , a few oocytes mature each month passing through 3 stages ; prenatal , astral, preovulatory

33
Q

what happens to oocytes during childhood

A

most oocytes undergo atresia during childhood

34
Q

describe the prenatal stage

what do granulosa cells do

A

primordial follicles grow , surrounding follicular cells change from flat to cuboidal and proliferate to produce Strat epithelium of granulosa cells (secrete glycoprotein layer forming zone pellucida)

35
Q

describe the antral stage

A

fluid filled spaces appear between granulosa cells and form the antrum

36
Q

what induces the preovulatory stage

A

surge in LH

37
Q

describe PO stage

A

meiosis 1 complete ( created 2 haploid cells unequal size) each daughter cell has 23 chromosome and one cell receives most of the cytoplasm whereas the others are polar bodies

cell enters meiosis 2 but stops in metaphase before ovulation

meiosis 2 only completed if oocyte fertilised otherwise cell degenerates

secondary oocyte formed here

38
Q

describe process of ovulation

A

FSH and LH stim rapid growth of folic before this begins

now called graafian follicle

LH surge incr collagenase activity and prostaglandins incr response to LH and cause muscle contractions in ovarian wall

oocyte break free from ovary

39
Q

what is the corpus luteum

A

remaining granulosa become vascularised

develop yellow pigment and change into lutein cells which form this

secrete oestrogen and progesterone

stimulate uterine mucosa to enter secretory stage for emery implantation

die if no fertilisation happen

40
Q

describe how an oocyte is transported

A

fimbraie sweep over ovary before ovulation

uterine tube contract and oocyte carried into tube by sweeping movement of Fimbria and cilia

oocyte move by peristaltic contraction of tube and cilia

41
Q

what is corpus albicans

A

no - degenerated corpus luteum form scar tissue ( this ) and progesterone incr causing menstraul bleeding

yes - degeneration stop by human chorionic gonadotropin secreted by developing embryo . CL grow and cells secrete progesterone

42
Q

briefly describe ovarian cycle

A

GnRH GSH and LH control

follicles stim to grow via FSH and mature by FSH and LH

ovulation occur on LH surge

LH promote CL development

Respiratory (4 decks)

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