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A Level Biology Flashcards - BB > 18 Fertility and assisted reproduction > Flashcards

18 Fertility and assisted reproduction Flashcards

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1
Q

where is the site of oogenesis?

A

germinal epithelial cells in the ovaries

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2
Q

what is the function of the fallopian tubes/oviducts?

A

transport secondary oocyte from ovaries to uterus via ciliary action and peristalsis

site of fertilisation

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3
Q

what is the function of the uterus?

A

site of implantation of fertilised ovum

development of foetus and placenta during pregnancy

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4
Q

what are the two layers of the uterus and their functions?

A

myometrium - smooth muscle fibres - contractions during labour

endometrium:

  • stratum basalis
  • stratum functionalis - supports growing foetus (shed during menstruation)
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5
Q

what is the function of the cervix?

A

controls the opening of the uterus during pregnancy, menstruation or intercourse

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6
Q

what is the function of the vagina?

A

passageway for menstrual flow

receptacle for the penis during intercourse

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7
Q

how does the lining of the vagina change each month? how is this used in medicine?

A

cyclical change in degree in keratinisation

used in PAP smears

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8
Q

what is the composition of the mucosa in the vagina? how does this relate to its function?

A

contains glycogen granules, which are decomposed to organic acids

giving low pH

which reduces microbial growth and sperm motility

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9
Q

what is the function of the labiae minora and majora?

A

produce lubricant mucus secretion

prevent clitoris from abraision

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10
Q

what is oogenesis?

A

the formation of secondary oocytes

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11
Q

what occurs during the multiplication phase of oogenesis? {when does it occur?}

A

{before birth in developing biological female}

primordial follicles in germinal epithelium of ovaries undergo mitosis

producing oogonia

these go through a growth phase to produce a diploid primary oocyte

meiosis stopped at prophase I

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12
Q

when and how is the maturation phase of oogenesis stimulated?

A

at puberty

FSH is secreted from the anterior pituitary gland and stimulates 12-20 primary oocytes to become haploid secondary oocytes

produces a polar body

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13
Q

what happens during ovulation?

A

LH secreted following positive feedback of oestrogen

a single secondary oocyte is released from Graafian follicle (which becomes corpus luteum)

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14
Q

what is the fate of the corpus luteum?

A

secretes progesterone (and oestrogen) to maintain a potential pregnancy

eventually dies

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15
Q

what are the features of the secondary oocyte after ovulation?

A

corona radiata (granulosa cells)

zona pellucida

cytoplasm

centrioles

haploid nucleus

CSM

polar body

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16
Q

what is the function of the testes?

A

to produce sperm by spermatogenesis in seminiferous tubules

to produce testosterone and other androgens in interstitial tissue (e.g. Leydig cells) under the influence of LH from the anterior pituitary gland

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17
Q

what is the function of the scrotum?

A

to regulate the temperature of the sperm by elevating or lowering testicular tissue with the cremaster muscles

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18
Q

what is the function of the epididymis?

A

to mature and store spermatozoa for up to four weeks

to move sperm into the vas deferens using ciliated epithelial cells and smooth muscle

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19
Q

what is the function of the vas deferens?

A

to store sperm for several months until ejaculation

to move sperm to the urethra via peristalsis during ejaculation

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20
Q

what is the function of the seminal vesicles?

A

to secrete a viscous alkaline fluid which contains fructose to act as a respiratory substrate for sperm mobility

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21
Q

what is the function of the prostate gland?

A

to secrete an alkaline fluid that neutralises the acidity of the vagina

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22
Q

what is the function of the Cowper’s (bulbourethral) gland?

A

to produce an antacid fluid and a mucus secretion which lubricates the penis during intercourse and flushes out the urethra in preparation for the sperm

23
Q

what is the function of the penis?

A

to deliver sperm to the neck of the cervix

24
Q

what are the two types of erectile tissue in the penis?

A

corpus cavernosa (dorsal)

corpus spongiosa (ventral)

(become erect from vasodilation)

25
Q

what is the role of testosterone in males?

A

development of male sex characteristics:
- primary: male genitalia growth in utero

  • secondary: causes physiological changes at puberty (e.g. voice drop; hair growth; growth of genitals)
26
Q

how does oogenesis/spermatogenesis increase genetic variation?

A

independent orientation at metaphase I and II

independent assortment at anaphase I and II

crossing over at prophase I

mutation

random fertilisation

27
Q

what occurs during the multiplication phase of spermatogenesis?

A

mitotic division of a diploid spermatogonium (type B) in the seminiferous tubules

producing two diploid primary spermatocytes

28
Q

what occurs during meiosis I in spermatogenesis?

A

primary spermatocyte moves into adluminal compartment of the seminiferous tubules

undergoes meiosis I to produce 2x haploid secondary spermatocytes

29
Q

what occurs during meiosis II in spermatogenesis?

A

secondary spermatocytes divide into haploid spermatocytes

30
Q

what occurs during spermiogenesis?

A

differentiation of spermatids:

  • tail = flagellum and axial filaments in 9+2 microtubule bundles (elongated centriole)
  • organelles (e.g. helical mitochondria)
  • acrosome
  • haploid nucleus (DNA packaged with specific nuclear basic proteins which are replaced by protamines during spermatid elongation which makes them transcriptionally inactive)
31
Q

what are the advantages of genetically varied offspring??

A

adapted better to changing environment

advantageous alleles retained in gene pool

high evolutionary potential

32
Q

how is gametogenesis initiated?

A

release of gonadotrophin-releasing hormone (GnRH)

GnRH stimulates anterior pituitary gland to secrete LH and FSH, which act separately on the gonads

33
Q

outline hormonal control of spermiogenesis

A

GnRH produced in hypothalamus and stimulates anterior p.g. to secrete LH and FSH

LH binds to Leydig cells which are stimulated to produce testosterone

FSH binds to Sertoli cells, making them more receptive to testosterone

testosterone binds to Sertoli cells and initiates spermatogenesis (also prevents apoptosis of type A cells)

34
Q

what are the two separate cycles that make up the menstrual cycle?

A

ovarian

uterine

35
Q

what are the four phases of the menstrual cycle?

A

proliferative - regeneration of uterine lining

ovulation - secondary oocyte release into oviduct

secretory - uterine lining secretes nutrients to prepare for blastocyst implantation

menstrual - lining of uterus sheds following implantation failing to occur

36
Q

what are the two most common reasons for cessation of the menstrual cycle?

A

pregnancy (temporary)

menopause (permanent)

37
Q

outline hormonal control of the menstrual cycle/oogenesis

A

anterior p.g. secretes FSH into blood plasma –> ovaries, where it induces proliferation of granulosa cells for follicle development

oestrogen concentration rises as it is secreted from the maturing follicle –> thickening of the endometrium of the uterus

oestrogen inhibits FSH –> GnRH production –> LH secretion –> ovulation

LH stimulates follicle to become corpus luteum

corpus luteum secretes progesterone, which stimulates the development of blood vessels in the endometrium

if implantation does not occur, corpus luteum dies –> oestrogen and progesterone concentrations fall –> menstruation

38
Q

how are sperm capacitated?

A

removal of glycoproteins from sperm head

enzymes specific to the glycoprotein break peptide bonds

producing a polypeptide

which makes the plasma membrane more permeable to Ca2+

39
Q

what are the components of semen?

A

sperm

mucus

proteins

fructose - respiratory substrate

citrate + calcium ions

water

alkaline prostate fluids

40
Q

outline the acrosome reaction in fertilisation

A

acrosome swells and fuses with sperm head membrane

releasing hydrolytic enzymes by exocytosis

which digest the corona radiata and zona pellucida

specific proteins on sperm head bind to plasma membrane of secondary oocyte

plasma membranes of secondary oocyte and sperm head fuse

haploid nucleus of sperm enters the secondary oocyte forming a diploid zygote

41
Q

outline the cortical reaction in fertilisation

A

entry of sperm nucleus activates cortical granules (specialised lysosomes) in secondary oocyte, which release hydrolytic enzymes

which digest the sperm-binding proteins on the plasma membrane

and cause the zona pellucida to harden and thicken, before separating from the ovum

this prevents polyspermy (which would lead to an non-viable ovum)

42
Q

which hormone is used to test for human pregnancy? why is it used?

A

human chorionic gonadotrophin (hCG)

secreted from the placenta when a blastocyst successfully implants

43
Q

outline the procedure of a pregnancy test using urine

A

the test stick is dipped in a urine sample from the woman believed to be pregnant

dipstick has monoclonal antibodies (mABs) with a coloured latex particle attached

mABs remain mobile when urine is introduced

hCG binds to specific, complementary mAB –> hCG-mAB complex

complexes carried up stick in urine

to a line of immobile mAB specific antibodies, which they bind to, developing a dark line

uncombined mABs continue to move to form a second line to show that the test is working

44
Q

why might a pregnancy kit give a false negative?

A

tested too early - hCG only produced after implantation

urine too dilute - do it first thing

hCG concentration extremely high - so many molecules that they can’t bind properly

45
Q

outline some causes of infertility in females

A

ovulatory disorders - e.g. PCOS; thyroid problems

blockages in oviducts - e.g. endometriosis; infections

surgery scarring - pelvic or cervical scarring

cervical mucus defects

submucosal fibroids

medication/drugs - e.g. chemo; NSAIDs; neuroleptics

pelvic inflammation disease

46
Q

outline some causes of infertility in males

A

semen problems - e.g. low/no sperm count; abnormal sperm

damaged testicles - e.g. infection; cancer; congenital defects

ejaculation disorders - retrograde or premature

hypogonadism - abnormally low levels of testosterone

medication/drugs - e.g. anabolic steroids; chemo; NSAIDs

excessive alcohol consumption

47
Q

outline causes of infertility in all sexes

A

weight

STIs - e.g. chlamydia –> damage to fallopian tubes/tenderness of scrotum

smoking

occupational/environmental factors

stress

48
Q

outline in vitro fertilisation (IVF) as a means of treating infertility

A

gametes surgically removed from the parents

one secondary oocyte and 100,000 sperm are incubated in the same petri dish for ~ 4 hours

if sperm are struggling to fertilise the ovum, intracyctoplasmic sperm injections (ICSI) are used

once fertilised, zygote continues dividing and genetic tests are carried out

if the zygote is viable, it implanted in the uterus using a canula

49
Q

what is an advantage and disadvantage of IVF?

A

+ increases probability of becoming pregnant

  • incr. risk of multiple births (several zygotes impanted) ∴ incr. risk of still births/maternal mortality
50
Q

what are GIFT and ZIFT?

A

GIFT - sperm and secondary oocyte inserted into the oviduct and fertilisation occurs naturally inside the woman’s body

ZIFT - fertilisation occurs in the lab, then the zygote is transferred to the oviduct

51
Q

what is ovulation induction? how is it used to treat infertility?

A

used when oocytes do not develop normally

anti-oestrogen administered from day 5 to 10

–> incr. production of GnRH

–> incr. secretion of LH and FSH from the anterior p.g.

ultrasound detects developing follicles (if present)

52
Q

what is intrauterine insemination? how is it used to treat infertility?

A

sperm are removed and washed to remove mucus and non-mobile sperm

concentrated in a specialised medium

sperm can then be injected into the uterus via artificial insemination

53
Q

what are the four most common forms of artificial insemination?

A

intravaginal

intracervical

intrauterine

intratubal

A Level Biology Flashcards - BB (35 decks)

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