18 Fertility and assisted reproduction

Question 1

where is the site of oogenesis?

Answer 1

germinal epithelial cells in the ovaries

Question 2

what is the function of the fallopian tubes/oviducts?

Answer 2

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

site of fertilisation

Question 3

what is the function of the uterus?

Answer 3

site of implantation of fertilised ovum

development of foetus and placenta during pregnancy

Question 4

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

Answer 4

myometrium - smooth muscle fibres - contractions during labour

endometrium:

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

Question 5

what is the function of the cervix?

Answer 5

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

Question 6

what is the function of the vagina?

Answer 6

passageway for menstrual flow

receptacle for the penis during intercourse

Question 7

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

Answer 7

cyclical change in degree in keratinisation

used in PAP smears

Question 8

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

Answer 8

contains glycogen granules, which are decomposed to organic acids

giving low pH

which reduces microbial growth and sperm motility

Question 9

what is the function of the labiae minora and majora?

Answer 9

produce lubricant mucus secretion

prevent clitoris from abraision

Question 10

what is oogenesis?

Answer 10

the formation of secondary oocytes

Question 11

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

Answer 11

{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

Question 12

when and how is the maturation phase of oogenesis stimulated?

Answer 12

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

Question 13

what happens during ovulation?

Answer 13

LH secreted following positive feedback of oestrogen

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

Question 14

what is the fate of the corpus luteum?

Answer 14

secretes progesterone (and oestrogen) to maintain a potential pregnancy

eventually dies

Question 15

what are the features of the secondary oocyte after ovulation?

Answer 15

corona radiata (granulosa cells)

zona pellucida

cytoplasm

centrioles

haploid nucleus

CSM

polar body

Question 16

what is the function of the testes?

Answer 16

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

Question 17

what is the function of the scrotum?

Answer 17

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

Question 18

what is the function of the epididymis?

Answer 18

to mature and store spermatozoa for up to four weeks

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

Question 19

what is the function of the vas deferens?

Answer 19

to store sperm for several months until ejaculation

to move sperm to the urethra via peristalsis during ejaculation

Question 20

what is the function of the seminal vesicles?

Answer 20

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

Question 21

what is the function of the prostate gland?

Answer 21

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

Question 22

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

Answer 22

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

Question 23

what is the function of the penis?

Answer 23

to deliver sperm to the neck of the cervix

Question 24

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

Answer 24

corpus cavernosa (dorsal)

corpus spongiosa (ventral)

(become erect from vasodilation)

Question 25

what is the role of testosterone in males?

Answer 25

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)

Question 26

how does oogenesis/spermatogenesis increase genetic variation?

Answer 26

independent orientation at metaphase I and II independent assortment at anaphase I and II crossing over at prophase I mutation random fertilisation

Question 27

what occurs during the multiplication phase of spermatogenesis?

Answer 27

mitotic division of a diploid spermatogonium (type B) in the seminiferous tubules producing two diploid primary spermatocytes

Question 28

what occurs during meiosis I in spermatogenesis?

Answer 28

primary spermatocyte moves into adluminal compartment of the seminiferous tubules undergoes meiosis I to produce 2x haploid secondary spermatocytes

Question 29

what occurs during meiosis II in spermatogenesis?

Answer 29

secondary spermatocytes divide into haploid spermatocytes

Question 30

what occurs during spermiogenesis?

Answer 30

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)

Question 31

what are the advantages of genetically varied offspring??

Answer 31

adapted better to changing environment advantageous alleles retained in gene pool high evolutionary potential

Question 32

how is gametogenesis initiated?

Answer 32

release of gonadotrophin-releasing hormone (GnRH) GnRH stimulates anterior pituitary gland to secrete LH and FSH, which act separately on the gonads

Question 33

outline hormonal control of spermiogenesis

Answer 33

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)

Question 34

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

Answer 34

ovarian uterine

Question 35

what are the four phases of the menstrual cycle?

Answer 35

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

Question 36

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

Answer 36

pregnancy (temporary) menopause (permanent)

Question 37

outline hormonal control of the menstrual cycle/oogenesis

Answer 37

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

Question 38

how are sperm capacitated?

Answer 38

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+

Question 39

what are the components of semen?

Answer 39

sperm mucus proteins fructose - respiratory substrate citrate + calcium ions water alkaline prostate fluids

Question 40

outline the acrosome reaction in fertilisation

Answer 40

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

Question 41

outline the cortical reaction in fertilisation

Answer 41

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)

Question 42

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

Answer 42

human chorionic gonadotrophin (hCG) secreted from the placenta when a blastocyst successfully implants

Question 43

outline the procedure of a pregnancy test using urine

Answer 43

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

Question 44

why might a pregnancy kit give a false negative?

Answer 44

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

Question 45

outline some causes of infertility in females

Answer 45

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

Question 46

outline some causes of infertility in males

Answer 46

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

Question 47

outline causes of infertility in all sexes

Answer 47

weight STIs - e.g. chlamydia --> damage to fallopian tubes/tenderness of scrotum smoking occupational/environmental factors stress

Question 48

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

Answer 48

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

Question 49

what is an advantage and disadvantage of IVF?

Answer 49

+ increases probability of becoming pregnant - incr. risk of multiple births (several zygotes impanted) ∴ incr. risk of still births/maternal mortality

Question 50

what are GIFT and ZIFT?

Answer 50

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

Question 51

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

Answer 51

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)

Question 52

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

Answer 52

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

Question 53

what are the four most common forms of artificial insemination?

Answer 53

intravaginal intracervical intrauterine intratubal