fertilisation, male and female development

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  • Created by: Sarah
  • Created on: 29-04-17 18:36
what cells produce testosterone?
leydig cells
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what hormone stimulates testosterone?
luteinizing hormone
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what cells respond to luteinising hormone?
leydig cells
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what is a zygote?
a single somatic cell formed from fertilisation
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how does the sperm protect its DNA from damage?
contains supercoiled chromatin
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what is syngamy?
where 2 cells or their nuclei fuse
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where does syngamy happen?
in the ampulla
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how many hours after ovulation does fertilisation happen?
12-24 hours
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how big is the human egg?
100-150um
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what does sperm capacitating in the female tract involve?
chemicals act on the sperms acrosome so receptors become avaliable, motility changes
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after the blastocyst reaches the uterine cavity what does it attach to?
the endometrium
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what 3 levels does random selection happen at?
random chromosome, random fertilisation and crossing over
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how long does gestation (pregancy) takes?
F-266 Ms- 265 days
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how many autosomes does a egg have?
22 autosomes plus a X
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when is sex determined?
at the point the sperm pronuclei fuse, determined by if the sperm has X or Y
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who showed that sexual phenotype depends on gonads?
Jost
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where is the testis-determining gene?
on the Y chromosome
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what phenotype develops if you have no gonads?
female
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what is required for normal ovary development in females?
oocytes
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can normal testes develop if theres no sperm?
yes testes develop normally
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where do gonads develop?
in gonadal ridges
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what do gonadal ridges contain?
contain mesonephros (primitive kidney) and internal ducts and tubes
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how many weeks after fertilisatoon do gonadal ridges form?
a few weeks
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what doesthe gonadal ridges form on?
the abdominal wall
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primordial germ cells appear close to what?
allantois
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what does allantois help with?
gas exchange
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gonads initially look similar but when do PGCs start to differentiate?
5 weeks
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PGCs become what before they differentiate?
gonia
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primitive oogonia increases in pregnancy to how many by 7 months?
9 million primitive oogonia
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how does primitive oogonia ncrease?
by mitosis
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by birth primitive oogonia has fallen to what?
half a million
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why is there a decline in primitive oogonia from 7 months to birth?
1) transformation into oocytes 2) degeneration (due to low FSH)
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what converts oogonia to oocytes?
meiosis inducing substance
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are oocytes mitotic or meiotic?
meiotic
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where does meiosis inducing substance come from?
mesonephric ducts
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what sex is meiosis inducing substance released from the mesonephric ducts?
both sexes- male and female
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what is produced in just males that overrides meiosis inducing substance?
meiosis preventing substance
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where is meiosis preventing substance produced from?
testis cords
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what does meiosis preventing substance do?
overides MIS, prevents meiotic transfer until testis cords --> testes in puberty
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are females born with all their eggs?
yes, no new oogonia are formed
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what do testis cords transform into?
semiferous tubules
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what is the structure of testis cords?
solid rods of tissue
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what produces sperm after puberty?
semiferous tubules
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what are the primitive sperm producing cells that remain inactive till puberty?
spermatogonia
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what is the criteria for chromosomal sex?
**- F or XY-M
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what gene induces testes formation?
Sry gene
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what do testes produce?
anti mullerian hormon/mullerian inhibiting substance and testosterone
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what cell fate does the product of the Sry gene trigger?
serotoli cells
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what cell will develop if the Sry gene is absent?
a follicle cell
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what is the key to becoming a sertoli or follicle cell?
transcriptional control of Sry gene
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how long does Sry exoression last?
not long approx 2 hours, is transient
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what does the Sry protein contain?
a HMG box type of DNA binding domain
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what does the HMG box type of DNA binding domain bind to?
minor grooves of DNA
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what happens when the HMG box binding domain binds to minor grooves?
alters its configuration so alters transcription by affecting neighbouring interactions between between pros+DNA(stops pros binding to DNA or weakens)
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what is SOX9 role with Sry thought to be?
involved in long term maintenance
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where and when does SOX9 increase?
in sertoli cells a few days after Sry is activated in Ms
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what happens to sox9 in females?
sox9 levels fall
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what are the supporting cells that provide nourishment in males?
sertoli cells
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what is the CT in female reproductive organs?
stroma cells
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what is the steroid cells in females?
theca cells
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what are the supporting cells in females?
follicle cells
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what are steroid cells in male?
leydig cells
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what do myoid cells do?
in males contract to move sperm as immobile
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what is the CT in males?
testicular cord and myoid cells
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what do autosomal genes do in sex differentation?
produce enzymes that are needed eg carriers for making support systems
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what happens in the definecy of the autosomal gene, definecy of 5 alpha reductase?
male genitalia do not differentiate properly
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why do male genitalia not differentiate if theres a 5 alpha reductase deficiency?
5alpha reductase is an enzyme that converts testosterone to more active 5 dihyrdoxytestosterone (5DT)
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what is the syndrome where you look female (phenotype) but have male genetics (genotpe)
testicular feminisation syndrome
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what is the karotype for testicular feminisation syndrome?
46 XY
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what causes testicular feminisation syndrome?
low levels of cytosolic carrier protein for testosterone means it doesnt work
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why do you get a female phenotype in testicular feminisation syndrome?
because oestrogen (from testes and adrenal gland) acts on body unopposed
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how do external genetalia have an effect on how the individual is perceived?
psychological or behavioural role (gender), assignment or rearing (social teaching)
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when is assignment to sex usually assessed
at birth by external genetalia and put on birth certificate
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when is adult external genatalia seen?
only after puberty when secondary sex characteristics are seen
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secondary sex characteristics?
menarche, pubic hair, breasts, skeletal changes and pigmentation
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when in the womb are clear differences seen in external genatalia?
by 12 weeks (similar at 10)
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what happens by 10 weeks to the duct in the male?
the mullerian (PARAmesonephric) duct dgenerates
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what happens by 10 weeks to the duct for a female?
the mesonephric (wolferrian) duct degenerates
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what is gender dysmorphia?
believe they are opposite sex to their physical assigned sex
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when is normal appereance of external genatalia?
at 34 weeks
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what is the condition where testes fail to descend?
crytorchidism
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what happens as a result of crytorchidism?
no sperm produced as need lower temp but havent descended so too hot
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what are the 2 stages that testes drop in?
1) transabdominal 2)ingino scrotal (dep on testosterone)
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the seminal vesicles secrete seminal fluid what is this high in?
K+ (potassium) and fructose (for sperm energy), prostaglandins
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what is the normal PH of semen?
7.35-7.5
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what is semen?
sperm and complex fluid
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what gland first contributes to semen?
bulbourethral gland
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what is the order that the male repro glands contribute to semen in?
bulbouethral glands --> prostate -> testicular -> seminal vesicles
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what are the components of the male reproductive tract?
penis, seminferous tubules, accesory glands that contribute to semen (bulbourethral, prostate, testicular and seminal vesicles)
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how much do testes weigh?
12g
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what does the bulbourethral gland contribute? makes up what?
sial-proteins, mucoproteins (lubricates) makes pre-ejaculate
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approximately how long does it take for sperm to develop?
64 days
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what are the stages of sperm development?
[spermatogonia A, spermatogonia B]- mitosis;spermatocyte 1, spermatocyte 2, spermatid, sperm
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when does meiosis 1 and meiosis2 happen in sperm development?
at spermatocyte 1 and spermatocyte 2 (spermatocyte 2 ->spermatid
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what part of the testes collects sperm from the semiferous tubules?
rete testes
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what covers the testes?
tunica vaginalis
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what is the tunica albuginea?
CT covering the testes
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what is the mediastinum?
the midline of the testes
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what does the septa do?
fibrous separates the seminiforous tubules into lobules
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how many lobules does the septa divide testes into? how many semiferous tubules in each lobule?
250 lobules each with 1-4 seminferous tubules
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what are myoid cells?
muscle/epithelia cells, peritubular contractile cells by actin
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what are tall epithelia for in the testes?
vacoules to develop sperm as barrier from blood, if got to blood IS would kill their own sperm!
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features of sertoli cells?
are in males, are non-proliferative, steroidogenic, secretory-push sperm along, FSH sensitive, phagocytic
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how are serotoli cells slightly steroidogenic?
synthesis of C21 to testosterone
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main role of sertoli cells?
support cells, provide nourishment and mechanical support
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what is the diameter of leydig (male steroid) cells?
20um
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features of leydig cells?
20um diamter, polyhedral and have lots of microvilli + SER (to make steroids)
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what do leydig cells produce? with what stimulation?
produce testosterone stiulated by LH (from pituitary gland)
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normal volume of semen?
3.4+- 1.6ml
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where are leydig cells?
in CT between semiferous tubules
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what do sertoli cells secrete?
transferrin, inhibin, androgen binding protein
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what are sertoli cells?
tall simple columnar epithelial cells from basal lamina to lumen
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what is the total length of ST in males?
255m
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what is the size of the ST?
150-250um diamter and 80cm long
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what factors affect testicular function?
temperature (crytorchidism-testes dont descend no spem too hot), age, irradiation, vasectomy
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what does prostate add to semen? (its the marker of prostate)
acid phosphatase
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how many enzymes does the acrosome have?
60
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as sperm travel through the tract what happens?
mucus scrapes off decapcitation fluid and reveals Z3P
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what are the cervix and vagina for?
expulsion of infant and decapitation of sperm
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whats the function of the ovary?
is the centre of cyclicity, produces oocytes and sex steroids
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what is ovarian asymmetry?
where one ovary is active each month
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what is hypaemia to the ovaries?
increased blood flow to the ovaries
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how long is the menstrual cycle?
25-35 days, avg 28 days
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what are the 2 parts of the menstrual cycle?
pre-ovulatory and post ovulatory
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how long does each part of the menstrual cycle last?
14 days each
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what is the ovarian follicle?
a cellular sac in which the oocyte matures (in response to FSH+LH)
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what is a synergistic effect?
cooperation or interaction of things
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what shows a synergestic and sequential effect?
progesterone and oestrogen
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what do progesterone and oestrogen working together at different times cause?
cyclical changes in the uterus
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what is the function of fallopian/uterine tubes for?
gamete transport, site of fertilisation
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why is the ovarian cycle called the menstrual cycle?
cyclic degeneration in the uterus is recognised by vaginal release of the endometrium tissue debris (where egg implants) + blood each month of reproductive life
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what happens to the crpus luteum if theres no fertilisation?
it degenerates to a corpus albicans
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how many oocytes are ovulated over a 30-40 reproductive life?
approx 400 oocytes
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what happens to the remaining 99% of oocytes that are not ovulated?
they undergo atresia
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what is atresia?
natural process of cell death that destroys follicles at all stages of development
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when does one follicle become dominant at the expense of others?
day 9 in the menstrual cycle
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what happens in polycystic ovarian disease?
no one follicle becomes dominant, many small follicles develop
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what happens to the corpus luteum of pregnancy if fertilisation does occur?
it develops to maintain the endometrium(approx 2-3months)
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why does the corpus luteum of pregnancy give up its job after 2-3 months?
placenta develops takes over hormonally and supports
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when is a crucial time in pregnancy?
transition from corpus luteum support to placental support
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how many follicles do females have at birth?
approx 400,000
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how does one follicle dominant?
the biggest folicle inhibits the others
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what do growing follicles produce?
oestrogen
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what are the stages in female repro development?
primary follicle -> secondary follicle -> graafian follicle -> corpus luteum -> corpus albicans
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what do secondary follicles cause?
proliferation of cells in the uterus
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what does the corpus luteum release?
progesterone
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what does the placenta produce that takes over?
human gonadotrophin
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when what hormone degenerates does the uterus lining shed?
progesterone degenerates
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what releases oestrogen?
secondary follicles
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what does oestrogen do?
1)stops FSH working 2) stimulates pituitary to produce LH
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what happens in atresia?
follicles degenerate and reabsorbed into follicular phase
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what does FSH do?
makes follicle grow/increases follicle size,causes oestrogen to rise
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what does LH do?
promotes egg maturation, gets egg to be released
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when does LH peak?
18-24 hours before ovulation
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Other cards in this set

Card 2

Front

what hormone stimulates testosterone?

Back

luteinizing hormone

Card 3

Front

what cells respond to luteinising hormone?

Back

Preview of the front of card 3

Card 4

Front

what is a zygote?

Back

Preview of the front of card 4

Card 5

Front

how does the sperm protect its DNA from damage?

Back

Preview of the front of card 5
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