Reproductive System Flashcards
in humans what is sex determined by?
X and Y chromosomes
how many chromosomes are in diploid cells?
46 or 23 pairs
how many chromosomes are found in haploid gametes?
23 chromosomes including one of either X or Y
what is the role of the Y chromosome in sex determination?
determines sex
how are haploid gametes created?
meiosis
how does meiosis differ between spermatocyte and oocyte?
cell division in oocyte is uneven and produces one egg cell and the polar bodies to ensure egg receives all essential materials
what are 2 abnormalities of sex chromosomes?
Turners Syndrome
Klinefelter’s Syndrome
what is the genotype of someone with Turners Syndrome?
X0 - one X, no Y
what is the genotype of someone with Klinefelter’s Syndrome?
XXY - two X and one Y
what is the phenotype of someone with Turner’s syndrome?
female
what is the phenotype of someone with Klinefelter’s Syndrome?
male (male genitalia, may have feminine characteristics)
what does the Y chromosome determine?
maleness - presence of testis
what gene on the Y chromosome determines presence of testis?
SRY gene
what is the role of the SRY gene?
determines production of TDF
what is TDF?
testis determining factor
what is the role of TDF?
causes undifferentiated gonad to become testis
what is androgen insensitivity syndrome?
partial or complete inability to respond to androgens - genetic makeup is male but due to AIS there is female phenotype
what are sex hormones responsible for in development?
sex determination
what hormone is from the family prostagens?
progesterone
what hormone is from the family androgens?
testosterone
what hormone is from the family oestrogens?
oestrogen (oestrodiol 17beta)
what is the precursor to the sex hormones?
cholesterol
what type of hormones are sex hormones?
steroid
what are the main female sex hormones?
oestrogen (oestrodiol 17beta)
progesterone
what is the main male sex hormone?
testosterone
how are oestrogens produced?
cholesterol is converted to progesterone through enzyme action. Progesterone is converted to testosterone and then testosterone to oestrogens via enzyme action for both stages.
what occurs in the ampulla of the uterine tube?
fertilisation of the egg
what is the role of the fimbria?
uptake of the ovulated ovum from the ovary
what are the 2 main functions of the ovary?
gametogenic and endocrine
what is gametogenic function?
production of gametes
what is the purpose of the endocrine function of the ovaries?
ensures right environment for development of gametes
what is the oestrous cycle named after?
oestrus
what is oestrus?
behavioral changes associated with sexual receptivity (heat)
what is the oestrous cycle formed of?
physiological changes that occur between one oestrus and the next
what is the oestrous cycle known as in humans?
menstrual cycle
what is the importance of oestrus?
occurs just before ovulation and optimises the chance of successful fertilization
what occurs in the follicular phase of the oestrous cycle in the ovary?
primordial follicles grow and develop with the oocyte within them
what happens during pro-oestrus?
follicles develop
what happens during oestrus?
behavioral changes
what happens at ovulation?
oocyte is released from the follicle
when does metoestrus occur?
between ovulation and formation of the corpus luteum
what occurs during the luteal phase of the oestrous cycle?
corpus luteum is formed from the degraded follicle and then breaks down
what is the dominant hormone during the follicular phase of the oestrous cycle?
oestrogen
what is the dominant hormone during the luteal phase of the oestrous cycle?
progesterone
what oocytes are female mammals born with?
finite number of primary oocytes
what stage of development do primary oocytes remain in until ovulation?
arrested state of development in prophase of first meiotic division
when does the menopause occur?
when no oocytes remain in the ovary
what is the name of the fist oocyte found pre-birth?
oogonium
how is the primary oocyte created pre-birth?
growth of the oocyte from oogonium
when does the first meiotic division of oocyte occur?
ovulation
what does the first meiotic division of oocyte at ovulation produce?
secondary oocyte and a first polar body
when does second meiotic division of the oocyte take place?
fertilisation
what does the second meiotic division of oocyte at fertilisation produce?
ootid (ovum) and second polar body
what cells is the primordial follicle surrounded by?
flat cells
what happens during stage 1 of follicular development?
oocyte increases in size
granulosa cells switch from flat to cuboidal
what is formed in stage 2 of follicular development?
zona pellucida
what is the zona pellucida?
acellular glycoprotein layer around the oocyte
what happens to granulosa cells during stages 3-5 of follicular development?
mitosis to produce 4 layers around the zona pellucida
what happens to the cells around the follicles during stages 3-5?
blood capillaries invade cells surrounding follicles (theca interna)
what is the theca interna?
connective tissue layer surrounding the granulosa cells
what happens during stage 6 of follicular development?
fluid forms in between granulosa cells
what is the name for the fluid filled spaces created during stage 6 of follicular development?
antrum
what is the name of the follicle at stage 7?
Graafian follicle
what happens at stage 7 of follicular development?
liquor folliculi builds up to from antrum
oocyte is pushed to one side and is surrounded by cumulus oophorus
what is the name of the fluid that creates the antrum in follicular development?
liquor folliculi
what is the cumulus oophorus?
1-2 layers of granulosa cells which surround the oocyte after the formation of the antrum
what happens during stage 8 of follicular development?
innermost layer of cumulus oophorus becomes columnar and forms corona radiata
what happens during stage 9 of follicular development?
ovulation has occurred, corpus oophorus remains in place around oocyte. The follicle becomes corpus luteum
what is the corpus luteum formed from?
follicle that remains after ovulation
what stages of follicular development are hormone independent?
stage 1-5
what stages of follicular development are hormone dependent?
stage 6-9
what are cyclical events in the ovary coordinated by?
the hypothalamus and hormones from the pituitary gland
where do the coordinating hormones of the cyclical events in the ovary come from?
the pituitary gland
what part of the pituitary do coordinating hormones of the cyclical events in the ovary come from?
anterior pituitary
what hormones are released from the anterior pituitary which control cyclical events in the ovary?
follicle stimulating hormone (FSH)
luteinising hormone (LH)
prolactin (PL)
what are FSH and LH formed from?
glycoproteins
what cell are FSH and LH secreted from?
gonadotrophs in the anterior pituitary
what are FSH and LH known as collectively?
gonadatrophic hormones
what type of hormone is prolactin?
peptide
what cells is prolactin secreted by?
lactotrophs
what factor from the hypothalamus causes release of LH and FSH?
gonadotropin releasing factor (GnRH)
what is the effect of GnRH?
tonic or surge release of FSH or LH from the anterior pituitary
what is prolactin release controlled by?
prolactin inhibitory factor (PIF) from hypothalamus
what is prolactin inhibitory factor (PIF) made from?
dopamine
what does an increase in PIF lead to?
decrease of prolactin (PF)
how would the tonic release of GnRH be described?
pulsatile
in the follicular phase what does increase in frequency of GnRH pulses lead to?
increase of FSH and LH release
what does FSH promote?
development and differentiation of follicle
what does development and differentiation of follicle lead to the synthesis of?
increased amounts of oestrogen
how do the frequency of GnRH pulses differ in the luteal phase?
reduced frequency of GnRH pulses
what does a reduced frequency of GnRH pulses during the luteal phase lead to?
fall in FSH and LH secretion
increase in progesterone synthesis from corpus luteum
what hormone is synthesised by the corpus luteum?
progesterone
what effect does GnRH have on its own release?
negative feedback
what effect does LH and FSH have on GnRH release?
negative feedback
what effect does progesterone have on GnRH release?
negative feedback
what is the effect of inhibin on LH/FSH?
inhibition of LH/FSH
particularly FSH to allow LH surge for ovulation
what effect does progesterone have on GnRH?
negative feedback
what effect does oestrogen have on LH/FSH and GnRH?
negative feedback until just before ovulation where it switches to positive feedback in order to initiate surge release of LH
what is the effect of prolactin on PIF?
positive feedback - increased prolactin increases PIF production in order to reduce PIF levels
what external factors can influence GnRH production and so production of sex hormones?
olfactory visual auditory temperature stress
is initial follicle development at all related to hormones?
no - there is continuous follicle growth in early stages irrespective of hormones
what leads a follicle to become dominant and lead to ovulation?
slightly increased FSH binding
what does increased FSH binding to a developing follicle lead to the secretion of?
increased IGF secretion from follicle which in turn increases FSH binding
what type of feedback is there on FSH binding and IGF production in the developing follicle?
positive
what hormone is synthesised due to increased FSH binding to a developing follicle?
oestrogen
what cells of the follicle secrete oestrogen?
granulosa
what type of feedback effect is seen in granulosa cells producing oestrogen in the developing follicle?
positive
what is ovulation induced by?
LH surge
what is ovulation induced by in spontaneous ovulators?
switch from negative to positive feedback of oestrogen on GnRH leading to surge of LH
what is ovulation induced by in induced ovulators?
surge of LH triggered by mating
what is positive feedback of oestrogen on GnRH induced by?
prolonged high levels of oestrogen leading to increase in GnRH pulses
what receptors does oestrogen act via?
alpha and beta
what oestrogen receptors are found in GnRH neurones within the hypothalamus?
beta
what is the role of beta oestrogen receptors on GnRH neurones?
mediate negative feedback of oestrogen on tonic GnRH release
what receptors does positive feedback of oestrogen on GnRH occur via?
alpha
are there alpha oestrogen receptors on GnRH neurones?
no - work through intermediate neurones
what neurones may be involved in inducing LH surge due alpha oestrogen receptors?
Kisspeptin - synapse onto GnRH neurones in hypothalamus
what does increased frequency of GnRH pulses lead to?
surge release of LH
what is the role of PGF 2a?
causes degeneration of the corpus luteum at the end of the luteal phase
what does polyoestrus mean?
continually cycles until pregnancy
what does seasonally monooestrus mean?
one cycle per season
what doe seasonally polyoestrus mean?
series of cycles in a certain season
what type of cycle do humans have?
polyoestrus
what causes menses?
support for endometrial lining is lost as progesterone level reduces so it is shed
what happens during the follicular phase?
endometrium lining grows and develops
follicle develops
what happens during the luteal phase?
endometrium lining grows and develops and is maintained by progesterone
corpus luteum releases progesterone
what changes during the oestrus cycle?
biosynthetic activities of follicles and corpus luteum
what is the hypothesis for the mechanism for switch from oestrogen to progesterone synthesis?
two cell hypothesis
what are theca cells?
those which surround the follicle
what are granulosa cells?
those which surround oocyte
in what 3 ways do theca and granulosa cells differ?
hormone receptors
steroidogenic (those which are involved in producing hormones) enzyme activity
micro-environment (e.g. blood supply)
what does prolactin influence?
switch of follicle to corpus luteum and so production of progesterone
how does the micro-environment of granulosa cells influence the hormones they can produce?
no blood supply so cholesterol is reduced - difficult to synthesise any hormones
what happens during ovulation?
oocyte is shed from primary follicle and meiosis is resumed
what is ovulation triggered by?
LH surge
what are the 2 types of ovulation?
spontaneous and induced
what does the primary oocyte become after ovulation?
secondary oocyte
what happens to the secondary oocyte after ovulation?
enters oviduct
what surrounds the secondary oocyte as it enters the oviduct?
corona radiata and cumulus oophorus
what is the movement of the secondary oocyte into the oviduct aided by?
the cilia on fimbria
what effects does LH have that lead to ovulation?
induces protease and collagenase activity in the follicle
what does increased protease and collagenase activity in the follicle lead to?
increase in follicular fluid and so thinning of granulosa cell layer
what is the role of the Stigma in ovulation?
blister which bursts and releases oocyte
what is the corona radiata formed from?
innermost granulosa cells
what makes up the cumulus oophorus?
all granulosa cells
where does the first polar body come from?
1st meiotic division of oocyte
what is the infundibulum?
open end of oviduct
what is the oviduct lined with?
cilliated and secretory epithelium
what is the movement of oocyte in the oviduct due to?
action of cilia within the ampulla and muscular contractions in the isthmus
what is the ampulla?
first section of the oviduct after the infundibulum
where is the oocyte held within the oviduct until fertilization?
ampulla/isthmus junction
what is found at the ampulla/isthmus junction which holds the oocyte until fertilisation?
physiological sphincter (no physical presence)
when is the ampulla/isthmus junction physiological sphincter closed?
when oestrogen is high
when is the ampulla/isthmus junction physiological sphincter open?
when progesterone is high
how long does the early embryo take to reach the uterus after fertilisation?
2-3 days
why is there a delay of 2-3 days between fertilization and implantation into the uterus?
to ensure that the hormone environment is correct before the embryo arrives and implants
what happens to the follicle once the oocyte has been released?
collapses and forms corpus luteum
what cells make up the corpus luteum?
granulosa cells and cells of theca interna
where do blood vessels invading the corpus luteum originate from?
theca interna
what hormone does the corpus luteum begin to synthesise?
progesterone
what happens during lutinization?
cells cease dividing and are transformed into lutein cells
what do lutein cells contain?
yellow pigment
what hormones do thecal cells produce in the corpus luteum?
progesterone and androgens
what are thecal cells?
smaller lutein cells
what is the role of progesterone released by the corpus luteum?
many roles including decrease in GnRH leading to no LH surges so no more ovulation
what do large lutein cells produce?
progesterone
in humans what else is produced by the corpus luteum?
oestrogens (particularly oestradiol 17beta)
inhibin
oxytocin
what is the role of inhibin released from the corpus luteum?
promotes progesterone synthesis and inhibits FSH/LH
what is the role of oxytocin produced by the corpus luteum?
has a role in luteolysis
what happens to teh corpus luteum if a pregnancy does not occur?
undergoes luteolysis
what does luteolysis enable?
another follicular phase to start
what is involved in luteolysis?
ischaemia, leading to progressive cell death. This leads to a fall in progesterone output
what is left of the corpus luteum after luteolysis?
whitish scar tissue remains
what is the name of the whitish scar tissue that remains after luteolysis?
corpus albicans
in non primate species what effect does hysterectomy have on the corpus luteum?
prolongs lifespan
in non primate species what effect does injection of homogenised endometrium have on the corpus luteum?
causes luteolysis
in sheep what is the effect on the corpus luteum of ligating blood vessels between the uterus and ovary?
prolongs lifespan
what factor is thought to trigger luteolysis in non-primates?
prostaglandin F2alpha
how is luteolysis thought to occur in non-primates?
prostaglandin (PGF) is synthesised by the uterus and released into uterine veins. Due to the close proximity of the uterine artery to the uterine pedicle, PGF is picked up by the ovarian artery and delivered back to the ovary where it causes luteolysis
where is prostaglandin F2alpha synthesised?
endometrium
what is prostaglandin F2alpha production stimulated by?
oxytocin from corpus luteum
is luteolysis in primates related to prostaglandin?
no
what is the possible cause of luteolysis in primates?
low levels of LH in luteal phase are insufficient to maintain corpus luteum which slowly regresses
what is the influence of oestrogens on the oviduct?
movement of oocyte:
increased secretions
increased cilia and increased activity
increased muscle activity
what is the influence of progestagens (progesterone) on the oviduct?
no oocyte movement:
reduced secretions
cilia number and activity decline
reduced muscle activity
what is the influence of oestrogens on the cervix?
allow passage of sperm:
relaxation of cervical muscle
thinner alkaline secretions - allow the penetration of sperm
what is the influence of progestagens (progesterone) on the cervix?
stop passage of sperm:
cervix is ‘firmer’
thick acidic secretions - prevent secretion of sperm
what is the influence of oestrogens on the mammary gland?
primes glandular tissue
what is the influence of progestagens (progesterone) on the mammary gland?
stimulates growth of glandular tissue
what is the influence of oestrogens on the uterus?
increased myometrium activity
increased number and size of endometrial glands
increased watery secretions
increases synthesis of progesterone receptors in endometrium
what is the influence of progestagens (progesterone) on the uterus?
reduced myometrium activity
further glandular growth
increased thick glycoprotein/sugar/amino acid rich secretions
development of spiral arteries in stroma
what is the purpose of increased thick glycoprotein/sugar/amino acid rich secretions from the uterus?
provides nutrition for the early embryo
what are the 2 functions of the testis?
gametogenic
endocrine
where are the 2 functions of the testis carried out?
seminiferous tubule
endocrine cells within connective tissue
where does spermatogenesis occur?
seminiferous tubules
what cells of the seminiferous tubules provide nourishment, control and coordination of spermatogenesis?
sertoli cells
what are developing sperm engulfed by that is part of sertoli cells?
adluminal compartments
where do developing sperm move from?
basal compartment
where are developing sperm shed?
into the lumen of the tubule once they are fully differentiated
what forms the blood testis barrier?
junctional complexes between Sertoli cells
where does mitosis occur during spermatogenesis?
in basal compartment near basal lamina
where does meiosis occur during spermatogenesis?
in the adluminal compartment, on the other side of tight junctions
what are developing sperm protected from in the adluminal compartment?
immune system
what does the adluminal compartment allow?
a different seminiferous tubular fluid micro-environment for the late stages of spermatogenesis
is sperm production temperature sensitive?
yes
how is the scrotal temperature maintained several degrees below core temperature?
testis is removed from body core in the scrotum
heat exchanger in blood supply before it enters the testis
what function of the testicular artery makes it an efficient heat exchanger?
is superficial for a long distance
what is the name of the muscle which raises and lowers the testicles in response to temperature changes?
cremasteric muscle
what is the name of the products of meiosis 2 found in the adluminal compartments?
spermatid
do spermatid look like sperm?
no
what happens during spermiogenesis?
head, midpiece and tail of sperm are formed
what is formed by spermiogenesis?
spermatozoa
what happens to spermatozoa?
shed into the lumen of the tubule
what are the 3 processed of spermiogenesis?
condensation of nucleus
acrosome formation
flagellogenesis
what is the process of condensation of nucleus essential for?
transfer of genetic material
what is the process of acrosome formation essential for?
enabling fertilisation
what is flagellogenesis?
development of flagellum
what is the flagellum of sperm essential for?
independent and rapid movement
what are the 4 phases of spermiogenesis?
golgi phase
cap phase
acrosomal phase
maturation phase
what happens during the golgi phase of spermiogenesis?
alignment of centrioles and golgi apparatus at either end of the nucleus.
Increase in activity within the cell
DNA becomes condensed
what happens during the cap phase of spermiogenesis?
golgi apparatus expands to form a cap over nucleus
centriole elongates to form flagellum
what happens during the acrosomal phase of spermiogenesis?
cap expands to form acrosome
mitochondria migrate to midpiece
residual cytoplasm is removed
what is the acrosome?
enzyme filled sac
what happens during the maturation phase of spermiogenesis?
last of unnecessary cytoplasm removed in residual bodies
tail begins to elongate
mitochondria wrap around proximal region of tail in midpiece
what does the head of the spermatozoa contain?
nucleus with highly condensed chromatin covered by acrosomal cap
what does the midpiece of the spermatozoa contain?
packed spiral of mitochondria
what is the role of mitochondria in the midpiece of the spermatozoa?
provides ATP for movement of flagellum
what is found in the tail of the spermatozoa?
9+2 microtubule arrangement for motility
what is the 9+2 tubule arrangement in the spermatozoa tail for?
motility
what is the key element that provides motility to spermatozoa?
dynein arms attaching to adjacent microtubules
what is the activity of dynein arms in spermatozoa flagellum provided by?
Ca2+ dependent ATPase activity
what does hydrolysis of ATP in the flagellum of spermatozoa cause?
microtubules sliding past each other due to a conformational change in dynein
how does dynein cause flagella bending?
axoneme is fixed to the sperm head the microtubules sliding past each other due to a conformational change in dynein results in flagellar bending
what generates the wave of bending in the spermatozoa flagellum?
sequential activation of dynein arms
how long is the spermatogenic cycle in a man?
64 days
when do stem cells start to divide in spermatogenesis?
every 16 days
when does the cycle of spermatogenesis start in the seminiferous tubule?
at different times along the length of the seminiferous tubule
what ensures sperm are produced constantly not periodically?
spermatogenic waves starting at different times along the length of the seminiferous tubule
what is testosterone responsible for?
male characteristics
what is testosterone secreted by?
Leydig cells
where are Leydig cells located in the testis?
interstitial tissue between seminiferous tubules
what is most testosterone converted to in tissues?
dihydrotestosterone
what is 98% of blood testosterone bound to?
albumin or sex hormone binding protein (SHBP)
what anterior pituitary hormone is testosterone release stimulated by?
LH
what enhances testosterone?
prolactin
where is prolactin released from?
anterior pituitary
what does episodic release of LH peak lead to in the male?
release of testosterone 45 minutes later
what hormone from the hypothalamus causes release of LH and FSH?
pulses of GnRH
what effect does testosterone have on GnRH and LH release?
negative feedback
what is the role of prolactin in the male?
enhances binding of LH to Leydig cells
what are the 3 effects of testosterone on the foetus?
development of testis
development of genital tract
testicular descent
what are the 3 effects of testosterone during puberty?
increase in testosterone levels enlargement of genital tract anabolic effects masculine behaviour including libido secondary sexual characteristics (beard growth etc)
what are the 3 effects of testosterone in adulthood?
maintenance of sexual activity
maintenance of genital tract
spermatogenesis
what happens to testosterone in the seminiferous tubule?
converted to DHT
where is there androgen receptors within the seminiferous tubule?
adluminal space where sperm are developing
what else is located in the adluminal space?
androgen binding protein
what is the role of androgen binding protein?
keeps more testosterone in the space where it is required
what is the role of FSH in spermatogenesis?
increased levels of androgen binding protein in adluminal spaces which further focuses testosterone binding
what is the role of inhibin?
negative feedback on FSH release
what is inhibin produced by in the male?
sertoli cells in response to FSH
what vitamin is an essential component of spermatogenesis?
vitamin A
what state are sperm in when they are released from seminiferous tubules into the lumen?
immature and immobile
what 2 mechanisms carry sperm in fluid to epididymis?
hydrostatic pressure in tubule from fluid produced by Sertoli cells
feeble peristalsis of seminiferous tubule
where do sperm enter the epididymis from the seminiferous tubule?
head
what is the role of the tail of the epididymis?
sperm storage and exit to ductus defrens
what is the movement of sperm through the epididymis due to?
cilia and contractions of smooth muscle due to oxcytocin
what are the 4 functions of the epididymis?
storage of spermatozoa until release
sperm concentration (removal of fluid)
maturation
phagocytosis of sperm in times of sexual abstinence or after vasectomy
in what condition are sperm when they leave the epididymis?
motile and fertile
what are the 3 E’s of transport of sperm through the male reproductive tract into the female reproductive tract?
erection
emission
ejaculation
what is spermatozoa transported through after leaving the epididymis?
ductus (vans) defrens
what transports spermatozoa along the ductus (vans) defrens?
smooth muscle contractions
what is added to spermatozoa to make semen?
fluids from accessory glands
what are the accessory sex glands?
prostate
seminal vesicles
bulbo-urethral
what are the 7 constituents of seminal fluid?
high concentration of fructose/sorbitol buffer glycoproteins constituents to stimulate female reproductive tract coagulants leukocytes infective agents (HIV/hepatitis)
what is the role of fructose/sorbitol in seminal fluid?
energy source
what is the role of glycoproteins in seminal fluid?
to coat sperm head
what is the role of coagulants in seminal fluid?
after deposition semen may act like slow release gel or form a plug to prevent further penetration of sperm
what does the penis provide the means for?
deposition of sperm into the female reproductive tract
what type of response is erection?
reflex
what makes up the erectile tissue?
2 corpus cavernosa and 1 corpus spongiosum
what are the venous sinuses of the penis bound by?
fibroelastic tissue
how does erection occur?
vasodilation of arteries lead to increased blood flow
veins become compressed causing sinuses to fill with blood and penis becomes turgid
what type of nervous stimulation causes erection?
parasympathetic stimulation
what are helicine arteries?
branches of main artery surrounded by smooth muscle
what is vasodilation of helicine arteries in the penis due to?
stimulation by acetylcholine
vasoactive peptide
nitrous oxide
what does nitrous oxide cause?
relaxation of the smooth muscle by increasing presence of cyclic GMP
how does viagra have its effect?
inhibits phosphodiesterase type 5 (PDE5) enzyme and so prevents breakdown of cGMP so encouraging vasodilation to continue for longer
what is the role of cGMP?
relaxation of smooth muscle - vasodilation
what is the role of phosphodiesterase type 5 (PDE5)?
breakdown of cGMP leading to contraction of smooth muscle in arteries
what is intromission?
thrusting behaviour that resembles a reflex - follows insertion of penis into the vagina
what is seminal emission caused by?
increase in sympathetic outflow to:
tail of epididymis
vans defrens
accessory glands
what happens during seminal emission?
contents of vans defrens are expelled into the pelvic urethra and provide stimulus for ejaculation
what does sympathetic innervation of the neck of the bladder during seminal emission cause?
contraction and prevents urine mixing with semen
what causes ejaculation?
further rhythmic contractions of the urethra under somatic control
why is semen not mixed evenly?
overlap between emission and ejaculation
what are the 3 different fractions of ejaculate?
pre-sperm
sperm
post-sperm
where is the ovum held in the oviduct until fertilisation?
ampulla/isthmus junction
what effect does age of the gamete have on the stability of the zygote?
older gamete makes zygote more unreliable
where is the usual site of deposition of sperm?
vagina
what is the pH of the vagina?
low/acidic
what may happen to the ejaculate to protect it from acidic conditions within the vagina?
may be coagulated
what may the ejaculate form to prevent backflow of sperm?
plug (rats/mice)
what are the 2 speeds of sperm transport?
rapid (sperm may be seen in ampulla 5 mins after deposition)
sustained (sperm may be held up at different points)
what is the cervix made of?
connective tissue and muscle
what may happen to sperm in the crypts of the cervix?
may become held in crypts
what are micelles in the cervix?
strands of mucus
what is the role of micelles in the cervix?
help guide sperm through the cervix
what does the fluid secreted by the cervix prevent?
infection
what is fluid in the cervix like under the influence of oestrogen?
watery, alkaline, hospitable, formation of micelles
what is fluid in the cervix like under the influence of progesterone?
thick, acidic, inhospitable
what is transport of sperm through cervix aided by?
uterine muscular contractions creating negative pressure
what is passage of sperm through the uterus achieved by?
own propulsion aided by currents of fluid set up by action of uterine cilia
what is passage of sperm through the uterotubule junction regulated by?
intermittent sphincter
what happens to sperm once in the isthmus of oviduct?
become immobile
how are sperm attracted to isthmus/ampullary junction?
by chemo attractant from oocyte-cumulous oophorous mass
what essential process must happen to sperm for fertilisation to occur?
capacitation
what is capacitation due to?
exposure of sperm to environment of female reproductive tract
what happens during capacitation?
changes in macromolecular structure of sperm membrane - enabling acrosome reaction
activation
what is involved in activation of sperm?
changes in beating pattern of flagellum from wavelike to whiplash
what are the 4 stages of fertilization?
get sperm to oocyte
sperm nucleus enters oocyte
activation of oocyte
fusion of pro-nuclei
what happens during fertilization?
penetration of cumulus/zona pellucida by swimming action of sperm and acrosome reaction
what is the corona radiata designed to do?
guide sperm to zona pellucida
what do sperm release to aid attachment to zona pellucida?
hyaluronidase on sperm membrane
what do ZP3 receptors do?
bind to proteins on sperm head leading to acrosome reaction
where are ZP3 receptors located?
zona pellucida
what does binding of sperm to ZP3 receptors cause?
acrosomal membrane and plasma membrane to fuse releasing acrosomal enzymes
what does release of acrosomal enzymes cause?
digestion of zona pellucida to allow sperm to reach plasmalemma and attach
what is the plasmalemma?
membrane surrounding oocyte
what happens once the sperm reach the plasmalemma?
fusion of oocyte and acrosomal membrane so nucleus enters oocyte
what process resumes when sperm penetrates zona pellucida with aid of acrosomal enzymes?
meiosis resumes
what is the role of cortical granules in the cytoplasm of oocyte?
fuse with plasma membrane and enzymes cause changes in zona pellucida
how is polyspermy prevented?
fusion of cortical granules with plasma membrane and action of enzymes
what triggers second meiotic division?
fertilization
what is sygamy?
formation of diploid nucleus by fusion of sperm and oocyte nuclei
what is the role of the zona pellucida once the oocyte is fertilised?
prevents 2 embryos from sticking together
what happens during compaction of the embryo?
cells flatten against each other within zona pellucida
where in the fallopian tube does fertilization take place?
ampulla
why is there a need for time delay between fertilization and arrival/implantation of embryo to endometrium?
need to ensure hospitable environment for embryo so progesterone levels need to rise due to corpus luteum
what stage is the embryo at when it reaches uterus?
morula or blastocyst stage
what does the time to implantation usually exceed?
life of corpus luteum
how does the decline of corpus luteum affect the embryo?
leads to fall in progesterone levels so myometrium contractions increase which can lead to loss of the foetus
what prevents luteolysis until the placenta is established?
factors produced by the early embryo
what factor is produced by the embryo in humans which prevents luteolysis until the placenta has developed?
human chorionic gonadotrophin (HCG)
what must happen to endometrium to allow implantation?
must be oestrogen primed
what levels of hormone must be adequate at the time of implantation?
progesterone
what is the role of progesterone in aiding implantation?
decreases myometrial activity, increases glandular secretions (proteins, carbohydrates, lipids, steroids and ions)
what are the glandular secretions of the uterus essential for in early pregnancy?
early nutrition and implantation
what happens to the trophoblast during implantation?
comes into contact with the endometrium
what happens to the blastocyst in implantation in humans?
blastocyst penetrates epithelium of endometrium
what is the name for the type of implantation which occurs in humans?
interstitial implantation
what allows invasion of epithelium by embryo?
proteolytic enzymes from trophoblast and maternal epithelium
what does implantation of the embryo lead to the formation of?
the placenta
what happens during the adhesion phase of interstitial implantation of the placenta?
microvilli on embryo and epithelium interlock
proteases from endometrium and trophoblast are secreted and lead to the embryo invading through endometrium
increased permeability of blood vessels and oedema around blastocyst
what is the decidual cell reaction?
membranes between the cells break down
where on the embryo does the decidual cell reaction take place?
syncitiotrophoblast
what cells come into direct contact with maternal blood?
trophoblast cells
what is exchanged by the placenta?
nutrients, gases and foetal waste
what is the role of the placenta as well as nutrient exchange?
immunological barrier to prevent rejection of foetus
what 4 hormones are produced by the placenta?
human chorionic gonadotrophin
oestrogen
progesterone
human placental lactogen
what is the role of human chorionic gonadotrophin?
prolongs life of cor[us luteum
what is the role of oestrogen in the placenta?
stimulates uterine growth and development
what is the role of progesterone released by the placenta?
stabilises uterus and prevents myometrial contractions
what is the role of human placental lactogen released from the placenta?
growth hormone like activity
what are the 5 main human maternal changes during pregnancy?
uterus expands blood volume increases heart workload increases kidneys filter more blood woman gains on average 10-15kg of weight
what are the 2 main requirements for parturition?
coordinated contractions of myometrium to expel foetus
softening and reduced resistance of cervix
is the mechanism of parturition common to all mammals?
yes
what aspect of parturition differs within species?
the trigger
how is parturition initiated in the goat?
levels of circulating hormones change
how do levels of hormones change in the goat to initiate parturition?
progesterone and oestrogen switch (progesterone increases, oestrogen decreases)
levels of prostaglandin rise
is there change in hormone levels in humans to initiate parturition?
no change in oestrogen:progesterone ratio
prostaglandin levels do not change until well into labour
describe the initiation of parturition in the goat
foetus produces steroids from adrenal gland
leads to increased oestrogen production in the placenta
PGF2alpha synthesis increases so myometrial excitability increases
oxytocin release is enhanced by distention of cervix and vagina
what provides the initial stimulus for initiation of parturition in the goat?
the foetus
what is the effect of increased oestrogen release from the placenta on the myometrium during labour?
increase in excitation and calcium
increased oxytocin receptors
increased PGF2alpha release
what is the role of oxytocin?
amplifies effects of oestrogen on myometrium
what is the effect of PGF2alpha?
softening of cervix
what is thought to initiate parturition in humans?
changes in local receptor populations
what happens during stage 1 of parturition?
overt uterine contractions
positioning of the foetus
dilation of the cervix
transition leading to stage 2
what happens during transition to stage 2?
contractions of the myometrium change
what happens during stage 2 of parturition?
expulsion of foetus
when does stage 2 of parturition start?
full dilation of cervix
what hormone is the uterus highly sensitive to during stage 2?
oxytocin
what is oxytocin release enhanced by?
vaginal stimulation
what happens during stage 3 of parturition?
expulsion of placenta
involution of uterus
what is the goal of involution of the uterus?
prevents excessive blood loss
what type of tissue are mammary glands formed of?
glandular tissue
how is glandular tissue arranged to form mammary glands?
alveoli that in turn are arranged in clusters
what are milk secreting cells formed of?
single layer of epithelial cells surrounded by myoepithelial cells
what is the hormonal stimulus for lactation?
sudden decline in oestrogen and progesterone and increased secretion of prolactin
where do epithelial cells secrete milk into?
alveoli/lumen
what is lactation maintained and initiated by?
prolactin from anterior pituitary
what is required to initiate and maintain lactation?
suckling to stimulate hormone release
what is milk release stimulated by?
action of oxytocin on myoepithelial cells
what happens during the milk ejection reflex?
contraction of myoepithelial cells to expel milk from alveoli
where is oxytocin secreted from?
posterior pituitary
what is milk ejection reflex and maintenance of lactation initiated by?
mechanical stimulation of nipple
what does milk production require?
prolactin and suckling
what does milk ejection require?
oxytocin
can milk ejection occur without stimulation of the nipple?
yes - is a conditioned reflex
define contraception
the prevention of pregnancy and disease
what are the 2 main contraceptive options?
hormonal and barrier
how does a lot of hormonal contraception work?
negatively feeds back on/inhibits GnRH and LH/FSH so that ovulation does not occur
what is the mode of action of the combined pill?
negative feedback on gonadotrophins (GnRH) to inhibit ovulation
what are the advantages of the combined pill?
high efficacy
regular/controlled menstruation
acne may improve
what are the disadvantages of the combined pill?
low risk venous thrombosis
breast/cervical carcinoma
can’t be used while lactating as partially suppresses lactation
why does the combined pill suppress lactation?
oestrogen inhibits milk production
what is the mode of action of the progesterone only pill?
makes cervical mucous hostile to sperm
what are the advantages of the progesterone only pill?
can be used in lactating women
what are the disadvantages of the progesterone only pill?
less effective than combined pill
need for meticulous timing
what is the mode of action of the morning after pill?
delays ovulation beyond lifespan of sperm
prevents sperm transport
what are the advantages of the morning after pill?
95% success if used within 24 hours
what are the disadvantages of the morning after pill?
lower success if delayed to 72hrs
provides no protection for rest of cycle
what is the mode of action of progesterone devices (IUD, implant or injection)?
similar to progesterone pill but may also prevent ovulation
what are the advantages of progesterone devices (IUD, implant or injection)?
high efficacy
cost effective
prevents ovulation
what are the disadvantages of progesterone devices (IUD, implant or injection)?
requires medical intervention
prolonged amenorrhea may follow cessation
what are the 2 main options for male contraception?
testosterone/progesterone combinations
blocking testosterone temporarily
how would testosterone/progesterone combinations aid prevention of pregnancy?
suppression of gonadotrophins and prevention of sperm production
how would blocking testosterone aid prevention of pregnancy?
inhibition of sperm production by lowering systemic testosterone
what is a disadvantage of blocking testosterone to prevent pregnancy?
fails to suppress spermatogenesis in all men
what is lactational amenorrhea?
breastfeeding can act as a contraceptive in 60-70% of lactating mothers
how does lactation act as a contraceptive?
suppresses follicular development
disrupts pulsatile action of GnRH - no LH surge
interferes with corpus luteum function
what is the mode of action of the copper coil?
prevents fertilization as toxic to sperm
what is the mode of action of the hormonal coil?
local progesterone release impairs implantation and fertilization
after what age does female fertility decline?
35
what are the 3 main classes of disorder that contribute to most infertility cases?
disorders of female tract
disorders of ovulation
poor quality spermatozoa
are many cases of infertility explained?
no - high proportion don’t have a known cause
what is ART?
assistive reproductive technologies
what does ART include?
fertility drugs intra uterine insemination in vitro fertilisation in vitro maturation intracytoplasmic sperm injection embryo testing cryopreservation
what are fertility drugs used to overcome?
anovulation
what is the role of anti-oestrogens?
block oestrogen receptors in hypothalamus and pituitary which release negative feedback of oestrogen and so increases release of FSH and LH leading to increased likelihood of LH surge and ovulation
what is the role of gonadotrophins?
stimulates follicular growth
what are gonadotrophins often used in conjunction with?
IVF treatment cycles
how is the natural cycle suppressed during IVF?
administration of GnRH agonist
what is the role of the GnRH agonist in suppressing the natural cycle in IVF?
prevents endogenous LH surge and premature ovulation
how does ovulation hyperstimulation occur during IVF?
using recombinant FSH followed by injection of LH or human chorionic gonadotrophin to mature follicles
how are eggs collected for IVF?
needle passes through vaginal wall and into follicle to retrieve egg
what happens when eggs are fertilized during IVF?
incubated in sperm harvested from male partner in vitro for 24-48 hours
when does embryo transfer occur?
at 4 cell stage
how is the embryo placed in the uterus?
transcervical catheter
what is administered to aid egg implantation after embryo transfer?
progesterone
what happens during cryopreservation?
any remaining fertilised oocytes/embryos may be frozen for later use
what are the 2 key reasons for embryo testing?
preimplantation genetic screening to check for chromosome abnormalities
pre implantation tissue typing for saviour siblings
what are the 4 main dangers of ART?
multiple births
ovarian hyperstimulation syndrome
lower birth weight
congenital abnormalities
what is the purpose of mitochondria replacement?
targets diseases caused by faulty mitochondria
what happens during pronuclear transfer?
parent and donor eggs are fertilized by father
parents nuclear material removed and transferred into donor egg (nuclear material removed) which is healthy
then implanted as with IVF
