(endo) male & female reproductive systems Flashcards
what is the function of the testes?
site of spermatogenesis
where are the testes suspended and why?
suspended in scrotum to keep temperature 2-3 degrees lower than in body
= as if temperature increases, spermatogenesis ceases
what is the function of the epididymis?
stores and matures the sperm
what happens to sperm that is not ejaculated?
if not ejaculated -> broken down
what is the function of the ductus deferens?
transports sperm to penis
what is the function of the prostate and seminal vesicles?
secrete seminal fluid to support ejaculated sperm
what is the function of the penis?
deposits sperm in vagina
what are the components of seminal fluid?
fructose
citric acid
bicarbonate (neutralise vaginal acidity)
fibrinogen
fibrinolytic enzymes
what muscles make up the penis?
x2 corpora cavernosa
x1 corpora spongiosum
explain the nervous control of an erection
erection is due to arterial relaxation due parasympathetic stimulation, which results in increasing arterial pressure which obstructs venous drainage
(‘point & shoot’)
explain the nervous control of ejaculation
ejaculation is due to sympathetic stimulation
‘point & shoot’
what is the function of the bulbo-urethral glands?
secrete sugar-rich mucus into urethra for lubrication and contribute to pre-ejaculatory emissions from penis
describe the route of the spermatic cord
suspends the tests, is formed at deep inguinal ring and passes along inguinal canal and then down to scrotum
name some structures of the spermatic cord
vas deferens
testicular artery
pampiniform plexus of veins
autonomic nerves
lymph vessels
artery of vas
cremasteric artery
genital branch of genitofemoral nerve
remnants of processus vaginalis
what are the tissue layers surrounding the testes?
tunica vasculosa
tunica albuginea
tunica vaginalis
what is the function of the tunica vasculosa of the testes?
contains the blood vessels
what is the function of the tunica albuginea of the testes?
thick layer that forms the septa dividing the testis into lobules
what is the function of the tunica vaginalis of the testes?
covering testis AND epidydimis
explain the structure of the testes
approx 300 lobules in each testis separated by septa
= each lobule contains 1-4 coiled seminiferous tubules which have closed loops
explain the path of sperm from the serminiferous tubules to the vas deferens
seminiferous tubules
= rete testis
= epidydimis
= vas deferens
what is the arterial blood supply of the testes?
testicular arteries from the aorta via the spermatic cord
what is the lymphaic drainage of the testes?
para-aortic lymph nodes
what term is used to describe male sterilisation?
vasectomy
= cutting of the vas deferens
where does the vas deferens empty?
into the junction w the duct of the seminal vesicle
describe the structure of the fallopian tubes
extend from the fimbrae connected to the ovary all the way to the uterus
where does fertilisation occur?
in the ampulla of the fallopian tubes (widest part)
explain how the fallopian tubes are adapted to their function
1) contain cilia = that waft to direct the zygote towards the uterus
2) made up of spiral muscle = that is sensitive to oestrogen levels +
how does an oocyte move down the fallopian tube?
via peristalsis of the spiral muscle and wafting of the cilia
what happens if motility is reduced in the fallopian tube?
increased risk of ectopic pregnancy
how is the uterus supported in place? (2)
1) tone of the pelvic floor muscles (levator ani, coccygeus muscles)
2) ligaments (broad, round, uterosacral)
why is it important that the uterus is supported in place?
to prevent uterine prolapse
what is the top of the uterus called?
uterine fundus
what are the layers of the uterus called?
serosa/perimetrium
myometrium
endometrium
which uterine layer is sensitive to hormonal action?
myometrium
explain how menstruation occurs
endometrial layer = spiral arterioles
= progesterone levels fall at the end of the menstrual cycle = intermittent vasoconstriction = ischaemia/necrosis = shedding of the endometrial lining = haemorrhage that is menstruation
why is the intermittent vasoconstriction of the spiral arterioles of the endometrial layer important?
intermittent vasoconstriction leads to ischaemia/necrosis of the of the endometrial lining
= shedding/haemorrhage
which structure is lateral to the cervix and why is this important?
approx 1cm lateral to the cervix is the ureter
= important when considering cervical cancer
how is sterility maintained in the female reproductive tract?
all areas superior to the cervix are sterile
1) frequent shedding of the endometrium
2) thick cervical mucus
3) narrow external ox
4) acidity as ph < 4.5
explain how the acidic vaginal pH is achieved
oestrogen stimulates the vaginal epithelium to secrete glycogen
lactobacilli digest the glycogen releasing lactic acid
= lowers the pH of the vagina below 4.5 so preventing infection by other organisms
why is it important that the pH of the vagina is acidic?
preventing infection by other organisms
why can overuse of antibiotics be harmful for the vaginal environment?
natural flora of the vaginal environment
= disrupted by antibiotic use
= can cause overgrowth + infections (e.g. candiadiasis)
what is the arterial supply to the ovaries?
ovarian arteries (from aorta)
what is the arterial supply to the uterus/vagina?
uterine arteries (from the internal iliac artery)
what is the lymphatic drainage of the ovaries?
para-aortic lymph nodes
what is the uterus/vagina drainage of the ovaries?
Iliac, sacral, aortic and inguinal lymph nodes
which cells are examined in a smear test?
cells around the external os
oestrogen stimulates the production of which type of cervical mucus?
thin, watery mucus
= allows sperm to
progesterone stimulates the production of which type of cervical mucus?
thick, viscous mucus
i.e. mechanism of action of the progesterone-only pill
secretions from where lubricate the vagina during sexual arousal?
greater vestibular glands (i.e. Bartholin’s glands near the external vaginal orifice)
name the male gonads
testes
name the female gonads
ovaries
what is gametogenesis?
production of gametes for reproduction
males = spermatogenesis females = oogenesis
when does gametogenesis begin in males?
at puberty
explain what happens in spermatogenesis
spermatogonia undergo differentiate and self-renewal from puberty onwards
pool of spermatogonia available for subsequent spermatogenic cycles all throughout life
‘males have continuous fertility’ - what does this mean?
pool of spermatogonia available for subsequent spermatogenic cycles all throughout life
explain what happens in oogensis
BEFORE BIRTH
1) multiplication of oogonia to 6 million/ovary
2) oogonia to primary oocytes within ovarian follicles (primordial follicles)
3) primary oocytes undergo meiosis + HALT in prophase
4) some primoridal follicles undergo atresia and degenerate
PUBERTY
= due to further atresia <0.5 million/ovary
explain what happens in oogensis
BEFORE BIRTH
1) multiplication of oogonia to 6 million/ovary
2) oogonia to primary oocytes within ovarian follicles (primordial follicles)
3) primary oocytes undergo meiosis + HALT in prophase
4) some primoridal follicles undergo atresia and degenerate = so at birth 2 million/ovary
PUBERTY
= due to further atresia <0.5 million/ovary
what occur within primordial follicles?
oogonia converted into primary oocytes in ovarian follicles
how do primary oocytes develop before birth?
primary oocytes undergo meiosis and halt in prophase
how many oogonia are found per ovary before birth?
2 million/ovary
how many oogonia are found per ovary by puberty?
0.5 million/ovary
how does the number of oogonia change from before birth to puberty?
before birth = 6 million/ovary
at birth = 2 million/ovary
puberty = 0.5 million/ovary
due to further atresia
describe the process of stermatogenesis
spermatogonia
(mitosis)
primary spermatocytes
(first meiotic division) secondary spermatocytes (second meiotic division) spermatids (differentiation) spermatozoa
where does spermatogenesis take place?
intratubular compartment of the seminiferous tubules
how many days does spermatogenesis take?
approx 64 days until spermatozoa are ready for release
what surrounds the seminiferous tubules?
tunica propria
= made of flattened cells forming a basement membrane
explain the arrangement of cells in the seminiferous tubules
most of the cells that lie against the basement membrane and have round nuclei are spermatogonia
mature as they move inwards forming primary and secondary spermatocytes (rarely seen)
ultimately spermatids are released into duct
explain how the structure of the seminiferous tubules helps achieve continuous fertility
from the outer basement layer to the inner duct, spermatogonia are at different progressive stages of spermatogenesis
= spermatids continuous released into the inner duct to provide a continuous pool
which cells support spermatogenesis?
1) Sertoli cells
2) Leydig cells
where are Sertoli cells found?
within the seminiferous tubules
where are Leydig cells found?
outside/in-between the seminiferous tubules
what main reproductive hormones are produced in males?
1) androgens
2) inhibin + activin
3) oestogens
which androgens are produced by males?
1) testosterone
2) dihydrotestosterone
3) androstenedione
how can oestrogens be produced in males?
androgen aromatisation
what is inhibin and what is its function?
a protein produced by Sertoli cells that circulates in the ‘inhibin B’ form
= exerts negative feedback on pituitary release of FSH
as inhibin B expression + secretion
1) negatively correlated with FSH
2) positively correlated with Sertoli cell function + spermatogenic status
how does inhibin affect FSH release?
inhibin B expression + secretion is negatively correlated with pituitary FSH
how does inhibin affected by Sertoli function?
Inhibin B expression + secretion is POSITIVELY correlated with Sertoli function and spermatogenic status
which receptors are found on Sertoli cells?
FSH receptors
Sertoli cells are found within the seminiferous tubules
which receptors are found on Leydig cells?
LH receptors
Leydig cells are found between the seminiferous tubules
what are the two main functions of Sertoli cells?
1) support developing germ cells
2) hormone synthesis
how do Sertoli cells support developing germ cells?
1) assist movement of germ cells to tubular lumen
2) transfer nutrients from capillaries to developing germ cells
3) phagocytosis of damaged germ cells
how do Sertoli cells support hormone synthesis?
1) inhibin and activin (effects on FSH secretion)
2) anti-Mullerian hormone (AMH)
3) androgen-binding protein (ABP)
what are the functions of inhibin and activin?
inhibin - inhibits FSH release from the pituitary gland via negative feedback
activin - stimulate FSH release from the pituitary gland via positive feedbackwhat
what is the function of AMH?
anti-Mullerian hormone produced by immature Sertoli cells
= aids in the regression of the Mullerian ducts in male sexual development which would otherwise go on to form the fallopian tubes/uterus/cervix
which cells release AMH?
immature Sertoli cells
how is Mullerian duct development prevented in men?
AMH (anti-Mullerian hormone) aids in the regression of the Mullerian ducts
= would otherwise go on and form fallopian tubes/uterus/cervix
what is the function of ABP?
androgen-binding protein
= directs testosterone from Leydig cells to germ cells
what stimulates ABP release?
FSH
as ABP is released from Sertoli cells, whose function depends on FSH receptor activation
why do Leydig cells have a pale cytoplasm?
contain lots of cholesterol to make testosterone
which receptors are found on Leydig cells?
LH receptors
what is the function of Leydig cells?
hormone synthesis
which hormones are synthesised by Leydig cells?
on LH stimulation:
- testosterone
- androstenedione
- dihydroepiandrostenedione (DHEA)
= can be aromatised to oestrogens
which stimulates and inhibits AMH transcription?
stimulates = FSH
inhibits = testosterone
what is the term used to describe female gametogenesis?
oogenesis
describe the process of oogenesis
oogonia
(mitosis)
primary oocytes
(first meiotic division) secondary oocytes (second meiotic division) ootids (differentiation) ova
what happens in terms of oogonia during the second trimester of pregnancy?
all oogonia in foetus develop into primary oocytes
forming primordial follicles
why are primary oocytes associated with primordial follicles?
primary oocytes arrest in the first meiotic division stage until menarche
= granulosa cells surround these primary oocytes and form primordial follicles
what happens to primordial follicles at menarche?
recommence growth, partly dependent on FSH
what is produced alongside secondary oocytes?
(secondary oocytes, capable of fertilisation, produced following menarche)
first polar body = small haploid cell w no cytoplasm
what stimulates the second meiotic division in oogenesis?
fusion of the secondary oocyte + sperm
= causes calcium influx that stimulates the 2nd meiotic division forming the ova
describe the stages of folliculogenesis
1) primodrial follicle (primary oocytes)
2) pre-antral follicle (primary)
3) antral follicle (secondary)
4) mature/Graafian follicle
5) ruptures surface of ovary
6) corpus luteum
what is a primary/pre-antral follicle?
one in which the primary oocytes are surrounded by layers of granulosa and theca cells
what is a secondary/antral follicle?
- antrum develops
- contain FSH and LH receptors
what is the mature/Graafian follicle?
- forms due to the LH surge
- secondary ooycte forms
what is the function of the corpus luteum?
oestrogen & progesterone production (stimulated by LH/HCG)
what happens to corpus luteum function in pregnancy?
normally CL = progesterone + oestrogen production BUT in pregnancy, placenta takes over this role
how is the mature/Graafian follicle selected?
loads of follicles develop initially
BUT the one that produces most oestrogen
= dominant follicle
= takes over
= inhibits FSH stimulation of other follicles
at which stage in life are primary follicles most numerous?
before menarche as primary follicles form at birth and remain arrested until menarche
describe the cells found in a mature/Graafian/preovulatory follicle
1) inner granulosa cells bind FSH = to aromatise androgens into oestrogens
2) outer theca cells bins LH = to produce androgens
which reproductive hormones are produced by females?
1) oestrogens
2) progestogens
3) androgens
4) relaxin & inhibin
in females, where are oestrogens produced and which ones?
inner granulosa cells
= oestradiol, oestrone, oestriol
in females, where are progestogens produced and which ones?
outer theca cells
= progesterone
in females, where are androgens produced and which ones?
outer theca cells
= testosterone, androstenedione, DHEA
in females, where is relaxin produced and what is its function?
ovaries and placenta (esp corpus luteum)
= relaxes pelvic ligaments ans softens cervix for childbirth
in females, where is inhibin produced?
ovaries and placenta
where are theca cells found?
associated with the OUTER part of the ovarian follicles
where are granulosa cells found?
associated with the INNER part of the ovarian follicles
what are the two main functions of theca cells?
1) support folliculogenesis
2) hormone synthesis
how are theca cells involved in folliculogenesis?
structural and nutritional support of growing follicle
how are theca cells involved in hormone synthesis?
LH stimulates androgen synthesis
so overactivity - high androgen levels (common cause of infertility)
why is overactivity and underactivity of theca cells harmful?
overactivity = leads to hyperandrogenism (common cause of infertility)
underactivity = infertility due to subsequent lack of oestrogen
what are the two main functions of granulosa cells?
1) hormone synthesis
2) turn into granulosa lutein cells after ovulation
how are granulosa cells involved in hormone synthesis?
1) FSH stimulates granulosa cells to convert androgens to oestrogens (by aromatase)
2) secrete inhibin and activin (act on pituitary FSH secretion)
where does androgen aromatisation occur in females?
granulosa cells
on FSH stimulation, androgens are aromatised to oestrogens
from where are inhibin and activin secreted in females and males?
females = inner granulosa cells
males = inner Sertoli cells
(both controlled by FSH stimulation)
what happens to granulosa cells after ovulation?
after ovulation, turns into granulosa lutein cells that produce
1) progesterone
2) relaxin
what is the function of progesterone in females?
under negative feedback
= promotes pregnancy by maintaining the endometrium
what is the function of relaxin in females?
helps the endometrium prepare for pregnancy by relaxing the pelvic ligaments & softening the cervix
besides, granulosa cells in females, where else is inhibin released from?
also synthesised in the placenta
what is the function of inhibin and activin?
inhibin = inhibits pituitary FSH secretion
activin = stimulates pituitary FSH secretion
which structure is mainly responsible for progesterone secretion?
corpus luteum
what does progesterone negatively feed back to?
anterior pituitary and hypothalamus
which structure release relaxin into circulation in females?
granulosa cells
= specifically the corpus luteum and placenta
where does androgen aromatisation occur in males and in females?
males = outer Leydig cells (androgens also produces here)
females = inner granulosa cells (from androgens produced in outer theca cells)
describe the hypothalamic-pituitary axis for LH/FSH
kisspeptin
GnRH
LH/FSH
gonads
oestrogen, testosterone production
= reproduction
describe the hypothalamic-pituitary axis for TSH
TRH
TSH
thyroid gland
T3/T4
= metabolism
describe the hypothalamic-pituitary axis for prolactin
dopamine
prolactin
breast
= lactation
describe the hypothalamic-pituitary axis for ACTH
CRH
ACTH
adrenal gland
cortisol & androgen production
= stress response
describe the hypothalamic-pituitary axis for GH
GHRH
GH
liver
IGF-1
= growth
describe the hypothalamic-pituitary axis for ADH
ADH act on the kidneys
= water reabsorption
describe the hypothalamic-pituitary axis for oxytocin
oxytocin acts on the uterus/breast
= parturition/lactation
in what manner are GnRH and LH released?
pulsatile
in what manner are the sex steroids released?
diurnal
explain the effect of hyperprolactinaemia on the HPG axis
excess prolactin
= binds to receptors on kisspeptin neurones
= INHIBITS kisspeptin release
= decreases downstream GnRH/LH/FSH/testosterone/oestrogen release
= oligomenorrhoea, amenorrhoea, erectile dysfunction, infertility, osteoporosis, low libido
in hyperprolactinaemia, what does prolactin bind to?
prolactin receptors on KISSPEPTIN neurones
= to inhibit kisspeptin release into the hypothalamus
what are the four main hormones involved in the menstrual cycle?
LH
FSH
oestrogen
progesterone
which two cycles make up the menstrual cycle?
1) ovarian cycle - associated w folliculogenesis and corpus luteum formation
2) uterine cycle - associated w state of the endometrial lining
= both cycles driven by hormonal level changes
what are the different stages of the ovarian cycle?
- follicular phase
- ovulation
- luteal phase
what are the different stages of the uterine/endometrial cycle?
- menstrual phase
- proliferative phase
- secretory phase
what are the first 14 days of the menstrual cycle called?
follicular phase
what are the last 14 days of the menstrual cycle called?
luteal phase
why is day 14 of the menstrual cycle important?
ovulation
what is the average length of a normal menstrual cycle?
approx 28 days
can range from 21-35
what occurs on the first day of the menstrual cycle?
first day of bleeding
blood + cellular debris from necrotic endometrial lining
what is the term used to describe a menstrual cycle that lasts greater than 35 days?
oligomenorrhoea
which feedback loops drive the menstrual cycle?
- hypothalamic kisspeptin + GnRH
- pituitary LH and FSH
- ovarian oestrogen, progesterone, activin, inhibin
which stage of the menstrual cycle is variable?
follicular phase
usually this is prolonged in women w a longer than usual menstrual cycle
what happens in the follicular phase, in terms of hormones?
1) LH & FSH rise
2) this rise stimulates follicular development and subsequent oestrogen secretion from the maturing follicles
3) oestrogen levels subsequently rise
4) FSH falls a little due to negative feedback
5) a high enough oestrogen level causes a switch to positive feedback at the APG, resulting in an LH surge (and to a lesser extent FSH)
where is oestrogen primarily secreted from in the menstrual cycle?
developing, maturing follicles during folliculogenesis (stimulated by FSH)
(most oestrogen is secreted from the dominant/Graafian follicle)
in the follicular phase, what does oestrogen stimulate in granulosa cells?
(oestrogen, produced by the developing follicles, acts on granulosa cells)
= to stimulate the development of LH receptors and accelerate growth
(? to increase the responsiveness of granulosa cells to the LH surge)
in the follicular phase, what impact does the rising oestrogen level have?
as oestrogen levels rise there is a switch to positive feedback at the pituitary, resulting in an LH surge and lesser extent FSH
why is the LH surge required?
results in the final maturation and subsequent release of the dominant follicle
(other follicle regress)
what happens to the other follicles after ovulation?
undergo follicular atresia (regress)
in terms of the uterine/endometrial cycle, what happens in the menstrual phase?
degenerating spiral arteries
= blood + ischaemia/necrotic functional layer of the endometrium is shed
what happens in the proliferative phase of the uterine cycle and which hormone stimulates this?
stimulated by OESTROGEN
= endometrium proliferates to form a new functional layer + cervical mucus thins to allow sperm passage
what is the function of the corpus luteum and when does it form?
secretes progesterone + oestrogen
= forms after ovulation, in the luteal phase
what happens, in terms of hormones, in the luteal phase?
1) corpus luteum secretes loads of progesterone
2) progesterone inhibits LH/FSH secretion and slowly the CL involutes (unless rescued by hCG produced by the implanting conceptus)
3) involution of the CL causes progesterone and oestrogen levels to fall
4) FSH/LH can then rise for the next cycle
what is the main source of oestrogen in the luteal phase?
corpus luteum
what are the two ways in which the corpus luteum is maintained?
1) if egg not fertilised = LH
2) if fertilisation has occurred = hCG produced by the implanting conceptus
why does the corpus luteum involute if fertilisation does not occur?
CL releases progesterone + oestrogen
= negative feedback inhibits LH/FSH secretion
= with no hCG either, from the implanting conceptus, CL cannot be maintained
what happens in the secretory phase of the uterine cycle?
1) endometrium differentiates and secretes a glycogen-rich fluid in preparation for a potential embryo
2) spiral arteries constrict causing ischaemia + necrosis due to falling progesterone levels
in which scenario does the endometrial layer not shed in the menstrual cycle and why?
when there is a successful pregnancy
hCG secreted by the conceptus –> maintains CL –> continuous secretion of progesterone (and oestrogen) –> maintains endometrial lining
what happens to basal body temperature after ovulation and why?
increase by approx 0.5 degrees Celsius
= due to progesterone secretion (from the newly formed CL)
