reproductive endocrinology 1 Flashcards
what is the reproductive system needed for?
Not required for maintaining homeostasis or survival of an individual but essential for the survival of the species
what is the main role of the male reproductive system?
to manufacture male gametes called sperm and deliver them to the female reproductive tract where fertilisation can occur.
what is the main role of the female reproductive system?
in addition to producing female gametes called Ova or egg, the female system is equipped to house and nourish the offspring to a developmental point until it can survive independently in the external environment
what are the primary reproductive organs in the males?
testes
what are the primary reproductive organs in females?
ovaries
what do the primary reproductive organs produce?
Gametes (sperm and ova)
Sex hormones
Testosterone in the male
Estrogens and progesterone in the female
what are the accessory reproductive organs?
Reproductive tract
Accessory sex glands
External genitalia
Breast in the female
what does the male reproductive system consist of?
Testes Epididymis Ductus deferens or Vas deferens Ejaculatory duct Urethra
what are the accessory sex glands in the male reproductive system?
Seminal vesicles
Prostate gland
Bulbourethral gland or Cowpar’s gland
what are the external genitalia of the male reproductive system?
the scrotum and the penis
what is the role of the scrotum?
Holds testes outside abdominal cavity at ~ 3ºC below body temp
what is the role of the penis?
Copulatory organ which deliver sperm into female reproductive tract
what does each testes consist of?
seminiferous tubules
leydig or interstitial cells
where are the seminiferous tubules found?
250-300 lobules containing 1-4 tightly coiled seminiferous tubules
what are the functions of leydig/interstitial cells?
secrete testosterone
what is the route that sperm takes?
Seminiferous tubules –>
Epididymis –> Vas deferens –> Ejaculatory duct –> Urethra
what is spermatogenesis?
production of the male gametes - the sperm
where does spermatogenesis take place?
in seminiferous tubules of the testes
which cells of the seminiferous tubules that are involved in spermatogenesis?
Germ cells
Sertoli cells
what is the process of spermatogenesis?
process by which undifferentiated germ cells, the spermatogonia , proliferate and are converted to spermatozoa (sperm).
how many chromosomes in a spermatogonia?
diploid - 46 chromosomes
how long does spermatogenesis take?
64-72 days
what are the 3 major stages of spermatogenesis?
Mitotic proliferation (forming spermatocytes)
Meiosis (Spermatocytes to spermatids)
Packaging or spermiogenesis (spermatids to sperm)
what are functions of Sertoli cells?
- Form blood-testicular barrier
- Provide nourishment to developing sperm
- Phagocytose cytoplasm extruded from the spermatids
- Secrete seminiferous tubule fluid into the lumen
- Sertoli cells secrete Androgen Binding Protein (ABP) which binds testosterone, required to maintain high level of testosterone in the seminiferous tubules
- Site of action of testosterone and FSH to control spermatogenesis
- Release inhibin which acts in negative-feedback fashion to regulate FSH secretion
how does sperm gain motility?
when they pass through the epididymis
what happens during ejaculation?
sperm are expelled through the urethral opening together with the secretion of accessory sex glands
what do foetal testis secrete?
testosterone which direct masculine development of reproductive tract
what happens to testis after birth?
testes becomes quiescent until puberty
what happens to hypothalamus during the peripubertal period?
hypothalamus is under neural inhibition and is extremely sensitive to negative feedback effect of testosterone
what happens to hypothalamus during puberty?
the neural inhibition is removed and hypothalamus become less sensitive to testosterone
how long does the maturation of brain testicular axis take?
3 years
what is the role of testosterone?
Stimulation of lineal body growth
Induction of secondary sexual characteristics
what does the female reproductive system consist of?
Ovaries Uterine or Fallopian tube Uterus Cervix Vagina
what is the external genitalia in the female reproductive system?
valva
Labia majus
Labia minus
Clitoris
what is different about the urethra in females than males?
Urethra is much shorter in female and urethral opening is separate from the opening of the reproductive tract, the vaginal orifice.
when is a females total supply of eggs determined?
at birth
what happens to oogonia in the foetal period?
the oogonia multiply rapidly by mitosis, become primordial follicles, and then become primary follicles that begin the first meiotic division
what happens in the female reproductive system after puberty?
a few oocytes are activated each month but only one will continue to meiosis I.
what happens to the oocyte in meiosis I?
2 haploid cells are produced - a polar body and a secondary oocyte.
what happens to the secondary oocyte?
stops in metaphase II and if a sperm penetrates it, it will complete meiosis II, producing a second polar body and a large ovum
what is the ovarian cycle?
Monthly series of events that take place in the ovaries, which are associated with the maturation of the egg
what are the 2 phases of the ovarian cycle?
- follicular phase
- luteal phase
what happens in the follicular phase?
The period of follicular growth typically lasting from day 1 to 14.
Produce mature oocyte ready for ovulation at midcycle
what happens in the luteal phase?
The period of corpus luteum activity lasting from day 14 to 28.
Prepare the female reproductive tract for pregnancy if fertilization occur
when does the ovarian cycle start?
The cycle starts at puberty and is normally interrupted only by pregnancy and is finally terminated by menopause
what are the steps of the development of ovarian follicle?
slide 24
what is the uterine/menstrual cycle?
Monthly series of cyclic changes that the uterine endometrium goes through each month in response to changing levels of ovarian hormones in the blood
what are the 3 consecutive phases of the menstrual cycle?
- menstrual phase
- proliferative phase
- secretory phase
what happens during the menstrual phase?
endometrium is shed from the uterus
what happens during the proliferative phase?
Endometrium is rebuilt becoming velvety, thick and well vascularised
what happens during the secretory phase?
Endometrium prepares for implantation of an embryo
what hormones are involved in the control of menstrual cycle?
- Gonadotropin-releasing hormone (GnRH) of hypothalamus
- Anterior pituitary gonadotropins
- Follicle stimulating hormone (FSH)
- Leutenising hormone (LH)
- Ovarian sex steroids
- Estrogens
- Progesterone
which hormones are apparent on day 1 of the menstrual cycle?
levels of GnRH rise and stimulate increased production of FSH and LH.
what doe FSH and LH do in the menstrual cycle?
Stimulate follicle growth and maturation, and oestrogen secretion
what happens with the rising level of oestrogen?
initially exerts negative feedback on the anterior pituitary, inhibiting release of FSH.
what happens when oestrogen levels exert positive feedback on the anterior pituitary?
results in a burst of LH triggering ovulation and transforming the ruptured follicle into corpus luteum.
what causes rising levels of oestrogen and progesterone during the menstrual cycle?
released by the corpus luteum under the influence of LH
what is the effect of rising oestrogen and progesterone levels?
exert negative feedback on LH and FSH release
what happens when LH levels fall?
the corpus luteum degenerates dropping the levels of estrogens and progesterone and the cycle starts again
what is the role of oestrogen?
- Promote oogenesis and follicle growth in the ovary
- Cause epiphyses of the long bones to close during growth spurt in puberty
- antagonizes the effects of the parathyroid hormone, minimizing the loss of calcium from bones and thus helping to keep bones strong.
what is the role of progesterone?
- continues the preparation of the endometrium for a possible pregnancy
- inhibits contraction of the uterus
- inhibits development of a new follicle
how long is an oocyte available for fertilisation?
12-24 hrs
how long can sperm survive in the female reproductive tract?
24-72 hrs
when does fertilisation occur?
when a sperm fuses with an egg to form a fertilised egg called zygote approximately one third of the way down the length of the uterine tube.
what is capacitation?
a process involving weakening of the sperm cell membrane in order to allow release of acrosomal hydrolytic enzymes
what happens when sperm binds to the egg?
they undergo an acrosomal reaction, where acrosomal enzymes are released to the oocyte.
what happens when a sperm cell binds to membrane receptors on the oocyte?
the nucleus of the sperm is pulled into the cytoplasm of the oocyte.
what is polyspermy?
fertilisation by more than one sperm cell
what can polyspermy lead to?
leads to a lethal number of chromosomes.
what is the fast block to polyspermy?
The fast block to polyspermy occurs when the membrane of the oocyte depolarises and prevents similar binding by other sperm cells.
what is the slow block to polyspermy?
The slow block to polyspermy results in destruction of sperm receptors, and the formation of a swollen membrane that removes other sperm cells from the surface of the oocyte.
what happens to a sperm cells after it enters an oocyte?
it loses its tail and midpiece, and migrates to the center of the oocyte while the oocyte completes meiosis II.
what happens after meiosis II is completed?
male and female pronuclei fuse and produce a zygote, which almost immediately enters into mitosis.
what is classed as pre-embryonic development?
pre-embryonic development begins with fertilisation and continues with the movement of the pre-embryo to the uterus where it impacts in the uterine wall.
what is the result of cleavage during mitosis?
two identical cells, blastomeres, which then form a morula, a hollow ball of cells, by 72 hours.
what happens after 4-5 days of fertilisation?
the blastocyst escapes from the degrading zona pellucida to implant in the uterine wall.
when does implantation occur?
occurs 6-7 days after fertilisation.
how does implantation occur?
- Uterine capillaries become permeable and leaky, and the trophoblast proliferates, forming the cytotrophoblast and the syncytiotrophoblast.
- Trophoblast cells secrete human chorionic gonadotropin (used in pregnancy test), which acts on the corpus luteum.
what is placentation?
formation of the placenta, and is the process of proliferation of the trophoblast.
what is function of placenta?
The placenta is fully functional as a nutritive, respiratory, excretory, and endocrine organ by the end of the third month of gestation.
what hormones does the placenta produce?
- Oestrogens
- Progesterone
- Human placental lactogen (Human chrionic somatomammotropin)
- Human chorionic thyrotropin
- Relaxin
what is the function of human chorionic gonadotropin?
- Maintain corpus luteum of pregnancy
- Stimulates secretion of testosterone by developing testes in XY embryos
what is the function of oestrogen?
- Stimulates growth of myometrium, increasing uterine strength for birth
- Helps prepare mammary glands for lactation
what is the function of progesterone?
- Suppresses uterine contractions to provide quiet environment for foetus
- Promotes formation of cervical plug to prevent uterine contamination
- Helps prepare mammary glands for lactation
what is the function of human placental lactogen?
- Helps prepare mammary glands for lactation
- Reduce maternal utilization of glucose so that greater quantities of glucose can be made available to the fetus
what is the function of Human chorionic thyrotropin?
Increases maternal metabolism during pregnancy
what is the function of relaxin?
Softens cervix in preparation for parturition
what are the anatomical effects of pregnancy?
Reproductive organs become increasingly vascular, uterus and breasts enlarge, relaxin causes pelvic ligaments and pubic symphysis to relax, widen and become more flexible.
Weight gain (of approximately 13 kg) occur by the end of pregnancy.
what are the metabolic changes that occur during pregnancy?
Human placental lactogen works cooperatively with oestrogens and progesterone to stimulate maturation of the breasts for lactation and produce glucose-sparing effect.
Human chorionic thyrotropin increases rate of metabolism throughout the pregnancy.
what are the 3 developmental process that pregnancy can be divided into?
- embryonic period
- foetal period
- perinatal period
when do the gonads develop?
The gonads of both males and females begin to develop during week 5 of gestation.
when do the gonads begin to become testes in males?
week 7
when do the gonads begin to form the ovaries in females?
week 8
what happens to the testes 2 months before birth?
the testes begin their descent toward the scrotum, dragging their nerve supply and blood supply with them.
what happens to ovarian function with age?
Ovarian function declines gradually with age; menstrual cycles become more erratic and shorter until menopause, when ovulation and menstruation stop entirely.
what initiates labour?
During last few weeks estrogens reach their highest level resulting in stimulation of expression of oxytocin receptors in the myometrium and antagonises progesterone’s quietening effect on the uterus
what is the role of oxytocin in the initiation of labour?
Certain foetal cells begins to produce oxytocin which causes placenta to release prostaglandins both of which initiate contraction of uterus
what is lactation?
Lactation is the production of milk by the hormone-prepared mammary glands.
what promotes the secretion of prolactin?
Rising levels of placental estrogens, progesterone, and lactogen stimulate the hypothalamus to produce prolactin-releasing hormone (PRH).
where is prolactin secreted from?
the anterior pituitary
what is colostrum?
a high-protein, low-fat product that is initially secreted by the mammary glands, but after two to three days, true milk is produced.
what is the role of nipple stimulation in lactation?
Nipple stimulation during nursing sends neural signals to the hypothalamus, resulting in production of PRH and a burst of prolactin that stimulates milk production for the next feeding.
what is the role of oxytocin in lactation?
Oxytocin causes the let-down reflex, resulting in the release of milk from the alveoli of the mammary glands in both breasts.
what are the forms of contraception?
natural methods of contraception
combined oral contraceptives (COC)
progestogen only pills (POP)
what are the natural methods of contraception?
- the temperature method
- the cervical secretion monitoring method
- the lactational amenorrhoea method (LAM)
what is the temperature method based on?
The temperature method is based on the fact that there is a small rise in body temperature after ovulation takes place.
what happens to cervical secretion during a menstrual cycle?
There is a change in the amount and consistency of the mucus secreted from your cervix during different times in your menstrual cycle.
when can the lactational amenorrhoea method be used?
Women who are fully (or nearly fully) breastfeeding can use the LAM for the first six months after their baby is born, as long as:
- the woman has complete amenorrhoea (no periods at all)
- she’s fully or very nearly fully breastfeeding (the baby is having breastmilk only)
- the baby is less than six months old
when does LAM become unreliable?
- other foods or liquids are substituted for breastmilk
- your baby reaches six month old
- you have a period
what are the advantages of combined oral contraceptives?
The risk of ovarian and endometrial cancer is halved with COC use and this continues for at least 15 years after stopping.
what are some of the risks of combined oral contraceptives?
- there is a small increase in the risk of blood clots
- there is a very small increase in the risk of heart attack and stroke
- any increased risk of breast cancer is likely to be small and returns to no increased risk 10 years after stopping COC
- there may be a very small increase in the risk of cervical cancer that increases with increasing duration of use
what do combined oral contraceptives include?
they contain an oestrogen and a progestogen
what type oestrogens are used in combined oral contraceptives?
- ethinylestradiol (most common)
- estradiol
- mestranol
what progestogens are used in combined oral contraceptives?
- levonorgestrel
- norethisterone
- norgestimate
- gestodene
- desogestrel
how and when are combined oral contraceptives started?
1-5 day- immediate protection (unless short cycle)
how are combined oral contraceptives taken?
daily within 24 hours
what happens if a combined oral contraceptive pill is missed?
if it is only one pill you take it as soon as you remember
if more than one pill is missed you are not protected for 7 day s
what are the advantages of progestogen only pills?
- Safe while breastfeeding
- Useful if you cannot take estrogens,
- Useful if you smoke and are 35 or over
- Help with premenstrual symptoms and
painful periods.
what are the disadvantages of progestogen only pills?
- Irregular periods
- You have to remember to take the pill at the same time every day
- Temporary: spotty skin, breast tenderness, weight change and headaches
what happens if you miss a progestogen only pill?
if it is more than 3 hours late you are not protected for 2 days
how/when to start taking progestogen only pills?
1-5 day- immediate protection (unless short cycle)
Protection after 2 days
how do you take progestogen only pills?
Same time of the day within 3 hours
what are the contraindications of progestogen only pills?
- heart disease or a stroke
- disease of the liver
- systemic lupus erythematosus (autoimmune disease)
- current breast cancer or breast cancer within the last five years.
what are the contraindications of combined oral contraceptive pills?
- smoke and are 35 or older
- stopped smoking less than a year ago and are 35 or older
- are very overweight
- take certain medicines (antiepileptics, retrovirals, liver inducing antibiotics )
- thrombosis(a blood clot)
- a heart abnormality or heart disease, including high blood pressure
- severe migraines, especially with aura (warning symptoms)
- breast cancer
- disease of the gallbladder or liver
- diabeteswith complications or diabetes for the past 20 years
what is the correct mode of administration of combined hormonal contraceptive patches?
to be applied weekly
1 week drug free after every 3 weeks
what is the correct mode of administration of parenteral progestogen-only implants?
To be inserted/injected: every 2-3 years
what is the correct mode of administration of Intra-uterine progestogen only system ?
To be inserted/injected: every 5 years
what is the correct mode of administration of Intra-uterine copper contraceptive devices?
To be inserted : every 5-10 years
what is the correct mode of administration of Combined hormonal contraceptives- Rings?
To be inserted every4 weeks (1 week drug free)
what is the correct mode of administration of Parenteral progestogen-only contraceptives- Injections (Depo-Provera®)?
To be injected: every 3 months
