PBL 5 Conception and Female Reproduction

Question Answer
Outline the female reproductive system Paired gonads (ovaries), duct system: paired uterine tubes and single midline uterus and vagina, located in the pelvis (vagina extends through pelvic floor)
Name the three ligaments relevant to the female reproductive system Broad ligament, ovarian ligament, suspensory ligament of ovary
Describe the broad ligament Peritoneal sheet draped over the uterus and uterine tubes
what three parts is the broad ligament made up of? mesometrium, mesosalpinx, mesovarium
what's the mesometrium? mesentery of the uterus, largest part of the uterine tube
what's the mesosalpinx? mesentery of the uterine tube
what's the mesovarium? mesentery of the ovaries
describe the ovarian ligament fibrous cord that links the ovary to the uterus
describe the suspensory ligament of ovary ligament running from the lateral part of the pelvis to the ovary. It also carries the ovarian artery and vein
what are the ovaries? what hormones do they produce? what two types of functions do they carry out? the female gonads which produce gametes and hormones (oestrogen, progesterone, inhibin and relaxin) and carry out endocrine and exocrine functions
What shape is an ovary? almond shaped, roughly 3cm long in young women, but can often be smaller in older women (especially post-menopausal women)
what stabilises the ovaries position? It is variable in position, especially after childbirth. It's position is stabilised by the 3 ligaments: broad ligament, ovarian ligament and suspensory ligament
give the ovaries blood supply Ovarian artery (arises from the aorta at level of the renal artery), ovarian vein (drains to the IVC on the right and left renal vein on left)
where do ovary lymphatics drain? Lymphatics drain at the aortic nodes at the level of the renal vessels
How long is the uterine tube and where is it located? about 13cm long and is located in the free margin of the broad ligament – it is not directly connected to the ovary
What's the infundibulum? Funnel-shaped opening to the peritoneal cavity, fringed by finger like fimbriae
what's the ampulla? Middle section where fertilisation typically occurs. The ampulla has complex mucosal folds, each with a covering of epithelium and a core of lamina propria
What is the epithelium of the mucosa in the ampulla composed of? both ciliated columnar (cilia help beat the fertilised egg along the tube) and secretory cells (provide nutrients for the egg)
what's the isthmus of the uterine tubes? short narrowed section connected to the uterine wall
what's the uterus? The midline part of the reproductive tract where the embryo and foetus grows
give the dimensions of the uterus and what shape it is an inverted pear shape, about 7-8cm long, 5cm wide and 2.5cm thick in its resting state. Flattened from front to back
what does the cervix (neck of the uterus) project into? vagina
what's the blood supply of the uterus? uterine artery – branch of the internal iliac artery. uterine vein – drains into the internal iliac vein
what is the lymphatic drainage of the body of the uterus? para-aortic nodes
what is the lymphatic drainage of the cervix of the uterus? internal iliac nodes
histology of the uterus: perimetrium part of the visceral peritoneum composed of simple squamous epithelium and areolar connective tissue
histology of the uterus: myometrium 3 layers of the smooth muscle fibres
what is the endometrium of the uterus made up of? simple columnar epithelium, stratum functionalis (supplied by spiral arteries), stratum basalis
what is the stratum functionalis of the uterus supplied by? spiral arteries
what's the stratum basalis? the mucosa of the uterus where the gland bases are found
what's the vagina? a tubular (10cm long) canal lined with a mucous membrane that extends from the exterior of the body to the uterine cervix
what is the vaginal mucosa continuous with? that of the uterus
what is the vaginal mucous mainly produced from? uterine glands, and the mucous then drips down into the vagina
what sort of epithelium does the vagina have and why is this important? non-keratinised stratified squamous epithelium and areolar connective tissue that lies in a series of transverse folds called rugae. Important because the vagina experiences a lot of wear and tear (sex, childbirth)
what does the mucosa of the vagina contain? large stores of glycogen, the decomposition of which produces organic acids.
what does the acidic environment of the vagina do? retards microbial growth, but is also harmful for sperm
what protects the sperm from the acidic environment of the vagina? Alkaline components of semen, mainly from the seminal vesicles, raise the pH of fluid in the vagina and increase viability of the sperm
what is oogenesis ovum production
when does oogenesis begin, accelerate, and end? begins before a woman's birth, accelerates at puberty, and ends at menopause
between puberty and menopause, when does oogenesis occur? occurs on a monthly basis as part of the menstrual cycle
what do reproductive stem cells do before birth? undergo mitotic production from oogonium to primary oocytes before birth
what stage do primary oocytes reach in division, and when do they remain like this until? Proceed as far as prophase of meiosis 1, and remain quiescent until the individual reaches puberty
after puberty, what triggers the start of the ovarian cycle? the rising levels of FSH
what are some of the primary oocytes stimulated to do each month after the ovarian cycle begins? some of them are stimulated to undergo further development. Meiosis is then completed, yielding a secondary oocyte and a polar body
what happens to one or more of the secondary oocytes each month after the ovarian cycle begins? one or more of the 2ndary oocytes leave the ovary suspended in metaphase of meiosis 2 (which will only complete if fertilisation occurs)
define oogonia diploid germ cells that have the potential to develop into ova/precursor stem cells in females
oocyte cell in an ovary which may undergo meiotic division to form an ovum
follicle an oocyte surrounded by follicle cells
ovulation the release of secondary oocyte from the ovaries
polar body each of the small cells which bud off from the oocyte at the two meiotic divisions and do not develop into an ova
Prophase I of meiosis where primary oocytes pause development
Metaphase II of meiosis where secondary oocytes pause development, and remain until fertilised
when is all of a female's oogonia created when they're still a fetus
what happens 1-2months before a girl is born? Most of her 7million oocytes die, and the remaining oogonia enter meiosis I and become primary oocytes
where do primary oocytes pause their development? In prophase I after they've replicated their genomes but before they've made the first meiotic division
how long do primary oocytes stay arrested in prophase I for? over a decade until the girls first menstrual cycle
Once the girls first menstrual cycle, what then happens for the next 30-45 years Until menopause, on a monthly basis, primary occytes resume meiosis where they left off and complete their first meiotic division
what does the primary oocyte do when it completes its first meiotic division? It divides the chromosomes evenly, but there's an unequal division of cytoplasm – almost all the cytoplasm remains in one of the two daughter cells – the other is called the polar body
what does the daughter cell of the primary oocyte that receives the most cytoplasm become? the secondary oocyte – the other is the polar body (gets half the chromosomes but very little cytoplasm)
what happens to the polar body? it is not a functional oocyte – degenerates and dies
what does formation of a polar body allow the primary oocyte to do? to reduce its genome by half and conserve most of its cytoplasm in the secondary oocyte
what does the secondary oocyte have and what does this mean it has to do to become a functional ovum? still has 2 copies of each chromosome, so needs to undergo its second meiotic division in order to become a fully functional ovum
how even is the second meiotic division of the secondary oocyte? also uneven, like the first meiotic division of the primary oocyte – half the chromosomes go to another very small polar body, and the other half are retained by the ovum, along with almost all of the cytoplasm
what does the ovum reach its haploid state conserving? as much cytoplasm as possible
where does oocyte development occur and what is each oocyte surrounded by? occurs in ovaries and each oocyte is surrounded by a number of follicle cells
what happens when the menstrual cycle begins? 1, or maybe a few oocytes begin to grow larger and the follicle cells increase in number and cause the follicle to grow larger too
why, usually, does only one follicle mature? usually, some of the developing oocytes will degenerate and only leave one follicle that matures
what happens if 2 or 3 follicles mature? the birth of genetically distinct fraternal twins/triplets
what are circulating oestrogens a mix of? oestrone and oestradiol
what does the primary oocyte do as the follicle reaches maturity? completes its first meiotic division and becomes a secondary oocyte. Very soon after, the follicle ruptures, and the secondary oocyte is released into the fallopian tube even though the second meiotic division hasn't occurred yet
whats ovulation the release of the secondary oocyte from the ovaries
what happens to the oocyte once its released from the ovary? it slowly travels down the fallopian tube towards the uterus
where does fertilisation usually occur? ampulla of the uterine tube – widest part
how long is the oocyte viable for after ovulation ? up to 24 hours, otherwise it never completes the second meiotic division, so never becomes an ovum
what happens if the secondary oocyte is fertilised by a sperm? it immediately finishes its 2nd meiotic division, releases a polar body to leave only a haploid female genome in the ovum, then becomes a zygote as the nuclei of the sperm and egg fuse together
ovum female gamete
what phase does the secondary oocyte remain in until fertilisation, and then what happens? remains in metaphase II of meiosis until fertilisation, where it finishes meiosis II to produce the mature ovum (egg cell)
what is an ovarian follicle? a fluid filled structure that consists of the developing oocyte as well as other cells involved in the maturation process. during ovulation, secondary oocyte released into fallopian tube while the remainder of cells develop into corpus luteum
other than the oocyte itself, what other cell types are present in the ovarian follicles? Theca and granulosa cells – they regulate the oogenesis process and produce sex steroid hormones such as oestrogens
what produces oestradiol ovary, derived by direct synthesis in developing follicles or through conversion of oestrone
what is female reproduction regulated by interactions between? the hypothalamic-pituitary-ovarian axis and the uterus
what does the primordial follicle develop into? primary follicle
what triggers the start of the ovarian cycle? Rising levels of FSH
what does the mini pill contain? progestin
what does the combined pill contain oestrogen and progestins
when does the progesterone-only pill need to be taken? same time every day
what does the mini pill do that stops you getting pregnant? the progesterone thickens the mucous in the cervix, preventing the sperm from reaching the egg. Sometimes it may also prevent ovulation. However the continuous use of progestins alone doesn't always inhibit ovulation
what does the combined pill do to prevent pregnancies? prevents the ovaries from releasing the oocyte, they also thicken the cervical mucous and endometrial lining to prevent the sperm from reaching the egg
what mechanism means the combined pill can work? Progesterone + oestrogen have a negative feedback mechanism on the anterior pituitary gland, thus reducing the pulsatile frequency of the gonadotropin release (LH and FSH) from the anterior pituitary. The lack of LH surge mid-cycle prevents oocyte release
what STI can cause infertility in females? Chamydia – blockage of the uterine tube
what syndrome in females leads to an inability to ovulate polycystic ovary syndrome (partially developed eggs due to high androgens)
what's a common endocrine abnormality in females? polycystic ovary syndrome
give some symptoms of polycystic ovary syndrome lack of menses, weight gain, hirsutism and acne
what's the gonadotropin secretion like in polycystic ovary syndrome? out of balance because there is no negative feedback. Therefore there is continuous oestrogen production
in what condition is there continuous oestrogen production? polycystic ovary syndrome
give two other diseases that can cause infertility in females pelvic inflammatory disease (tuberculosis), endometriosis (normal uterine tissue grows outside the uterus)
maternal age and infertility? advanced maternal age
tobacco and infertility? harmful to the ovaries (interferes with oestrogen)
turner syndrome and infertility? turner syndrome – missing X chromosome – only 45 chromosomes in total
list four causes of infertility in males poor quality of semen or low quantitiy, Klinefelter's syndrome – XXY – can cause infertility, erectile dysfunction – unable to maintain an erection, obstruction (vas deferens, ejaculatory duct)
what are progestins? synthetic progestogens
give the three main features of polycystic ovary syndrome irregular periods, excess androgen, ovaries become enlarged and contain many fluid filled sacs
what is klinefelter syndrome? when boys are born with an extra chromosome – XXY – affects one in every 660 males
what two stages can the menstrual cycle be split into? a preovulatory follicular phase and a postovulatory luteal phase – corresponding phases in the endometrium are termed the proliferative and secretory phases
how long's the follicular stage? 10-14 days
what is the follicular stage characterised by? growth of dominant follicle
what is progesterone production like in the follicular stage? low
what is happening to oestrogen in the follicular phase and why? oestrogen is rising due to conversion of androgens to oestrogens via aromatase
what happens to FSH secretion during development of the secondary follicle in the follicular stage in the menstrual cycle? increases slightly, stimulating further growth of recruited follicles
what happens to circulating LH levels during development of the secondary follicle? They increase slowly, beginning 1-2 days after the increase in FSH
what do granulosa cells do during development of the secondary follicle? develop FSH, oestrogen and androgen receptors
what does the development of the theca during the development of the secondary follicle mean? Follicle gains an independent blood supply
what do recruited follicles do during development of the secondary follicle increase production of oestradiol via conversion of androgens produced in the theca interna into oestrogens by granulosa cells – aromatase
name the three layers of the follicular wall granulosa, theca interna and theca externa
what does oestradiol do to FSH and LH in the follicular stage of the menstrual cycle? stimulates LH and FSH synthesis but inhibits their secretion. FSH levels decrease, so FSH and LH levels diverge partly because oestradiol inhibits FSH secretion MORE than LH secretion
what do developing follicles produce and what does this do? the hormone inhibin, which inhibits FSH secretion but not LH secretion. Levels of oestrogen, particularly oestradiol, increase exponentially
what uterine changes are there in response to hormones in the follicular/proliferative phase of the menstrual cycle? oestrogens from the ovary act on the endometrium – thickening of the stroma, elongation of uterine glands, growth of the spiral arteries
what happens to oestradiol/progesterone levels towards the end of the follicular stage, near ovulation? oestradiol peaks and progesterone levels begin to decrease
why is there an LH surge just before ovulation? High levels of oestradiol trigger LH secretion by gonadotropes (positive feedback)
when does ovulation occur? around day 14
what happens to levels of oestradiol/progesterone after ovulation occurs around day 14? oestradiol decreases, but progesterone continues to increase
ovulation: what does the LH surge do? stimulates enzymes that initiate breakdown of the follicle wall and release of mature oocyte within about 16-32hr
how long is the luteal/secretory phase of the menstrual cycle? averages about 14 days
what happens during the luteal/secretory phase of the menstrual cycle formation of the corpus luteum from the follicle
what does the corpus luteum do? secretes primarily progesterone in increasing quantities, peaking at about 6-8 days after ovulation
what does progesterone do? stimulates development of the secretory endometrium
what happens to FSH and LH levels in the luteal/secretory phase and why? Because levels of circulating oestradiol, progesterone, and inhibin are high during most of the luteal phase so they decrease
what happens to oestradiol and progesterone levels later on in the luteal/secretory phase? decrease
what happens to the corpus luteum if implantation occurs? it does not degenerate but remains, supported by human chorionic gonadotropin that is produced by the developing embryo
what's oestradiol? a steroid hormone made from cholesterol and is the strongest of the three naturally produced oestrogens – primary female sex hormone x

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