human development - fertility Flashcards
what is the oviduct?
it is the passage way from the ovaries, where eggs travel.
it is more commonly known as the fallopian tube or the uterine tube.
the eggs that travel along the oviduct will either fertilise into a zygote by a sperm, or degenerate in the body
what is the vulva?
the part of the female genitals outside the body
what is the main function of the uterus?
to nourish the developing fetus prior to birth
what is an oocyte?
an immature egg
oocytes can develop into maturity from within a follicle. These follicles are found on the outside layer of the ovaries
describe the two parts to the ovaries
- medulla: contains connective tissue and vascular system to provide the blood supply to the ovaries
- cortex: contains follicles in all stages of development. these follicles are responsible for the maturation of oocytes
what is an early primary follicle?
a follicle recruited for development, at the start of each menstrual cycle.
consists of a single oocyte surrounded by a single layer of follicular cells
how many eggs does a woman have before birth?
7 million
how many eggs does a woman have at birth?
2 million
how many eggs does a woman have when they hit puberty (first period)
0.5 million
how many eggs does a woman have when they hit their menopause?
none
what is the zona pellucida?
thin band of glycoproteins that separates the oocyte and the follicular cells. Specific proteins on the sperm will bind to complementary glycoproteins in the zona pellucida
what is the antral follicle count?
the number of follicles visible in the ovary at any given time. measured using an ultrasound scan
what is the difference between a primordial follicle cells and primary follicle cells?
- primordial: first class of follicles formed in the ovaries and consist of a single oocyte surrounded by a single layer of SQUAMOUS granulosa cells. they are in the dormant state until they receive signals otherwise
- primary: consists of a central oocyte surrounded by a layer of CUBOIDAL granulosa cells
what is the normal number of follicles in both ovaries?
10 - 20 follicles at any given time
if a woman has less than 10-20 follicles in both ovaries at any given time, what does this suggest?
that they have a lower reproductive potential
what hormone test can we use to test the ovarian reserve (egg count?)
anti-mullerian hormone test
what are the 3 phases of the ovarian cycle?
- follicular phase
- ovulatory phase
- luteal phase
what days does the follicular phase occur?
days 1-10
what days does the ovulatory phase occur?
days 11-14
describe what happens during the follicular phase
- pituitary glands secrete FSH, which signals the ovaries to grow 10-20 follicles
- only one follicle fully matures
- the other grown hormones contribute to the endocrine function of the ovary by producing oestrogen
why does FSH begin to drop?
oestrogen feedback to the pituitary glands
how many follicles can withstand the drop in FSH and why?
only one follicle can withstand the drop in FSH because they have a higher concentration of FSH receptors. The other follicles die out (atresia)
describe what happens during the ovulatory phase
- dominant follicle causes significant rise in oestrogen
- positive feedback mechanism of oestrogen causes a surge in LH
- oocyte undergoes cell division
- follicular wall thins and ruptures
- oocyte enters abdominal cavity near fimbriae of fallopian tube
- shortly before ovulation, fimbriae sweep over surface of ovaries
- oocyte enters tube and is propelled by cilia, fallopian tube contracts
what are fimbriae?
finger like projections in the fallopian tube
describe what happens during the luteal phase
- corpus hemorrhagicum structure is formed. This is a temporary structure that is formed immediately after ovulation from the ovarial follicle, as it collapses and fills with blood, which quickly clots
- this develops into the corpus luteum (yellow body)
- accumulation of lutein (yellow lipid pigment) and other lipids marks the transition to granulosa lutein cells
what happens to the corpus luteum if implantation doesn’t occur?
corpus luteum degrades to corpus albicans
what happens to the corpus luteum if fertilisation occurs?
corpus luteum persists and secretes progesterone
why is the corpus luteum important?
it is an important support for the embryo as it the source of oestrogen and progesterone
what is the function of progesterone?
maintains the uterus lining
what is the difference between an oocyte and an ovum?
- oocyte: developing egg
- ovum: mature egg
- oogenesis: differentiation of the ovum
what are the actions of oestrogen?
- stimulates oogenesis and follicular development
- stimulates growth of breasts during pregnancy
- stimulates GH secretion, which promotes bone growth in adolescence
- promotes proliferative-phase uterine conditions
- decrease output of kidneys, which promotes fluid retention
what are the actions of progesterone?
- promotes secretory-phase uterine conditions
- suppresses uterine contractile activity during pregnancy
- promotes growth of glandular tissue in breasts
- inhibits movement of the bowel
what is the normal position of the uterus?
- 80% anteflexion (flexed towards abdominal wall)
- 20% retroflexion (tilted back to the back wall)
what are the 4 sets of suspensory ligaments?
- broad ligament: side of uterus
- uterosacral ligament: behind uterus
- round ligament: front of uterus
- lateral (cardinal) ligament: behind uterus
what are the functions of the uterus?
- provides mechanical protection of the fetus
- transports sperm from the site of deposition to uterine tubes for fertilisation
- provides suitable environment for implantation of embryo and nourishment of embryo and fetus during pregnancy
- expels the mature fetus at the end of pregnancy
what is the menstrual cycle?
series of cyclic changes in the endometrium in response to changes in levels of ovarian hormones
describe what happens on days 1-5 of menstrual cycle
- menstrual phase
- functional layer of endometrium becomes detached from uterine wall and causes bleeding (menses)
describe what happens on days 6-14 of menstrual cycle
- proliferative phase
- FSH and LH increase
- follicular development causes increase in oestrogen
- endometrium begins to proliferate and thicken; tubular glands and spiral arteries form
- stimulation of progesterone receptors synthesis in endometrial cells
describe what happens on days 13-14 of menstrual cycle
- late proliferative phase
- time of ovulation
- glands become long and tortuous due to active growth
- storm gradually becomes oedematous (getting nutrients from endometrium)
describe what happens on days 15-22 of menstrual cycle
- secretory phase
- progesterone levels rise
- enlargement of glands which begin secreting mucus and glycogen, in preparation of implantation of fertilised ovum
- increased fluid in stroma
what are the segments of the uterine tube?
- also known as the fallopian tube or oviduct
- muscular
- infundibulum: consists of fimbriae. inner surfaces contain cilia
- ampulla
- isthmus: lies next to the uterine body
how many layers does the uterine tube consist of?
4 tunicas / layers
what are the 4 tunicas/layers of the uterine tube?
- tunica serosa
- tunica muscularis
- tunica submucosa
- tunica mucosa
what are the 3 issues that can lead to female infertility?
- issue with eggs
- issue with transport
- issue with implantation
what is anovulation?
occurs when an egg is not released from the ovary during your menstrual cycle.
chronic anovulation is a common cause for infertility
what are the main causes for anovulation?
- hypothalamic dysfunction
- pituitary dysfunction
- thyroid dysfunction
- ovarian failure
- polycystic ovarian syndrome (most common cause)
what is the lifestyle intervention required for those with polycystic ovarian syndrome?
- weight loss
- this restores ovulation
what medical treatment can be used to treat polycystic ovarian syndrome?
- ovulation induction drugs
- clomiphene citrate
what is clomiphene citrate?
- ovulation induction drug
- used to treat women with irregular or absent ovulation, but have normal basal levels of estradiol
- stimulates endogenous FSH production
- FSH stimulates ovulation
what are the most common causes for hyperprolactinemia?
- prolactin-secreting pituitary tumour
- use of psychiatric medication
what should all women diagnosed with hyperprolactinemia be tested for?
- hypothyroidism
- pregnancy
what can be used to stimulate ovulation in women with hyperprolactinemia?
- dopamine agonists
- directly suppresses prolactin secretion by tumour
- increases GnRH secretion, which stimulates FSH and LH release
- therefore stimulating ovulation
what is the ovarian reserve?
- the number and quality of follicles in the ovaries at any given time
what is the effect of age in pregnancy?
- decrease pregnancy rate
- increase in miscarriage rate
what are the reasons for decreased fertility?
- germ cells in the female are not replenished during life
- decrease in number of oocytes from birth
- quality of existing oocytes decrease with age
- on average, intercourse frequency decreases with age
what are the effects of age in gonadal function in males?
- they do not experience gamete exhaustion
- they do not experience a sudden fall of in fertility
- they DO experience senescent (deterioration due to age) changes in reproductive potential
what is the menopause?
- last menstrual period
- diagnosed after 1 year of amenorrhea (no periods)
what are the FSH and estradiol levels in menopausal women?
- FSH is high (30 or higher)
- estradiol is low (below 30)
what is the climacteric?
- the period of time around the last menstrual period
- also known as the perimenopause
- body makes transition into menopause
when can you make a menopause diagnosis?
- age over 45 years
- when the woman has not had her period for a year or more
what symptoms can suggest perimenopause?
- vasomotor symptoms (hot flashes and night sweats)
- irregular bleeding
what happens to oocyte numbers, oestrogen and FSH levels?
- oocyte numbers decline
- oestrogen levels decrease therefore ovulation terminates
- FSH levels increases as their no feedback mechanism from oestrogen to the hypothalamus to cease GnRH production
what are the symptoms of menopause?
- reduced libido
- vasomotor symptoms (hot flushes and night sweats)
- headaches
- leg cramps
- mood changes
- urogenital symptoms (ie. pain during urination)
- palpitations
what is the average age of menopause in the UK?
52 years
what are the long term effects of menopause?
- osteoporosis (oestrogen is really important for maintenance of bone mass. prevents bone resorption by osteoclasts, and promotes bone formation by osteoblasts)
- cardiovascular disease
- vaginal dryness or atrophy (thinning, drying and inflammation)
- Alzheimer’s
what are the hormonal treatment options for postmenopausal women?
- oestrogen (reverse symptoms)
- progesterone (important to protect endometrium if uterus is present)
- testosterone (increases sexual desire and overall energy level)
what are the non-hormonal treatment options for postmenopausal women?
- lifestyle measures
- SSRI’s (selective serotonin re-uptake inhibitors) to treat hot flushes
- alpha 2 agonists (clonidine) to reduce hot flushes and headaches
- replens (long lasting vaginal moisturiser to alleviate dryness symptoms)
- gabapentin (anti-seizure medication that relieves hot flushes)
what are the benefits of hormonal replacement therapy for postmenopausal women?
- alleviates symptoms
- protects bones
- reduces incidence of colorectal cancer
- improves quality of life
what are the risks of hormonal replacement therapy for postmenopausal women?
- endometrial cancer
- breast cancer
- venous thromboembolism (blood clot forms in vein)
what is premature ovarian insufficiency?
- ovaries stop functioning as they should before the age of 40
- amenorrhea for 4 months
- FSH levels >30 on 2 occasions, 6 weeks apart
what is the treatment available for premature ovarian insufficiency?
- hormone replacement
- fertility treatment
- psychological support
what causes POI?
- most cases are idiopathic
- the cases with causes identified are usually, autoimmune or cytogenetic
what is the function of the testicles?
- sperm production
- production of androgens (mainly testosterone)
what are the testicles divided into?
- divided into lobules by dense fibrous tissue
- in each lobule, there is seminiferous tubules, lined by multiple layers of cells
- in between lobules, there’s interstitial cells (leydig cells)
describe the structure of a seminiferous tubule
each tubule has a lumen in the centre surrounded by sperm producing cells
what are the 2 types of sperm producing cells?
- spermatogonial stem cells: sperm production. they differentiate into spermatogonia which remain dormant until puberty
- Sertoli cells: support, nutrition, protection, secretory and excretory
what are spermatogonial cells always in contact with?
basal lamina of the tubule
what is the difference between type A and type B spermatogonial cells?
type A:
- rounded nucleus with very fine chromatin grains
- they are stem cells which divide to form new generations of type A and type B spermatogonial cells
type B:
- rounded nuclei with chromatin grains of variable size
- do not function as stem cells
what do type B spermatogonia give rise to?
- primary spermatocytes
- secondary spermatocytes
- spermatids
- spermatozoa
what is spermiogenesis?
the process of spermatids becoming spermatozoa
when does spermatogenesis begin?
puberty
how long does spermatogenesis take?
whole cycle takes 72 days
what happens to the number of chromosomes during spermatogenesis?
diploid to haploid (half the number of chromosomes)
what processes occur during spermatogenesis?
mitosis followed by meiosis
when does spermiogenesis occur?
occurs when it reaches haploid spermatid stage
what happens in spermiogenesis?
repackaging of spermatid to mature sperm fit for function
what is the function of leydig cells?
to produce androgens, mainly testosterone
what are the functions of testosterone?
- libido / sexual desire
- to stimulate Sertoli cells and spermatogenesis
- to increase bone and muscle mass
what hormones do the leydig cells produce?
- inhibin
- ABP
- AMH
- growth factors
what are the stages of sperm transport?
- ejaculation
- cervix
- uterus and tubes
- ampulla
what happens during ejaculation of sperm transport?
deposition of sperm in vagina
what does FSH release do?
FSH stimulates the Sertoli cells to produce ABP and inhibin. ABP binds to testosterone, which stimulates spermatogenesis. Inhibin feeds back to the hypothalamus and pituitary to suppress FSH secretion
what does LH do?
stimulates the Leydig cells to produce testosterone. Testosterone feeds back to the pituitary to suppress LH secretion
what happens in the cervix of sperm transport?
mucous barrier and crypts act as sperm reservoirs to protect it from the acidity of the vagina
what is sperm capacitation?
- cholesterol loss and calcium influx
- required to ‘switch on’ the sperm and make it hyperactive
- this takes 4 hours after ejaculation
- this is important so that the sperm moves quickly across the acidity of the vagina and immune system
what is polyspermic penetration?
penetration of the oocyte by 2 or more spermatozoa (sperm)
what happens in the ampulla portion of the tube in sperm transport?
fertilisation
what is the acrosome reaction?
- when sperm meets oocyte, sperm interacts with ZP3 protein on outer membrane of oocyte
- this leads to the release of sperm digestive enzymes: hyaluronidase and acrosin
- this helps the sperm to penetrate the oocyte
what happens in the uterus and tubes during sperm transport?
mild contractions to properly the sperm towards the egg
how does the oocyte prevent polyspermic penetration?
they release cortical granules
how does excessive amounts of testosterone affect sperm production?
- inhibits FSH and LH secretion
- interrupts spermatogenesis
what is Klinefelter syndrome?
- absence / interruption of spermatogenesis
- 47XXY chromosomes (extra X chromosome)
what environmental factors affect sperm production?
- air pollution
- radiation
- smoking
- food chain pollution
what is the difference between mosaic and non-mosaic Klinefelter syndrome?
- mosaic: little sperm production; need to retrieve sperm from seminiferous tubule surgically
- non mosaic: no sperm production
what are the symptoms of Klinefelter syndrome?
- reduced facial and body hair
- small testes
- taller than average height
- feminine fat distribution
- development of breasts
- osteoporosis
what is Kallman syndrome?
- absence / interruption of spermatogenesis
- this is due to absence of GnRH production, which means little FSH and LH and therefore lack of sperm production and testosterone
- treated using hormone replacement therapy
what are the applicable grounds in which an abortion may take place?
- pregnancy hasn’t exceeded 24th week and continuation with pregnancy would involve greater risk to the health, life or mental well-being of the pregnant mother or to any other existing children
- there’s a substantial risk of the child were it born, to suffer from such physical or mental abnormalities
what change has been made regarding medical termination of early pregnancy (first 10 weeks)?
can now be done at home.
it may be self-administered by the pregnant woman
what is the difference between the gestational age and embryonic age?
gestational: time 0 = first day of last menstrual period
embryonic: time 0 = fertilisation
what days does implantation take place?
days 6/7
what day is implantation completed by?
day 10 (4 days prior to expected menstrual period)
what are the 3 stages of implantation?
- apposition
- attachment
- penetration
what are the effects of oestrogen and progesterone on the endometrium?
oestrogen: primes the endometrium
progesterone: maintains the endometrium
what changes occur in the endometrium, to make it responsive to the embryo?
- secretory changes
- becomes rich in glands, capillaries and stroma
- this is induced by oestrogen and progesterone
what happens in apposition in implantation?
- occurs in the endometrial cavity
- microvilli on the surface of blastocysts line up with the pinopodes (villi) on the endometrium
what enzymes are involved in prostaglandin synthesis?
COX1 and COX2
what is a trophoblast?
cells forming the outer layer of a blastocyst, which provides nutrients to the embryo and becomes a large part of the placenta
what are the 2 layers of a trophoblast?
- inner layer: mononuclear cells, also known as the cytotrophoblastic layer
- outer layer: multi-nucleated cells, also known as the syncytiotrophoblastic layer. involved in the synthesis of HCG, which is important to feedback to the corpus luteum and continue producing progesterone
what is HCG composed of?
- glycoprotein
- alpha and beta subunit held together by ionic and hydrophobic forces
- alpha subunit is identical to LH, FSH and TSH
- beta subunit is unique and is tested for in pregnancies
what is the blood supply to and from the baby?
- 2 umbilical arteries and 1 umbilical vein running through the umbilical cord
- the umbilical arteries carry deoxygenated blood away from the baby
- the umbilical vein carries oxygenated blood from the placenta, to the baby
what is the intervillous space?
pools of maternal blood in the placenta
what is the placental membrane?
thin membrane in the placenta that forms the barrier between the maternal and fetal blood. diffusion can occur across this membrane
what are the physiological events required for conception?
- ovulation
- spermatogenesis
- intercourse
- ejaculation
- fertilisation
- implantation
define infertility
a woman of reproductive age, who has not conceived after 1 year of unprotected sexual intercourse
what can cause infertility?
- male factor
- anovulation (ovaries do not release an oocyte during the menstrual cycle, therefore ovulation does not take place)
- tubal factor (fallopian tube damage)
- unexplained other factors
