Female Reproductive Health Flashcards
What are the two main functions of ovaries?
- Produce, mature and periodically release egg cells (ova), which lie within the ovarian follicles
- Secrete main female sex hormones, oestrogens and progesterones
What is the most biologically active oestrogen?
Oestradiol. Other oestrogens such as oestrone and oestriol are also produced by the body
What is the most biologically active progestogen?
Progesterone
What is the general role of oestrogens?
Promote the growth and proliferation of cells within female reproductive organs and other tissues
What is the general role of progesterones?
Promote the final preparation of the uterus for implantation of a fertilised ovum, as well as affecting the vagina and cervix
What are the target organs of oestrogens and progesterones?
Reproductive organs
Bladder
Urethra
Breasts
How do oestrogens stimulate target organs?
- Circulate through bloodstream until they are delivered to target cells, which they enter passively through the cell membrane
- After entering cell, binds to an oestrogen-receptor proteins within the cytoplasm
- Oestrogen-receptor complex then migrates to the nucleus, where it interacts with certain parts of the cell’s DNA to activate transcription of various different genes within the DNA
- This can then change the structure or function of the cell, depending on which genes are activated
What are some of the functions of oestrogens?
- Stimulating development of secondary sexual characteristics
- Maintaining lining of womb by suppressing FSH and LH production in pituitary gland
- Controlling puberty and menstrual cycle
- Vaginal lubrication
- Increasing bone formation and reducing bone resorption (breakdown)
What are the 3 naturally occurring oestrogens?
Oestradiol
Oestrone
Oestriol
What are all oestrogens synthesised from?
A steroid hormone called androstenedione
What is the most potent type of oestrogen?
Oestradiol, although oestriol is present in greater quantities
Where is most oestradiol produced?
In the ovaries, small amounts in adrenal glands
Where are most oestrogens produced in menopausal women and those with ovarian failure?
Adrenal glands
What cells are affected by oestrogens?
Only those with oestrogen receptors
Where are oestrogens metabolised?
Liver
What are the products of oestrogen metabolism?
Oestradiol is converted to oestriol (least potent form). Oestriol and other metabolites then excreted in urine
What is the most abundant form of oestrogen in women with non-function ovaries?
Oestrone
Production of which oestrogen increases significantly during pregnancy?
Oestriol
What does progesterone promote?
Tissue differentiation (a change in the way a tissue functions)
How does progesterone promote tissue differentiation?
Binds to a progesterone receptor within target cells which influences DNA expression within the cell, thereby influencing cell function
What increases the expression of progesterone receptors?
Oestrogen receptors
E.g. in pregnancy increased exposure to oestrogen allows progesterone to stimulate differentiation of glandular breast tissue
What does progesterone prevent?
Endometrial shedding
During development of an embryo, what do germ cells give rise to?
Oogonia - several smaller cells that proliferate by mitosis. They degenerate or differentiate to become primary oocytes by the time an individual is born
What do not form after birth?
New oocytes
What stimulates the menstrual cycle?
Gonadotrophin from the pituitary gland stimulates the meiosis of an oocyte during each menstrual cycle, stimulating the release of an ovum
What is fertilisation?
The union of egg and sperm to produce a zygote
Where does fertilisation usually occur?
Ampulla of the fallopian tube
What does seminal fluid raise the pH of the vagina to?
pH 3.5-4.5 to as much as 7.2 within 10 seconds. Allows sperm to survive
What acts as a barrier to abnormal sperm?
Cervical mucous
What aids the transport of sperm after they have entered the uterus?
Contractions of uterine muscles
What is capacitation?
Physiological maturation of the sperm. Biochemical change causes the sperm to become hyperactive and acrosome reaction becomes possible. Sperm cannot fertilise an ovum until they have remained in the reproductive tract for several hours and have been acted on by secretions
Sperm cell structure
Describe the acrosomal reaction
- Biochemical acrosome changes allow spermatozoon to bind to corona radiate of ovum
- Enzymes that can digest a pathway through the zona pellucida are released by the acrosome
- Spermatozoon penetrate the entire zona pellucida and reach ova’s cell membrane, fuses and passes to ova’s cytoplasm
- Viability of formed zygote depends on ability to avoid fusing with any other spermatozoa
- Second meiotic division
- Zygote remains in fallopian tube for 5-6 days, increasing levels of progesterone that relax smooth muscle of fallopian tube allowing zygote to enter the uterus
- Zygote transported down fallopian tube, sheds zona pellucida and attaches to uterus lining
- Once implanted in uterus lining, zygote is referred to as an embryo
What are capable of hormone production from birth?
Pituitary gland and ovaries
What is not mature at birth to stimulate hormones?
Hypothalamus, cannot yet stimulate production of gonadotrophic hormones by the pituitary gland. Gradually increases production from around age 8
What does the production of gonadotrophic hormones stimulate?
The pituitary gland to produce LH and FSH. This stimulates oestrogen synthesis by ovaries
What axis controls the levels of of oestrogen and progesterone?
Hypothalamic-pituitary-gonadal axis (find diagram)
What is an anovulatory cycle?
In first few cycles after menarche, ovaries do not release an egg
What are the two phases of the ovarian cycle?
Follicular phase
Luteal phase
What are the levels of hormones throughout the ovarian cycle?
What happens during the follicular phase?
- Oestrogen levels low - hypothalamus releases GnRH causing pituitary gland to release FSH, inducing follicular maturation. Only one matures to become a Graafian
- Graafian matures, approaches surface of ovary. It secretes increasing amounts of oestrogens until peak at day 14 and small amount of progesterone
- As follicle matures, rising oestrogens stimulate LH surge and smaller FSH release. Surge in LH = ovulation
- Post-ovulation, LH drops sharply and FSH also decreases
Graafian follicle structure
What happens during the luteal phase?
- After ovulation, ruptured follicle fills with blood (corpus haemorrhagicum). Follicular cells proliferate, clotted blood replaced with yellow, lipid-rich cells (corpus luteum)
- Corpus luteum produces progesterone, suppressing FSH and LH production
- Progesterone gradually increases until day 27 when rapidly decreases
What happens in the luteal phase if fertilisation occurs?
- Corpus luteum continues to grow until one-half volume of ovary
- Secretes enough progesterone to support early stages of pregnancy
What is the oestrogen activity in the luteal phase?
- After ovulation levels decline slightly 4-5 days
- At time progesterone levels peak, oestrogen levels also increase (lower than ovulation peak)
- Oestrogen levels then drop day 20-23
What are the three phases of the uterine cycle?
- Menstrual phase
- Proliferative phase
- Secretory phase
What happens during the menstrual phase?
Discharge of endometrial tissue and blood from uterus
What happens during the proliferative phase?
Increasing levels of oestrogens stimulate rapid growth of endometrial tissue. Glands and blood vessels grow
What three related events must occur for the endometrium to fully prepare itself to receive a fertilised ovum?
- Ovulation, followed by
- Formation of corpus luteum, which leads to
- Increased secretion of progesterone
What is the secretory phase characterised by?
Secretions from glandular tissue in the endometrium. Roughly corresponds to luteal phase
What happens during the secretory phase if fertilisation does not occur?
- Corpus luteum begins to degenerate, ceasing hormone secretion
- Unable to maintain thickened endometrium due to lack of oestrogen and progesterone
- Menstruation
What happens during the secretory phase if fertilisation and implantation do occur?
Thickened endometrium persists. Provides nutrients and allows implantation of zygote.
Corpus luteum maintained to secrete sex hormones in early pregnancy to maintain myometrium and prevent menstruation (later regulated by placenta)
What do combined oral contraceptive pills contain?
Oestrogen and progesterone
What does the mini-pill contain?
Progesterone only
What does the transdermal patch release?
Oestrogen and progesterone
What does the vaginal ring release?
Low-does oestrogen and progesterone
How do barrier methods prevent pregnancy?
Prevent sperm from reaching uterus
What do injectable contraceptives release?
Progesterone only
Given every 8-13 weeks
What does IUD contain?
No hormones