Female Reproductive System Flashcards
what are the ovaries?
- female gonads
- responsible for producing haploid gametes
- attached to wall of uterus
- suspended from side of uterus by ovarian ligament and mesovarium ligament to keep ovaries in correct position
what is the fallopian tube?
- oviduct is an open cavity that starts the fallopian tube
- finger-like projections called fimbriae form a cup over the ovary to collect the ova and project it down the fallopian tube
- infundibulum is the first section of the tube
- ampulla is the curving section of the tube
- isthmus connects fallopian tube to uterus
what is the uterus?
- thick-walled structure with cavity in centre
- fertilised ovum is implanted here to the embryo can develop
what are the functions of the female reproductive system?
- produce haploid gametes: ova
- facilitate fertilisation of ova by sperm
- provide a site of implantation of the fertilised egg
- provide physical and nutritional needs throughout gestation period
- nurture the neonate after birth by producing milk
what are the structures of the ovaries?
cortex: outer zone with germinal epithelial layer containing oocytes
inner medulla: blood vessels and lymph
- supporting tissue for developing oocytes
follicle: where oocytes are enclosed
- as follicle matures, it forms other structures in a continuous process
follicular cells: secrete steroid hormones
what are the two types of follicular cells and what hormones do they secrete?
- granulosa cells: secrete 17-beta-oestradiol (oestrogen)
- theca cells: secrete progesterone
hormones have endocrine and paracrine function ova development, uterus, breasts and bone
what is the role of the fallopian tubes?
- transport egg from ovary to uterus
- infundibulum with fimbriae help capture egg as it is released from ovary
- smooth muscles: inner circular muscle layer and outer longitudinal muscle layer for peristalsis
- highly folded mucosa which is ciliated and contains secretory cells for helping movement of ova
what are the 3 walls of the uterus?
- perimetrium: external serosa
- myometrium: thick inner muscle layer
- endometrium: changes over course of menstrual cycle
what are the components of the endometrial wall of the uterus?
- simple columnar epithelium
- compound tubular glands which are highly branched
- spiral arteries which move between glands and connective tissue of the lamina propria
- supporting tissue contains leukocytes and macrophages to form the stroma
- basal layer zona basalis: static layer
what is the functional layer of the uterus?
- endometrial layer can vary along cycle
- sheds during menses and builds thicker again
- when thick layer, fertilised egg is implanted
- if no fertilised egg is implanted, the thick layer sheds
what is the cervix?
- cervical canal connects uterus to vagina
- interior os and exterior os at its margins
- cervical glands secrete mucus to prevent microbes from reaching uterus
what is the vagina?
- birth canal (8-10cm)
- thin distensible wall with 3 layers:
- adventitia on outside
- muscularis: thick muscular layer
- mucosa: inner layer of stratified squamous epithelium rich in glycogen
- glycogen is fermented by bacteria to lactic acid to produce pH 3.5-4 which inhibits pathogens
- contains antigen-presenting dendritic cells
what are the two female cycles?
- ovarian
2. endometrial (menstrual)
what is the neuroendocrine control of the female cycles?
- hypothalamic-pituitary-gonadal axis drives menstrual cycle
- hypothalamic neurons release gonadotropin-releasing hormone (GnRH) once per hour
- hypophyseal portal system connects hypothalamus to anterior pituitary
- metabotropic GnRH receptor increases IP3, DAG, Ca2+ and exocytosis of FSH and LH
what is the hypothalamic-pituitary-gonadal axis?
- neurons in hypothalamus release GnRH
- GnRH binds to receptors in gonadotrophs within the anterior pituitary
- pituitary secrets FSH and LH to stimulate the ovary
what are the actions of FSH and LH on the ovary?
- theca release progesterone
- feedback to pituitary and hypothalamus
- positive/negative feedback - granulosa release oestrogen
- feedback to pituitary and hypothalamus
- positive/negative feedback
- inhibin negatively feeds back at anterior pituitary
- activin positively feeds back to antierior pituitary
how are the ovarian hormones produced?
- theca cells synthesise and secrete progesterone from cholesterol
- LH induces synthesis of progesterone - androstenedione diffuses from theca to granulosa cells
- granulosa cells convert testosterone to oestrogen via enzyme aromatase
- FSH and LH both stimulate this pathway
what are the actions of oestrogen and progesterone?
- develops ovum
- maintains corpus luteum which is derived from follicles which surround the ovum
- maintains pregnancy
what does the hypothalamic-pituitary axis control depend on?
- it is controlled by positive or negative feedback depending on the phase
how is the hypothalamic-pituitary axis controlled in the follicular phase?
- hypothalamus releases GnRH
- GnRH stimulates anterior pituitary to release FSH and LH which have positive effect on ovary
- oestrogen is released which has negative feedback on anterior pituitary and hypothalamus
how is the hypothalamic-pituitary axis controlled in the midcycle phase?
- feedback of oestrogen to hypothalamus is negative throughout cycle, except prior to ovulation when it is positive
- oestrogen now has a positive feedback on anterior pituitary and hypothalamus during ovulation
how is the hypothalamic-pituitary axis controlled in the luteal phase?
- progesterone secreted from ovary becomes major hormone of negative feedback to the anterior pituitary and hypothalamus
how do the ovarian and endometrial cycles overlap?
- during the follicular phase of ovarian cycle, the endometrial cycle is in the proliferative phase as the endometrial lining thickens
- after ovulation, endometrial cycle transitions to secretory phase
- in follicular phase, ovum is contained in a developing follicle
- during ovulation when the egg is released, the follicle is termed the corpus luteum and enters the luteal phase
how do hormones change across the ovarian and endometrial cycles?
- ovarian cycle is governed by FSH which peaks in day 12 and causes proliferation of theca and granulosa cells
- surge of oestrogen and progesterone after follicular stimulation
- critical level of oestrogen causes a switch to positive feedback in H-P axis which upregulates LH secretion from pituitary, leading into the secretory phase
what do oestrogen and progesterone control in the uterus?
- endometrium thickening
- feedback regulation of FSH and LH from anterior pituitary
- follicular phase: oestrogen causes cervical mucus to become copious, water and elastic to form channels in the follicular phase for sperm to be propelled through
- secretory phase: progesterone decreases and mucus thickens
what does oestrogen stimulate in the proliferative phase of the endometrial cycle?
- secretion of oestrogen is dominant in this phase
- stimulates growth of endometrium, glands, stroma and elongation of spiral arteries
what does progesterone stimulate in the secretory phase of the endometrial cycle?
- following ovulation, the secretory phase is dominated by progesterone
- endometrial proliferation slows and thickness decreases
- glands accumulate with glycogen vacuoles and increase in mucus secretion
- stroma becomes swollen
- spiral arteries elongate and coil
- if there hasn’t been fertilisation, cycle ends in menses
what is menses?
- when the endometrial wall breaks down
- period
what are the different kinds of hormonal contraceptives?
oral contraceptive pill with different combinations:
- oestrogen and progesterone
- progesterone-only minipill
- monophasic or fixed-combination
- multiphasic or varying-dose
how do hormonal contraceptives work?
- feedback directly to hypothalamus to decrease stimulation of GnRH
- negative feedback on anterior pituitary to inhibit FSH/LH release and prevent ovulation
- low FSH is insufficient to stimulate folliculogenesis
- lack of LH surge inhibits ovulation
- progestin increases thickness of cervical mucus to prevent sperm entering fallopian tube
how does the morning after pill work?
- alters endometrium
- prevents the womb lining from preparing to receive an egg
- even if an egg has been released, it cannot embed itself into the lining - influences cervical fluid
- thickens cervical mucus to prevent sperm from reaching the uterus - stops ovulation
- prevents release of an egg from the ovaries by making the body think it has already occured
how can the morning after pill be used?
- higher dose inhibits ovulation and interferes with implantation
- can be used as postcoital contraceptive
what are the steps in fertilisation?
- gametes transported to ampulla of oviduct
- sperm move into the oviduct
- sperm acrosomal reaction
- oocyte activation
how are gametes transported to the ampulla of the oviduct during fertilisation?
- oocyte is surrounded by granulosa cells and is helped to be moved by cilia/smooth muscles
how do sperm enter the oviduct during fertilisation?
- sperm move via flagellum, contraction of smooth muscle in uterus, fallopian tube contractions and cervical mucus channels which enable propelling
- only 50-100 sperm reach the ampulla of the oviduct
what is the sperm acrosomal reaction during fertilisation?
- penetration of granulosa to reach the glycoprotein layer
- sperm attach to layer ZP3 binding proteins on zona pellucida
- acrosome secretes hydrolysing enzymes to penetrate zone pellucida and move in
how are oocytes activated in fertilisation?
cortical reaction:
- increase in intracellular Ca2+ in oocyte triggers second meiotic division
- 2 polar bodies are formed, one from first division and once from second
- cortical granules contain enzymes and fuse with membrane
- exocytosis of enzymes act on zona pellucida to harden layer and destroy ZP receptors to prevent entry of other sperm: prevents polyploidy
what completes fertilisation?
- fusion of haploid pronuclei to form diploid zygote
what is pre-implantation?
- zygote undergoes cleavages until after 3 days it forms a Morella, a solid mass of cells kept in oviduct by contraction of isthmus until uterus is ready
- when uterus is ready for implantation, cilia in oviduct transport Morella to uterus
- when free-floating in uterus, Morella becomes a blastocyst,
what is a blastocyst?
- a hollow ball of cells with a fluid-filled cavity
- lined with a trophectoderm layer which transforms to a yolk sac
- contains an inner mass cell accumulating on one side which later forms the embryo (6 days)
what occurs during implantation?
- endometrium reception of blastocyst during secretory phase (high progesterone levels)
- blastocyst invasion promotes stromal cells to trigger predecidualisation
- decidual cells spread across surface of endometrium to form zona compactum
- contains an underlying zona spongiosa
what are the steps in the invasion of the endometrium (implantation)?
- Hatching: zona pellucida layer degenerates
- apposition: zona pellucida has completely cleared
- formation of a more compact zone of cells with underlying spongy cells
- blastocyst contains trophoblast layer and inner cell mast - adhesion: mediated by intracellular integrins
- invasion: blastocyst invades endometrial layer
what are blastocyst trophoblastic cells?
- contains inner cytotrophoblast
- contains outer syncytiotrophoblast
what is the placenta?
- life support system of embryo
- provides oxygen and nutrients
- collects waste material
- dominant mode of transport from 9 weeks after fertilisation
- 120 spiral arteries bring pulsatile blood
- intervillous space reduce force and velocity to allow time for exchange
how is the placenta formed?
- syncytiotrophoblast lacunae merge/fuse and fill with maternal blood
- cytotrophoblast and syncytiotrophoblast form villi/microvilli projecting into maternal blood
what separates foetal and maternal blood in the placenta?
- foetal capillary endothelium
- mesenchyme: additional cells within structure
- cytotrophoblasts
- syncytiotrophoblast
what substances are transported from maternal blood to foetal blood?
- glucose: facilitated diffusion
- amino acids: secondary active transport via cotransport with another molecule
- vitamins: active transport as vitamins are needed in high concentrations
- large molecules are transported by receptor-mediated endocytosis: LDL, hormones and antibodies
what substances are transported from foetal blood to maternal blood?
- waste urea
- creatinine
- both via diffusion
how is oxygen transport from maternal to foetal blood facilitated?
- oxygen exchange is facilitated by higher affinity of foetal Hb for O2
- foetal Hb has a gamma-globin chain to replace one of the beta-globin chains, causing higher affinity for O2
- at same partial pressure, foetal Hb has 45% affinity, adult Hb has 20%
how do hormones change in trimester 1?
- placental HCG is released from trophoblast which has similar effect as LH and restores corpus luteum
- corpus luteum secretes oestrogen and progesterone to support the endometrium and prevent menses
how do hormones change in trimester 2-3?
- placenta becomes primary hormone source of HCG
- human placental lactogen (HPL) coordinates fuel economy: converts glucose to fatty acids for energy, stores ketone and develops mammary glands
- progesterone is synthesised from circulating cholesterol
- oestrogen is involved in placenta-foetal synthesis
how is progesterone secreted into maternal system and to the foetus?
- cholesterol derived from maternal system crosses into placenta to form pregnenedione
- pregnenedione diffuses back into maternal system and foetus
how is estriol secreted into the maternal system?
- cholesterol comes from maternal system and crosses into placenta to form pregnenedione
- pregnenedione crosses into foetus which contains enzymes to synthesis intermediatory steps
- pregnenedione crosses back into the placenta and is converted into estriol which crosses back into maternal system
what is parturition stage 0?
- quiescence: insensitive to hormones which trigger contraction
- prelude to birth from contraception to intitation of parturition
- makes up 95% of gestation (32+ weeks)
- uterus is relaxed and insensitive to uterotonic hormones
- myometrium grows and leads to distension which can cause Braxton-Hicks contractions in preparation for birth
- progesterone suppresses myometrial contractions
what is parturition stage 1?
- preparation for birth (prior to labour)
- foetal H-P adrenal axis causes increase in cortisol, which causes increase to oestrogen:progesterone ratio
- oestrogen increases contractility and stimulates prostaglandin (PG) release
- PG promotes formation of gap junctions to increase communication between muscle cells
- PG causes thinning and dilation of cervix
- gene expression: contraction-associated proteins (CAPs) e.g. oxytocin and PG
- cervical gene expression: enzymes to hydrolyse collagen matrix
what is parturition stage 2?
process of birth:
- increase PG and OT levels for myometrial contraction and cervical dilation
- increased myometrial connectivity
- PG and OT increase myometrial connectivity
- positive feedback: Ferguson reflex by neuroendocrine regulation of OT and uterine contraction stimulating more PG
what are the stages of labour and delivery?
- dilation: placental relaxation
- expulsion
- placental: separation from decidua
what is parturition stage 3?
recovery from birth: involution
- haemostasis: vasoconstriction of spiral arteries by OT contracting the myometrium, so less chance of haemorrhage
- pre-pregnancy hormone levels
- decrease in placental oestrogen
- myometrial atrophy and regression of uterine vasculature
- cervix remodelling
- re-establishment of fertility and endometrial cycle in 3-5 months
what is the secretory unit of the breast in lactation?
alveoli:
- contain contractile myoepithelial cells to aid milk expulsion and adipose tissue
what is first milk?
colostrum:
- high fat and protein but low volume
- antibodies for within the GI tract
what are the components of milk lactation?
- fat emulsion in aqeuous solution
- lactose
- protein: lactalbumin and casein
- cations and anions
how is lactation controlled by hormones during pregnancy?
- oestrogen and progesterone stimulate breast growth
- oestrogen stimulates prolactin (PRL): major milk production hormone
- PRL stimulates breast development and lactogenesis
- in pregnancy oestrogen and progesterone inhibit PRL action on the breast
what is the postpartum hormone action on lactation?
- mammogenic: promotion of cell proliferation by oestrogen
- lactogenic: promote milk production by PRL
- galactokinetic: promote myoepithelial contraction by OT
- galactopoietic: maintain milk production by PRL and cortisol
how do neuronal and hormonal systems interact to enable lactation?
suckling is the most powerful stimulus:
- inhibits dopamine release from hypothalamus
- PRL is released from anterior pituitary to produce milk
- OT is released from posterior pituitary to release milk
- downregulates GnRH release to inhibit ovarian cycle
