deck_17174947 Flashcards
WHAT ARE THE TWO CYCLE within the female reproductive cycle
1) OVARIAN CYCLE
2) UTERINE CYCLE (menstrual cycle)
1) Ovarian cycle =
Events that occur during & after OOCYTE MATURATION
Focused on the changes in the follicle
—> Follicular phase and luteal phase
what are the phases in the OVARIAN CYCLE
a) follicular phase
b) ovulation
c) luteal phase
2) UTERINE CYCLE (menstrual cycle) =
Changes in endometrium in preparation of fertilized ovum
Regulation of the ovarian AND Uterine cycles
how regulated?
controlled by cyclical changes in hormones
All coordinated by GnRH from the hypothalamus
are two cycles (ovarian and uterine) interdependent?
YES
The two cycles must operate synchronously for proper reproductive function
The regulation of the ovarian (AND UTERINE) cycle(s) begins with …
1) Begins with the release of gonadotropin-releasing hormone (GnRH)
where is GnRH released from?
From hypothalamus
what does GnRH cause?
Causes production and secretion of FSH
Causes production (not secretion) of LH
Cyclical rise in GnRH creates (OVARIAN) cycle
DAY 0 of ovarian cycle
= GnRH levels begin to rise
DAY 0 to DAY 14 (FOLLICULAR PHASE)
= GnRH levels rise steadily until just before day 14
—> GnRH causes LH/FSH levels to rise SUDDENLY (as opposed to gradual rise of GnRH)
after DAY 14, till DAY 28 (LUTEAL PHASE)
= GnRH levels gradually begin to decrease to levels at day 0
= LH & FSH sharp DECLINE shortly after sharp rise.
—-> LH/FSH back to previous decreased levels shortly after day 14
LH levels
in FOLLICULAR PHASE (day 0-14)
—-> LH levels are slightly above base level
—-> they gradually reduce (as tertiary follicles develop, FSH levels decline as a result of negative feedback effects of INHIBIN)
2) Follicular phase of the ovarian cycle
TERTIARY FOLLICLES are formed via FSH stimulation
(Follicular phase begins when FSH stimulates some follicles to become TERTIARY FOLLICLES)
how do FSH levels decline? (around day 14)
As (TERTIARY) follicles develop, FSH levels decline
What causes FSH to decline?
INHIBIN
(as a result of negative feedback effects of INHIBIN)
what do developing follicles secrete?
ESTROGENS
How is LH secretion regulated?
LOW LEVELS of estrogens INHIBIT LH SECRETION
Inhibition DECREASES as estrogen levels climb (released by developing follicles)
I.e.
ESTROGENS INCREASE LH SECRETION
(whereas GnRH is responsible for LH PRODUCTION)
estrogen and basal body temperature
Estrogen decreases basal body temperature about 0.3ºC (0.5ºF) lower than during the LUTEAL PHASE
in which phase does FSH (follicle stimulating hormone) stimulate follicles to become TERTIARY follicles?
FOLLICULAR PHASE
3) OVULATION (OVULATORY PHASE)
GnRH and elevated estrogen levels stimulate LH secretion
Massive surge in LH on or around day 14 triggers:
Completion of meiosis I by the primary oocyte
Forceful rupture of the follicular wall
Ovulation (~9 hours after LH peak)
Formation of CORPUS LUTEUM
when does luteal phase begin?
Luteal phase begins after ovulation
—> AROUND day 14
Mittelschmerz
pain from follicular swelling, ovarian wall rupture, small amount of blood leaking into pelvic cavity surrounding ovulation
4) Luteal phase of ovarian cycle
..
the CORPUS LUTEUM secretes …
PROGESTERONE
Corpus Luteum secretes PROGESTERONE
—> “Stimulates and sustains endometrial development”
as progesterone levels INCREASE, estrogen levels ____, which causes ____.
FALL
—> Suppresses GnRH
What happens if pregnancy does not occur at this stage?
corpus luteum lasts 2 weeks
stops secreting hormones & degenerates into CORPUS ALBICANS
What happens if pregnancy does occur at this stage?
Early cells of the placenta produces hCG (human chorionic gonadotropin)
it rescues corpus luteum to keep it alive & it continues secretory functions
RECAP of events during OVARIAN (& uterine) cycle
1) Release of GnRH
—> leads to production/secretion of FSH @ anterior pituitary
—> leads to PRODUCTION (not secretion) of LH @ anterior pituitary
FSH @ ovary causes
a) ovarian follicle development (tertiary follicle)
b) inhibin secretion (which causes FSH to decline = NEG FEEDBACK)
c) Estrogens secreted (causes LH secretion)
secreted LH causes ____ in ovary
a) Meiosis 1 completion
b) Ovulation
c) Corpus Luteum formation —> which secretes PROGESTERONE (which stimulates ENDOMETRIAL development)
high progesterone —> low estrogen
—> supresses GnRH
NOTE FOLLICLE STAGES DURING OVARIAN CYCLE
recall that FOLLICULAR phase begins when FSH stimulates some follicles to become TERTIARY FOLLICLES
FOLLICULAR PHASE = tertiary follicle development
@ day 14
= OVULATION
(Ovum released)
after day 14 (LUTEAL PHASE)
= corpus luteum formation
—> to mature corpus luteum
—> CORPUS ALBICANS forms if pregnancy DOES NOT occur
IF PREGNANCY DOES* OCCUR, which hormone is formed by which structure
EARLY CELLS OF PLACENTA PRODUCES hCG (human chorionic gonadotropin)
ovarian hormone levels during the ovarian cycle
at day 0
= estrogen > inhibin > progesterone
= all three levels low
towards day 14
= estrogen rises above the other 2
= inhibin also has slight rise (later, just before day 14)
RECALL:
FSH causes estrogen and inhibin to rise
—> inhibin the causes FSH to decline
—> estrogens decline occurs with Progesterone RISE
AFTER DAY 14:
= estrogen levels begin to DECLINE
= progesterone levels RISE with estrogen DECLINE
basal body temperature during ovarian cycle
slightly lower during FOLLICULAR PHASE of Ovarian cycle
small dip @ day 14
then rise slightly high during LUTEAL PHASE
ENDOMETRIAL CHANGES DURING UTERINE CYCLE
.. (will outline after slides on review of hormones)
Follicle Stimulating Hormone (FSH)
Source
ANTERIOR PITUITARY
FSH
Stimulation
GnRH stimulates FSH production/secretion
GnRH released from HYPOTHALAMUS
FSH
Inhibition
inhibin from granulosa cells and corpus luteum, estrogen
—> FSH stimulates INHIBIN, which inhibits FSH
FSH
function
initiates follicle growth
stimulates ovarian follicles to release ESTROGENS and INHIBIN
Luteinizing hormone (LH) is from
source: from Anterior Pituitary
LUTEINIZING hormone promotes formation of corpus LUTEUM
..
LH production is via ____ and secretion is via ____
stimulation: production by GnRH, secretion by ESTROGEN and GnRH
LH inhibition is via
inhibition: INHIBIN from granulosa cells and CORPUS LUTEUM
LH functions
functions:
—> triggers ovulation
—> promotes formation of corpus luteum
—> stimulates corpus luteum to produce ESTROGENS, PROGESTERONE, RELAXIN & INHIBIN
Estrogen is made from ____
cholesterol
estrogen, THREE types
estradiol, estrone, estriol
estrogen, source
granulosa cells, theca cells, then corpus luteum
granulosa cells
“Granulosa cells are a type of cell in your ovaries that produce hormones including estrogen and progesterone. Hormones released from the base of your brain (anterior pituitary) control the numbers and function of granulosa cells.”
theca cells
“Theca cells are the endocrine cells associated with ovarian follicles that play an essential role in fertility by producing the androgen substrate required for ovarian estrogen biosynthesis.”
granulosa cells vs theca cells
“Granulosa lutein cells are closest to the central connective tissue core of the corpus luteum and produce progesterone. Theca lutein cells are smaller cells than the former with dark-staining nuclei.”
“These cells produce estrogen and are located peripherally between the folds of the granulosa lutein cells.”
how are granulosa cells / theca cells related to CORPUS LUTEUM
“The surge also causes the luteinization of thecal and granulosa cells, forming the corpus luteum,”
—> somewhat related structures – the same? or in very close proximity?
Estrogen, Stimulation? (what stimulates its release?)
via FSH/LH
Estrogen function
Triggers SECRETION of LH (LH surge)
develop & maintain secondary sex characteristics
—> adipose deposit: breasts, hips, mons pubis
—> broad pelvis
—> hair growth on head, pubic, axillae
Increases PROTEIN ANABOLISM (?)
DECREASES osteoclast activity
PROGESTERONE – made from?
Made from cholesterol
progesterone – SOURCE
corpus luteum
PROGESTERONE, stimulated via
VIA LH
Progesterone – functions
prepares endometrium for implantation
prepares MAMMARY GLANDS for milk secretion
INHIBIN Source
granulosa cells then corpus luteum (similar structures?)
INHIBIN, stimulation
Stimulation: FSH and LH
Inhibin, Functions
inhibits FSH & LH secretion
Inhibin and estrogen from same source, but opposite effects ????
(granulosa cells / corpus luteum)
inhibin decrease LH secretion
estrogen increases LH secretion
Relaxin – SOURCE
corpus luteum then placenta (if implantation occurs)
Relaxin – STIMULATION is via
LH
Relaxin function
RELAXES myometrium
RELAXES pubic symphysis (during pregnancy)
DILATES cervix (during pregnancy)
Uterine cycle (menstrual cycle)
the uterine cycle is the changes in endometrium in preparation of fertilized ovum
THREE phases of the uterine cycle
1) Menstruation (menses / “period”)
2) Proliferative phase
3) Secretory phase
1) Menstruation (menses / “period”)
Day 1-7 (day 1 is the first day of bleeding)
Uterine Changes during menstruation
DECREASE in prog. & estrogen = spiral arteries constrict & cells die
entire STRATUM FUNCTIONALIS sloughs off
2-5 mm of stratum basalis is left
endometrium stratum functionalis
Endometrium: consists of a
—> thin base layer (stratum basalis)
—> and a thicker functional layer (stratum functionalis).
The stratum functionalis is a highly vascularized mucosal layer that undergoes monthly cyclical changes and is lost during menstruation.
what happens in OVARIES during menstruation
FSH influences primordial follicles to develop into primary, then secondary follicles
can take several months, so a follicle that starts development at the beginning of a cycle, may not be mature until many months later
2) Proliferative phase of uterine cycle
day 7-14, but variable
uterine changes during proliferative phase of uterine cycle
estrogens from growing follicles build endometrium
—> stratum basalis undergoes mitosis to produce stratum functionalis
—> endometrial glands & arterioles grow & develop
What happens in OVARIES during PROLIFERATIVE phase of uterine cycle?
secondary follicles in ovaries begin secreting estrogens & inhibin
usually dominant follicle becomes the mature follicle and enlarges until ready for ovulation
—> increases estrogen production
3) SECRETORY PHASE of uterine cycle
day 15-28, but variable
uterine changes during secretory phase of uterine cycle?
progesterone & estrogens from corpus luteum cause:
—> endometrial glands to grow & secrete glycogen
—> endometrium to vascularize (increase in spiral artery size) & thicken
—> uterus is ready for a fertilized ovum to arrive
Secretory phase of uterine cycle if NO FERTILIZATION (pregnancy)
corpus luteum degenerates & progesterone & estrogen production declines and begins the menstrual phase
what is happening in the OVARIES during the uterine cycle
LH promotes formation of CORPUS LUTEUM
—> stim by LH, corpus luteum secretes estrogens, progesterone, relaxin & inhibin
if pregnancy does NOT occur?
corpus luteum lasts 2 weeks
stops secreting hormones & degenerates into CORPUS ALBICANS
If pregnancy DOES occur?
Early cells of the placenta produces hCG
it rescues corpus luteum to keep it alive & it continues secretory functions
Pregnancy and labour
…
CLEAVAGE
Rapid division of cells to create multiple cells
Happens on the journey to the uterus
cell cleavage ends with …
Ends with a BLASTOCYST
Implantation of fertilized egg – starts @
Starts around day 7
Begins with the attachment of the blastocyst to the uterine endometrium
Blastocyst erodes endometrial lining and becomes enclosed within the endometrium by DAY 10
how is PLACENTAL MEMBRANE formed?
Trophoblast cells invade (invade the blastocyst?) and become syncytiotrophoblasts
Eventually forms the placental membrane
syncytiotrophoblast — etymology
syncytiotrophoblast (from the Greek ‘syn’- “together”; ‘cytio’- “of cells”; ‘tropho’- “nutrition”; ‘blast’- “bud”)
how does embryo form?
Inner cell mass becomes embryo
“The syncytiotrophoblast is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother.”
implantation day 9
Around day 9, AMNIOTIC CAVITY forms
Filled with amniotic fluid
—> Protects and supports embryo
AMNIOCENTESIS is usually carried outbetween the 15th and 20th weeks of pregnancy
around day 10
Around day 10, implantation finishes and the YOLK SAC forms
—> Site of early hematopoiesis from stem cells
(Week 3 – 8)
Gives nutrients to developing fetus prior to placental formation
The PLACENTA
Fully formed and functional around week 12
Site of exchange between maternal blood and fetal blood
placenta BLOOD SUPPLY
A) Umbilical arteries
B) Chorionic villi
C) Umbilical vein
Umbilical arteries
—> Carry blood from the developing fetus to the placenta
—> Blood is deoxygenated and full of waste products
Chorionic villi
Provide surface area for exchange of gases, nutrients, and wastes between fetal and maternal bloodstreams
Umbilical Vein
—> Carries blood from the placenta to the fetus
—> Blood contains nutrients and oxygen
Hormone production from PLACENTA
Human chorionic gonadotropin (hCG)
—> Maintains corpus luteum until about week 12
Human placental lactogen (hPL)
—> Helps prepare mammary glands for milk production
Relaxin
—> relaxes myometrium
—> relaxes pubic symphysis & dilates cervix during pregnancy
Estrogen and progesterone
—> Takes over progesterone production from corpus luteum at week 12 (Maintains uterine lining)
—> During third trimester, rising estrogen plays a role in stimulating labour and delivery
how long does corpus luteum last during pregnancy?
“If you’re pregnant, your corpus luteum usually goes away around week 12, when the placenta starts making enough progesterone to keep the fetus healthy. If the egg doesn’t get fertilized, your corpus luteum usually goes away 10 days after the egg left your ovary.”
MULTIPLE BIRTHS
Dizygotic (“fraternal”) twins
Monozygotic (“identical” or “maternal) twins
Dizygotic (“fraternal”) twins
Develop when two separate oocytes are ovulated and fertilized
70 percent of twins are dizygotic
Monozygotic (“identical” or “maternal) twins
Result from separation of blastomeres early in cleavage
Can also result when inner cell mass splits before gastrulation
Genetic makeup of twins is identical (both formed from the same set of gametes)
Changes during pregnancy
Uterus ascends to the abdominal cavity
The abdominal contents displaced in response to the increased size of the uterus
what GI issues are common?
GERD and increased urination are possible results
pregnancy and cervix & mucus
(CERVICAL MUCUS PLUG)
enlarged mucus glands of the cervix duringpregnancy secrete a mucus, which forms a plug
—> acts as a seal for the uterus and protects it from ascending infection
cervical mucus plug
A cervical mucus plug (operculum) is a plug that fills and seals the cervical canal during pregnancy.
It is formed by a small amount of cervical mucus that condenses to form a cervical mucus plug during pregnancy.
operculum (cervical mucus plug) etymology
operire – to cover
operculum = lid, covering
pregnancy and fluid retention
Fluid retention can compress nerves passing through narrow canals, such as the carpal tunnel, causing pain, numbness and weakness in the hand
pregnancy and cardiac output
Cardiac output increases to meet increased demand
—> Up to 30-50% of baselinewhat does
what does estrogen do to mediate rise in CO
estrogen mediates this rise in cardiac output by increasing the PRE-LOAD and STROKE VOLUME, mainly via a higher overall blood volume
recall PRELOAD – heart
“Preload, also known as the left ventricular end-diastolic pressure (LVEDP), is the amount of ventricular stretch at the end of diastole”
how much higher blood volume?
Up 40-50%
heart rate during pregnancy?
The heart rate increases, but generally not above 100 beats/ minute
pregnancy and diaphragm / thorax
Thediaphragmis elevated by about 4cm due to the enlarged uterus
Ligaments connecting ribs to sternum become lax during pregnancy
—> Leads to increased tidal volume (30-50%)
recall tidal volume
Tidal volume is the amount of air that moves in or out of the lungs with each respiratory cycle.
pregnancy and respiratory rate
respiratory rate more than normal
note pregnancy and permanent increase in size of thorax
structural changes?
decreases elasticity and higher position of ribs?
increased size of costal cartilages?
both?
pigmentation during pregnancy
Pigmentation changes occur during pregnancy include darkening of:
areola on the breasts
linea nigra
increased facial pigmentation
pregnancy and striae
Stretch marks (striae gravidarum) occur on the abdomen, breasts, thighs and buttocks to varying degrees.
pregnancy and breasts
enlargement under the influence of relaxin, progesterone and estrogen, prolactin, and hPL
—> Breast tenderness is common in the early stages of pregnancy
Montgomery’s tubercles developing from enlarging sebaceous glands around the areolar
—> Protect nipple from cracking
