Pregnancy and Development Lab 18 Flashcards
menstrual cycle
Series of changes that occur in the endometrium of a non-pregnant female. There is no blastocyst, fertilization, and implantation so endometrium is shed
What does the endometrium prepare for
prepared to receive a blastocyst which is the early form of an embryo that is implanted into the surface of the uterus.
ovarian cycle
monthly series of events associated with the formation and release of the female gamete.
what initiates the uterine cycle, ovarian cycle,
and other changes associated with puberty in the female.
Gonadotropic hormones: FSH, LH
fsh - females
stimulates the initial development of the ovarian follicles and the secretion of estrogens and inhibin
by the follicles.
LH - females
stimulates
-further development of ovarian follicles
- ovulation
-readies the mammary glands for milk secretion.
-Causes follicle to rupture
Also stimulates the corpus luteum to secrete progesterone, estrogens, relaxin, and inhibin
LH males
LH stimulates cells in the testes to secrete testosterone.
FSH on Males
Stimulate testes for sperm production
estrogens
1) They promote the development and maintenance of
female reproductive organs, the secondary sex characteristics, and the breasts.
2) They control fluid and electrolyte balance. 3) increase protein anabolism.
4) They are believed
to contribute to the female sex drive.
5) Moderate levels of estrogens in the blood inhibit the
secretion of FSH by the anterior pituitary gland. This inhibition provides the basis for the
action of one kind of contraceptive pill. Also GnRH, LH
-stimulate proliferation of basal layer to form new functional layer after menstruation
-lowers blood cholesterol
-
Progesterone
works with estrogens to prepare the endometrium for implantation and to
prepare the breasts for milk secretion.
High level inhibit release of GnRH, FSH, LH
Relaxin
during labour, increase the flexibility of the pubic symphasis
4 phases of the uterine cycle
- menstruation
- preovulatory phase
- ovulation
- postovulatory
menstruation
-uterine cycle:
periodic discharge
of blood, tissue fluid, mucus, and epithelial cells from the endometrium of the uterus. Lasts the first 5 days of the cycle.
-Functional layer sheds resulting in bleeding and uterine glands discharging their contents.
-only the basal layer remains
-ovarian cycle:
Several primordial ovarian follicles in each ovary start developing into primary and then secondary ovarian follicles due to FSH
Granulosa cells
Granulosa cells are cells inside the ovaries that surround and support the developing oocyte (egg cell). They produce hormones like estrogen and inhibin, which are crucial for the ovarian and uterine cycles
primordial ovarian
follicles
develop into primary and secondary follicles. Multiple ovarian follicles begin development but usually only one becomes mature.
What happens to the secondary ovarian follicles that don’t finish maturation?
follicle degenerates and is reabsorbed
What happens if more than one mature ovarian follicle is ovulated?
Can lead to the development of multiple fetuses.
THE PREOVULATORY PHASE /follicular phase
-between the end of menstruation and ovulation.
-lasts from day 6 to 13 in a 28-day cycle.
Ovarian cycle
-secondary follicle matures into a mature ovarian follicle, ready for ovulation.
-During
the maturation process, the granulosa cells increase their production of estrogens.
Uterine cycle
-FSH and LH stimulate ovarian follicle to secrete estrogens. this increase in estrogens stimulates the repair of the endometrium in
the uterus. During the process of repair, basilar cells (stratum basale) undergo mitosis and
produce a new functional layer.
ovulation
-rupture of the mature follicle with the release of the secondary oocyte into the pelvic cavity.
- occurs on
day 14 in a 28-day cycle
-high estrogen levels in the preovulatory phase inhibit fsh and LH levels
-As LH and estrogens secretion
increase and FSH secretion is inhibited, ovulation occurs
-
What happens if the secondary oocyte is not swept into the uterine tube as it usually is?
degenerate or ectopic pregnancy (fertilized egg developing outside the uterus)
postovulatory phase/luteal phase/ secretory phase
-15 to 28 in a 28-day cycle
-between ovulation and the onset of the next menses
-FSH secretion gradually increases and LH
secretion decreases. The functionally dominant hormone during this phase is progesterone.
ovarian cycle:
-luteal phase: mature follicle collapses,
and the blood within it forms a clot.
-corpus hemorrhagicum becomes corpus luteum. Corpus luteum increasing estrogen and progesterone levels
-uterine cycle:
- secretory phase of the uterine cycle prepares the endometrium for implantation of blastocyst. Maximum one week:
1. filling of endometrial glands
2. vascularization of the superficial endometrium (new blood vessels form and grow into the functional layer)
3. thickening of the
endometrium
4. increase in the amount of tissue fluid
phases of the ovarian cycle
Follicular phase
ovulation
-luteal phase
ruptures follicle is called
corpus hemorrhagicum
what does the corpus hemorrhagicum turn into?
corpus luteum
What does the corpus luteum do?
Secrete estrogens and progesterone which is responsible for the changes in the endometrium
Why does FSH gradually increase in the secretory phase
To prepare for the next ovarian cycle if no fertilization occurs
Why does LH decrease in the secretory phase
LH stimulates the follicular cells to form the corpus luteum, which then produces progesterone and estrogen. Once the corpus luteum is established and functioning, the need for high levels of LH diminishes.
If fertilization and implantation do not occur
corpus luteum degenerates into the corpus albicans. No inhibin, estrogen, and progesterone produced by corpus luteum leading to a new
ovarian cycle and the resumption of follicular growth.
if fertilization and implantation do occur
corpus luteum is “rescued” from degeneration
by the human chorionic gonadotropin produced by the chorion of the newly implanted
embryo. The estrogens and progesterone secreted by the corpus luteum maintain the uterine
lining, preventing menstruation.
uterine cycle normally occurs
once each month from menarche (the first uterine cycle)
until menopause
human chorionic gonadotropin
Produced by the chorion of the placenta after implantation.
hCG helps to maintain the corpus luteum, preventing it from degenerating. This is crucial because the corpus luteum produces progesterone and estrogen, which are essential for maintaining the pregnancy. When corpus luteum not needed, HCG drops.
No fertilization occurred, what happens to the corpus luteum
turns into the corpus albicans, no secretion of progesterone or estrogen, Fsh and luteinizing hormone goes up causing a new cycle
When do periods start and end
menarche until menopause
What days are the menstrual cycle
1 - 5
pre-ovulatory phase days
6-13
ovulation day
14
postovulatory phase days
15-28
How long does a usual cycle last
28 days
capacitation
tail of the spem beats more vigorously and the plasma membrane of the head can respond to chemicals released by the oocyte
How does the sperm reach the ovum
Sperm cell must pass through the corona radiata and the zona pellucida. The head of the sperm has an acrosome which contains enzymes hyaluronidase and acrosin that digest the layers.
What triggers the release of enzymes that digest the layers
ZP3 receptors bind in the zona pellucida bind to he head which triggers an ACROSOMAL REACTION. Contents of the acrosome get released.
How does fertilization occur
hyaluronidase digests the cells of the corona radiata while the beating tail forces the sperm cell to contact w the zona pellucida where acrosin digests the zona pellucida and the membrane of the oocyte. When sperm enters the ovum, a membrane is produced the prevents other sperm from entering
Movement of fertilized egg until implantation
morula moved from the fallopian tube and moves towards the uterus. blastocyst implants into the endometrium
morula
solid mass of cells
What does the trophoblast turn into
chorion which develops into a big part of the placenta
What does the embryoblast develop into
embryo
When is the embryonic period
first 8 weeks
yolk sac
provides the embryo with nutrients during the 2nd to the third week of fetal development. The placenta takes over after. Yolk sac also prevents drying out of the embryo
amnion
surrounds the fetal portion of the placenta and the umbilical cord. Filled w amniotic fluid
amniotic fluid
made of fetal urine and maternal blood. Prevents the embryo from drying out, adhesion to other tissues.
chorion
from the trophoblast. Secretes HCG. Forms the placenta, protects the embryo and fetus from the mothers immune system
How does the fetus receive nutrients from the maternal blood.
Chorionic villi have fetal blood vessels that are in close proximity to the maternal blood. This allows oxygen and nutrients from the maternal blood to diffuse into the umbilical veins.
How does waste leave the fetus?
Waste leaves from the umbilical arteries, and diffuses into the maternal blood
What can cross the barrier of the placenta
AIDS, alcohol, measels
placenta
stores carbohydrates, proteins, calcium, and iron that can be released into fetal circulation. The placenta maintains pregnancy after 3-4 months by maintaining high levels of estrogen and progesterone.
allantois
forms the wall of the yolk sac and functions in early formation of blood and blood vessels .
What happens to the hormones at 4 months when the placenta is fully developed
secretion of hCG drops causing the corpus luteum to disintegrate as it is not needed to maintain the uterine lining to prevent menstruation
gestation
time that the embryo/fetus is carried in the uterus. around 280 days
labor
the process of giving birth
stage of dilation
cervix dilates until 10 cm
How does progesterone and estrogen affect the myometrium
In the early stages of gestation, progesterone and relaxin prevent contractions of the myometrium. But when there are high levels of estrogen, the myometrium contracts, causing labour.
essentially estrogen causes the myometrium to contract, but with relaxin and progesterone, it inhibits the contraction. When estrogen takes over, that when contractions occur.
true labour
regular, gradually shortening intervals between contraction
false labour
irregular intervals between contractions
stage of expulsion
full Cervical Dilation: The expulsion phase begins when the cervix is fully dilated (10 cm).
Strong Uterine Contractions: The uterus contracts forcefully and rhythmically, pushing the fetus down the birth canal.
can be up to many hours
placental stage
10-30 mins after baby is released, placenta detaches from the uterus and is expelled through the vagina.
lactation
mammary glands are prepared for lactation by prolactina and progesterone. Starts 3-4 days after delivery, in the meantime, colostrum is secreted which provides adequate nutrients.
milk ejection reflex
lactation is stimulated and maintained by the suckling action of the infant.
Suckling Stimulus: The infant suckles at the breast, stimulating sensory receptors in the nipple.
Hypothalamic Activation: These sensory signals travel to the hypothalamus in the brain.
Oxytocin Release: The hypothalamus stimulates the posterior pituitary gland to release oxytocin.
Myoepithelial Cell Contraction: Oxytocin travels through the bloodstream to the mammary glands, where it causes the myoepithelial cells surrounding the alveoli (milk-producing sacs) to contract.
Milk Ejection: The contraction of myoepithelial cells forces milk from the alveoli into the ducts, making it available to the infant.
what does breast milk contain
Antibodies: Provide immune protection to the infant.
What can cause a false positive
high levels of LH
