PMS III Week 2 - Maternal-Fetal Physiology Part I & II

When does oogenesis begin and when is it completed?

Oogenesis begins in fetal life but is not completed until fertilization.

At what stage are primary oocytes arrested before ovulation?

Primary oocytes are arrested in prophase of meiosis I.

What happens when the primary oocyte completes meiosis I?

It produces one haploid secondary oocyte that receives most of the cytoplasm and one polar body that fragments and disappears.

At what stage is the secondary oocyte arrested?

The secondary oocyte arrests in metaphase of meiosis II.

What event allows the secondary oocyte to complete meiosis II?

Fertilization allows completion of meiosis II.

What does the secondary oocyte become after fertilization and completion of meiosis II?

It becomes an ovum and releases a second polar body.

What happens to the secondary oocyte if fertilization does not occur?

It degenerates.

How does mitosis differ from meiosis?

Mitosis produces identical diploid daughter cells; meiosis produces genetically varied haploid cells.

What is the purpose of meiosis in reproduction?

Meiosis creates genetic variation and produces haploid gametes.

What is the hypothalamic-pituitary-ovarian axis?

A reproductive hormone axis in which the hypothalamus releases GnRH, the anterior pituitary releases FSH and LH, and the ovary produces estrogen and progesterone.

What hormone does the hypothalamus release in the HPO axis?

The hypothalamus releases gonadotropin-releasing hormone, or GnRH.

What hormones does the anterior pituitary release in response to GnRH?

The anterior pituitary releases follicle-stimulating hormone, FSH, and luteinizing hormone, LH.

What does FSH do in the ovary?

FSH stimulates follicles to develop within the ovary, and developing follicles produce estrogen.

What does LH do in the ovary?

The LH surge causes ovulation and formation of the corpus luteum, which produces progesterone.

What happens to estrogen and progesterone levels if pregnancy does not occur?

Estrogen and progesterone levels drop, allowing FSH and LH release to begin again.

How does estradiol affect gonadotropin release?

Estradiol enhances LH release and inhibits FSH release.

How do inhibins A and B affect gonadotropin secretion?

Inhibins A and B reduce FSH secretion.

How does progesterone affect GnRH and LH after ovulation?

Progesterone increases hypothalamic opioid activity and slows GnRH pulse secretion, favoring FSH production and decreasing LH release.

When does inhibin B peak?

Inhibin B peaks early in the follicular phase and rises in the midfollicular phase to suppress FSH biosynthesis.

When does inhibin A peak?

Inhibin A peaks in the midluteal phase.

What happens when inhibin A decreases at the end of the luteal phase?

FSH levels can rise again.

What is leptin and how is it related to reproduction?

Leptin is produced by adipose tissue and acts on the hypothalamus and GnRH to assist reproduction.

How can illness or exercise affect reproductive hormone output?

Signals such as beta-endorphins from exercise and IL-1 during illness can inhibit reproductive function at times.

How are prolactin and dopamine related to fertility?

Prolactin and dopamine can regulate gonadotropin output and may contribute to infertility when altered.

What is the two-cell theory of ovarian steroidogenesis?

The presentation identifies two-cell theory as part of reproductive physiology, linking ovarian cell cooperation in hormone production.

What is perimenopause?

Perimenopause is the period before menopause, roughly the last 10 years before menopause.

What is the typical age range for perimenopause?

Perimenopause usually occurs from age 40 to 50.

What is premature ovarian failure according to the presentation?

Ovarian failure before age 40 is considered premature ovarian failure.

What hormone levels decline during perimenopause?

Estrogen, progesterone, and inhibin decline during perimenopause.

Which gonadotropin increases first during perimenopause?

FSH increases before LH.

What menstrual change is typical during perimenopause?

Menses become irregular.

What symptoms may occur during perimenopause?

Irritability, hot flashes, and sleep disturbances may occur.

What is menopause?

Menopause is a normal stage of life marked by loss of ovarian follicular function and disappearance of sexual cycles.

What is the median age of menopause?

The median age of menopause is 51 years.

What age range contains 95% of menopause onset?

About 95% of menopause occurs between ages 45 and 55.

What ovarian change causes menopause?

There is decline and gradual loss of primordial follicles, causing the ovaries to become unresponsive to gonadotropins.

What happens to FSH and LH after menopause?

FSH and LH rise because feedback from estrogen and inhibins is lost.

What reproductive tract changes occur after menopause?

The uterus, vagina, and cervix become atrophic.

What symptoms intensify during menopause?

Hot flashes, insomnia, and decreased breast size can intensify.

What ovarian phase corresponds to the proliferative phase of the endometrium?

The follicular phase of the ovary corresponds to the proliferative phase of the endometrium.

What days of the menstrual cycle are usually the follicular phase?

The follicular phase is usually days 1 to 14 of the cycle.

What is day 1 of the menstrual cycle?

Day 1 is the first day of menses.

What hormone predominates during the follicular/proliferative phase?

Estrogen predominates during the follicular/proliferative phase.

What does estrogen do to the endometrium during the proliferative phase?

Estrogen stimulates proliferation of the uterine endometrium in preparation for implantation.

What ovarian event occurs during the follicular phase?

Follicles develop within the ovaries and produce estrogen; one dominant follicle takes the lead.

What triggers ovulation?

Ovulation is stimulated by the LH surge.

When does ovulation usually occur?

Ovulation usually occurs around day 14 of the menstrual cycle.

What happens to the dominant follicle during ovulation?

The dominant follicle ruptures and releases the ovum.

Where is the ovum released during ovulation?

The ovum is expelled into the abdominal cavity and then picked up by the fimbriated ends of the fallopian tube.

Where does fertilization usually occur?

Fertilization usually occurs in the ampulla of the fallopian tube.

What happens to meiotic division during ovulation?

When ovulation occurs, meiotic division continues but stops at metaphase II of the second meiotic division.

What ovarian phase corresponds to the secretory phase of the endometrium?

The luteal phase of the ovary corresponds to the secretory phase of the endometrium.

When does the luteal phase occur?

The luteal phase occurs after ovulation.

What hormone predominates during the luteal/secretory phase?

Progesterone predominates during the luteal/secretory phase.

Why is progesterone considered proof that ovulation occurred?

Progesterone is produced by the corpus luteum, which forms from the ruptured follicle after ovulation.

What does the ruptured follicle become after ovulation?

The ruptured follicle becomes the corpus luteum.

What does progesterone do to the endometrium?

Progesterone causes secretory changes and helps the proliferated endometrium differentiate into a better environment for implantation.

What nutrients are stored in progesterone-transformed endometrial stromal cells?

They contain glycogen, protein, lipids, and minerals for early nutrition of the implanting blastocyst.

What happens to the corpus luteum if pregnancy occurs?

The corpus luteum persists and is the initial source of progesterone until the placenta forms and takes over.

What happens to the corpus luteum if pregnancy does not occur?

The corpus luteum degenerates around day 24.

How long do sperm live after ejaculation according to the presentation?

Sperm live less than 72 hours after ejaculation.

How many sperm typically reach and bind the ovum?

About 50 to 100 sperm reach the ovum and bind to the zona pellucida.

Within what time after ovulation must fertilization occur?

Fertilization must occur within 24 hours from the time of ovulation.

What is the acrosome?

The acrosome is a cap-like structure over the anterior half of the sperm head.

What is the acrosomal reaction?

The acrosome breaks down and releases enzymes that facilitate sperm penetration through the zona pellucida.

What is the zona pellucida?

The zona pellucida is the outer glycoprotein layer surrounding the ovum that sperm must penetrate.

How is polyspermy prevented immediately after sperm-ovum fusion?

Sperm fusion with the ovum membrane reduces membrane potential, helping prevent polyspermy.

How is long-term protection against polyspermy provided?

A structural change in the zona pellucida provides long-term protection against polyspermy.

What happens to the sperm nucleus after fertilization?

The sperm nucleus is released into the cytoplasm of the ovum.

What do cortical granules do during fertilization?

Cortical granules in the ovum release contents that prevent multiple sperm from fertilizing one ovum.

What is formed after sperm and egg fusion?

The zygote is formed after sperm and egg fusion.

How does the zygote travel through the fallopian tube?

It is propelled by epithelial ciliary movement and rhythmic contractions of smooth muscle walls.

When does the embryo enter the uterine cavity as a blastocyst?

The embryo enters the uterine cavity as a blastocyst about day 7 after fertilization.

How long does the blastocyst take to move down the fallopian tube into the uterus?

The blastocyst moves down the fallopian tube into the uterus over about 3 days.

What cell stage is reached before implantation?

The blastocyst reaches the 8- to 16-cell stage before implantation.

When does implantation begin after the blastocyst reaches the uterus?

Implantation begins within another 2 to 3 days.

What cells on the blastocyst invade the endometrium?

Trophoblastic cells on the surface of the blastocyst invade the endometrium.

What two trophoblast layers form during implantation?

The outer syncytiotrophoblast layer and inner cytotrophoblast layer form.

Where does implantation usually occur?

Implantation usually occurs on the dorsal uterine wall.

What develops after implantation?

The fetus and placenta develop after implantation.

What do trophoblast cells become?

Trophoblast cells become the placenta.

What does the inner cell mass or embryoblast become?

The inner cell mass becomes embryonic structures, including the embryo, amnion, and related structures such as the umbilical cord.

What is the placenta?

The placenta is a maternalfetal organ that is fetal in origin and acts as the interface between mother and fetus.

What are the main functions of the placenta?

The placenta attaches the fetus to the uterine wall, supplies nutrients and oxygen, transfers fetal waste products to the mother, and produces hormones.

How do gases cross the placenta?

All gases involved cross the placenta by simple diffusion.

What does the blastocyst differentiate into after fertilization?

The blastocyst differentiates into trophoblast and inner cell mass.

What may trophoblast invasion of the maternal endometrium cause clinically?

Trophoblast invasion may cause spotting.

What is the chorionic plate?

The chorionic plate is the maternal-fetal interface that gives rise to chorionic villi.

What is the chorion?

The chorion is the outer placental layer closer to the uterine wall.

What is the amnion?

The amnion is the inner layer and sac that surrounds the fetus.

What is the embryonic body stalk?

The embryonic body stalk is the precursor to the umbilical cord and establishes placental-fetal circulation.

What happens if the embryonic body stalk does not form?

The umbilical cord cannot form and the embryo cannot develop into a fetus.

How many arteries and veins are in the umbilical cord?

The umbilical cord contains two arteries and one vein.

What do the umbilical arteries carry?

The two umbilical arteries carry deoxygenated blood from fetus to mother/placenta.

What does the umbilical vein carry?

The single umbilical vein carries oxygenated blood from mother/placenta to fetus.

What is the decidua basalis?

The decidua basalis is maternal tissue: the endometrial region between the blastocyst and the myometrium of the uterus.

What is the intervillous space?

The intervillous space is maternal tissue surrounding chorionic villi and containing maternal blood.

What are chorionic villi?

Chorionic villi are fetal tissue that sprout from the chorion and form the border between maternal and fetal blood; they serve as the feeding system for umbilical vessels.

What is hCG?

Human chorionic gonadotropin is a hormone produced by trophoblasts before placental development is complete.

What does hCG stimulate in early pregnancy?

hCG stimulates the corpus luteum to grow and secrete estrogen, progesterone, and relaxin during the first 6 to 8 weeks of pregnancy.