Flashcards in Lecture 6 Deck (30):
Where does fertilization occur?
Ampulla, oviduct, or upper third of fallopian tube.
Journey of the egg:
Start in ovary.
Travel through fallopian tube (infundibulum, ampulla, isthmus) to uterus.
As it travels, it grows up from a morula to a blastocyst.
Journey of the sperm to meet the egg:
Enter uterus through cervix.
Capacitation to be able to penetrate zona pellucida - modify acrosome (protein hat).
Acrosome fuses with plasma membrane of egg to liberate contents.
8 steps of fertilization:
1. Sperm binds to zona pellucida.
2. Ca2+ in sperm rises and acrosome releases contents.
3. Acrosomal hydrolytic enzymes locally dissolve zona pellucida.
4. Sperm cell enters.
5. Ca2+ in oocyte rises. Cortical reaction hardens zona pellucida to stop more sperm from getting in.
6. Ca2+ induces completion of meiosis II.
7. Sperm pronucleus enlarges.
8. Male and female pronuclei merge.
How long does the fertilized egg hang out in the fallopian tube?
3 days. Receive nourishment from fallopian tube secretions. Becomes morula.
How does the egg get from the fallopian tube to the uterus?
Cilia of tubal epithelium and contraction of fallopian tube.
Morula development in uterus:
72 hours. Becomes blastocyst.
Blastocyst's fight to stay alive:
Releases immunosuppressants and promoters of implantation and placental development. Burrows into basement membrane.
hCG as a implantation helper:
Immunosuppressant to keep bb safe. Supports corpus luteum as maternal LH falls. Helps outer layer of blastocyst (trophoblast) grow and attach to endometrium.
In vitro fertilization and embryo transfer:
Hyperstimulate ovulation with gonadotropin to develop multiple follicles. GnRH to downregulate hyp pit axis, then gonadotropins. Stimulate ovulatory LH surge with hCG.
Oocytes are aspirated from follicular fluid.
Purified sperm are used to inseminate the eggs.
Embryos are transferred to uterus by catheter.
When does blastocyst implantation occur?
6-7 days following ovulation.
Timeline of decidualization:
Predecidualization occurs for the first 9 days after ovulation. If conception does not occur, endometrial glands regress for 9 days and menstruation happens. If pregnancy is successful, predecidual changes are extended.
What does hPL do? Where is it produced?
Converts glucose to fatty acids and ketones.
Promotes maternal mammary gland development during pregnancy.
Progesterone/estrogen levels upon conception:
Progesterone goes crazy. Estrogen goes slightly less crazy. Estriol and estrone appear as a source of estrogen for the morula.
What does the unfertilized follicle produce mostly when it learns it isn't pregnant?
Luteal phase: progesterone.
Progesterone's early function in pregnancy:
Reduces uterine motility and inhibits contractions so you don't squish the beb.
In early pregnancy, what is the major source of prog and est? At 8 weeks?
Early: corpus luteum.
8 weeks: placenta.
Fetal adrenal glands:
So powerful wow. As big as adult glands at birth.
Why doesn't the fetus make its own progesterones/estrogens?
Lacks enzymes to catalyze estrone/estradiol/estriol synthesis.
Normal levels of prog and est are too high for beb.
Placenta as sink:
Eats the weak androgens that the fetus synthesizes, to prevent masculinization of female fetuses.
Placenta modifies pregnenolone before passing it to the fetus.
Placenta sulfates preg to decrease biological activity and protect beb.
Mean duration of pregnancy: from ovulation? from first day of last menstrual period?
266 days (38 weeks) from ovulation.
280 days (40 weeks) from last menstrual period.
Maternal changes in blood volume during pregnancy: what happens?
Increases in first trimester, expands rapidly in second trimester, rises slowly in third trimester. Plateaus in the last weeks.
May increase 45% in single baby pregnancy, 75-100% in multiple baby pregnancy.
Maternal changes in blood volume during pregnancy: why?
Elevated progesterone/estrogen causes vasodilation. Response to angiotensin decreases.
Maternal changes in cardiac output during pregnancy: what happens?
Increases a bunch in first trimester, increases slowly in second and third trimesters. Heart rate is more responsive to exercise. Mean arterial pressure decreases in mid-pregnancy and rises in third trimester.
Maternal changes in cardiac output during pregnancy: why?
Vasodilatory effect of prog/est causes decreased peripheral vascular resistance.
Maternal changes in posture and cardiac output during pregnancy:
In late pregnancy, cardiac output is higher when in lateral recumbent position than in supine.
Pressure in brachial artery is highest when sitting, lowest in lateral recumbent, intermediate in supine.
Other maternal changes during pregnancy:
Increased demand for dietary protein, iron, folic acid.
Weight gain: lower BMI = more gain.