Lecture 6

Question 1

Where does fertilization occur?

Answer 1

Ampulla, oviduct, or upper third of fallopian tube.

Question 2

Journey of the egg:

Answer 2

Start in ovary.
Travel through fallopian tube (infundibulum, ampulla, isthmus) to uterus.
As it travels, it grows up from a morula to a blastocyst.

Question 3

Journey of the sperm to meet the egg:

Answer 3

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.

Question 4

8 steps of fertilization:

Answer 4

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.

Question 5

How long does the fertilized egg hang out in the fallopian tube?

Answer 5

3 days. Receive nourishment from fallopian tube secretions. Becomes morula.

Question 6

How does the egg get from the fallopian tube to the uterus?

Answer 6

Cilia of tubal epithelium and contraction of fallopian tube.

Question 7

Morula development in uterus:

Answer 7

72 hours. Becomes blastocyst.

Question 8

Blastocyst’s fight to stay alive:

Answer 8

Releases immunosuppressants and promoters of implantation and placental development. Burrows into basement membrane.

Question 9

hCG as a implantation helper:

Answer 9

Immunosuppressant to keep bb safe. Supports corpus luteum as maternal LH falls. Helps outer layer of blastocyst (trophoblast) grow and attach to endometrium.

Question 10

In vitro fertilization and embryo transfer:

Answer 10

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.

Question 11

When does blastocyst implantation occur?

Answer 11

6-7 days following ovulation.

Question 12

Timeline of decidualization:

Answer 12

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.

Question 13

What does hPL do? Where is it produced?

Answer 13

From placenta:
Converts glucose to fatty acids and ketones.
Promotes maternal mammary gland development during pregnancy.

Question 14

Gestational diabetes:

Answer 14

hPL dysfunction.

Question 15

Progesterone/estrogen levels upon conception:

Answer 15

Progesterone goes crazy. Estrogen goes slightly less crazy. Estriol and estrone appear as a source of estrogen for the morula.

Question 16

What does the unfertilized follicle produce mostly when it learns it isn’t pregnant?

Answer 16

Luteal phase: progesterone.

Question 17

Progesterone’s early function in pregnancy:

Answer 17

Reduces uterine motility and inhibits contractions so you don’t squish the beb.

Question 18

In early pregnancy, what is the major source of prog and est? At 8 weeks?

Answer 18

Early: corpus luteum.

8 weeks: placenta.

Question 19

Fetal adrenal glands:

Answer 19

So powerful wow. As big as adult glands at birth.

Question 20

Why doesn’t the fetus make its own progesterones/estrogens?

Answer 20

Lacks enzymes to catalyze estrone/estradiol/estriol synthesis.
Normal levels of prog and est are too high for beb.

Question 21

Placenta as sink:

Answer 21

Eats the weak androgens that the fetus synthesizes, to prevent masculinization of female fetuses.

Question 22

Placenta modifies pregnenolone before passing it to the fetus.

Answer 22

Placenta sulfates preg to decrease biological activity and protect beb.

Question 23

Mean duration of pregnancy: from ovulation? from first day of last menstrual period?

Answer 23

266 days (38 weeks) from ovulation.
280 days (40 weeks) from last menstrual period.

Question 24

Maternal changes in blood volume during pregnancy: what happens?

Answer 24

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.

Question 25

Maternal changes in blood volume during pregnancy: why?

Answer 25

Elevated progesterone/estrogen causes vasodilation. Response to angiotensin decreases.

Question 26

Maternal changes in cardiac output during pregnancy: what happens?

Answer 26

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.

Question 27

Maternal changes in cardiac output during pregnancy: why?

Answer 27

Vasodilatory effect of prog/est causes decreased peripheral vascular resistance.

Question 28

Maternal changes in posture and cardiac output during pregnancy:

Answer 28

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.

Question 29

Other maternal changes during pregnancy:

Answer 29

Increased demand for dietary protein, iron, folic acid.

Weight gain: lower BMI = more gain.

Question 30

Maternal changes in breathing during pregnancy: what and why?

Answer 30

Increased alveolar ventilation.

Diaphragm rises due to relaxing effect of progesterone. Costovertebral angle widens. Pulmonary resistance decreases.