Lectures 8 & 9 - Fertilization and Pregnancy Jan 22 & 24, 2025

Question 1

Where does fertilization occur?

Answer 1

In the ampulla, the upper third of the fallopian tube or the oviduct.

Question 2

What is capacitation?

Answer 2

A physiological process by which spermatozoa acquire the ability to penetrate the zona pellucida of the ovum.

Question 3

What is the acrosomal reaction?

Answer 3

A process by which the membrane surrounding the acrosome fuses with the plasma membrane of the sperm to liberate the contents of the acrosome.

Question 4

What are the three glycoproteins that compose the zona pellucida?

Answer 4

• ZP1
• ZP2
• ZP3

Question 5

What initiates the acrosomal reaction?

Answer 5

The sperm-ZP3 interaction.

Question 6

What happens during the cortical reaction?

Answer 6

Exocytosis of small electron-dense granules releases enzymes that act on glycoproteins in the zona pellucida, causing them to harden.

Question 7

What triggers the completion of the oocyte’s second meiotic division?

Answer 7

A rise in [Ca2+]i in the oocyte caused by the sperm cell.

Question 8

What is formed when the male and female pronuclei fuse?

Answer 8

A new cell called the zygote.

Question 9

How many chromosomes does the zygote contain?

Answer 9

46 chromosomes, 23 from the maternal gamete and 23 from the paternal gamete.

Question 10

What is a morula?

Answer 10

A mulberry-shaped solid mass of 12 or more cells.

Question 11

What is a blastocyst?

Answer 11

A ball-like structure with a fluid-filled inner cavity.

Question 12

When does implantation of the human blastocyst normally occur?

Answer 12

6 to 7 days following ovulation.

Question 13

What role does progesterone play during implantation?

Answer 13

It causes the endometrium to become more vascularized, increases in thickness, and the endometrial glands become tortuous and engorged with secretions.

Question 14

What is predecidualization?

Answer 14

The process where stromal cells transform into rounded decidual cells, making the endometrium more compact.

Question 15

What happens if conception fails to occur?

Answer 15

The secretory activity of the endometrial glands decreases, followed by regression of the glands and ultimately menstruation.

Question 16

What substances does the endometrium secrete for embryo nourishment?

Answer 16

• Cholesterol
• Steroids
• Nutrients (including iron and fat-soluble vitamins)

Question 17

What is the function of immunosuppressive agents released by the blastocyst?

Answer 17

To avoid rejection by the maternal cellular immune system.

Question 18

What hormone does the early blastocyst secrete?

Answer 18

Human chorionic gonadotropin (hCG).

Question 19

Fill in the blank: Fertilization occurs in ______ steps.

Answer 19

eight

Question 20

What must the blastocyst do to survive?

Answer 20

Avoid rejection by the maternal cellular immune system

The blastocyst achieves this by releasing immunosuppressive agents.

Question 21

What is the role of human chorionic gonadotropin (hCG) during early pregnancy?

Answer 21

Sustains the corpus luteum and has immunosuppressive characteristics

hCG also promotes trophoblast growth and placental development.

Question 22

What are some immunosuppressive agents secreted by the blastocyst?

Answer 22

• Platelet-activating factor (PAF)
• Human chorionic gonadotropin (hCG)
• Early pregnancy factor
• Immunosuppressive factor
• Prostaglandin E2
• Interleukins 1α and 6
• Interferon-α
• Leukemia inhibitory factor
• Colony-stimulating factor
• Metalloproteases
• Collagenases
• Gelatinases
• Stromelysins
• Serine proteases

These agents facilitate the implantation process.

Question 23

What is the purpose of ovarian hyperstimulation in IVF-ET?

Answer 23

To obtain multiple oocytes for fertilization

This is necessary because female typically develops only a single dominant follicle each cycle.

Question 24

What hormones are typically administered for ovarian stimulation?

Answer 24

• FSH (Follicle-stimulating hormone)
• LH (Luteinizing hormone)

These can be given intramuscularly or subcutaneously.

Question 25

What is the function of GnRH analogues during controlled ovarian stimulation?

Answer 25

To downregulate the hypothalamic-pituitary axis ## Footnote This prevents a premature LH surge and ovulation.

Question 26

When does ovulation typically occur after the LH surge?

Answer 26

36 to 39 hours ## Footnote Oocyte retrieval is planned to occur just before ovulation.

Question 27

What is the process of oocyte retrieval in IVF?

Answer 27

Oocytes are aspirated from individual follicles under sonographic guidance ## Footnote The procedure is performed with the patient under conscious sedation.

Question 28

What is the fertilization detection timeframe post-insemination?

Answer 28

16 to 20 hours ## Footnote Fertilization is indicated by the presence of two pronuclei in the egg cytoplasm.

Question 29

What is the embryo transfer process in IVF?

Answer 29

Embryos are transferred to the uterus at the 4-to 8-cell stage or blastocyst stage ## Footnote The procedure is guided by ultrasound.

Question 30

What is Gamete intrafallopian transfer (GIFT)?

Answer 30

Direct transfer of oocytes and sperm to the fallopian tube ## Footnote Fertilization occurs within the tube itself.

Question 31

What hormones does the placenta produce?

Answer 31

* Human chorionic gonadotropin (hCG) * Human chorionic somatomammotropin (hCS) * Human placental lactogen (hPL) ## Footnote These hormones play crucial roles in pregnancy maintenance and fetal development.

Question 32

What is the effect of human placental lactogen (hPL) on maternal metabolism?

Answer 32

* Reduces maternal insulin sensitivity * Causes hyperglycemia and gestational diabetes in some females * Enhances maternal lipolysis ## Footnote These effects ensure adequate fetal nutrition.

Question 33

What factors increase insulin secretion during pregnancy?

Answer 33

* Elevated blood glucose levels * Acetylcholine * ACTH * Glucagon * β-adrenergic agonists * Glucose-dependent insulinotropic peptide (GIP) * hCG * hCS ## Footnote These factors stimulate pancreatic beta cells to release more insulin.

Question 34

What inhibits insulin secretion?

Answer 34

* Somatostatin * α-adrenergic agonists ## Footnote These substances counteract factors that promote insulin release.

Question 35

What changes occur in progesterone and estrogen levels during pregnancy?

Answer 35

Rise to levels substantially higher than in a normal cycle ## Footnote Progesterone is produced mainly by luteal cells after ovulation.

Question 36

What hormones rise to levels higher than their peaks in a normal cycle after ovulation?

Answer 36

Progesterone and estrogens ## Footnote This increase occurs if pregnancy does not take place.

Question 37

What do the cells of the ovarian follicle transform into after ovulation?

Answer 37

Luteal cells

Question 38

How long does the corpus luteum last after ovulation?

Answer 38

About 12 days

Question 39

What happens to progesterone and estrogen levels after the demise of the corpus luteum?

Answer 39

They both fall

Question 40

During pregnancy, what happens to maternal levels of progesterone and estrogens?

Answer 40

They increase and reach levels higher than those observed during the menstrual cycle

Question 41

What are the three forms of estrogens that increase during pregnancy?

Answer 41

* Estradiol * Estrone * Estriol

Question 42

What is the role of progesterone during pregnancy?

Answer 42

Reduces uterine motility and inhibits propagation of contractions

Question 43

What hormone rescues the corpus luteum during the first trimester of pregnancy?

Answer 43

hCG

Question 44

What becomes the major source of progesterone and estrogens by 8 weeks of gestation?

Answer 44

The placenta

Question 45

What major estrogen is produced during pregnancy that is not significant in non-pregnant women?

Answer 45

Estriol

Question 46

What are the contributions of the mother in steroid biosynthesis during pregnancy?

Answer 46

* Progesterone * Estrone * Estradiol * LDL cholesterol * Adequate synthetic capacity for progesterone and estrogens

Question 47

What enzyme is necessary for converting pregnenolone to progesterone?

Answer 47

3β-Hydroxysteroid dehydrogenase

Question 48

What is the role of the fetal adrenal gland and liver in steroid hormone synthesis?

Answer 48

Supply necessary enzymes to the placenta

Question 49

What is a significant limitation of the placenta in synthesizing hormones?

Answer 49

It cannot manufacture adequate cholesterol

Question 50

What happens to maternal blood volume during pregnancy?

Answer 50

It increases

Question 51

By how much can maternal blood volume increase in singleton pregnancies?

Answer 51

By 45%

Question 52

What physiological change occurs due to elevated progesterone and estrogens during pregnancy?

Answer 52

Vasodilation that decreases peripheral vascular resistance

Question 53

How does cardiac output change during the first trimester of pregnancy?

Answer 53

Increases by 35%-40%

Question 54

What is the typical pattern of mean arterial pressure (MAP) during pregnancy?

Answer 54

Decreases during mid-pregnancy and rises during the third trimester

Question 55

How does posture affect cardiac output in late pregnancy?

Answer 55

Higher when the mother is in the lateral recumbent position than in the supine position

Question 56

What is the effect of the maternal-placental-fetal unit on steroid biosynthesis?

Answer 56

Overcomes placental shortcomings through cooperation

Question 57

Fill in the blank: The placenta lacks enzymes needed to synthesize _______.

Answer 57

Estrone and estradiol

Question 58

True or False: The placenta can synthesize all hormones needed during pregnancy independently.

Answer 58

False

Question 59

How does the lateral recumbent position affect cardiac output during pregnancy?

Answer 59

Cardiac output is typically higher in the lateral recumbent position than in the supine position. ## Footnote This is due to the improved venous return in this position.

Question 60

In which posture is arterial blood pressure highest during pregnancy?

Answer 60

Blood pressure is highest when sitting. ## Footnote This is in contrast to the lateral recumbent position where it is lowest.

Question 61

What is the relationship between the mother's posture and brachial artery blood pressure?

Answer 61

Blood pressure in the brachial artery is highest when sitting, lowest in the lateral recumbent position, and intermediate when supine. ## Footnote This highlights the impact of posture on blood pressure during pregnancy.

Question 62

What effect do increased levels of progesterone have on alveolar ventilation during pregnancy?

Answer 62

Increased levels of progesterone during pregnancy increase alveolar ventilation. ## Footnote Progesterone has relaxing effects on respiratory muscles.

Question 63

How much does the diaphragm rise during pregnancy, and what causes this change?

Answer 63

The diaphragm rises about 4 cm due to the relaxing effects of progesterone on the diaphragm muscle and fascia. ## Footnote This elevation impacts lung function and capacity.

Question 64

What change occurs in the transverse diameter of the thoracic cage during pregnancy?

Answer 64

The transverse diameter of the thoracic cage increases about 2 cm. ## Footnote This change helps accommodate the growing fetus and increases lung capacity.

Question 65

What happens to total pulmonary resistance during pregnancy?

Answer 65

Total pulmonary resistance falls, facilitating airflow. ## Footnote This allows for easier breathing as the pregnancy progresses.

Question 66

How does the size of abdominal contents during pregnancy affect the abdominal muscles?

Answer 66

The abdominal muscles are less effective in aiding forced expirations due to the increased size of abdominal contents. ## Footnote This can lead to changes in respiratory mechanics.

Question 67

What percentage of total maternal weight gain during pregnancy represents the fetus?

Answer 67

Less than one third of the total maternal weight gain represents the fetus. ## Footnote This indicates that most weight gain is due to other factors.

Question 68

What is the recommended weight gain during a singleton pregnancy for a woman with a normal weight/height ratio?

Answer 68

The recommended weight gain is 11.5 to 16 kg. ## Footnote This guideline varies based on the woman's body mass index.

Question 69

How does pregnancy affect dietary needs in terms of protein, iron, and folic acid?

Answer 69

Pregnancy increases the demand for dietary protein, iron, and folic acid. ## Footnote These nutrients are essential for fetal development and maternal health.

Question 70

How much additional protein is needed each day during pregnancy?

Answer 70

An additional 30 grams of protein are needed each day. ## Footnote This increase supports the growing fetus, placenta, uterus, and breasts.