10. Embryology, Pregnancy, + Lactation

Question 1

What is fertilization?

Answer 1

The union of the nuclei of a sperm and an ovum, forming a zygote.

Question 2

Where does fertilization typically occur?

Answer 2

In the outer third of the fallopian tube.

Question 3

How long after ovulation can fertilization occur?

Answer 3

Within 12 to 24 hours.

Question 4

What is a zygote?

Answer 4

A fertilized egg with a diploid number of chromosomes (2n).

Question 5

What is implantation?

Answer 5

Attachment of the blastocyst to the endometrium about 6–8 days post-fertilization.

Question 6

What hormone does the trophoblast produce?

Answer 6

Human chorionic gonadotropin (hCG).

Question 7

What is the role of hCG in pregnancy?

Answer 7

Maintains the corpus luteum to keep secreting progesterone and estrogen.

Question 8

When does the placenta begin to form?

Answer 8

After implantation, from the chorion and endometrium.

Question 9

What are the three primary germ layers?

Answer 9

Ectoderm, mesoderm, and endoderm.

Question 10

What does the ectoderm form?

Answer 10

Nervous system, skin, and related structures.

Question 11

What does the mesoderm form?

Answer 11

Muscles, bones, circulatory system, kidneys.

Question 12

What does the endoderm form?

Answer 12

Lining of the digestive, respiratory, and urogenital systems.

Question 13

What are the extra-embryonic membranes?

Answer 13

Chorion, amnion, yolk sac, and allantois.

Question 14

What is the function of the chorion?

Answer 14

Forms part of the placenta and secretes hCG.

Question 15

What is the function of the amnion?

Answer 15

Provides cushioning and maintains temperature with amniotic fluid.

Question 16

What does the yolk sac contribute to in humans?

Answer 16

Forms part of the umbilical cord and provides early blood cells.

Question 17

What is the role of the allantois?

Answer 17

Forms the stalk of the umbilical cord and contributes to the bladder.

Question 18

What is the placenta?

Answer 18

A temporary organ for nutrient, gas, and waste exchange between mother and fetus.

Question 19

What hormones does the placenta produce?

Answer 19

Estrogen, progesterone, and hCG.

Question 20

What is the umbilical cord made of?

Answer 20

1 vein (to fetus), 2 arteries (from fetus), formed by allantois and yolk sac.

Question 21

What is the function of fetal circulation?

Answer 21

To bypass non-functional fetal lungs and deliver oxygenated blood from placenta.

Question 22

What does the foramen ovale do?

Answer 22

Allows blood to flow from the right atrium to the left atrium, bypassing the lungs.

Question 23

What does the ductus arteriosus do?

Answer 23

Connects pulmonary trunk to aorta to bypass the lungs.

Question 24

What is the ductus venosus?

Answer 24

A vessel that allows oxygenated blood from the umbilical vein to bypass the liver.

Question 25

What changes occur after birth in circulation?

Answer 25

Foramen ovale → fossa ovalis; ductus arteriosus → ligamentum arteriosum; vessels close off.

Question 26

What is parturition?

Answer 26

The act of giving birth (childbirth).

Question 27

What hormonal changes trigger labor?

Answer 27

Estrogen rises and progesterone drops, increasing oxytocin receptors in the uterus.

Question 28

What does oxytocin do during labor?

Answer 28

Stimulates strong uterine contractions (positive feedback loop).

Question 29

What are the three stages of childbirth?

Answer 29

Dilation, expulsion (birth), and placental stage (afterbirth).

Question 30

What is pulmonary surfactant?

Answer 30

A substance that reduces surface tension in alveoli, produced from week 26–28 by fetal lungs.

Question 31

What triggers the first breath after birth?

Answer 31

Low oxygen, high CO2, thoracic compression, and stimulation of the medulla.

Question 32

What stimulates milk production?

Answer 32

Prolactin, which increases after childbirth when estrogen and progesterone drop.

Question 33

What triggers milk ejection?

Answer 33

Oxytocin released in response to suckling.