Development 2

Question 1

What is a fertilized egg called? What does it become and through what process?

Answer 1

Zygote, undergoes cleavage from mitotic divisions

after around 8 equal divisions without change in cell size, the zygote becomes a morula

Question 2

What is a blastocyst?

Answer 2

By the time the zygote reaches the uterus (~6 days) it differentiated into different layers

the zygote is now called a blastocyst

the outer layer (chorion) secrets HUMAN CHORIONIC GONADOTROPIC HORMONE (hGC) which prevents the corpus luteum from degenerating for 3 months

progesterone and estrogen will continue to be made, endometrium is maintained, contractions are prevented

Question 3

What is implantation?

Answer 3

the blastocyst embeds itself into the endometrium

Question 4

Why does menstruation not occur during pregnancy?

Answer 4

progesterone and estrogen have negative feedback on the hypothalymus

no secretion of FSH (no new follicles)

no secretion of LH (no ovulation)

Question 5

What does the chorion do?

Answer 5

outermost layer, secretes hCG

the part that intermingles with the endometrium forms the placenta

Question 6

What does the placenta do?

Answer 6

contains maternal and fetal blood

diffusion of nutrients, gasses, wastes

continues production of hCG, estrogen and progesterone

maintains the endometrium

corpus lutuem is not needed -> dissolves

Question 7

What does the amnion and amnionic fluid do?

Answer 7

innermost layer, fluid filled sac

protects embryo from trauma and temp fluctuations

allows freedom of movement, prevents limbs from sticking to body

Question 8

What does the allantois do?

Answer 8

helps the embryo exchange gases and handle liquid wastes

provide umbilical blood vessels to placenta

Question 9

What does the umbilical chord do?

Answer 9

connection between mother and baby, carries baby blood to and from the placenta

contains 2 fetal arteries (fetus to placenta)
1 fetal vein (placenta to fetus)