Embryo introduction

Question 1

Clinical significance of meiosis? (4 points)

Answer 1

1. Reduction division
2. allows for constant chromosome #
3. random assortment
4. recombination

Question 2

When do oogonia form?

Answer 2

All form before birth- no more are made after birth

Question 3

When is meiosis I of primary oocyte completed?

Answer 3

Before ovulation

Question 4

When is meiosis II of secondary oocyte completed?

Answer 4

Upon fertilization

Question 5

LH surge?

Answer 5

ovulation

Question 6

At what stage are the primary oocytes arrested after birth?

Answer 6

Prophase of meiosis I

Question 7

What does FSH do?

Answer 7

Stimulated by GnRH from hypothalamus, FSH stimulates the growth of ~ 15 follicular cells per menstrual cycle

Question 8

What is the antrum?

Answer 8

Defining characteristic of secondary oocyte- large space

Question 9

When and where does fertilization normally occur?

Answer 9

12-24 hours after ovulation in the ampullar region of fallopian tube

Question 10

Sex differences in gametogenesis?

Answer 10

Female- begins during embryogenesis, arrests until puberty, one germ cell gives rise to one mature ovum and 2 polar bodies, all 23X

Male- begins at puberty, 1 germ cell gives rise to 4 mature spermatozoa, 23X or 23Y

Question 11

Spermiogenesis?

Answer 11

transition from spermatids to spermatozoa

marked by loss of cytoplasm, growth of tail, and acrosome (derived from golgi)

Question 12

Phases of fertilization- 7 steps

Answer 12

1. penetration of corona radiata
2. penetration of zona pellucida
3. fusion of plasma membranes
4. zona reaction occurs, causing ovum fenestrations to close
5. meiosis II completes (2nd polar body)
6. Fusion of male and female pronuclei
7. formation of zygote

Question 13

When does fertilization occur with respect to the last menstrual period (LMP)?

Answer 13

2 weeks after the LMP (different than gestational age which is counted from fertilization)

Question 14

Blastomere cells are…

Answer 14

totipotent

Question 15

Characteristics of blastocyst

Answer 15

loss of zona pellucida, development of blastocyst cavity, outer (trophoblast) v. inner cell mass (embryoblast)

Question 16

Before spermatazoa can fertilize egg, it must undergo 2 things:

Answer 16

1. capacitation

2. acrosome reaction

Question 17

The 2nd week of development is known as the week of 2’s (bilaminar disc) - 4 points

Answer 17

1. trophoblast divides into 2 layers: cytotrophoblast and syncytiotrophoblast
2. The embryo forms 2 layers, the epiblast and hypoblast
3. Extraembryonic mesoderm splits into 2 layers: somatic and splanchnic layers
4. 2 cavities form, the amniotic and yolk sac cavities

Question 18

Epiblast gives rise to…

Answer 18

embryonic ectoderm
ectoderm of amnion
primitive streak

primitive streak –> extraembryonic mesoderm, embryonic mesoderm, notochordal process, embryonic endoderm

Question 19

Hypoblast gives rise to…

Answer 19

endoderm of yolk sac –> extraembryonic mesoderm

prechordal plate

Question 20

embryonic endo, meso, ectoderm derived from epi or hypoblast?

Answer 20

epi

Question 21

prechordal plate derived from epi or hypo?

Answer 21

hypo

Question 22

primitive streak derived from epi or hypoblast?

Answer 22

epi

Question 23

extraembryonic mesoderm derived from epi or hypo?

Answer 23

both

Question 24

endoderm of yolk sac derived from epi or hypoblast?

Answer 24

hypo

Question 25

how many chromosomes in a primary oocyte?

Answer 25

46- has not undergone meiosis yet.

Question 26

how many chromosomes in a secondary oocyte?

Answer 26

23- has undergone meiosis I but not MII

Question 27

what is spermiogenesis?

Answer 27

spermatids mature into spermatozoa

loss of cytoplasm
tail
acrosome