Ch. 3 Embryology

Question 1

Embryology

Answer 1

Development of the embryo

Question 2

When does ovulation occur?

Answer 2

14th day of menstrual cycle

Question 3

When does fertilization occur?

Answer 3

12-24 hours after ovulation

Question 4

Where does fertilization occur?

Answer 4

In the Fallopian tube or oviduct

Question 5

Gametes are….

Answer 5

Haploid (n) cells… only 23 chromosomes
Occur during meiosis
Sperm and oocyte cells

Question 6

What is the pre-embryonic development order?

Answer 6

1st two weeks of development

1. Zygote
2. Cleavage
3. Morula
4. Blastocyst
5. Implantation

Question 7

Zygote

Answer 7

Memborous layer - Zona Pellucida
Single Diploid (2n) Cell- half from each side
23 pairs of chromosomes
Divides once it reaches 2 cell stage

Question 8

Cleavage

Answer 8

Early mitotic sequence
First Division: 12-16 hours after fertilization
One cell becomes two
Does not increase in size

Question 9

Morula

Answer 9

Solid ball of more than 12-16 cells
72 hours after fertilization (day 3)
by day 4 —> in uterus and 60 cells

Question 10

Blastocyst

Answer 10

Days 4-7

a. Deterioration of zona pellucida - fluid begins to leak through (resulting in a blastocyst cavity)
b. Cavity forms
c. Inner cell mass (embryoblast) - rightly packed group of cells located only within one side of the blastocyst
d. trophoblast - outer ring of cells surrounding the fluid filled cavity (forming the chorion)

Question 11

Implantation

Answer 11

A process where the blastocyst burrows into and embeds within the uterine wall (endometrium)

Begins around day 6 (completed 2nd week)

a. trophoblast cells “invade” wall of the uterus
b. Invading cells (chorion) from finger like processes around blood vessels in the uterus
c. chorion cells produce HCG
d. Uterine tissue grows in response to invading trophoblast

Question 12

Chorion

Answer 12

Invading cells form finger like processes around blood vessels in the uterus

• – Produce HCG
• the outermost extraembryonic membrane –> eventually will form the placenta

Question 13

Human Chorionic Gonadotrophin

Answer 13

HCG

Maintains production of ovarian hormones

Question 14

What do ovarian hormones do?

Answer 14

Prevents menstruation & causes uterine growth

Question 15

trophoblast

Answer 15

outer ring of cells surrounding the fluid filled vacity

Question 16

Prenatal Period

Answer 16

38 weeks; begins with fertilization & ends with birth

Question 17

What is pre-Embryonic Development?

Answer 17

process of becoming a multicellular structure…blastocyst. First 2 weeks after fertiliization.
- Single cell (zygote) produced by fertilization, becomes a spherical; multicellular structure ( blastocyst)

Question 18

Decidua

Answer 18

The thick layer of modified mucous membrane that lines the uterus during pregnancy and is shed with the afterbirth.