Embryology Weeks 1 and 2

Question 1

what is the end result of mitosis?

Answer 1

-2 diploid cells

Question 2

What is the end result of meiosis?

Answer 2

-4 haploid cells

Question 3

describe the difference between eggs and sperm with meiosis?

Answer 3

eggs: makes 4 haploid cells, but one is functional and 3 are non functional
Sperm: all 4 haploid cells are functional

Question 4

polar bodies

Answer 4

-non functional haploid germ cells

Question 5

fertilization is also known as what stage?

Answer 5

-pronuclear

Question 6

what is the new cell called that is the result of a haploid sperm fusing with a haploid egg

Answer 6

zygote

Question 7

what does a zygote contain?

Answer 7

-diploid complement of chromosomes and a 2 nucleus quantity of DNA

Question 8

what day does cleavage happen?

Answer 8

day 1!!

Question 9

what kind of divisions are cleavage?

Answer 9

mitotic

Question 10

do the cells increase in number during cleavage?

Answer 10

• yes!

- the cells increase in number, but the zygote does not increase in size

Question 11

what are the daughter cells after cleavage called?

Answer 11

Blastomeres

Question 12

are the daughter cells completely separated during cleavage?

Answer 12

nope

Question 13

what number of cells indicates when compaction should start?

Answer 13

8 cells!

-usually 72 hours

Question 14

what is compaction?

Answer 14

-cell surfaces flatten and cells tightly adhere to each other

Question 15

how many cells typically make up a Morula?

Answer 15

16-32

-usually 4 days

Question 16

Morula appearance

Answer 16

• more tightly join together than compaction

- start to look more like one instead of a lot of separates

Question 17

what are the blastomeres that segregate to the center of the morula called?

Answer 17

-embryoblasts

Question 18

what are the blastomeres that segregate to the outside of the morula called?

Answer 18

-trophoblasts

Question 19

what do the embryoblasts eventually give rise to?

Answer 19

-embryo proper

Question 20

trophoblasts are a primary component of what?

Answer 20

-placenta

Question 21

what is a Blastocoel??

Answer 21

-blastocyst cavity made when morula absorbs fluid

Question 22

What day does the embryo become a blastocyst?

Answer 22

Day 5(96 hours)

Question 23

what are the two poles of the blastocyst and where are they?

Answer 23

• embryonic pole: side of blastocyst that contains inner cell mass
• abembryonic pole: opposite side

Question 24

what day does the morula reach the uterus?

Answer 24

3-4 days into development

Question 25

after arriving in the uterus, what does the blastocyst adhere to?

Answer 25

-uterine lining

Question 26

What is the decidual reaction?

Answer 26

-cells from endometrial stroma differentiate into secretory cells (decidual cells)

Question 27

what triggers the decidual response?

Answer 27

-the blastocyst entering the uterus and the corpus luteum secreting progesterone

Question 28

what does corpus luteum do?

Answer 28

- when there is no fertilization, it withers away | - when there is fertilization, it releases progesterone to help aid in implantation

Question 29

how many epithelial layers does the embryoblast have?

Answer 29

- 2 | - its bilaminar

Question 30

what are the epithelial layers within the embryoblast?

Answer 30

- epiblast | - hypoblast

Question 31

Epiblast: internal or external, and what kind of epithelial cells? dorsal or ventral?

Answer 31

- external layer - columnar cells - dorsal

Question 32

hypoblast: Internal or external, and what kind of epithelial cells? Dorsal or ventral?

Answer 32

- internal layer - cuboidal cells - ventral

Question 33

what is the two layered embryoblast called?

Answer 33

-bilaminar embryonic disc

Question 34

what is the amniotic cavity?

Answer 34

- appears in day 8 | - fluid collects between epiblast and trophoblast

Question 35

what day is the embryo completely implanted in the uterine endometrium?

Answer 35

-9

Question 36

what cells migrate to form Heuser's membrane?

Answer 36

-cells from hypoblast

Question 37

Heuser's membrane merges to form what? (cavity for hypoblast cells)

Answer 37

-primary yolk sac

Question 38

what is the space between heuser's membrane and cytotrophoblast?

Answer 38

- loosely associated extraembryonic mesodermal cells | - around 10-11 days

Question 39

what is the space between the two layers of extraembryonic mesoderm?

Answer 39

chorionic cavity

Question 40

when does the definitive yolk sac develop?

Answer 40

-migration of hypoblast cells over the extraembryonic mesoderm to push the primary yolk sac in front of the mesoderm.

Question 41

primary yolk sac splits into what?

Answer 41

- definitive yolk sac | - remnants of primary yolk sac

Question 42

what day does the primary yolk sac split?

Answer 42

13

Question 43

the definitive yolk sac is connected to the amnion by a connecting stalk in what cavity?

Answer 43

chorionic cavity

Question 44

what is the embryonic disk?

Answer 44

-the place at which the amnion and definitive yolk sac meet. that's it.

Question 45

meckel's diverticulum

Answer 45

- as a result of the persistence of the yolk sac after birth | - really rare, usually goes away because we dont need eggs