Cleavage Stages and Placental Development

Question 1

Where does fertilization usually occur?

Answer 1

Ampulla

Question 2

Events of fertilization

Answer 2

1. Corona radiata
2. Zona pellucida
3. Zona reaction

Question 3

Corona radiata

Answer 3

layer of cuboidal cells surrounding the egg; sperm enter by secreting proteolytic enzymes

Question 4

Zona pellucida and cortical reaction

Answer 4

• layer of glycoproteins; acrosome reaction happens where acrosome (cap) over the head of the sperm ruptures and releases digestive enzymes that degrade the glycoproteins
• When the first sperm penetrates, cortical granules lining the ovum membrane rupture, releasing enzymes like peroxidases (cortical reaction)

Question 5

Zona reaction

Answer 5

release of enzymes in cortical reaction inactivate receptors for spermatozoa binding on the outside of the zone, preventing further sperm from penetrating

Question 6

Sperm nucleus enters egg cytoplasm and becomes…

Answer 6

male pronucleus

Question 7

Once male pronucleus forms, the egg is now ________ and is called a _______.

Answer 7

fertilized; zygote

Question 8

Once female pronucleus develops, pronuclei drawn together during….via….and then they….

Answer 8

first mitotic division via mitotic spindle; membranes break down and intermix

Question 9

Cells of early embryo…

Answer 9

Blastomeres

Question 10

After 3rd cleavage, 8 cell embryo is called…

Answer 10

Morula

Question 11

Compaction

Answer 11

Separation of inner (fetus) and outer (chorion and placenta) cells

Question 12

After organization of ICM, trophoblast, and blastocoel, embryo known as…

Answer 12

Blastocyst

Question 13

ICM produces…

Answer 13

Fetus, yolk sac, and extraembyonic mesoderm

Question 14

Outer mass fate…

Answer 14

trophoblast

Question 15

Trophoblast produces….

Answer 15

extraembyonic layers (cytotrophoblast, synctiotrophoblast)

Question 16

Hatching

Answer 16

Blastocyst prepares for implantation by hatching from zona pellucida

Question 17

Morphogenesis of embryonic circulatory system

Answer 17

a. Mesenchymal cells differentiate into angioblasts > primitive RBCs OR endothelial cells to produce capillaries > interconnect to establish embryonic circulatory system

Question 18

Primary villi

Answer 18

cytotrophoblast core surrounded by synctiotrophoblast

Question 19

Secondary villi

Answer 19

Mesodermal core develops w/i cytotrophoblast

Question 20

Tertiary villi

Answer 20

Blood vessels invade mesoderm

Question 21

Once villi invade all the way to endometrium, they form a layer called…

Answer 21

Outer trophoblast shell

Question 22

Terminal villi

Answer 22

Branch off of stem villi

Question 23

Nutrient exchange b/w fetal and maternal circulation through…

Answer 23

Terminal tertiary villi

Question 24

Maternal component of placenta begins with…

Answer 24

Trophoblastic lacunae forming in the synctiotrophoblast

Question 25

Maternal sinusoids

Answer 25

Expanded trophoblastic lacunae that have coalesced with glands and capillaries in overlying endometrium

Question 26

Overlying endometrium known as...

Answer 26

Decidua

Question 27

Where does maternal blood flow?

Answer 27

Intervillous space

Question 28

Where does embryonic blood flow?

Answer 28

Within vessels in villi