Embryology - Videos

Question 1

Corona radiata

Answer 1

Dense layer of cells surrounding the oocyte

Question 2

Zona pellucida

Answer 2

Glycoprotein protective coat surrounding oocyte, acts in sperm binding, fertilization, block to polyspermy and premature implantation

Question 3

ZP3

Answer 3

Receptor protein in zona pellucida, binds to sperm

Question 4

Sperm binding

Answer 4

Reaction where sperm binds to ZP3 receptors on zona pellucida

Question 5

Acrosomal reaction

Answer 5

Activated when sperm binds to zona pellucida, acrosomal enzymes released and digest zona pellucida proteins

Question 6

Perivitalline space

Answer 6

Space between oocyte and zona pellucida

Question 7

Fast block to polyspermy

Answer 7

Oocyte cell membrane depolarization in reaction to sperm fusion, stops other sperm from fusing

Question 8

Slow block to polyspermy

Answer 8

Sperm fusion activates calcium wave that triggers cortical granule secretion and destruction of ZP3 blocking sperm binding

Question 9

Cortical granule

Answer 9

Specialized granule just beneath the plasma membrane of oocyte that contains enzymes that destroy ZP3

Question 10

Pronucleus

Answer 10

Term describing the maternal and paternal nuclei before fusion in the oocyte

Question 11

Zygote

Answer 11

Diploid cell formed when maternal and paternal pronuclei fuse

Question 12

Cleavage

Answer 12

Rapid mitotic division after fertilization, first on happens at 30 hours

Question 13

Blastomere

Answer 13

Diploid cells formed by early zygotic divisions through cleavage

Question 14

Morula

Answer 14

Cluster of 16-32 identical blastomeres, enters the uterus cavity around day 4

Question 15

Blastocoele

Answer 15

Cavity formed when uterine milk penetrates the blastomere and form a cavity during day 5

Question 16

Blastocyst

Answer 16

Early developmental stage of embryo following morula, consists of trophoblast, embryoblast and blastocoele, forms around day 5 and hatches from zona pellucida

Question 17

Implantation

Answer 17

Happens 6-7 days after fertilization, can happen only if the endometrium wall is properly prepared

Question 18

Decidua

Answer 18

Name for the endometrium during pregancy

Question 19

Decidua basalis

Answer 19

Decidua surrounding the embryo

Question 20

Decidua capsularis

Answer 20

Decidua wall between the embryo and uterus

Question 21

Decidua parietalis

Answer 21

All other decidua that is not d. basalis or d. capsularis

Question 22

Trophoblast

Answer 22

Outer cell mass of the blastocyst, goes on to form the placenta and related structures, forms during day 5

Question 23

Embryoblast

Answer 23

Inner cell mass of the blastocyst, goes on to form the embryo, forms during day 5

Question 24

Cytotrophoblast

Answer 24

Cellular inner layer of trophoblast, forms during impantation around day 7

Question 25

Syncytiotrophoblast

Answer 25

Outer layer of the trophoblast, consists of fused cells that go on to form lacunae, forms during implantation around day 7

Question 26

Hypoblast

Answer 26

Also known as primitive endoderm, forms the membrane of the yolk sac, part of bilaminar embryonic disc, later replaced by epiblast cells, forms around day 8

Question 27

Epiblast

Answer 27

Part of bilaminar embryonic disc, goes on to form all structure of the embryo proper, forms around day 8

Question 28

Amniotic cavity

Answer 28

Forms between epiblast cells and cytotrophoblast cells, goes on to surround the whole embryo, forms around day 8

Question 29

Exocoelemic membrane

Answer 29

Membrane formed from migrating hypoblast cells during day 8, lines the primitive yolk sac

Question 30

Bilaminar embryonic disc

Answer 30

Early embryonic strucure that consists of epiblast and hypoblast, forms around day 8

Question 31

Lacunae

Answer 31

Small holes in syncytiotrophoblast that later fuse forming lacunar networks and fuse with maternal sinusoids, start forming around 9 and start fusing around day 12

Question 32

Maternal sinusoid

Answer 32

Dilated maternal capillaries of the endometrium that go on to fuse with lacunar networks

Question 33

Extraembryonic mesoderm

Answer 33

Layer of cells between inner membrane of sytotrophoblast and primitive yolk sac, forms the chorionic cavity, form around day 12

Question 34

Chorionic cavity

Answer 34

Cavity formed by extraembryonic mesoderm, surrounds the early embryo

Question 35

Secondary yolk sac

Answer 35

Formed after part of the exocoelemic membrane is pinched of and expulsed to the abembryonic side, forms around day 13

Question 36

Connecting stalk

Answer 36

Extraembryonic mesoderm structure that connects the bilaminar embryo to the cytotrophoblast, forms around day 13 after the chorionic cavity expands

Question 37

Gastrulation

Answer 37

Process where the bilaminar embryonic disc undergoes reorganization to form a trilaminar disc and the three germ layers

Question 38

Caudal end

Answer 38

Tail end

Question 39

Primitive streak

Answer 39

Thickened structure that forms around the midline of the epiblast near the caudal end, defines the major body axis, forms around day 15

Question 40

Cranial end

Answer 40

Towards the head

Question 41

Primitive node

Answer 41

Expansion of the primitive streak on the cranial end, forms a depression known as primitive pit, formed around day 15

Question 42

Primitive pit

Answer 42

Circular depression of the primitive node in the cranial end of the primitive streak, forms around day 15

Question 43

Primitive groove

Answer 43

Name for the depression from primitive pit towards the caudal end along the primitive streak

Question 44

Invagination

Answer 44

Process where epiblast cell dip and migrate through the primitive streak towards the interior of the embryo

Question 45

Definitive endoderm

Answer 45

Germ layer formed by migrating epiblast cells when they replace hypoblast cells, goes on to form the gastrointestinal tract and related organ as well as respitorary tract

Question 46

Capacitation

Answer 46

Destabilization of the sperm cell membrane by uterine secretions