Glossary

Question 1

polyspermy

Answer 1

polyspermy The condition of (an egg) being fertilized by more than one sperm

Question 2

dispermy

Answer 2

dispermy The condition of (an egg) being fertilized by two sperm

Question 3

zygote

Answer 3

zygote Fertlized egg

Question 4

morula

Answer 4

morula (from L for mulberry) a preimplantation embryo with 8-32 cells

Question 5

blastocyst

Answer 5

A preimplantation embryo with inner cell mass, trophectoderm and blastocoele (similar to the blastula of other species)

Question 6

blastocoele

Answer 6

blastocoele The fluid filled-cavity of a blastocyst

Question 7

inner cell mass

Answer 7

inner cell mass The inner cells of a blastocyst. It will give rise to the embryo, fetus and adult

Question 8

trophectoderm

Answer 8

trophectoderm The outer cells of a blastocyst. It will only give rise to placental tissues.

Question 9

conceptus

Answer 9

conceptus The products of fertiization, including embryo and placenta

Question 10

organogenesis

Answer 10

organogenesis The process of generating organs in the early embryo

Question 11

embryo

Answer 11

embryo Prior to completion of organogenesis, the portion of the conceptus which will give rise to the fetus and adult

Question 12

fetus

Answer 12

fetus After organogenesis, the portion of the conceptus which will give rise to the adult

Question 13

implantation

Answer 13

implantation The attaching and invasion of the endometrium by the blastocyst

Question 14

hypoblast

Answer 14

hypoblast Derived from the inner cell mass, one of the two layers of the bilaminar embryo. Gives rise to yolk sac endoderm

Question 15

epiblast

Answer 15

epiblast A derivative of the inner cell mass, one of the two layers of the bilaminar embryo. Gives rise to amniotic ectoderm, primordial germ cells and the

Question 16

amnion

Answer 16

amnion The membrane surrounding the amniotic cavity dorsad to the epiblast.

Question 17

amniotic cavity

Answer 17

The fluid filled cavity originally bounded by the amniotic ectoderm and the epiblast or ectoderm

Question 18

primordial germ cells

Answer 18

primordial germ cells The germ cells from the time when they first form from the epiblast until the time when they enter the somatic gonad several days later

Question 19

yolk sac

Answer 19

yolk sacThe membrane surrounding the yolk sac cavity, composed of yolks sac endoderm and yolk sac mesoderm.

Question 20

yolk sac cavity

Answer 20

yolk sac cavity: The fluid filled cavity originally bounded by the yolk sac endoderm and the hypoblast or endoderm

Question 21

cytotrophoblast

Answer 21

cytotrophoblast Diploid cell layer derived from the trophoblast

Question 22

syncytiotrophoblast

Answer 22

syncytiotrophoblast A polyploid tissue derived from the trophoblast arising from cell fusion.

Question 23

extraembryonic mesoderm

Answer 23

extraembryonic mesoderm Mesoderm in the placenta, external to the embryo. Its prescuror tissue in humans is not certain. Gives rise to amniotic and yolk sac mesoderm, connecting stalk, parts of chorion.

Question 24

chorion

Answer 24

chorion The outer membrane of the conceptus, consisting of cytotrophoblast, syncytiotrophoblast and extra-embryonic mesoderm

Question 25

chorionic cavity

Answer 25

chorionic cavity. A large fluid-filled cavity in the extra-embryonic mesoderm later obliterated by expansion of the amnion

Question 26

connecting stalk

Answer 26

connecting stalk: The connection between the chorion and the remainder of the conceptus which suspends it in the chorionic cavity. Derives from extra-embryonic
mesoderm and contirbutes to the umbiliicus.

Question 27

monozygotic

Answer 27

Of twins originating from one zygote (identical twins)

Question 28

dizygotic

Answer 28

Of twins originating from two zygotes (fraternal twins)

Question 29

hydatidiform mole

Answer 29

hydatidiform mole An abnormal conceptus consisting almost exclusively of chorionic tissue

Question 30

ectopic

Answer 30

ectopic In the wrong place, as in ectopic implantation or pregnancy