Embryology Terms

Question 1

Gamete

Answer 1

Sperm in males

Oocyte in females

Question 2

Sperm Head

Answer 2

Majority of the sperm, contains nucleus

Question 3

Sperm Neck

Answer 3

Junction between head and tail

Question 4

Sperm Tail

Answer 4

Provides the motility to the fertilization site

Question 5

Acrosome

Answer 5

Located in the head of the sperm, contains digestive enzymes required to penetrate egg membrane

Question 6

Corona radiata

Answer 6

Outer layer of cells that is firmly anchored to the zona pellucida

Question 7

Zona pellucida

Answer 7

Thick later of glycoproteins surrounding the oocyte

Question 8

Primary oocyte

Answer 8

Cell that has completed meiosis I

Question 9

Secondary oocyte

Answer 9

Enters meiosis II, but stops at metaphase II until fertilization or the menstrual cycle

Question 10

Granulosa cells

Answer 10

Cells responsible folliculogenesis

Question 11

Cumulus oophorous

Answer 11

Anchor oocyte to the follicle wall

Question 12

Mural granulosa cells

Answer 12

Line of wall of the follicle

Question 13

Female pronucleus

Answer 13

Nucleus of oocyte after fertilization

Question 14

Male pronucleus

Answer 14

Nucleus of sperm after fertilization

Question 15

Zygote

Answer 15

Fusion of male and female pronuclei, giving 46 chromosomes

Question 16

Polyspermy

Answer 16

Multiple sperms penetrating the oocyte

Question 17

Compaction

Answer 17

Number of cells will increase, but the size of each cell will decrease. Occurs after 9-cell stage

Question 18

Morula

Answer 18

“Little blackberry”, grouping of cells, at about 12-32 cells, in development

Question 19

Blastocyst

Answer 19

The embryo and its membranes

Question 20

-blast

Answer 20

To turn into

Question 21

Trophoblast layer

Answer 21

Cells that will become the placenta

Cytotrophoblast + syntiotrophoblast layers

Question 22

Embryoblast

Answer 22

Forming the embryo, also known as embryonic stem cells. Presents after ‘hatching’ of blastocyst from zona pellucida

Question 23

Blastogenesis

Answer 23

Formation of blastocyst

Question 24

Mosaics

Answer 24

Individuals with numeric mosaicism

Common in trisomies

Question 25

Cytotrophoblasts

Answer 25

Inner layer of trophoblasts layer

Question 26

Syncytiotrophoblasts

Answer 26

Multinucleated protoplasm is mass without cell boundaries. These cells will ‘chew up’ and evade the endometrium to have blastocyst burrow into the wall

Question 27

Hypoblasts

Answer 27

Formation by Day 7. Small cuboidal cells adjacent to the exocoelomic cavity.

Question 28

Epiblast

Answer 28

Layer of columnar cells deep to the hypoblast, forms the embryo

Question 29

Amniotic cavity

Answer 29

Cavity that will eventually fill with amniotic fluid, used for nutrition and support

Question 30

Amnion

Answer 30

Cells that form the amniotic cavity

Question 31

Primary umbilical vesicle

Answer 31

Hypoblast + exocoelomic membrane

Question 32

Extraembryonic mesoderm

Answer 32

Surrounds the amnion and umbilical vesicle

Question 33

Extraembryonic coelom

Answer 33

large, fluid-filled cavity surrounds the amnion and primary umbilical vesicle

Question 34

Secondary umbilical vesicle

Answer 34

Formation from hypoblast cells, site of primordial germ cells. The majority of the primary umbilical vesicle will pinch off and leave this.

Question 35

Extraembryonic somatic mesoderm

Answer 35

Lines the trophoblast and amnion

Question 36

Extraembryonic splanchnic mesoderm

Answer 36

Surrounds the umbilical vesicle

Question 37

Chorion

Answer 37

Extraembryonic somatic mesoderm + trophoblast Outermost fetal membrane, forms wall of the chorionic sac

Question 38

Connecting stalk

Answer 38

Connection between extraembryonic splanchnic mesoderm and extraembryonic somatic mesoderm, becomes umbilical cord

Question 39

Primary germ layers

Answer 39

‘Most important step of development’ Gives rise to all adult structures, establishes the body plan ‘tube within a tube’

Question 40

Primitive streak

Answer 40

Thin depression on the surface of epiblast

Question 41

Trilaminar embryonic disc

Answer 41

When endoderm, ectoderm, and mesoderm is present

Question 42

Embryonic endoderm

Answer 42

Displacement of hypoblast Forms epithelial linings of respiratory and digestive tracts, glands opening into the GI tract, and glandular cells of accessory of GI organs (such as liver or pancreas)

Question 43

Embryonic ectoderm

Answer 43

Cells remaining in the epiblast Give rise to epidermis of skin and epidermal derivatives, central and peripheral nervous systems, neural crest cells, eyes and internal ears.

Question 44

Embryonic mesoderm

Answer 44

Cells that remain in between the endoderm and ectoderm Give rise to all skeletal muscle, visceral smooth muscular coats, serosal linings of all body cavities, urogenital ducts and organs, most of cardiovascular system, blood cells, and lining of Vasculature, and cartilage, bones, tendons, ligaments, dermis, and stroma of internal organs in the trunk

Question 45

Ingression

Answer 45

Movement of epiblast cells through the primitive streak to relocate between the epiblast and hypoblast layers

Question 46

Primitive pit

Answer 46

Depression in the primitive node

Question 47

Primitive node

Answer 47

Area of primitive streak

Question 48

Notochordal process

Answer 48

Forms from primitive node and pit toward the cranial end

Question 49

Prechordal plate

Answer 49

Becomes the site of future mouth, end point of growth of notochordal process

Question 50

Notochord canal

Answer 50

Lumen of the notochordal process

Question 51

Notochord

Answer 51

Solid rod derived from the primitive node (mesodermally) derived. This functions as a primary inductor (signaling center) in the early embryo.

Question 52

Nucleus pulposus

Answer 52

Early form of intervertebral discs. Created from the degeneration of notochord to form vertebral bodies.

Question 53

Caudal eminence

Answer 53

Tail bud of organism