BYU Anatomy Lecture 2 (Embryology)

pre-embryonic (period)

the gestational period of prenatal development from weeks 1-2 (fertilization to implantation)

embryonic (period)

the gestational period of prenatal development weeks 3-8 (implantation to organogenesis)

fetal period

the gestational period of prenatal development weeks 9-38 or birth

embryonic (period)

the gestational period of prenatal development where the baby grows from about a millimeter to about an inch in size

oocyte

the developed female egg awaiting fertilization

fertilization

the act of conception: when a sperm and egg come together

zygote

the product of when a sperm and egg come together. it will undergo mitotic cell divisions as it moves towards the uterus

cleavage

the mitotic cell divisions that the zygote undergoes on its way to the uterus

morula

the product of the zygote undergoing enough mitotic cell divisions to total at least 16 cells.

blastocyst

the product of a morula undergoing enough mitotic cell divisions to total at least 100 cells

trophoblast

the outer layer of the blastocyst

inner cell mass

the portion of the blastocyst that will eventually become the embryo

blastocoel

the fluid-filled portion of a blastocyst

implantation

when the blastocyst hits the uterine lining and successfully burrows inside, ending the pre-embryonic period

cytotrophoblast

one of the two types of cells that the trophoblast cells transform into after making first contact with the uterine lining (endometrium). This type remains in a cellular form/structure

syncytiotrophoblast

one of the two types of cells that the trophoblast cells transform into after making first contact with the uterine lining (endometrium). This type is the result of trophoblast cells fusing together and breaking down endometrium cells for nutrients.

chorion

the outermost extra-embryonic membrane that surrounds the yolk sac, epiblast, etc.

placenta

takes over the yolk sac's job of nourishment of the embryo around week 4

inner cell mass

the part of the blastocyst that becomes the bilaminar disc

bilaminar disc

the epiblast and hypoblast cells developed from the inner cell mass make up the:

epiblast

the upper layer of the bilaminar disc that separates the amniotic sac (amnion) from the hypoblast cells

hypoblast

the layer of the bilaminar disc that separates the epiblast cells from the yolk sac.

epiblast

the layer that becomes the three primary germ layers of the embryo

primitive streak

the cavity that forms in the epiblast just prior to gastrulation. it's formation means that the embryonic stage has already ended

gastrulation

the process that causes the epiblast and hypoblast to develop into the 3 primary germ layers.

invagination

Name the process of the migration of epiblast cells through the primitive streak becoming the mesoderm and ectoderm

ectoderm

In the transformation of the epiblast during gastrulation into this germ layer, this layer faces the amnion and later becomes the nervous system and skin

mesoderm

In the transformation of the epiblast during gastrulation into this germ layer, this layer is in the middle of the three and later becomes the muscular and skeletal systems (also the heart and kidneys).

endoderm

In the transformation of the epiblast during gastrulation into this germ layer, this layer faces the yolk sac and later becomes the respiratory and digestive systems

transverse (body folding)

the folding of the 3 primary germ layers into a tube-like structure

cephalocaudal (body folding)

the "head-to-tail" folding of the 3 primary germ layers after they have already folded into the tube-like structure. induces pinching off of yolk sac

neurulation

the process of the ectoderm transforming into the neural tube

neural plate

a special, thickened portion of the ectoderm (induced by the notochord) that is destined to become the neural tube

notochord

a special portion of the mesoderm that induces neurulation

neural groove

the intermediary structure in neurulation that folds the neural plate into a crevice-like structure

neural tube

the resulting structure of neurulation that is destined to become the brain and spinal cord.

organogenesis

the process through which we have all organs present in some form by about week 8, ending the embryonic period

premature (birth)

any birth that takes place before week 38

30

at which week of development could an infant technically be born and possibly not require any lifesaving measures?

22

at which week of development could an infant technically survive, but likely requiring significant lifesaving measures.

Epiblast

"A"

Hypoblast

"B"

Ectoderm

"C"

Mesoderm

"D"

Endoderm

"E"

trophoblast

"A"

inner cell mass

"B"

hypoblast

"C"

epiblast

"D"

Cytotrophoblast

"E"

Syncytiotrophoblast

"F"

Yolk Sac

"G"

Amnion

"H"

neural plate

"A"

ectoderm

"B"

mesoderm

"C"

notochord

"D"

neural groove

"E"

ectoderm

"F"

neural tube

"G"

epiblast

Does the epiblast, hypoblast, trophoblast, endoderm, mesoderm, or ectoderm represent what will later become the entire embryo?

trophoblast

What helps to build the placenta, as well as the chorionic membrane surrounding the fetus?