Introductory Embryology, Oral-Facial Development And Associated Developmental Anomalies Flashcards
Stages of human development: (3)
Proliferation Period (0-3 weeks)
Embryonic Period (3-8 weeks)
Fetal Development Period
(9 weeks to term)
Fertilization of ovum yields —
zygote
mitotic cleavage of zygote forms —
blastomeres
more than 32 blastomeres is called a —
morula
The 64 cell stage morula develops an internal blastocystic cavity and thereafter is referred to as a
blastocyst
The blastocyst also develops an inner cell mass at days 6-7
and thereafter is referred to as the
embryoblast
Implantation of the embryoblast in the uterine wall begins
at day - and is complete at day -
4, 10
The inner cell mass of the embryoblast transitions into the
bilaminar embryonic disc
two layers
Outer cell mass becomes the (2)layers which are precursor to the placenta
cytotrophoblast & syntrophoblast
Epiblast Layer (2)
Ectoderm
Mesoderm
Hypoblast Layer (1)
Endoderm
Structures associated with the bilaminar embryonic disc (6)
- Epiblast Layer
- Hypoblast Layer
- Amniotic Cavity
- Blastocyst Cavity
- Syntrophoblasts
- Cytotrophobasts
Enlargement of the amniotic cavity and migration of cells out of the hypoblast to form
Heuser’s membrane
Heuser’s membrane will form the internal lining of the blastocyst cavity – now called the
yolk sac
Cell layers (3)
Epiblast
Embryonic mesoderm
Hypoblast
Embryonic cavities (3)
Amniotic
Yolk sac
Chorionic
During the 3rd week of development, the bilaminar
embryonic disc is characterized by formation of the: (3)
Primitive Streak
Notochord
Neural Tube
And the three distinct embryonic germ layers: (3)
Ectoderm (formerly the epiblast layer)
Mesoderm
Endoderm (formerly the hypoblast layer)
Primitive Streak (3)
Pit
Node
Groove
steps in formation of the notochord
Primitive node → Notochordal Process → Notochord
— cells invaginate within the — and migrate towards the cephalad until the reach the —. They detach themselves from the ectodermal layer to line within the mesoderm forming the —
Pre-notochordal
primitive node
prechordal plate
notochord
The notochord functions as a
primitive skeletal support of the
embryo around which the axial skeleton later forms
The notochord also induces formation of —, the precursors
of the vertebral column, ribs, associated back muscles and
overlying dermis.
somites
formed from ectodermal cells derived from the —. The cells then migrate within the mesodermal layer to their appropriate midline position. The notochord functions as a primitive axial skeleton for the embryo, establishing symmetry and polarity of development and induction of the —
primitive node
somites
Lateral Plate Mesoderm (2)
Parietal
Visceral