Introductory Embryology, Oral-Facial Development And Associated Developmental Anomalies Flashcards
Stages of human development:
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?
blastomere
≥ 32 Blastomeres
is called a?
morula
The 64 cell stage
morula develops? referred to as?
internal blastocystic
cavity and thereafter
is referred to as a
blastocyst
embryoblast
The blastocyst also develops an inner cell mass at days 6-7
and thereafter is referred to as the embryoblast.
implantation, structure that accomplsihes it? occurs when?
Implantation of the embryoblast in the uterine wall begins
at day 4 and is complete at day 10. accomplished with syncytiotrophoblasts projections of blastocyst. will slowly move deeper into uterine wall.
inner cell mass of the embryoblast becomes?
bilaminar embryonic disc
two layers
outer cell mass of the embryoblast becomes?
Outer cell mass becomes the cytotrophoblast & syntrophoblast layers which are precursor to the placenta
layers of bilaminar embryotic disc
epiblast: meso/ectoderm
hypoblast: endoderm
structures associated with the bilaminar embryotic disc
Epiblast Layer • Hypoblast Layer • Amniotic Cavity • Blastocyst Cavity (yolk sac) • Syntrophoblasts • Cytotrophobasts
Heuser’s membrane-formation and purpose (new term?)
formed by enlargement of the amniotic cavity and migration
of cells out of the hypoblast
Heuser’s membrane will form the
internal lining of the blastocyst cavity – now called the yolk sac
cell layers and embryotic cavities of the embryoblast
cell layers: Epiblast Embryonic mesoderm Hypoblast embryonic cavities: Amniotic Yolk sac Chorionic
During the 3rd week of development, the bilaminar
embryonic disc is characterized by formation of what structures?
Primitive Streak
Notochord
Neural tube
AND the 3 germ layers (ecto formerly the epiblast and endo formerly the hypoblast)
portions of primitive streak (gives rise to? order?)
Primitive Streak>
Notochord>
>Neural Tube
(in this order)
the primitive node will give rise to?
notochord
notochord formation, when it occurs
Primitive node → Notochordal Process → Notochord
• Pre-notochordal cells invaginate within the primitive
node and migrate towards the cephalad until the
reach the prechordal plate. They detach themselves
from the ectodermal layer to line within the
mesoderm forming the notochord.
completed by week 3: proliferation period
notochrod functions
• The notochord functions as a primitive skeletal support of the
embryo around which the axial skeleton later forms. establishes symmetry and polarity of development
• The notochord also induces formation of somites, the precursors
of the vertebral column, ribs, associated back muscles and
overlying dermis.
notochord formed by?
ectodermal cells derived from the primitive node. The cells then migrate
within the mesodermal layer
to their appropriate midline
position.
different mesoderms formed in development
• Paraxial Mesoderm (central) • Intermediate Mesoderm (between) • Lateral Plate Mesoderm (more lateral) Parietal Visceral
derivatives of the different mesoderms
• Paraxial mesoderm → somites (stimulated by notochord)
• Intermediate mesoderm →urogenital system
• Lateral plate mesoderm:
Parietal mesoderm → mesothelial (serous)
membranes that cover the peritoneal, pleural
and pericardial cavities.
Visceral mesoderm → forms the thin serous
membranes that cover individual organs,
e.g., stomach, pancreas, spleen, etc.
derivatives of ectoderm
• Epidermis, hair and nails • Epithelium of the oral and nasal cavities and paranasal sinuses • Salivary and endocrine glands • Nervous system • Tooth enamel
derivatives of endoderm
• GI tract epithelium and associated glands
development of neural tube with diagram
epiblast layer above notochord will fold to from the neural groove, tips of the waves=neural crest cells. neural crest cells join with continued folding and migrate towards the sides and form various structures (dorsal root ganglia, etc.). joining of the fold also produces the neural tube.
Neural Tube Related Developmental Defects
Spina Bifida, Meningocele, Meningomyelocele, Meningoencephalocele, Anencephaly
Spina Bifida cause (deficiency in?)
folic acid deficiency
Meningocele cause
extrusion of dura and arachnoid mater
Meningomyelocele cause
extrusion of neural tissue plus all three meninges
Meningoencephalocele cause
extrustion of a ventricular cistern plus neural tissue
Anencephaly
fatal defect characterized by lack of development of
the cranium and brain