Introductory Embryology, Oral-Facial Development and Associated Developmental Abnormalities Flashcards
What are the stages of human development?
-Proliferation period (0-3 weeks)
-embryonic period (3-8 weeks)
-fetal development period (9 weeks to term)
What forms after an ovum is fertilized?
zygote
What does mitotic cleavage of a zygote form?
blastomere
What is the stage of >32 blastomeres called?
morula
What happens at the 64 cell stage?
morula develops an internal blastocytstic cavity and becomes a blastocyst
What is a cyst?
a mass lined with usually epithelial tissue with a hollow cavity
(can be fluid filled)
What is an embryoblast ?
cell stage in development after the blastocyst develops an inner cell mass
When does implantation of embryoblast occur?
starting at day 4 and usually done by day 10
What are syncytiotrophoblasts?
finger like projections that help the embryoblast implant into the wall of the uterus
What is the bilaminar embryonic disc?
two layers of cells that form in the inner cell mass
When does the bilaminar embryonic disc form?
when the embryoblast starts getting engulfed into the uterine wall
What does the outer cell mass become?
cytotrophoblast and syntrophoblast layers
(precursors to the placenta)
What does the epiblast layer of the bilaminar embryonic disc become?
ectoderm and mesoderm
What does the hypoblast layer of the bliaminar disc become?
endoderm
What is the Heuser’s membrane?
the internal lining of the blastocyst cavity
What is the blastocyst cavity become?
yolk sac
What is the third cavity that forms during development?
chorionic cavity
What are the three distinct embryonic germ layers?
endoderm
mesoderm
ectoderm
What is formed during the 3rd week of development from the bilaminar embryonic disc?
primitive streak
notochord
neural tube
How is the notochord formed?
pre-notochordal cells invaginate within the primitive node and migrate toward the cephalad until the reach the prechordal plate
-they detach themselves from the ectodermal layer to line within the mesoderm forming the notochord
What is the order of steps to make the notochord?
primitive node -> notochordal process -> notochord
What is the function of the notochord?
functions as a primitive skeletal support of the embryo around which the axial skeleton forms later
What does the notochord induce the formation of?
the somites
-precursors of the vertebral column, ribs, associated back muscles, and overlying dermis
What are the three types of mesoderm?
-paraxial
-intermediate
-lateral plate
What are the two types of lateral plate mesoderm?
-parietal
-visceral
What does the paraxial mesoderm form?
somites
What does the intermediate mesoderm form?
the urogenital system
What does the parietal segment of the lateral plate mesoderm form?
mesothelial (serous) membranes that cover the peritoneal, pleural, and pericardial cavities
What does the visceral segment of the lateral plate mesoderm form?
the thin serous membranes that cover individual organs, stomach, pancreas, spleen, and other organs
What are the 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
What are the derivatives of the endoderm?
GI tract epithelium and associated glands
What is spina bifida?
developmental defect that occurs when the neural tube does not close properly
-due to folic acid deficiency
What is meningocele?
extrusion of dura and arachnoid mater
What is meningomyelocele?
extrusion of neural tissue plus all three meninges
What is meningoencephalocele?
extrusion of a ventricular cistern plus neural tissue
What is anencephaly?
fatal defect characteristics by lack of development of the cranium and brain