Flashcards in General Embryology Deck (52):
what are the three periods of general embryology?
fertilization causes the formation of what?
mitosis of the zygote leads to formation of what?
growth factors, and cell adhesion molecules act through what?
signaling complexes which activate various transcription factors, affecting cellular changes
what are some changes that may occur due to growth factor or cell adhesion molecules
proliferation, differentiation or apoptosis
what are the ways growth factors can act?
autocrine, paracrine, or endocrine
*mostly through paracrine
why is Bone Morphogenic Protein (BMP) important in craniofacial development?
induction, formation, determination and migration of neural crest cells
-patterning and formation of facial primordia
-negative regulator of myogenesis
-regulator of early tooth morphogenesis and differentiation
**at gastrulation, it switches between epidermal vs. neural fate
Homeobox genes code for what?
transcription factors that begin to make cells pattern into one tissue/organ type or another
*involved in segmentation
function in pattering the body axis(rostral caudal) and determine where limbs and other body segments will grow in developing fetus
control cellular process of differentiation and proliferation during development
control development of ectodermal tissues derived from lateral border of neural plate
-distal proximal of pharyngeal arches
Shh (sonic hedgehog) genes
play important role in early induction of facial primordium
cell adhesion molecules are responsible for what?
specific cell aggregation and sorting
after initial cleavage of the zygote the solid ball of cells is known as what?
morula and then later becomes a blastocyst
by the end of the first week the blastocyst stops traveling and does what?
implants into the thickened uterine wall in a processes called implantation
what are the components of a blastocyst
outer most cells are trophoblast, inner ball of cells is the embryoblast, and then the yolk sack fills the rest of the space
the embryonic period begins and ends when?
starts at the end of the second week
ends at the end of week eight
what occurs during the embryonic period
spacial and temporal events called pattering
what are some of the pattering structures that will form during the embryonic period?
pharyngeal arches, somtie development, face development, palate and tongue
embryonic phase: patterning
-tissue and organ specialization and formation
-dentition development regionally
what is induction
when one group of cells tells another group of cells (which are competent) to do something
cell division, increase in number and accumulation of cells products
development of specific structures and or functions by individual cells or group of cells
cell migration, interactions and proliferations causing the development of specific structures
attainment of adult size and function form proliferation, differentiation and morphogenesis
what is gastrulation
the formation of the 3 germ layers
*happens around week three
after the blastocyst implants, the embryoblast differentiates into two layers:
epiblast-form amniotic cavity
hypoblast-form roof of secondary yolk sac
what type of cells are the epiblast layer
what type of cells are the hypoblast layer
when does the primitive streak form?
after the bilaminar disk forms
what is the primitive streak
-a little groove formed by the epiblast cells
-defines the future bilateral symmetry along a rostral-caudal axis
what is the prochordal plate
forms at the rostral end and is where the ectoderm curves around and integrates with the endoderm
the ectodermal cells at the primitive streak invaginate at the primitive node forming what?
the primitive pit
what happens at the primitive pit?
ectodermal cells migrate between the ectoderm and endoderm to form the notochord and then move laterally to form the mesoderm
the notochord and mesoderm totally separate the ectoderm from the mesoderm everywhere but at two places, what are they?
the prochordal plate and the cecal plate
how do the ectodermal cells become mesoderm?
medial epiblast cells lose their cell-cell adhesion and become motile and invade inwards
-these mesenchymal cells are interspersed in matrix and have no polarity
- cell attachment proteins from E to N cadherin
head folding at the prochordal plate forms what?
oropharyngeal (buccopharyngeal) membrane
**remember no mesoderm between the two layers
this is the location of the stomodeum (primitive mouth)
what do the ectodermal cells give rise to?
-epidermis including (hair, nails, sebaceous and sweat glands)
-epithelium lining of oral, nasal, and sinus cavities
-part of intra oral glands
what does the endoderm give rise to?
epithelial lining of the respiratory and GI tract and all associated organs
what does the mesoderm give rise to?
muscles, all CT derived tissues ( bone, cartilage, blood, dentin, pulp, cementum and PDL)
what are the three key things that happen after gastrulation(after week 3)?
1. differentiation of nervous system
2. Formation/migration of neural crest
3. Head, lateral , and tail folds
what is the neuroectoderm
specialized group of cells that differentiates from the ectoderm, localized to the neural plate that extends from the cephalic to the caudal end
*undergoes further growth in thickening, which causes and inward invagination forming the neural groove
once the neural groove forms what happens
neural fold fusion begins at upper cervical levels and proceeds both rostrally and cuadallly
paraxial mesoderm gives rise to?
cartilage, segmented muslce
intermediate mesoderm gives rise to?
lateral plate mesoderm gives rise to?
heart and gut
differentiated mesoderm gives rise to?
somites, which are located on the sides of the developing CNS
once the neural tube forms it expands and forms what?
forebrain, midbrain, hindbrain
*hindbrain segments into rhombomeres which express Hox genes
*branchial arches develop
Neural crest formation and migration
develops from the neuroectoderm during week 3 and breaks away from the crests of the neural folds and disperses in mesenchyme
Treacher Collins syndrome
failure of neural crest cells to migrate to the facial region
how does the pharynx form
stomodeum remains separate, but will ultimately break down to form the oral opening of the GI
-foregut gives rise to primitive pharynx
-ultimately becomes oropharynx