Embryonic Period Flashcards
What happens during the embryonic period (stage)?
- blastocyst to embryo
- cytodifferentiation
- growths
- differentiation
- bilaminar embryonic disc
- trophoblastic layer
blastocyst becomes to embryo around what time frame?
from second to eighth week
differentiation occurs at various rates in the embryo. define cytodifferentiation
the development of different cell types
cytodifferentiation has receptors and processes. What are the receptors of the cytodifferentiation?
- none present
- couple receptors
- more receptors
- still more receptors
describe each receptors
- none present = cells die (cell death)
- couple receptors = cells survive
- more receptors = cells proliferate (come to life)
- still more receptors = cells differentiate (into different kinds of cells)
what are the two processes of the cytodifferntiation?
- autocrine process
2. paracrine process
what is meant by autocrine?
cell receives hormone or receptor stimulation from substances produce by itself
what is meant by paracrine process?
cell receives hormone or receptor stimulation from a substance produced by a different cell
receptor is also called?
hormone
what are the types of growth during the embryonic period?
- aptosis
- induction
- proliferation
- interstitial
- appositional
define each growth
- aptosis=programmed cell death (e.g. your webbed hand become fingers)
- induction=one group of cells starting the development of another cellular group
- proliferation=more cells
- interstitial = occurs deep within a tissue
- appositional=additional “outer” layer of cells
what are the differentiation types in the embryonic period
- histodifferentiation
- morphodifferentiation
- morphogenesis
- maturation
what is the definition of histodifferentiation?
development of different tissues within a structure
what is the definition of morphodifferentiation?
development of different forms (structure or shape)
what is the definition of morphogenesis?
process where tissues evolve into more complex structures or shapes
(the process of development of SPECIFIC tissue structure or shape; e.g. enamel)
what is the definition of maturation?
ongoing physiological processes which imparts the FINAL form/function
in the second week of embryonic period a _____ ______ ______ is developed from the blastocyst and appears as a flattened, essentially circular plate of bilayered cells
bilaminar embryonic disc
the bilaminar disc is suspended in the uterus’s endometrim b/w two fluid-filled cavities. Name them
- amniotic cavity
2. yolk sac
the amniotic cavity is fluid filled and faces what layer?
the epiblast layer
the yolk sac is fluid filled and faces what layer?
the hypoblast layer
the yolk sac also serves as what for the embryonic disc?
serves as initial nourishment for the embryonic disc until the placenta is established
the bilaminar embryonic disc has both a superior and inferior layer. What are they?
- epiblast layer, which is the superior layer
2. hypoblast layer, which is the inferior layer
the epiblast, hypblast, amniotic cavity and the yolk sac are surrounded by what layer?
surrounded by the trophoblastic layer
what is special about the trophoblast layer?
the trophoblast layer helps the bilaminar disc to embed in the uterine wall
the third week in the embryonic period another cell is created. how and what is the name?
some cells from the epiblast layer move or migrate toward the hypoblast layer only in the area of the primitive streak. these migratory cells locate in the middle b/w the epiblast and hypoblast layers and become MESENCHYMAL CELLS, an embryonic connective tissue
with three layers present, the bilaminar disc has become thickened into what kind of disc?
a trilaminar embryonic disc, thus the trilaminar disc has three embryonic cell layers.
with the creation of this new embryonic cell layer of mesoderm, what happens?
the epiblast layer is now ectoderm
the hypoblast layer is now endoderm
What are the three embryonic cell layers?
ectoderm
mesenchymal
hypoblast
during the beginning of the third week of prenatal development within the embryonic period what is formed within the bilaminar disc?
the primitive streak is formed
describe the primitive streak
furrowed, rod-shaped thickening in the middle of the disc
the primitive streak is a result of what?
from an increased proliferation of cells in the midline area
the primitive streak causes the disc to have bilateral symmetry, with a….
right half and left half
mesenchymel is also called and inter changeable with?
mesoderm
in addition, during the third week, another specialized group of cells are developed. what are they?
the neural crest cells
the neural crest cells arise from what?
arise from proliferation of ectoderm adjacent to primitive streak
the primitive streak matures into ____ which supports the ____ ______?
notochord; primitive embryo
the neural crest cells are responsible for what structures?
the head and neck structures
each embryonic cell layer is distinct from the others. how?
embryonic cell layer gives rise to specific tissue
What does the ectoderm give rise to?
skin, CNS and PNS, hair, nails, ENAMEL, and lining of the oral cavity
what does the mesoderm give rise to?
bone, muscles, circulatory and reproductive system, internal organs, DENTIN, PULP and CEMENTUM
what does the endoderm give rise to?
lining of respiratory passage, glandular organs and digestive
which cell layer gives the smallest contribution?
endoderm cell layer
which cell layer gives the largest contribution?
mesoderm cell layer
what should we remember about the mesoderm cell layer
the mesoderm cell layer arose from ECTODERM
