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Dental Embryology:Chapter 3, Overview of Prenatal Development

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Prenatal Develoment
begins with the start of pregnancy and continues until the birth of the child; the nine months of gestation is usually divided into three months time spans or trimesters.
embryology
is the study of prenatal development.
preimplantation period and the embryonic period make up the
first trimester
fetal period constitutes the last
two trimesters
primordium
earliest indication of a tissue types or an organ during prenatal development
congenital malformations
occur during both the preimplantation period and the embryonic period, thus involves the first trimester
infections, drugs, and radiation are considered
teratogens
preimplantation
is the first period and takes place during the first week after conception. a females ovum is penetrated by and united with a male's sperm during fertilization.
union of the ovum and sperm subsequently form a fertilized egg, or a
zygote
during fertilization the final stages of meiosis occur in the...
ovum
what is the proper number of chromosomes for a diploid
46
excess chromosomes is avoided by
meiosis
the ovum and sperm are able to reduce the chromosomes to
the haploid number of 23
the photographic analysis of a person's chromosomes is done by orderly arrangment of the pairs in a...
karyotype
After fertilization the zygote then undergoes...
mitosis, or individual cell division with cleavage
after the initial cleavage the solid ball of cells is called
morula
after more mitosis of the morula, the zygote then becomes a...
blastocyst
the rest of the first week during preimplantation peroid it is characterized by...
mitotic cleavage, blastocyst splits into smaller and more cells as it undergoes successive cell division
Mitosis takes place during _____or _____
growth, repair. takes place during REPRODUCTION
Mitosis that occurs during cell division is the...
self-duplication of the chromosomes of the parent cell and their equal distribution to daughter cell.
by the end of the first week, the blastocyst stops traveling and undergoes
implantation
implantation means that the blastocyst becomes embedded in the...
endometrium, the innermost lining of the uterus on its back wall
after a week of cleavage the blastocyst consists of a layer of peripheral cells(________), and a small inner mass of embryonic cells(______)
trophoblast layer, embryoblast layer
trophoblast layer
prenatal support tissue
embryoblast layer
embryo
developmental disturbances during PREIMPLANTATION period...
ectopic pregnancy and downs syndrome
the second period,_____ extends from the beginning of the second week to the end of the eighth week.
Embryonic period
________occurs during the Embryonic period
patterning
Physiological patterning processes include...
induction,proliferation,differentiation, morphogenesis, and maturation.
induction
the action of one group of cells on another, leads to the establishment of the developmental pathway in the responding tissue and which is now considered to be compartmentalized.
proliferation
controlled levels of cellular growth present during most of prenatal development
interstitial growth
tissue enlarges by the addition of layers on the outside of a structure
appositional growth
occurs deep within a tissue types or organ
differentiation
a change occurs in the embryonic cells. are identical genetically but later become quite distinct structurally and functionally. thus the cells perform specialized functions.
all major tissue types,organs, and organ systems are formed during...
first week of the embryonic period
cytodifferentiation
development of different cell types
histodifferentiation
development of differnt tissue types within a structure
morphodifferentiation
development of the differing structure and shape
morphogenesis
process of development of specific tissue structures of shape. occurs due to the migration of embryonic cells, which is followed by the inductive interactions of those cells.
process of maturation
of the tissue types and organs begins during the embryological period and continues later during the fetal period
physiological process maturation involves
proliferation, differentiation, and morphogenesis
embryo is easily recognized at the end of the ...
8th week of prenatal development
2nd week of embryonic period...
blastocyst grows by increased proliferation of the embryonic cells.
the increased number of embryonic cells creates the
embryonic cell layer within the blastocyst
A ______ is eventually developed from the blastocyst and appears as a flattened circular plate of bilayered cells.
bilaminar embryonic disc
the superior _____ is composed of high columnar cells
epiblast layer
inferior ____ is composed of small cuboidal cells
hypoblast layer
_____ faces the hypoblast layer and serves as initial nourishment for the embryonic disc.
yolk sac
placenta
prenatal organ that joins the pregnant female and developing embryo, develops from the interactions of the trophoblast layer and endometrial tissue.
placenta provides what kind of bloodborne substances
oxygen, carbon dioxide, nutritional and hormonal substances
within the 3rd week
the primitive streak forms within the bilaminar disc
cells move between the hypoblast and epiblast layer and then become
mesenchyme, and embryonic tissue
mesenchyme cells form
fibroblasts,chondroblasts, and osteoblasts
some of the mesenchyme begins to create a new embryonic layer called the
mesoderm
with three layers present the bilayer disc thickens and is called
trilaminar embryonic disc
after mesoderm is created the epiblast layer is now considered _____ and the hypoblast layer is now considered______
ectoderm, endoderm
ectoderm gives rise to the
epidermis
mesoderm gives rise to
connective tissue, dermis,cartilage, bone, blood, and muscle
endoderm gives rise to
the respiratory epithelium and cells of glands
areas without mesoderm,_____ and ____ fuse together preventing the migration of mesoderm between them
ectoderm and endoderm
Origin, morphology of the structure, future systemic tissues: Ectoderm
Epiblast layers, columnar, epidermis, sensory epithelium of the eyes, ears, nose, nervous system, and neural crest cells, mammary and cutaneous glands
Origin, morphology of the structure, future systemic tissues: Mesoderm
migrating cells from epiblast layer, varies, dermis, muscle, bone, lymphatics, blood cells,and bone marrow, cartilage, reproductive and excretory glands
Origin, morphology of the structure, future systemic tissues: Endoderm
Hypoblast, Cuboidal, respiratory and digestive system linings, liver, and pancreatic cells
Origin, morphology of the structure, future systemic tissues: Neural Crest Cells
migrating neuroectoderm, varies, components of nervous system pigment cells, connective tissue proper, cartilage, bone, and certain dental tissues
end of the 3rd week the mesoderm additionally differentiates and begins to divide on each side of the tube into 38 paired cuboidal segments of mesoderm called
somites
somites give rise to most of the
skeletal structures of the head, neck trunk as well as associated muscles and dermis of skin.
4th week of development
the disc undergoes embryonic folding which places forming tissue types into their proper positions.
the embryonic folding results from proliferation of the
ectoderm
The folding tissued mainly occurs near the
cephalic end, where the brain will form
the anterior part of the tube is the
foregut
the foregut forms the primitive
pharynx
the mature pharynx is formed from the
midgut and hindgut
during the development of the _______four pairs of pharyngeal pouches will form form evaginations on the lateral walls lining the pharynx
digestive tract
during the 4th week the...
face and neck begin to develope with the primitive eyes,ears,nose, oral cavity, and jaw areas.
Fetal period is
beginning of the ninth week or 3rd MONTH
end of 4th month
heartbeat and movements can be noted
Fetal period process involves
physiological process of maturation of the individual tissue types and organs but also further proliferation differentiation and morphogenesis, as discussed before with the embryo.
developmental disturbances in the fetal period
amniocentesis, tetracycline stain