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

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