H&E Ch 3 Key Terms

Embryology

the study of prenatal development

Prenatal development

begins with start of pregnancy and continues until birth

Primoridium

earliest recognizable structure during stages of development of organ or tissue during prenatal development

Developmental disturbance

congenital malformation or anomaly

Amniocentesis (amniotic fluid test or noninvasive prenatal testing)

advanced prenatal diagnostic procedure to detect chromosomal abnormalities late in pregnancy

Teratogens

environmental agents or factors causing developmental disturbances, can include infections, drugs and radiation

Preimplantation period

first period of prenatal development

Fertilization

sperm penetrates ovum

Ovum

female reproductive cell, or egg that can be fertilized

Sperm

male reproductive cell containing chromosomal information fertilizing female ovum

Zygote

fertilized egg from union of sperm and ovum

Meiosis

process of reproductive cell production guaranteeing correct number of chromosomes

Mitosis

cell division occurring in phases resulting in two daughter cells

Cleavage

mitosis coverts zygote to blastocyst

Blastocyst

trophoblast cells and inner mass of cells forming embryo

Implantation

embedding of blastocyst in endometrium

Endometrium

innermost lining of uterus on its posterior wall

Trophoblast layer

layer of peripheral cells of blastocyst

Embryoblast layer

small inner mass of embryonic cells in blastocyst

Down syndrome/Trisomy 21

Where an extra chromosome number 21 is present after meiotic division

Embryonic period

second period of prenatal development extends from beginning of second week to end of week eight.

Embryo

structure derived from implanted blastocyst

Induction

action of one group of cells on another leading to developmental pathway in responding tissue

Proliferation

controlled levels of cellular growth present during most of prenatal development

Appositional growth

growth by layering outside of tissue mass with firm or hard tissue such as cartilage, bone, enamel, dentin, and cementum

Interstitial growth

growth that occurs from deep within tissue or organ

Differentiation

change occurs in embryonic cells to become distinct structurally and functionally

Cytodifferentiation

development of different cell types

Histodifferentiation

development of different histologic tissue types within a structure

Morphodifferentiation

development, of differing form to create specific structure

Morphology

form of structure

Morphogenesis

process of development of specific overall tissue structure or shape

Maturation

attainment of adult size as well as adult form and function; fully developed

Embryonic cell layers

germ layers derived from increased number of embryonic cells

Bilaminar embryonic disc

circular plate of bilayered cells from blastocyst

Epiblast layer

superior layer in bilaminar disc, composed of high columnar cells

Hypoblast layer

inferior layer in bilaminar disc, composed of small cuboidal cells

Amniotic cavity

fluid

Yolk sac

faces hypoblast layer and serves as initial nourishment for bilaminar disc

Embryo

structure derived from implanted blastocyst

Placenta

temporary prenatal organ supporting developing embryo

Primitive streak

furrowed rod-shaped thickening in midline of embryonic disc

Bilateral symmetry

each half of embryo mirrors other half

Mesoderm

embryonic layer between ectoderm and endoderm

Endoderm

layer in trilaminar embryonic disc derived from hypoblast layer

Ectoderm

layer in trilaminar embryonic disc from epiblast layer and lining stomodeum

Trilaminar embryonic disc

ectoderm, mesoderm, endoderm

Cephalic head

head end of a structure

Caudal end

tail end of a structure

Neuroectoderm

specialized group of cells differentiating from ectoderm

Neural plate

centralized band of cells extending length of embryo

Neural groove

groove from further growth and widening of neural plate

Invagination

cavity or pouch formation by turning inside out or folded back

Neural folds

raised ridges in neural plate surrounding deepening neural groove

Neural tube

tube formed when neural folds meet and fuse superior to neural groove

Fusion

joining of embryonic tissue of two separate surfaces that eliminates furrow between two adjacent swellings of developmental disturbance in which adjacent tooth germs unite to form large tooth

Neural crest cells (NCCs)

specialized group of cells developed from neuroectoderm migrating from crests of neural folds and disperse within mesenchyme

Mesenchyme

embryonic connective tissue

Somites

paired cuboidal aggregates of cells differentiated from mesoderm

Embryonic folding

embryonic folding of embryo placing tissue in correct position

Oropharyngeal membrane

membrane at cephalic end of embryo

Cloacal membrane

membrane at caudal end of embryo, future anus

Foregut

anterior part of future digestive tract or primitive pharynx forming oropharynx

Midgut

middle part of future digestive tract

Hindgut

posterior part of future digestive tract

Ectodermal dysplasia

syndrome with developmental disturbances with one or more structures that develop from ectoderm

Syphilis

teratogenic infection effect that produces dental developmental disturbances resulting in Hutchinson incisor with screwdriver shape and mulberry molar with berry

Fetal alcohol syndrome

teratogenic drug effect during embryonic period, caused by high levels of alcohol crossing the placenta during pregnancy

Spina bifida

failure of fusion of neural tube

Fetal period

final period of prenatal development, begins at ninth week and continues to thirty

Fetus

structure of enlarged embryo

Tetracycline stain

teratogenic effect of antibiotic medication used during pregnancy on primary teeth, or as small child during their development of permanent teeth