Glossary

abfraction

The loss of tooth structure at the CEJ, often wedge-shaped or V-shaped, and is unrelated to cavities, bacteria, or infection.

accessory canals

Smaller access ways that branch off of the main root canals.

acellular

Without cells

acellular cementum

Cementum covering the cervical portion of the tooth root, important for attachment of the periodontal ligament (PDL) to the root surface.

acini

A small sac-like cavity in a gland, surrounded by secretory cells.

active eruption

Tooth movement in the occlusal direction as the tooth erupts from its osseous crypt.

adipocytes

The cells that primarily compose adipose tissue, specialized in storing energy as fat.

adipose tissue

A type of connective tissue composed primarily of adipocytes, which store high-energy triglyceride and other lipid molecules.

adult stem cell

A stem cell found in adult tissues (as opposed to embryonic stem cells found in embryos)

allele

a variant or different DNA sequence of a gene

alveolar bone

The part of the jaws that holds the teeth.

alveolar mucosa

The lining mucosa covering the alveolar ridges, attached to the buccal, lingual and palatal mucosa in one direction, and gingival mucosa in the other direction.

ameloblasts

Cells present only during the embryonic period that deposit tooth enamel.

amelogenesis

The formation of enamel.

amelogenesis imperfecta

A rare congenital disorder which presents with abnormal formation of enamel, unrelated to any environmental conditions.

amelogenins

Proteins found in enamel matrix which regulate the initiation and growth of hydroxyapatite crystals during the mineralization of enamel.

amorphous

Without shape

angiogenesis

Growth of endothelial cells, creating new blood vessels within a tissue.

ankyloglossia

A congenital malformation that may decrease the mobility of the tongue caused by an unusually short lingual frenulum.

ankylosis

Abnormal stiffening and immobility of a joint (including tooth-to-alveolar bone)

anodontia

absence of primary or permanent teeth.

antagonist

A biological structure or chemical agent that interferes with the physiological action of another.

apical

The top (or apex) side of a cell or tissue, usually facing the lumen.

apical-to-basolateral polarity

Top-to-bottom polarity, where the apical side of a cell (or tissue) is different from the basolateral side

apoptosis

Programmed cell death

appositional growth

The increase in diameter by the addition of tissue at the surface,

areolar connective tissue

A loose connective tissue composed of fibroblasts and other cell type, plus ground substance and all three fiber types.

artifacts

Artificial patterns or damage to a specimen seen under the microscope caused by the sampling or staining procedure.

ATP

Adenosine Tri-Phosphate, the energy molecule of cells.

attached gingiva

Region of oral mucosa firmly bound to the tooth and alveolar process.

avascular

Without blood vessels

basement membrane

A thin sheet of extracellular matrix between epithelial tissues and the underlying connective tissue of the lamina propria or dermis.

basolateral

The side of a cell or tissue oriented away from the lumen or external surface.

bell stage

The stage of early tooth development where the dental organ differentiates into 4 distinct cell types 9IEE, OEE, stellate reticulum and stratum intermedium), followed by differentiation of odontoblasts and ameloblasts.

benign

(of a disease) not harmful in effect, (of a tumor) not malignant.

bilateral

On both sides

bio-active

A compound that has an effect on a living organism, tissue or cell, such as by mimicking a morphogen or growth factor.

bio-compatible

Materials used in surgical implants, not harmful to living tissue and unlikely to be rejected by the host immune system.

black hairy tongue

A temporary, harmless condition that gives the tongue a dark, furry appearance, resulting from a buildup of dead skin cells on the papillae on the dorsal surface of the tongue.

blastula

A hollow ball of cells that develops after the morula stage of embryogenesis.

Bleeding on Probing

Bleeding that is induced by gentle manipulation of the tissue at the depth of the gingival sulcus.

blood

A type of connective tissue composed of cells (red and white blood cells) and ECM (plasma)

BMP

Bone Morphogenetic Proteins are a group of signaling molecules, initially discovered for their ability to induce bone formation, now known to play crucial roles in all organ systems.

Bohn’s nodules

Keratin cysts derived from remnants of odontogenic epithelium over the dental lamina, or remnants of minor salivary glands. They occur on the alveolar ridge, more commonly on the maxillary than mandibular.

bone graft

A medical procedure in which ground up bone tissue or synthetic bone tissue is placed in an injured site to act as a scaffold, promoting the formation of new bone tissue by the patient's own cells.

bone tissue

A hard connective tissue which is mostly ECM, including collagen fibers and a calcium-phosphate crystal.

branchial cleft cyst

A fluid-fille sac causing swelling in the upper part of neck anterior to sternocleidomastoid.

buccal mucosa

The lining mucosa of the cheeks and inner side of the lips.

bud

Outward-folding of an epithelium caused by interstitial growth.

bud stage

The first visible stage of odontogenesis, without a clear arrangement of cells.

calcium hydroxyapatite

Ca5(PO4)3(OH), the inorganic ECM material composed of calcium, phosphate and hydroxide ions that makes up the bulk of bone tissue.

CAMs

Cell Adhesion Molecules: proteins located on the cell surface involved in binding with other cells or with the extracellular matrix.

canaliculi

Microscopic canals between the lacunae of ossified bone or cementum, containing thin cell processes linking distant cells together.

cap stage

An early stage of tooth development where ectodermal cells grow around the dental papilla to resemble a hat, and the first signs of cell arrangement occur.

capsule

Connective tissue casing or outer border of an organ.

carotene

An orange-to-yellow pigment made by plants that accumulates within the dermis of the skin. It is the precursor for Vitmain-A.

cartilage

A firm connective tissue, softer and more flexible than bone composed of chondrocytes and lots of ground substance.

CDJ

Cementum-Dentin Junction

CEJ

Cemento-Enamel Junction, found in the cervical region of the tooth.

cell cycle checkpoints

Control proteins and enzymes which ensure proper progression through the cell cycle, regulating the rate of mitosis.

cell fate

The type or types of cell(s) a stem cell can possibly differentiate into in the future, determined by which genes are methylated and stored around histones, or free to be transcribed.

cell-free zone

A region of pulp with fewer visible cell bodies, and a large amount of capillaries and nerve endings.

cell-rich zone

A region of the pulp containing numerous fibroblasts, mesenchymal stem cells and other connective tissue cells.

cell-to-cell contacts

Direct contact between cells allows the receptors on one cell to bind small molecules on the plasma membrane of different cell. In eukaryotes, many of the cells during early development communicate through direct contact.

cellular cementum

Cementum containing cells and collagen fibers anchoring the tooth to alveolar bone.

cemental caries

Decay of cementum.

cementicles

Spherical calcified bodies lying free in the periodontal membrane.

cementoblasts

Differentiated cell that deposits cementum matrix.

cementoclasts

Resorptive cell capable of demineralizing cementum by the secretion of acids and enzymes.

cementocytes

Terminally differentiated cell found within mature cementum lacunae.

cementogensis

The process of cementum formation which covers the tooth root by cementoblasts of mesenchymal origin.

cervical loop

The location on an enamel organ in a developing tooth where the outer enamel epithelium and the inner enamel epithelium join, fated to become Hertwig's Epithelial Root Sheath (HERS).

cervical lymph nodes

300 (of 800 total) lymph nodes found in the neck.

chondroblast

A cell actively producing the components of cartilage extracellular matrix, and may differentiate into a chondrocyte when trapped in the matrix it produced.

chondrocytes

The mature cells found within cartilage tissue.

chromatin

Unwound DNA and histone molecules, available for gene transcription.

chromosomes

DNA molecule packaged into thread-like structures found during mitosis, visible under a light microscope.

circum-pulpal dentin

The largest region of dentin, containing dentinal tubules, peri-tubular dentin and inter-tubular dentin

circumvallate papillae

Large circular bumps next to the sulcus terminalis on the dorsal surface of the tongue, contain numerous taste buds and minor salivary glands

cleavage divisions

The first few cellular divisions of a zygote are synchronized and divide along longitudinal planes, the second division is at 90 degrees to the plane of the first, and the third is perpendicular to the first two.

cleft lip

an opening or split in the upper lip that occurs when there is incomplete fusion of the maxillary process(es) with the inter-maxillary segment.

cleft palate

An opening or split in the roof of the mouth that occurs when the palatal shelves and/or primary palate fail to fuse completely.

cleido-cranial dysostosis

A rare congenital malformation that affects the collarbones, skull and teeth.

clinical attachment loss

Damage to the structures that support the tooth; results from periodontitis and is characterized by relocation of the junctional epithelium to the tooth root, destruction of the fibers of the gingiva, destruction of the periodontal ligament fibers, and loss of alveolar bone support from around the tooth.

collagen

The main structural protein in the ECM of connective tissues

commissural lip pits

The presence of pits and possibly associated fistulas in the lips.

compact bone

Dense bone tissue composed of osteons, found on the outer edges of bones.

complete cleft

A fully unfused cleft palate, where no bony connection is made.

concrescence

A condition of teeth where the cementum overlying the roots of at least two teeth join together.

congenital disorders

A medical condition that is present at or before birth, which can be acquired during development or from the genetic make up of the parents.

contour lines of Owen

Exceptionally-pronounced imbrication lines of von Ebner

copula

A swelling that forms from the second pharyngeal arch, it quickly gets overgrown by the 3rd and 4th arch during development of the tongue.

coronal pulp

The portion of pulp in the crown of the tooth.

cribriform plate

Sieve-like region of compact bone of the alveolar sockets or ethmoid bone.

crown stage

Sometimes referred to as the maturation stage or the late bell stage, characterized by the calcification of enamel and dentin in the crown region of a developing tooth.

cytoplasm

the gelatinous material within a living cell, excluding organelles.

cytoskeleton

A dynamic network of interlinking cytoplasmic proteins (mainly actin filaments, intermediate filaments and microtubules), involved in maintaining cell shape, polarity and migration.

de-differentiate

The reversal of differentiation, reverting to a more stem cell-like state.

dehiscence

A lack of the facial or lingual alveolar cortical plate resulting in a denuded root surface

DEJ

Dentin-Enamel Junction

dens in dente

A rare dental malformation found in teeth where there is an infolding of enamel into dentin.

dense irregular connective tissue

A connective tissue that has fibers that are not arranged in parallel bundles as in dense regular connective tissue. Dense irregular connective tissue consists of mostly collagen fibers. It has less ground substance than loose connective tissue.

dense regular connective tissue

A type of connective tissue found in tendons and ligaments that is composed primarily of parallel collagen fibers, secreted by fibroblasts, with very little ground substance.

dental caries

Damage to a tooth that can happen when decay-causing bacteria make acids that de-mineralize tooth tissues.

dental fluorosis

A condition that causes changes in the appearance of tooth enamel. It may result when children regularly consume fluoride during the teeth-forming years, age 8 and younger.

dental implants

An artificial tooth root that is surgically placed into bone tissue.

dental lamina

A band of epithelial tissue seen in histologic that is is the first evidence of tooth development and begins (in humans) at the sixth week of development.

dental papilla

A condensation of ecto-mesenchymal cells seen in histologic sections of a developing tooth.

dental pellicle

A protein film that forms on the surface enamel by binding of glycoproteins from saliva that prevents continuous deposition of salivary calcium phosphate.

dental sac

Neuro-mesenchymal cells and fibres surrounding the enamel organ and dental papilla of a developing tooth.

dentigerous cyst

A fluid filled pocket or sac around an impacted tooth.

dentin caries

A carious lesion that extends into dentin.

dentin hypersensitivity

Pain derived from exposed dentin in response to chemical, thermal tactile or osmotic stimuli which cannot be explained as arising from any other dental defect or disease.

dentin resorption

The removal of dentin matrix by odontoclasts (as opposed to erosion), which occurs in the roots during tooth exfoliation.

dentin-pulp complex

Dentin and pulp are the same tissue from a function and embryology viewpoint, and are therefore referred to together as a complex.

dentinal fluid

The lymph or ECF found within dentinal tubules, surrounding the odontoblastic process

dentinal tubule

Tiny canals that run through dentin, from the pulp cavity up to near the DEJ or CDJ

dentinogenesis

The formation of dentin.

dentinogenesis imperfecta

A genetic disorder that causes teeth to be discolored (most often a blue-gray or yellow-brown color) and translucent giving teeth an opalescent sheen.

dermal papillae

Fingerlike projections of the apical side of the dermis, increasing the surface area between the epidermis and dermis, strengthening their connection and increasing exchange of oxygen, nutrients, and waste.

dermis

Th connective tissue layer of the skin, found just deep to the epidermis, composed of areolar CT and dense irregular CT.

desmosome

Trans-membrane structure specialized for cell-to-cell adhesion.

development

The process by which animals and plants grow and change.

deviated septum

A condition where the bone and cartilage that divide the nasal cavity of the nose in half is significantly off center, or crooked, making breathing difficult.

differentiation

When one cell begins to look different from another. This process involves limiting cell fate by altering gene transcription to become more specialized.

dilaceration

An abnormal bend in the root or crown of a tooth.

distomolar

A supernumerary tooth which is located distal to third molars

DNA

deoxyribonucleic acid is the hereditary material in humans and almost all other organisms.

DNA methyation

Methyl groups added to DNA which change the activity of a gene without changing the sequence, typically repressing gene transcription.

dorsal surface of the tongue

The top surface of the tongue, containing lingual papillae and taste buds.

ECF

Extra-Cellular Fluid is the fluid surrounding cells, but not within blood or lymphatic vessels.

ECM

Extra-Cellular Matrix: Materials in the body, but outside of cells. A network of macromolecules, such as fibers, enzymes, and glycoproteins, that provide structural and biochemical support to surrounding cells.

ectoderm

he most exterior of the three primary germ layers formed in the gastrula, it gives rise to the epithelial tissue covering the body and the CNS.

ectodermal dysplasia

A group of disorders in which two or more of the ectodermally derived structures — the skin, sweat glands, hair, nails, teeth and mucous membranes — develop abnormally.

edema

Swelling caused by excess fluid trapped within tissues.

edentulous

Lacking teeth

elastic fibers

Thin protein fibers in the ECM, capable of stretching and returning to their original length, made of the protein elastin.

embryo

A human offspring during the period from approximately the second to the eighth week after fertilization.

Embryology

The branch of biology and medicine concerned with the study of embryos and their development.

embryonic disc

The part of the inner cell mass of a blastocyst from which the embryo of a placental mammal develops.

embryonic germ layers

The three layers of cells that arise from gastrulation: endoderm, mesoderm and ectoderm.

enamel hypoplasia

A defect of the enamel that occurs during tooth development, it results in thin enamel making teeth vulnerable to decay.

enamel organ

The ectodermal cells that lie above the dental papillae in a cap stage tooth bud.

enamel pearl.

A condition of teeth where enamel is found where enamel is not supposed to be, such as on a root surface.

enamel rod

The basic unit of tooth enamel, 4 μm wide, composed of a tightly packed and organized mass of hydroxyapatite crystals, hexagonal in shape.

enamel spindles

Extensions of odontoblastic processes past the DEJ into enamel, creating thin regions of hypomineralized enamel.

enamel tufts

Similar to enamel spindles, but shorter, bushier-shaped, and do not contain odontoblastic processes.

enamelins

Along with amelogenins, a second protein found in enamel, enamelins are necessary for the adhesion of ameloblasts to the surface of the enamel, and they bind to hydroxyapatite to promotes crystallite elongation.

endochondral ossification

The formation of bone tissue from a cartilage model

endochondralossification
endocrine

Secreting to the inside of the body, either blood or ECF.

endoderm

The innermost of the body's 3 embryonic tissues that form during gastrulation, it becomes the inner lining of hollow organs.

endodontic therapy

Also known as a root canal, is a treatment for infected pulp of a tooth, result in the removal and replacement of pulp and the protection of the decontaminated tooth from future microbial invasion.

endogenous

having an internal cause or origin; made by human cells.

endosteum

A thin membrane covering the inner surface of compact bone and the trabeculae of spongy bone, containing osteoblasts, osteoclasts and osteo-progenitor cells

epidermis

The superficial epithelial layer of the skin, composed of a stratified squamous epithelium.

epigenetic

Heritable DNA modifications that do not change the DNA sequence but do affect gene activity.

epithelial attachment

located at the bottom of the sulcus, consisting of approximately 1 mm of junctional epithelium and 1 mm of gingival fiber attachment.

epithelial rests of Malassez

Clusters of epithelial cells found within the PDL, remnants of Hertwig's Epithelial Root Sheath (HERS).

epithelial-to-mesenchymal transition

A process by which epithelial cells lose polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal stem cells, this normally occurs during embryonic development and wound healing.

Epstein Pearls

A white or yellow bump on the oral mucosa which are equivalent to Bohn's Nodules.

erosion

The wearing away of tooth enamel by excess acids.

exfoliation

A general term for peeling or shedding, in humans it refers to the loss of dead epithelial cells or structures (hair, teeth).

Exocrine

Secreting to a surface of the body, either the outer surface (skin) or inner surface (lumen of a hollow organ).

exogenous

Having an external cause or origin; not made by human cells

external root resorption

When the body's own immune system dissolves the tooth root structure. It can occur following tooth infection, orthodontic treatments or in the presence of unerupted teeth in the jaw.

extrinsic collagen fibers

Ends of the principal fibers of the periodontal ligament embedded within cementum.

fenestration

A roughly circular defect of the cortical plate which exposes the underlying root surface, but does not involve the alveolar margin of the bone.

fertilization

The fusion of haploid gametes, egg and sperm, to form the diploid zygote.

fetus

An unborn human baby more than eight weeks after conception.

FGF

Fibroblast Growth Factors are a family of morphogens involved in a wide variety of processes, including important roles in development and tissue regeneration, especially connective tissues.

fibers

The ECM proteins elastin and collagen, visible under the light microscope

fibrin

The insoluble (solid) form of a fibrous protein found in blood plasma that contributes to the formation of a blood clot.

fibroblasts

The basic connective tissue cell type capable of secreting ECM components, including fibers and ground substance proteins.

fibronectin

A large glycoprotein found in the ECM which binds to integrin proteins on the cell surface, involved in cell adhesion, growth, migration, and differentiation.

Filiform papillae

Fingerlike bumps on the dorsal surface of the tongue that contain epithelium for friction, but no taste buds.

floor of the mouth

Portion of the oral cavity underneath the tongue.

foliate papillae

Large bumps on the lateral edges of the tongue, they contain taste buds.

foramen cecum

The small depression at the border between the anterior (oral) and the posterior (pharyngeal) portions of the tongue. It is the point from which the thyroid gland formed by invagination.

Fordyce Spots

Whitish-yellow bumps found on the lips or oral mucosa, caused by the unusual presence of sebaceous glands (or possibly minor salivary glands) trapped below the epidermis.

fungiform papillae

Mushroom-shaped bumps on the dorsal surface of the tongue, they contain taste buds.

fuse

When two or more cells, tissues or organs join to become one.

gain-of-function

A type of mutation in which the altered gene product possesses a new molecular function or a new pattern of gene expression. Gain-of-function mutations are almost always Dominant.

gap junctions

A trans-membrane protein that when paired allows small cytoplasmic molecules to pass through from one cell to another cell.

gastrulation

A phase early in the embryonic development during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula.

gemination

Adental phenomenon that appears to be two teeth developed from one.

gene

A sequence of nucleotides in DNA that encodes the synthesis of a gene product, either RNA or protein.

gene expression

Copying DNA into a functional product, such as a RNA and/or protein. Controlled by the activity of transcription factors binding to gene promoter regions to recruit RNA polymerase.

geographic tongue

A condition where filiform papillae on the dorsal surface of the tongue become non-uniformly hyper-keratinized, creating dynamic regions of more white and more pink coloration.

germinal centers

Sites within lymphoid organs where mature B cells proliferate and differentiate.

gill arches

A series of bony or cartilaginous curved bars along the pharynx, supporting the gills of fish and amphibians.

gingival fibers

Collagen fibers in the gingiva that, in general, attach the tooth to the gingival tissue (rather than the tooth to the alveolar bone like the PDL fibers).

gingival graft

The use of connective and epithelial tissue from the roof of the mouth or neighboring gingiva, attached to the gum area being treated.

gingival hyperplasia

Overgrowth of gum tissue around the teeth, often associated with poor oral hygiene.

gingival recession

The exposure in the roots of the teeth caused by a loss of gum tissue and/or retraction of the gingival margin from the crown of the teeth.

gingival sulcus

Space between the gingiva and tooth.

gingivitis

Inflammation of gingival tissue

gingivo-crevicular fluid

Fluid exudate from gingival mucosa that collects within the gingival sulcus. Presence of bacterial enzymes, bacterial degradation products, connective tissue degradation products, inflammatory molecules, or extracellular matrix proteins can be detected in higher levels in gingival crevicular fluid during active phase of periodontiti

glia

The numerous and diverse group of cells in neural tissue that provide support for, guide the activity of, and organize the connections between neurons.

globular dentin

Darker-staining regions of dentin, found between mantle dentin and circumpulpal dentin.

glycoproteins

A protein that has had sugar residues attached to it in the Golgi apparatus and is often secreted.

goblet cells

Unicellular glands, or single epithelial cells, that secrete mucus.

Golgi apparatus

A membrane-bound organelle that modifies proteins from the rER and packages them up into vesicles, to be sent to lysosomes, the plasma membrane, or secreted from the cell.

ground substance

Gel-like substances in the ECM, composed of water held in place by large molecules (proteins, glycoproteins and glycosaminoglycans).

growth factors

A signaling molecule capable of stimulating cell proliferation, wound healing, and cellular differentiation.

guidance cues

Signaling molecules which control the navigation of other cells by causing attraction or repulsion.

guided tissue regeneration

Procedures attempting to regenerate (as opposed to replace) lost periodontal structures.

gumboil

A small swelling formed on the gum over an abscess at the root of a tooth.

H&E

Hematoxylin and Eosin stain, typically turns proteins pink and DNA purple.

hair follicles

An infolding of the epidermis that extends deep into the dermis, responsible for producing a hair.

hard palate

The horizontal bony plate that makes the anterior portion of the palate of the mouth, composed of parts of the palatine and maxilla bones.

hemi-desmosomes

Half of a desmosome, specialized for cell-to-ECM adhesion.

hemoglobin

A molecule made by Red Blood Cells that can bind and release Oxygen molecules. It switches from a red to a maroon color as it does so, which in turn contributes to skin color.

Hensen's node

The organizer for gastrulation in the embryo, it is the site where mesoderm migration occurs.

HERS

Hertwig's Epithelial Root Sheath: A proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth which initiates the formation of root dentin.

hidden caries

An occlusal dentine caries that is missed on a visual examination.

histology

The study of tissues under a microscope

histone

Highly basic proteins found in nuclei that compact DNA into a denser form, unavailable for gene transcription.

homeobox genes

A group of 235-300 related genes that code for a transcription factors, which control the activity of other genes involved in development, including directing the formation of limbs and organs along the anterior-posterior axis.

homologue

A similarity due to shared lineage between a pair of structures or genes in different taxa.

hormones

Signaling molecules secreted directly into the blood which travel throughout the body.

Hunter-Schreger bands

When cut enamel is viewed under reflected light, curves in the pattern of enamel rods can be seen; these curves strengthen the enamel and prevent cracks from propagating through the tooth.

hyaluronic acid

A very large glycosaminoglycan distributed widely throughout connective tissue ECM, epithelial, and neural tissues.

hyaluronidase

a family of enzymes that catalyse the degradation of hyaluronic acid.

hydrostatic

The pressure exerted by liquid.

hyoid arch

The second pharyngeal arch.

hyper-cementosis

Idiopathic, non-neoplastic condition characterized by the excessive buildup of normal cementum on the roots of one or more teeth.

hyper-keratosis

An abnormally high level of keratin production in an epithelium, causing a thickening and whitening of the outer layer of the skin or oral mucosa.

hyperdontia

the condition of having teeth in addition to the regular number of teeth.

hyperplasia

Growth of a tissue by an increased number of cells, an increased amount of ECM produced by cells, or both.

hypo-salivation

Decreased saliva production.

hypodontia

Partial anodontia, or the absence of some teeth.

idiopathic

A disease that arises from an unknown cause.

IEE

Inner Enamel Epithelium: a layer of columnar cells located next to the dental papilla, these pre-ameloblast cells will differentiate into Ameloblasts which are responsible for secretion of enamel during tooth development.

imbrication lines of von Ebner

Incremental lines in the peritubular dentin of the tooth that correspond to the daily rate of dentin formation.

implantation

The process by which a developing embryo makes contact with the uterine wall, attaches and digests its way internally, and remains within it until birth.

incisive foramen

The oral opening of the nasopalatine canal, located in the maxilla at the junction of the medial palatine and incisive sutures.

incomplete cleft

A partially unfused cleft palate, where at least some of the bone portion is intact.

induce

The embryonic process in which one group of cells directs the development of another group of cells.

inner cell mass

The mass of cells inside the blastula-stage embryo that will eventually give rise to the definitive structures of the fetus

integrin

A trans-membrane protein which allows cells to bind to the ECM protein fibronectin, it is involved in cell adhesion, growth, migration, and differentiation.

inter-dental septum
inter-globular dentin

Lighter-staining regions of dentin found between globular dentin spheres.

inter-maxillary segment

Or the globular process, is a mass of tissue formed by the merging of the median nasal processes, fated to become the philtrum and pre-maxilla.

inter-rod enamel

The type of enamel found between enamel rods.

inter-tubular dentin

Thicker layer of dentin found between the thin layers of peri-tubular dentin.

interdental gingiva

Portion of the attached gingiva between teeth, coronal to the free gingival margin on the buccal and lingual surfaces of the teeth

interdental septum

The bony partition across the alveolar process between adjacent teeth that forms part of the tooth sockets.

internal root resorption

A pulp disease characterized by the loss of dentin as a result of the action of osteoclastic cells stimulated by pulpal inflammation.

interradicular septum

The bony septum lying between tooth roots.

interstitial growth

Increase in size by the addition of tissue from the inside.

intra-membranous ossification

Formation of bone tissue from a dense connective tissue model

intrinsic collagen fibers

Fibers found within cementum oriented parallel to the root surface, mainly involved in the repair of cementum.

invagination

Inward folding of an epithelium caused by interstitial growth.

junctional epithelium

Epithelium on the inner wall of the gingiva that attaches to connective tissue of the lamina propria on the basolateral side and to the surface of the tooth on the apical side.

keratin

One of a family of tough fibrous structural proteins, the key material making up hair, nails, calluses, and the outer layer of skin.

keratinized

Having the protein keratin, which lends resistance to abrasion and water loss.

keratinocytes

A terminally differentiated epithelial cell capable of synthesizing large amounts of the protein keratin within its cytoplasm.

labial mucosa

The oral mucosa of the lips (both inner and outer surface)

lacunae

Lakes, or spaces within cartilage of bone connective tissue where cells reside.

lamina dura

Compact bone that lies adjacent to the periodontal ligament, in the tooth socket.

lamina propria

The areolar connective tissue layer of the oral mucosa (or hollow organ), homolgous to the papillary layer of the dermis.

lateral lingual swellings

Two swellings on the floor of the primitive pharynx which, along with the tuberculum impar, form the anterior 2/3rd of the tongue.

lateral nasal processes

Tissue on the lateral sides of the nasal pits that form the alae of the nose.

leukoplakia

Whitish patches or lesion of the oral mucosa caused by hyper-keratinization.

Linea Alba

A white line. In the oral cavity, refers to a line in buccal mucosa along the occlusal plane.

lineage

The developmental history of a differentiated cell traced back to the embryonic cell from which it arises.

linear mineralization

The calcification of pre-dentin in the circumpulpal region occurs linearly, not in globs.

lines of Retzius

Incremental growth lines seen in enamel.

lingual frenulum

A small fold of mucous membrane extending from the floor of the mouth to the midline of the underside of the tongue.

lingual papillae

Bumps on the tongue, giving it its rough texture

Lining mucosa

A non-keratinized stratified squamous epithelium found in the buccal mucosa, labial mucosa, alveolar mucosa, ventral surface of the tongue, floor of the mouth, and soft palate.

loss-of-function

A mutation that result in the gene product having less or no function (being partially or wholly inactivated).

lower labial pit

Depressions of the lower lip.

lumen

Hollow center or cavity inside a structure.

lymph nodes

A small bean-shaped structure that is part of the body's immune system.

lymphadenopathy

Palpable enlargement of lymph nodes.

lymphatic tissue

A type of connective tissue composed of cells (white blood cells) and ECM (lymph).

lysosomes

Membrane-bound vesicles that contains acids and hydrolytic enzymes that break down many kinds of molecules.

macrodontia

A condition in which one or more teeth grow to be a larger size than normal.

mandibular arch

The first branchial arch of the vertebrate embryo which in humans develops into the lower lip, mandible, masticatory muscles, and anterior tongue.

mandibular torus

Abony growth in the mandible along the surface nearest to the tongue.

mantle dentin

The outer layer of dentin closest to enamel, contains few odontoblastic processes.

marginal gingiva

A 1.5 mm strip of gingival tissue which surrounds the neck of the tooth.

masticatory mucosa

Areas of oral mucosa that have become partially keratinized due to the friction and abrasion of the masticatory process, including the gingivae and hard palate.

matrix metalloproteinase

Enzymes that degrade all kinds of extracellular matrix proteins, or process a number of bioactive molecules. They play a major role in cell proliferation, migration, differentiation, angiogenesis, and apoptosis.

maturation

The continued development of a cell, tissue, organ or organism as it takes on a more adult form.

maxillary process

A process that grows off the mandibular arch on each side and forms the lateral part of the upper lip, cheek, and upper jaw except the pre-maxilla.

McCall’s festoon

Semilunar-shaped enlargements of the marginal gingiva primarily on the labial surfaces of the anterior and premolar teeth.

mechanical failure of eruption

A type of failure of eruption takes place when the affected tooth is ankylosed to the bone around it.

Meckel’s cartilage

Apiece of cartilage from which the mandibles (lower jaws) of vertebrates evolved, originally the lower of two cartilages which supported the first branchial arch in early fish.

medial nasal processes

Tissue on the inner side of each nasal pit merge into the inter-maxillary segment and form the philtrum, crest and tip of the nose, and merge with the maxillary processes.

median lingual sulcus

A line that divides the dorsum of the tongue into symmetrical halves, from the anterior tip to the foramen caecum,

median palatine suture

The suture between the two palatine bones.

melanin

A group of red, dark brown or black pigments found in the hair, skin, and other places, capable of absorbing UV-B radiation.

melanocytes

Terminally differentiated cells derived from neural crest cells that produce one of the three forms of melanin.

membranes

A two-dimensional sheet that forms a selective barrier.

mesenchymal stem cells

Multipotent cells of a connective tissue that can differentiate into a variety of cell types, including osteoblasts, fibroblasts, chondrocytes, myoblasts, blood cells and adipocytes.

mesenchymal-to-epithelial transition

A reversible process that involves the transition from motile mesenchymal cells to planar arrays of polarized epithelial cells.

mesenchyme

An embryonic tissue composed of undifferentiated mesenchymal stem cells and mucous ground substance.

mesial drift

The tendency of teeth to move in a mesial direction within the arch, maintaining interproximal contact between teeth.

mesiodens

A supernumerary tooth present between the two central incisors.

mesoderm

The middle of the three embryonic layers that develop during gastrulaton, mesoderm becomes most of the body's muscle and connective tissues.

microdontia

A condition in which one or more teeth appear smaller than normal

mini-valves

Similar to venous valves, mini-valves are on the walls of lymphatic vessels, allowing them to absorb larger materials than blood vessels.

minor salivary glands

Small salivary glands located throughout the oral cavity that generally get no name.

mitochondria

Membrane-bound organelles that generate most of the chemical energy needed to power a cell's biochemical reactions.

mitosis

The process of cell division, where one cell divides into two identical clones (daughter cells).

morph

Slowly change shape

morphogen

A substance whose non-uniform distribution governs the pattern of tissue development and pattern formation.

morphogenesis

The biological process that causes a cell, tissue or organism to develop its shape.

morphology

The shape (or form) of.

morula

A solid ball of cells that develops by mitosis from the single-cell zygote.

mRNA

Single-stranded RNA molecule complementary to one strand of DNA of a gene. It leaves the nucleus and moves to the cytoplasm where it instructs the synthesis of a protein.

muco-serous acini

Glandular acini that make a mixture of watery and gelatinous secretions.

mucocoele

A mucous cyst

mucous

An adjective used to describe a gelatinous, slimy substance such as loose ground substance or mucus.

mucous acini

Glandular acini that secrete more gelatinous (or mucous) secretions.

mucus

A thin gelatinous secretion composed of primarily of glycoproteins and water.

mumps

A highly contagious viral disease caused by the mumps virus, causing swelling of the parotid salivary gland(s).

muscle tissue

A soft tissue whose cells contains a large amount of actin and myosin proteins, allowing it to change in size (contraction and elongation).

myo-epithelial cells

Epithelial cells found in glands, containing smooth muscle actin allowing them to contract and expel secretions of exocrine glands.

myo-satellite cell

A multi-potent stem cell that can generate more muscle tissue.

myoblasts

A more differentiated form of a myo-satellite cell that can differentiate into a muscle cell (myofibril)

nature

In the phrase nature vs nurture, nature refers to genetics (heritable traits).

necrosis

The death of most or all of the cells in an organ or tissue due to disease, injury, or failure of the blood supply.

neonatal line

A particularly pronounced incremental line in enamel or dentin, created on the day of birth.

neural crest cells

A temporary group of cells that arise from the embryonic ectoderm, and in turn give rise to a diverse cell lineage—including melanocytes, cranio-facial cartilage and bone, teeth and periodontal tissue, smooth muscle, peripheral and enteric neurons and glia.

neural tissue

The main component of the nervous system – both central and peripheral, composed of two types of cells: neurons and glia.

neural tube

The embryonic precursor to the central nervous system.

neuro-ectoderm

Cells derived from ectoderm fated to develop into the CNS or neural crest.

neuro-mesenchymal stem cells

A subset of mesenchymal stem cells derived from neural crest cells rather than mesoderm, or mesoderm-derived mesenchymal stem cells induced by neural crest morphogens to adopt a more neural fate.

neuro-mesenchyme

Mesenchyme tissue that contains neural crest cell derivatives.

neurons

Terminally differentiated and highly specialized cells of neural tissue, capable of firing electrical signals over long distances and releasing chemical signals across discrete locations called synapses.

neurulation

The folding process in vertebrate embryos, which includes the transformation of ectoderm into the neural tube.

nicotinic stomatitis

Hyper-keratinization of the hard palate mucosa-- but not minor samilvary gnds-- caused by cigarette smoke or other stresses,.

non-keratinized

A stratified squamous epithelium that does not contain the protein keratin, making it softer and moister than the skin.

non-vital

No longer containing living cells.

notochord

A flexible rod formed of a material similar to cartilage, which ultimately disappears in human (and most vertebrate) embryos.

nurture

In the phrase nature vs nurture, nurture means environmental factors that occur after fertilization, not DNA inherited from our parents.

odontoblast layer

The other layer of pulp containing the cell bodies of odontoblasts.

odontoblastic process

Arm-like extension of an odontoblast found within dentinal tubules.

odontoblasts

A cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is the formation of dentin.

odontoclasts

Resorptive cell capable of demineralizing dentin by the secretion of acids and enzymes.

odontogenesis

Formation and eruption of the teeth.

OEE

Outer Enamel Epithelium: a layer of cuboidal cells located on the periphery of the enamel organ in a developing tooth.

ontogeny

The development of an organism or anatomical or behavioral feature from the earliest stage to maturity.

oral epithelium

The stratified squamous epithelium of the oral mucosa.

oral mucosa

The mucous membrane lining the inside of the mouth. It is a stratified squamous epithelium, named the oral epithelium, and an underlying areolar connective tissue named the lamina propria.

oro-nasal cavity

The embryonic form of the oral cavity and nasal cavities before they are separated.

oro-pharyngeal membrane

The region where the ectoderm and endoderm come into direct contact with each other constitutes a thin membrane, which forms a septum between the primitive mouth and pharynx.

ortho-keratinized

An epithelium that is partially keratinized and contains visible nucleuses.

orthodontia

The treatment of irregularities in the teeth (especially of alignment and occlusion) and jaws, including the use of braces.

osteo-progenitor cell

A cell that differentiates from a mesenchymal stem cell, and can further differentiate into an osteoblast.

osteoblast

A differentiated connective tissue cell that secretes bone ECM, including collagen, calcium and phosphate.

osteoclast

A cell derived from bone marrow stem cells capable of demineralizing bone tissue by the secretion of acids and enzymes, releasing calcium into the blood.

osteocytes

The terminally differentiated cell type found in mature bone tissue (both compact and spongy), capable of repairing small amounts of damage.

osteodentin

Another name for reparative dentin, based on its resemblance to bone tissue, with cells trapped within dense ECM.

oxytalan

Elastic-like fibers made of the protein Fibrillin that run parallel to the tooth surface and bend to attach to cementum.

palatal shelves

The portion of the hard palate formed by the growth of two shelves off the maxillary process medially and their mutual fusion in the midline.

palatal torus

A harmless, painless bony growth located on the roof of the mouth.

palate

The roof of the mouth, separating the oral cavity and nasal cavities.

palatine raphe

A ridge running across the palate, from the palatine uvula to the incisive papilla.

para-keratinized

An epithelium that is partially keratinized that does not contain visible nucleuses.

para-nasal sinuses

Spaces within the frontal, sphenoid, ethmoid and maxillary bones surrounding the nasal cavity.

parotid glands

Two salivary glands that sit in front of the ears on each side of the face

passive eruption

Movement of the gingiva apically or away from the crown of the tooth to the level of the CEJ after the tooth has erupted completely.

pattern formation

The mechanism by which initially equivalent cells in a developing tissue in an embryo assume complex forms and functions.

PDL

Periodontal Ligament, a group of specialized connective tissue fibers that attach a tooth to alveolar bone.

peri-implantitis

A destructive inflammatory process affecting the soft and hard tissues surrounding dental implants.

peri-tubular dentin

The thin layer of dentin found bordering the dentinal tubule.

periapical abscess

A collection of pus at the root of a tooth, usually caused by an infection that has spread from pulp to the surrounding tissues.

pericardial patch

A medical procedure hat grafts connective tissue from cow or pig pericardium to human tissues to boost healing and regeneration.

perikymata

Incremental growth lines that appear on the surface of tooth enamel as a series of linear grooves.

perimolar

A supernumerary tooth in front of the molar teeth.

periodontal abscess

A localized collection of pus within the tissues of the periodontium.

periodontal pocket

A pathologically deepened gingival sulcus around a tooth at the gingival margin.

periodontitis

Inflammation that damages soft tissue and bone that anchors the teeh, including the gingiva plus PDL, cementum or alveolar bone tissue.

periodontium

Specialized tissues that surround and support the teeth, including gingival tissue, PDL, cementum and alveolar bone.

periosteum

A layer f dense regular connective tissue surrounding bones, also containing osteoblasts, osteo-progenitor cells and some osteoclasts.

pharyngeal arches

A series of externally visible anterior tissue bands lying under the early brain that give rise to the structures of the head and neck.

pharyngeal grooves

An ectodermal groove between two pharyngeal arches.

pharyngeal pouches

An endodermal pouch between two pharyngeal arches on the internal surface of the embryo.

philtrum

vertical indentation in the middle area of the upper lip, extending from the nasal septum to the tubercle of the upper lip.

phylogeny

The history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.

placode

Small bumps that give rise to bigger structures such as hair follicles and teeth.

planar cell polarity

A polarity axis that organizes cells in the plane (side-to-side) of the tissue.

plasma membrane

The border of every cell, made of a phospholipid bilayer and proteins.

pocket epithelium

The thin, overly-permeable epithelium that replaces junctional epithelium in a periodontal pocket.

positional information

In pattern formation, the development of spatial organization in the embryo that results from cells differentiating at specific positions, which requires that the cells have positional values as in a coordinate system

pre-ameloblasts

An intermediate cell type, differentiate from IEE cells, capable of inducing the differentiation of odontoblasts, which in turn induce pre-ameloblasts to differentiate into ameloblasts,.

pre-cementum

The thin unmineralized layer present on the surface of developing cementum.

pre-dentin

Newly formed dentin before calcification and maturation.

pre-enamel

The initial un-mineralized form of enamel secreted by ameloblasts.

pre-implantation period

The first two weeks of human development, starting with fertilization and ending with implantation of a morula.

primary curvature

The overall curve that odontoblastic processes take as seen in dentin.

primary dentin

The majority of dentin, formed before completion of the apical foramen, contains both mantle dentin and circum-pulpal dentin.

primary enamel cuticle

A thin membrane of remaining REE tissue that covers the tooth once it has erupted.

primary failure of eruption

Partial or complete failure of a tooth to erupt despite a healthy eruption pathway.

primary palate

The pre-maxilla, includes that portion of the alveolar ridge containing the four incisors.

primitive foregut

The anterior end of the primitive gut tube, derived from yolk sac endoderm, not yet connected to the oral cavity.

primitive streak

The visible line that forms on the dorsal side of the embryo as Hensen's node travels in a rostral-to-caudal direction, creating the embryos left/right symmetry.

principal fibers

The main principal fiber group is the alveolodental ligament, which consists of five fiber subgroups: alveolar crest, horizontal, oblique, apical, and interradicular on multirooted teeth. Principal fibers other than the alveolodental ligament are the transseptal fibers.

proliferation

The process that results in an increase of the number of cells, and is defined by the balance between cell divisions and cell loss through cell death or differentiation.

prominences

Five swellings that appear on the face in the fourth week

pseudopockets

A pocket depth over 3mm caused by enlargement of the gingival margin, but does not have harmful loss of the epithelial attachment.

pseudostratified epithelium

An epithelium that has more than one layer of cells, but the layers are not organized into distinct rows.

pulp core

The center of the pulp chamber with many cells and an extensive vascular supply; except for its location, it is very similar to the cell-rich zone.

pulp horns

A prolongation of coronal pulp extending toward the cusp of a tooth.

pulp stones

Discrete calcifications found in the pulp chamber of the tooth.

Pulp vitality testing

A test which helps establish the health of the pulp of a tooth.

pulpitis

Inflammation of the pulp.

radicular pulp

The portion of pulp in the roots.

RANKL

Receptor activator of nuclear factor kappa-Β ligand, a pro-apoptosis gene expressed in many tissues.

ranula

A cyst that forms in the mouth under the tongue.

Rathke's pouch

An evagination at the roof of the developing mouth in front of the oropharyngeal membrane, which gives rise to the anterior pituitary (adenohypophysis).

reactionary dentin

Tertiary dentin formed from a pre-existing odontoblast, contains narrow or filled-in dentinal tubules.

recapitulate

To state again, or to repeat.

receptors

A cell-surface, trans-membrane or cytoplasmic protein that binds to (receives) a signaling molecule and transmit the signal further.

reciprocal

Shared equally by two parties.

REE

Reduced Enamel Epithelium: the OEE and ameloblasts found on the surface of the crown prior to tooth eruption.

regeneration

After partial loss of as tissue, based on the remaining part, the tissue grows the same structure and function as the lost part.

remodeling

Reorganization or renovation of existing tissues, either physiological or pathological. The process can either change the characteristics of a tissue such as in blood vessel remodeling, or result in the dynamic equilibrium of a tissue such as in bone remodeling.

remodeling unit

Osteoblasts and osteoclasts working together to remove old bone tissue and replace it with new bone tissue, necessary for the maintenance of healthy bones.

reparative dentin

Dentin produced by the differentiation of pulp stem cells becoming later odontoblast and/or osteoblast-like cells, which form a bone-like structure

rER

rough Endoplasmic Reticulum, an organelle where membrane and secreted proteins are translated by bound ribosomes on the surface of the rER.

resorptive cells

Cells capable of removing a tissue, such as osteoclasts, cementoclasts and odontoclasts.

rete pegs

Fingerlike projections of the epidermis, the downward-pointing counterparts to the dermal papillae.

reticular connective tissue

A soft connective tissue composed of reticular fibers, ground substance, plus fibroblasts and blood cells.

Reticular fibers

A form of collagen, forms a web-like meshwork in ECM.

rhinoplasty

Cosmetic surgery that alters the appearance of the nose.

ribosomes

A small particle consisting of rRNA and proteins found in large numbers in the cytoplasm. They bind mRNA and tRNA to synthesize proteins.

RNA

Ribonucleic acid is a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins

rod enamel

The type of enamel found within an enamel rod

root resorption

The progressive loss of dentin and cementum by the action of odontoclasts (and cementoclasts).

saliva

Watery liquid secreted into the mouth, providing lubrication for chewing and swallowing, and protection for the teeth.

scaffold

Extracellular matrix material involved in the repair of injured and missing tissues, allows stem cells to migrate into the injured area. It is usually replaced during regeneration.

scar tissue

A strong but immovable connective tissue quickly made by fibroblasts, consisting primarily of highly cross-linked collagen fibers.

sebaceous glands

Microscopic exocrine glands in the skin that open into hair follicles to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin.

secondary curvature

A small curve to dentinal tubules observed in dentin, in the opposite direction of the primary curvature.

secondary dentin

Dentin formed after completion of the apical foramen, contains only circumpulpal dentin.

secondary palate

The portion of the hard palate formed by the growth of two palatal shelves medially and their mutual fusion in the midline.

septoplasty

A surgical procedure to straighten the bone and cartilage of the nasal septum.

sER

Smooth Endoplasmic Reticulum, an organelle where calcium and lipids are stored.

serous acini

Glandular acini that produce watery secretions.

Sharpey's fibers

Bundles of strong type I collagen that anchor the periosteum to bones by penetrating the outer layers of compact bone tissue

sialograph

Radiographic examination of the salivary glands, involving the injection of a contrast medium into the salivary duct of a single gland.

sialoliths

Calculus produced from saliva.

signal transduction cascade

When a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellular response.

simple columnar epithelia

Epithelia that have one layer of tall cells

simple cuboidal epithelia

An epithelium composed of one layer of square cells

simple squamous epithelium

An epithelium composed of one layer of flat cells

sinusitis

Inflammation of the sinuses.

soft palate

The posterior muscular portion of the roof of the mouth.

somites

Bilateral pairs of blocks of mesoderm that form along the rostral-caudal axis.

specialized mucosa

The epithelium found on the dorsal surface of the tongue, containing lingual papillae and taste buds.

spina bifida

A congenital malformation involving incomplete closure of the neural tube.

spongy bone

Softer bone material composed of thin trabeculae, found deep to compact bone.

stellate reticulum

A group of star-shaped cells located in the center of the enamel organ of a developing tooth, they synthesize glycosaminoglycans.

stem cells

Undifferentiated or partially differentiated cells that can differentiate into various cell types, and proliferate to produce more of the same stem cell.

Stillman cleft

A V-shaped region of gingival recession

stomodeum

A depression between the brain and the pericardium in an embryo, and is the precursor of the mouth and the anterior lobe of the pituitary gland.

stratified squamous epithelia

Epithelia that have more than one layer of cells, with the cells at the apical surface having a flat shape.

stratum intermedium

A stratified layer of cells situated between the IEE and the stellate reticulum.

sub-epithelial connective tissue graft

The most common method used to treat root exposure, involving the transplantation of healthy connective tissue from a donor site to the damaged area, which acts a scaffold aiding in tissue regeneration.

sub-lingual glands

Paired salivary glands on the floor of the oral cavity, underneath the tongue, bordered laterally by the mandible and medially by genioglossus muscle of the tongue.

sub-mandibular glands

Major salivary glands located beneath the floor of the mouth, superior to the digastric muscles.

sub-mandibular lymph nodes

Three to six lymph nodes beneath the body of the mandible in the sub-mandibular triangle, or the superficial surface of the sub-mandibular gland, whose afferent vessels drain the medial canthus, cheek, side of the nose, upper lip, lateral part of the lower lip, gums, and the anterior part of the margin of the tongue, and whose efferent vessels drain ino the superior deep cervical lymph nodes.

sub-mental lymph nodes

Lymph nodes in the mental region whose afferent vessels drain central portions of the lower lip, floor of the mouth and apex of the tongue, and whose efferent vessels drain partly into sub-mandibular lymph nodes and partly into deep cervical lymph nodes.

sub-mucosa

The dense irregular connective tissue layer found below the oral mucosa (or mucosa of a hollow organ), homologous to the reticular layer of the dermis.

sulcular epithelium

Epithelium lining the gingival sulcus.

sulcus terminalis

V-shaped groove separating the anterior two thirds of the tongue from the posterior third and containing the circumvallate papillae.

superior deep cervical nodes

Lymph nodes under the sternocleidomastoid muscle.

supernumerary roots

Extra roots on a tooth.

surface etching

The use of an acids to prepare enamel for the application of an adhesive, which roughens the surface and removes the smear layer, increasing retention of resin sealant.

temporo-mandibular joint

The synovial joint between the temporal bone and the mandible.

teratogens

Agents or factors which cause malformation of an embryo.

terminally differentiated

When a cell has finished its last possible differentiation step and lost the ability to undergo mitosis.

tertiary dentin

dentin formed as a reaction to external stimulation, such as cavities and wear, including both reactionary and reparative dentin.

tight junction

A type of cell-to-cell contact that prevents diffusion between cells.

tissue

A group of cells, all the same type, that work together to perform one or more functions.

Tomes' granular layer

A layer of dark granules that lie parallel to the outer surface of root dentin.

Tomes' process

A histologic landmark identified on an ameloblast.

tonsillitis

Inflammation of the tonsils

tooth bud
tooth buds

A mass of tissue having the potentiality of differentiating into a tooth.

tooth eruption

A process in tooth development in which the teeth enter the mouth and become visible.

tooth fusion

The union of two adjacent teeth at the crown level (enamel and dentin).

tooth germ

An aggregation of cells that eventually forms a tooth, composed of the enamel organ, dental papilla and dental sac.

trabeculae

Rod-like mineralized connective tissue structures found in spongy-bone.

trans-membrane proteins

Proteins embedded within the plasma membrane, with parts both the inside and outside of the cell.

transcription

The process of converting DNA into an mRNA copy

transcription factor

A protein that controls the rate of transcription of DNA to mRNA, by binding to a specific DNA sequence.

translate

The process of turning the sequence of a mRNA into a sequence of amino acids during protein synthesis

trimesters

A period of three months, especially as a division of the duration of pregnancy.

trisomy 21

The most common chromosomal anomaly in humans, also known as Down syndrome, caused by an extra chromosome 21.

trophoblast

Cells that form the outer layer of a blastula which provide nutrients to the embryo and develop into a large part of the placenta.

tuberculum impar

A swelling situated in the midline of the floor of the pharynx between the mandibular arch and of the second branchial arch that contributes to the formation of the anterior part of the tongue.

unilateral

On one side

vascular

Containing blood vessels

ventral surface of the tongue

The bottom surface of the tongue, which contains no lingual papillae.

vermilion zone

The lip, as opposed to adjacent skin or oral mucosa, named for its more reddish appearance than keratinized skin.

vesicle

A structure inside (or outside) a cell, consisting of liquid enclosed by a lipid bilayer.

Volkman’s canals

Small channels in the bone that transmit blood vessels from the periosteum into the bone and that communicate with the haversian canals, or small holes in alveolar bone through which PDL fiber bundles are embedded.

von Ebner salivary glands,

minor salivary glands associated with circumvallate papillae.

Waldeyer's ring

Four tonsils (pharyngeal, tubal, palatine and lingual tonsils) as well as small collections of lymphatic tissue disbursed throughout the mucosal lining of the pharynx.

Wnt

Signaling molecules first identified for their role in carcinogenesis, then for their function in embryonic development, including body axis patterning, cell fate specification, cell proliferation and cell migration.

xerostomia

The symptom of having a dry mouth due to reduced saliva production.

zygote

A diploid cell resulting from the fusion of two haploid gametes; a fertilized ovum.

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