Oral Anatomy and Histology: Tooth and Embryonic Development

Vocabulary practice flashcards covering embryonic germ layers, facial and palatal development, and stages of tooth development (odontogenesis) based on the lecture slides.

Germinal Period

The first 2 weeks of prenatal development.

Embryonic Period

The period of prenatal development spanning weeks 3 through 8.

Fetal Period

The period of prenatal development spanning week 9 until birth.

Ectoderm

The most exterior embryonic germ layer, which forms skin, lining of the oral cavity, tooth enamel, the nervous system, and other external tissues.

Mesoderm

The middle embryonic germ layer, which forms muscle, the skeletal system, the circulatory system, as well as dentin, pulp, and cementum.

Endoderm

The most internal embryonic germ layer, which forms the lining of the stomach, pharynx, and other internal organs.

Premaxilla

The primary palate forming the anterior portion of the palate, derived from the intermaxillary segment (median nasal process) between the 5th and 6th weeks.

Lateral Palatine Process

The secondary palate forming the sides of the hard palate, derived from the maxillary process between the 6th and 12th weeks.

Odontogenesis

The process of tooth development.

Induction

The developmental process where one tissue influences the development of another tissue.

Proliferation

The growth and increase in cell numbers within a tissue.

Differentiation

The biological process in which cells become more specialized and structurally distinct from one another.

Morphogenesis

The biological process that causes a cell, tissue, or organism to develop its structure and body system.

Maturation

The final stage of tissue development where the tissue reaches its mature form.

Initiation stage

The stage of tooth development occurring during the 6th to 7th week, where ectoderm gives rise to oral epithelium and the dental lamina with 10 dental enlargements/placodes per arch.

Bud stage

The stage of tooth development occurring during the 8th week, characterized by the growth of the dental placode into a bud shape that penetrates the growing ectomesenchyme.

Cap stage

The stage of tooth development occurring during the 9th to 10th week, where the tooth shape becomes evident and cells specialize to form the enamel organ, dental papilla, and dental sac.

Bell stage

The stage of tooth development occurring during the 11th to 12th week, characterized by differentiation of the enamel organ into four cell types and the dental papilla into two cell types.

Outer Enamel Epithelium (OEE)

A single layer of cuboidal cells covering the enamel organ that outlines developing enamel, organizes capillaries, and protects the enamel organ.

Stellate Reticulum (SR)

A star-shaped, multi-layered cellular network located between the OEE and IEE that protects, cushions, and nourishes the enamel organ.

Stratum intermedium (SI)

A layer 2 to 3 cells thick composed of flat epithelial cells lying between the SR and IEE that aids in ameloblast formation and nourishes the IEE.

Inner Enamel Epithelium (IEE)

The single concave layer of cuboidal cells lining the enamel organ that elongate into columnar cells and differentiate into ameloblasts.

Dental sac

Mesenchymal structure surrounding the developing tooth germ that produces cells to form the periodontal ligament, cementum, and alveolar bone proper.

Dental papilla

Condensed ectomesenchyme located on the concave side of the enamel organ whose peripheral cells differentiate into odontoblasts and central cells form dental pulp.

Preameloblasts

Cells differentiated from columnar IEE cells whose nuclei move away from the basement membrane, inducing dental papilla cells to differentiate into odontoblasts.

Dentinoenamel Junction (DEJ)

The inner junction formed between dentin and enamel tissues upon mineralization of the disintegrating basement membrane.

Hertwig's root sheath

A sheath formed by the fusion of the outer enamel epithelium and inner enamel epithelium that grows downward to shape the root and guide root dentin formation.

Active eruption

The actual vertical physical movement of a tooth as it emerges into the oral cavity.

Passive eruption

Apparent exposure of tooth structure due to age-related gingival recession without actual vertical movement of the tooth.

Reduced enamel epithelium (REE)

A compressed layer of flattened cells overlying newly formed enamel that fuses with oral epithelium to facilitate tooth eruption.

Nasmyth membrane

A green-gray extrinsic residue on newly erupted teeth formed by fused tissue of the REE, oral epithelium, and dental cuticle.

Supraeruption

The eruption of a tooth past the normal occlusal plane.

Ankylosis

Direct fusion of a tooth root to the alveolar bone caused by loss or absence of the periodontal ligament.

Ectopic teeth

Teeth developing outside normal dental arches and following an abnormal path of eruption.

Odontoclasts

Specialized cells that differentiate to resorb dental tissue during the shedding of primary teeth.