Embryology and Tooth Development

What is mitosis?

Cell division that produces 2 genetically identical diploid cells. Used for growth, repair, and replacement.

What is meiosis?

Cell division that produces haploid sex cells (gametes) with half the chromosome number.

What cells are produced by meiosis?

Sperm and egg cells.

What is the major difference between mitosis and meiosis?

Mitosis → 2 identical cells; meiosis → 4 genetically different haploid cells.

What are the 3 periods of prenatal development?

Germinal, embryonic, and fetal periods.

What happens during the germinal period?

Fertilization, rapid cell division, and implantation of the developing conceptus.

What happens during the embryonic period?

Major organ and body structure formation occurs.

What happens during the fetal period?

Mainly growth and maturation of organs and body structures.

When is the embryo most vulnerable to major congenital malformations?

During the embryonic period, when organs are forming.

What is a congenital malformation?

A structural abnormality that is present at birth.

What can cause congenital malformations?

Genetic factors, environmental factors/teratogens, infections, drugs, radiation, and other developmental disruptions.

What are the 3 primary germ layers?

Ectoderm, mesoderm, and endoderm.

What is the primitive streak?

A structure that forms during gastrulation and helps establish the three germ layers.

What does ectoderm primarily form?

Skin, hair, nails, nervous system, and enamel.

What does mesoderm primarily form?

Blood, bone, cartilage, muscle, connective tissues, and much of the cardiovascular system.

What does endoderm primarily form?

The epithelial lining of much of the digestive and respiratory systems and associated organs.

Hair, skin, and nails come from which germ layer?

Ectoderm.

Enamel comes from which germ layer?

Ectoderm.

Blood and cartilage come from which germ layer?

Mesoderm.

The digestive system lining comes primarily from which germ layer?

Endoderm.

What are the major stages of tooth development?

Initiation → bud → cap → bell → apposition → mineralization/maturation.

What occurs during initiation?

The oral epithelium begins forming the dental lamina, initiating tooth development.

What occurs during the bud stage?

The dental epithelium proliferates and grows into the ectomesenchyme, forming a tooth bud.

What happens during the cap stage?

The enamel organ takes on a cap-like shape and the dental papilla and dental follicle become identifiable.

What happens during the bell stage?

Cells differentiate and the shape/form of the tooth crown is established.

What is apposition?

The layer-by-layer deposition of dental hard tissues, such as enamel and dentin.

What does the enamel organ form?

Enamel.

What does the dental papilla form?

Dentin and dental pulp.

What does the dental follicle/sac form?

Cementum, periodontal ligament, and alveolar bone.

Which structure gives rise to ameloblasts?

The inner enamel epithelium of the enamel organ.

Which cells produce dentin?

Odontoblasts.

Which cells produce enamel?

Ameloblasts.

What does HERS stand for?

Hertwig's epithelial root sheath.

What is the main function of HERS?

It determines the shape, size, and number of roots and helps initiate root development.

HERS is derived from which structures?

The inner and outer enamel epithelium of the cervical loop.

What does HERS induce in the dental papilla?

Differentiation of cells into odontoblasts, which form root dentin.

When does root development begin?

After crown formation is substantially complete.

What determines the shape of the root?

Hertwig's epithelial root sheath (HERS).

What tissue forms first during root development?

Root dentin.

What happens to HERS after root dentin formation begins?

It fragments, allowing cells from the dental follicle to contact the dentin and differentiate into cementoblasts.

What are succedaneous teeth?

Permanent teeth that replace primary teeth.

Give examples of succedaneous teeth.

Permanent incisors, canines, and premolars.

What are nonsuccedaneous teeth?

Permanent teeth that do not replace primary teeth.

Which permanent teeth are nonsuccedaneous?

Permanent first, second, and third molars.

What are the 5 facial prominences/processes?

1. Frontonasal prominence

2. Right maxillary prominence

3. Left maxillary prominence

4. Right mandibular prominence

5. Left mandibular prominence

How many pharyngeal (branchial) arches are important in facial development?

Several develop, but the 1st, 2nd, 3rd, 4th, and 6th arches contribute significantly to head and neck development; the 5th arch is rudimentary/absent.

What is another name for the pharyngeal arches?

Branchial arches.

Which pharyngeal arch is the mandibular arch?

The 1st pharyngeal arch.

What nerve is associated with the 1st pharyngeal arch?

Trigeminal nerve (CN V), specifically mainly V2 and V3, with muscles of mastication primarily supplied by V3.

What major skeletal structures are associated with the 1st arch?

Structures of the mandible and maxilla, plus the malleus and incus.

What muscles are associated with the 1st pharyngeal arch?

Muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, and tensor veli palatini.

What forms the primary palate?

The intermaxillary segment, formed from fusion of the medial nasal prominences.

What does the primary palate contribute to?

The anterior portion of the hard palate, in front of the incisive foramen.

What forms the secondary palate?

The lateral palatine processes/shelves of the maxillary prominences.

How does the secondary palate form?

The palatal shelves elevate, move toward each other, and fuse with each other and the nasal septum.

What separates the oral and nasal cavities during development?

Formation and fusion of the palate.

What is cellular differentiation?

The process by which unspecialized cells become specialized cells with specific structures and functions.

Why is differentiation important during embryonic development?

It allows cells to specialize into different tissues, organs, and structures.

What is proliferation?

An increase in the number of cells, primarily through cell division.

What is morphogenesis?

The process by which cells and tissues organize and develop their shape and structure.

What is histodifferentiation?

Differentiation of cells into specific tissue types.

What is morphodifferentiation?

The process by which cells determine the shape and form of a developing structure, such as the tooth crown.