Embryology, Facial Development & Tooth Formation

Sixty practice flashcards in Q&A format covering embryologic stages, facial and palatal development, cleft conditions, pharyngeal arches, tongue formation, and early tooth development processes.

During which weeks does the period of the ovum occur?

From fertilization through week 2.

During which weeks does the period of the embryo occur?

Weeks 3–8.

During which timeframe does the period of the fetus occur?

Week 9 until birth.

Which embryonic germ layer gives rise to teeth, epidermis, fingernails, eye tissue, and hair?

Ectoderm.

Which germ layer forms the dermis, muscle, blood vessels, lymphatics, connective tissue, bone, and cartilage?

Mesoderm.

Which germ layer develops into the respiratory epithelium, digestive tract lining, liver, and pancreatic cells?

Endoderm.

Approximately how long is the embryo by week 3 of development?

About 3–4 mm.

What conspicuous cardiovascular structure is visible on the embryo at week 3?

The heart bulge.

Name the three regions of the primitive digestive tract present in week 3 embryos.

Foregut, midgut, and hindgut.

What is the stomodeum?

The primitive oral cavity.

Which membrane disintegrates to connect the oral cavity with the digestive tract?

The buccopharyngeal membrane.

Which pharyngeal arch is also called the mandibular arch?

Arch #1.

What two facial processes are derived from the mandibular arch?

Mandibular process and maxillary process.

Which pharyngeal arch is referred to as the hyoid arch?

Arch #2.

List the three major embryonic facial processes.

Mandibular process, maxillary process, and frontal prominence.

What three structures are found in the frontal prominence?

Nasal pits, medial nasal process, and lateral nasal process.

Which two processes must fuse to form the upper lip?

The maxillary process and the medial nasal process.

Failure of maxillary–medial nasal fusion results in what congenital defect?

Cleft lip.

The primary palate is formed by which embryonic structure?

The medial nasal process (which contains the maxillary incisors).

The secondary palate develops from which structures?

The palatal shelves of the maxillary processes.

Is cleft lip or cleft palate more common?

Cleft lip is more common.

Cleft lip occurs more frequently in which sex?

Males.

Cleft palate occurs more frequently in which sex?

Females.

Give three common complications of cleft palate.

Difficulty in feeding, increased risk of infection, and speech development problems.

Define cleft lip.

A gap or opening in the upper lip resulting from failure of tissue fusion during fetal development.

Define cleft palate.

An opening in the roof of the mouth caused by incomplete closure of the palate during pregnancy.

Which cranial nerve is associated with the first pharyngeal arch?

The trigeminal nerve (CN V).

Name two muscles derived from the first pharyngeal arch.

Muscles of mastication and the mylohyoid/anterior belly of the digastric (also tensor tympani and tensor veli palatini).

Tongue development involves which pharyngeal arches?

Arches 1, 3, and 4.

In what week do the first signs of tooth development (dental lamina) appear?

Week 6.

What is the dental lamina?

An internal thickening of oral epithelium marking future tooth positions.

Where does the dental lamina first appear?

In the anterior midline of the developing jaws.

The arrangement of the dental lamina corresponds to what future pattern?

The eventual arrangement of the teeth.

Defective ectodermal formation affecting teeth is known as what condition?

Ectodermal dysplasia.

During which week does the bud stage of the enamel organ occur?

Week 8.

How many tooth buds appear in the maxillary arch during the bud stage?

10.

During which weeks does the cap stage of tooth development occur?

Weeks 9–10.

During which weeks does the bell stage of tooth development occur?

Weeks 11–12.

What is the protective outer layer of the enamel organ called?

The outer enamel epithelium (OEE).

Which cells are formed from the inner enamel epithelium (IEE)?

Ameloblasts.

What is the role of the stellate reticulum in the enamel organ?

To cushion the IEE and facilitate nourishment via the stratum intermedium.

What is the function of the stratum intermedium?

It nourishes the IEE and assists ameloblasts in enamel formation.

What is the successional lamina?

A lingual extension of the dental lamina that forms permanent successor teeth.

Through which developmental stages does the successional lamina progress?

Bud, cap, and bell stages (all stages of tooth development).

When does the dental lamina attachment break down?

As the developing tooth reaches the bell stage.

To which teeth does the successional lamina not apply?

Permanent molars.

Which embryonic tissue gives rise to dentin and pulp?

The dental papilla.

Where is the dental papilla located relative to the enamel organ?

Deep to the inner enamel epithelium (IEE).

What structure surrounds the dental papilla during tooth development?

The dental sac (dental follicle).

What three hard/soft tissues are derived from the dental sac?

Cementum, periodontal ligament (PDL), and alveolar bone.

Which pharyngeal arch gives rise to the tensor tympani and tensor veli palatini muscles?

The first (mandibular) arch.

What two components characterize the primary palate?

Formation from the medial nasal process and inclusion of the future maxillary incisors.

What embryologic name is given to the primitive mouth cavity?

The stomodeum.

Which facial swelling contains the nasal pits during early development?

The frontal prominence.

Which embryonic processes give rise to the palatal shelves?

The maxillary processes.

Which facial defect is influenced by both hereditary and environmental factors?

Cleft palate.

What are palatal shelves?

Horizontal outgrowths from the maxillary processes that elevate to form the secondary palate.

After the buccopharyngeal membrane disintegrates, the primitive oral cavity opens into which system?

The digestive tract.

In which week does the internal thickening known as the dental lamina appear?

Week 6.

How many tooth buds are present in the mandibular arch during the bud stage?

20.