Embryology & Early Tooth Development (Ch. 18–19)

A set of 60 question-and-answer flashcards to review key points on embryologic stages, facial and palatal development, cleft anomalies, pharyngeal arches, and early tooth formation from Chapters 18–19.

During which timeframe does the period of the ovum occur?

From fertilization through week 2

The embryonic period spans which weeks of prenatal development?

Weeks 3–8

The fetal period lasts from what time until birth?

Week 9 to birth

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

Ectoderm

The dermis, muscles, blood vessels, lymphatics, connective tissue, bone, and cartilage arise from which germ layer?

Mesoderm

Respiratory epithelium, digestive system lining, and liver and pancreatic cells are derived from which germ layer?

Endoderm

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

3–4 mm

What prominent cardiovascular feature is visible by week 3?

The heart bulge

Name the three segments of the developing digestive tract that appear early in development.

Foregut, midgut, and hindgut

What is the stomodeum?

The primitive oral cavity

The disintegration of which membrane connects the oral cavity with the developing digestive tract?

Buccopharyngeal membrane

What is the common name for pharyngeal arch #1?

Mandibular arch

The mandibular arch gives rise to which two facial processes?

Mandibular process and maxillary process

What is the common name for pharyngeal arch #2?

Hyoid arch

Which facial process contributes to the formation of the lower jaw?

Mandibular process

Which facial process contributes to the formation of the upper jaw and cheeks?

Maxillary process

The frontal prominence eventually develops what depression that will become the nostrils?

Nasal pits

Name the two processes that form around each nasal pit.

Medial nasal process and lateral nasal process

The upper lip forms by the fusion of which two embryonic processes?

Maxillary process and medial nasal process

Failure of fusion between the maxillary process and medial nasal process results in what defect?

Cleft lip

The primary palate develops from which embryonic process?

Medial nasal process

Which group of teeth is contained within the primary palate?

Maxillary incisors

The secondary palate forms from which embryonic processes?

The right and left maxillary processes

What are the outgrowths from the maxillary processes that elevate and fuse to form the secondary palate?

Palatal shelves

Is cleft lip more frequent in males or females?

Males

Is cleft palate more frequent in males or females?

Females

Cleft defects are primarily hereditary but can also be influenced by what kind of factors?

Environmental factors

Name one common complication associated with cleft palate.

Difficulty feeding (others: infection, speech problems)

Define cleft lip.

A birth defect where the tissues of the upper lip do not fully join, leaving an opening

Define cleft palate.

A birth defect where the roof of the mouth fails to close completely, leaving an opening

Which cranial nerve is associated with the first (mandibular) pharyngeal arch?

Trigeminal nerve (cranial nerve V)

Name two muscles derived from the first pharyngeal arch.

Muscles of mastication and mylohyoid (also anterior belly of digastric, tensor tympani, tensor veli palatini)

Development of the tongue involves which pharyngeal arches?

Arches 1, 3, and 4

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

Week 6

Dental lamina is an internal thickening of which tissue layer?

Oral epithelium

The dental lamina first appears in which region of the mouth?

Anterior midline

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

Week 8

How many tooth buds form in each arch during the bud stage?

10 in the maxilla and 10 in the mandible

What key cellular activity characterizes the bud stage?

Proliferation of epithelial cells

The cap stage of tooth development occurs during which weeks?

Weeks 9–10

The bell stage occurs during which weeks of prenatal development?

Weeks 11–12

What is the primary function of the outer enamel epithelium (OEE)?

Protection of the developing enamel organ

Cells of the inner enamel epithelium (IEE) differentiate into what enamel-forming cells?

Ameloblasts

Which layer cushions the IEE and helps provide its nourishment?

Stellate reticulum

What is the role of the stratum intermedium?

To nourish the IEE and assist ameloblast function

The successional lamina is an extension on which side of each developing tooth?

Lingual side

Through which stages of tooth development does the successional lamina progress?

Bud, cap, and bell stages

The successional lamina does NOT apply to which group of permanent teeth?

Permanent molars

Relative to the inner enamel epithelium, where is the dental papilla located?

Deep to (beneath) the IEE

What two dental tissues are formed by the dental papilla?

Dentin and pulp

The dental sac surrounds which embryonic structure?

Dental papilla (and enamel organ)

What three adult tissues originate from the dental sac?

Cementum, periodontal ligament (PDL), and alveolar bone

Which genetic disorder listed in the notes can affect development of the dental lamina?

Ectodermal dysplasia

The buccopharyngeal membrane originally separates which two cavities?

Stomodeum (primitive oral cavity) and foregut (pharynx)

What is another term for the primitive oral cavity?

Stomodeum

Name the two nasal processes that fuse to form the bridge of the nose and philtrum.

Paired medial nasal processes

The palatal shelves must elevate and fuse during development; failure results in what oral defect?

Cleft palate

Which arch-derived muscles include the tensor tympani and tensor veli palatini?

First (mandibular) pharyngeal arch muscles

Approximately how many millimeters is the embryo when the heart bulge and digestive tract segments are visible?

3–4 mm

Which facial prominence gives rise to the medial and lateral nasal processes?

Frontal prominence