Ch. 3 & 4: Development of the Face & Oral Cavity

What is the primitive mouth opening called? 

stomodeum

When does the oropharyngeal membrane of the stomodeum rupture?

week 5

What are the branchial arches? 

identical paired bars of tissues that are the core of the mesoderm covered with ectoderm

Arch I is also called the…

mandibular arch

Arch I forms the…

future mandible and maxilla, body of the tongue, palatal shelves, and muscles of mastication

Arch II is also called the…

hyoid arch

Arch II forms the…

hyoid bone, base of the tongue, and the facial muscles

Arch III-V are not involved in the development of the oral cavity but they do…

cover the bulging heart of the embryo and are still part on the development of the face

The first pharyngeal/branchial groove becomes the…

external auditory canal

What will later become the palatine tonsils, inferior parathyroids, thymus, and superior parathyroids?

endodermal lining of the pharyngeal pouches

What do the palatine tonsils develop?

lymphocytes

The initial skeleton of the brachial arches develop as…

bars of cartilage

What forms the mandible?

meckel’s cartilage

What forms the maxilla?

zygomatic cartilage

How are facial bones usually formed?

intramembranous bone formation

What is the bulge of bone on an infant’s head called

fontanelle or “soft spot”

What areas does the development of the face involve? 

frontal process and brachial arch I

What weeks does the development of the face occur? 

weeks 4-7

What does the embryo look like at week 4? 

it has a large frontal process, prominent stomodeum, small maxillary process, and a large mandibular arch

Teratogens can be most dangerous during what part of the development of the child?

The period before the fifth week is the critical time during which environmental factors can affect facial development

What occurs at week 5? 

nasal placodes develop, the frontal process divides, and eye begin to appear laterally 

At week 5, the frontal process is now called the…

frontonasal process

At week 5, what structure rupture to connect the stomodeum and the foregut? 

oropharyngeal membrane 

What occurs at week 6?

maxillary and mandibular tissues merge, lips begins to close to form the philtrum, and eyes move more medially

What occurs from failure of the medial nasal process and maxillary processes to fuse?

cleft lip

What occurs at week 7? 

maxillary process fuses with the medial nasal and lateral nasal processes, the globular process forms, the eye move to the midline, and the ears are formed

formed by the extension of the medial nasal process that forms the philtrum and contributes to the primary palate?

globular process

wedge-shaped anterior portion of the palate formed by the fusion of the medial nasal processes

premaxilla or primary palate

formed by the right and left palatine process/shelves

secondary palate 

In what direction does the palate fuse together in? 

from anterior to posterior

When the palatal shelves start to fuse together it forces the tongue…

forward and down

What branchial arch does the body of the tongue come from?

branchial arch I

Why is the dorsal surface of the tongue considered to be a specialized mucosa?

because of its tastes buds and papillae 

What branchial arch does the base of the tongue come from? 

branchial arch II and III

What separates the body and base of the tongue?

terminal sulcus

center of the terminal sulcus that is the origin of the thyroid gland 

foramen cecum

What is caused if there is incomplete dissolution of epithelial cells when the thyroid gland migrates?

cysts can form

Clefts occur along…

fusion lines

involve incomplete fusion of the mesial nasal process and the right and/or left maxillary processes

cleft lips

What constitutes a complete cleft lip?

opening extends all the way through the lip and into the nostril

involve incomplete fusion of the primary palate and the right and/or left palatine processes

cleft palate

What causes a bifid uvula?

incomplete fusion of palatine shelves

abnormally large tongue

macroglossia

abnormally small tongue

microglossia

abnormally underdeveloped tissues on one side of the face

hemifacial microsomia

ectopic sebaceous glands

fordyce granules

What is the primary ability of the neural crest cells?

ability to migrate

disturbance of dentin formation
consists of opalescent teeth that have unmineralized dentin, obliterated pulp chambers, and shortened roots with bulbous crowns

dentinogenesis imperfecta

Which layer of epithelium contains the blood vessels?

connective tissue

What tooth tissue is not formed from the mesoderm?

enamel

What germ cell layer does the nerve system come from?

ectoderm