1: Development of the Head and Neck

CHAPTER 1

DEVELOPMENT OF THE HEAD AND NECK

Overview

Pharyngeal Arches

Pharyngeal Pouches, Membranes, and Clefts

Skull

Face

Palate

Tongue

Thyroid Gland

Clinical Correlates

Questions

Overview

GENERAL INFORMATION

3 major germ layers form the initial developing embryo:

Ectoderm

Mesoderm

Endoderm

Mesoderm differentiates into:

Paraxial mesoderm

Intermediate mesoderm

Lateral plate mesoderm

Ectoderm gives rise to 2 layers:

Neuroectoderm

Neural crest

The head and neck are formed by:

Paraxial mesoderm

Lateral plate mesoderm

Neural crest

Ectodermal placodes

Most of the head and neck is formed from the pharyngeal arches

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Pharyngeal Arches

GENERAL INFORMATION

Start forming in the 4th week of development

Develop as blocks separated by pharyngeal clefts

Initially, 6 arches develop, but the 5th regresses

Arising from the endoderm are compartments called pharyngeal pouches that extend toward the pharyngeal clefts

Help form 4 of the 5 swellings of the face:

2 mandibular processes (pharyngeal arch)

2 maxillary processes (pharyngeal arch)

1 frontonasal prominence

Composed of:

External surface–ectoderm

Internal surface–endoderm

Central part–lateral plate mesoderm, paraxial mesoderm, neural crest

Skeletal components develop from the neural crest tissue

Muscular structures develop collectively from the mesoderm

Each arch is innervated by a cranial nerve that migrates with the muscles

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DERIVATIVES OF THE PHARYNGEAL ARCHES

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Pharyngeal Pouches, Membranes, and Clefts

GENERAL INFORMATION

Pharyngeal pouches—4 develop from endoderm

Pharyngeal clefts—each is a groove formed from ectoderm

Pharyngeal membranes—each is composed of tissue located between a pharyngeal pouch and a pharyngeal cleft; composed of external ectoderm, mesoderm and neural crest in the core, and an internal endoderm lining

PHARYNGEAL POUCHES

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PHARYNGEAL MEMBRANES

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PHARYNGEAL CLEFTS

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Skull

GENERAL INFORMATION

Skull is formed from:

Lateral plate mesoderm (neck region)

Paraxial mesoderm

Neural crest

Bony skull is formed by either of 2 mechanisms:

Intramembranous ossification

Endocho/>

Jan 5, 2015 | Posted by in General Dentistry | Comments Off on 1: Development of the Head and Neck
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