04 Development of the Face and Neck -...

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Development of the Face Development of the neck

04 Development of the Face and Neck

+Development of the face

The fourth week ~ the twelfth week of prenatal development

Between developing brain and heart

All three embryonic layers are involved in facial development

Five facial processes

Single frontonasal process

Paired maxillary process

Paired mandibular process

Overview of facial development

stomodeum

Developing brain

Table 4-1 Branchial Arches and Derivative Structures

First arches(mandibular)

Trigenimal nerve, muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani, tensor veli palatine muscles

Malleus and incus of middle ear, including anterior ligament of the malleus, sphenomandibularligament, and parts of sphenoid bone

Second arches(hyoid)

Facial nerve, stapedius muscle, muscles of facial expression, posterior belly of the digastric muscle, stylohyoid muscle

Stapes and parts of malleus and incus of middle ear, stylohyoidligament, styloid process of the temporal bone, lesser cornu of hyoid bone, upper portion of body of hyoid bone

Third arches Glossopharyngeal nerve, stylopharyngeal muscle

Greater cornu of hyoid bone, lower portion of body of hyoid bone

Fourth throughSixth arches

Superior laryngeal branch and recurrent laryngeal branch of vagusnerve, levator veli palatine muscles, pharyngeal constrictors, intrinsic muscles of the laynx

Laryngeal cartilage


Facial processes are centers of growth for the face

Upper face : from frontonasal process

Middle face : from maxillary process

Lower face : from mandibular process

Growth pattern of the face

upper face – rapid

middle and lower face – slow



Fusion

fusion of tissue on the same surface of the embryoe.g.) Most of the facial structures

fusion of tissue on the different surface of the embryoe.g.) Palate



Stomodeum (stomatodeum)

a shallow depression in the embryonic surface ectoderm before fourth week

Oropharyngeal membrane separates the stomodeum from the primitive pharynx

Primitive pharynx (The cranial part of foregut, the beginning of the future digestive tract)

FIRST event during fourth week

Disintegration of the oropharyngeal membrane

Stomodeum will form the oral cavity

lined by oral epithelium

Stomodeum and oral cavity formation

Embryo at third to fourth weeks of development.

+Development of the faceMandibular arch and lower face formation

During fourth week, two bulges of tissue appear inferior to stomodeum two mandibular processes

These paired mandibular processes are formed in part by neural crest cells that migrated to the facial region, covered externally by ectoderm and internally by endoderm.

Paired mandibular processes BOTH fuse at midline to form the mandibular arch mandibular arch, first branchial arch

Meckel’s cartilage forms within each side of mandibular arch, IMPORTANT in alveolar bone development

Directly forms lower face, including lower lip.: mandible, mandibular teeth, associated tissues, tongue


During fourth week, frontonasal process is a bulge of tissue in upper facial area.

Frontonasal process will form upper face, which includes forehead, bridge of nose, primary palate, nasal septum.

Frontonasal process and upper face formation


<Placode development>

Rounded areas of specialized, thickened ectoderm

Lens placodes: future eyes and associated tissues

otic placodes: future internal ear and associated tissues

Nasal placodes: form nasal (olfactory) pits, which develop into nasal cavities.



<Nose and paranasal sinus formation>During the fourth week, the tissue around the nasal placodes

undergoes growth.

Nasal pits: Placodes become submerged, forming depression in center of each

Nasal pits develop into nasal cavities.medial nasal process

: the middle portion of the nose from root to apex, center portion of upper lip, philtrum region

lateral nasal processes: alae

premaxillary segment: maxillary incisor teeth and associated tissues, primary palate, nasal septum



During fourth week, the maxillary processes be formed from increased growth of mandibular arch.

These paired maxillary processes are formed in part by neural crest cells that migrated to the facial region, covered externally by ectoderm and internally by endoderm.

Maxillary process will form the midface: Includes sides of upper lip, cheeks, secondary palate posterior portion of maxilla with maxillary canines and posteriors,

associated tissues Zygomatic bones and temporal bones

Maxillary process and midface formation


< Upper and lower lip formation>

Upper lip: each maxillary process (sides)+ each medial nasal process(middle)

Lower lip: mandibular process

Maxillary process and midface formation

intermaxillarysegment

** Developmental disturbances of the lips and associated tissue• Cleft lip

+Development of the neck

The fourth week of prenatal development ~ fetal period

Develop from the primitive pharynx and the branchial apparatus

+Development of the NeckPrimitive pharynx formation

Derived from the anterior part of the foregut and will form the primitive pharynx, the future oropharynx

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+Development of the Neck

Branchial apparatus branchial arches, branchial grooves and membranes, pharyngeal

pouches

Branchial apparatus formation

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ARCH

GROOVE or CLEFT

POUCH

MEMBRANE

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The fourth week of prenatal development Stacked bilateral swellings of tissue First branchial arch(mandibular arch ) ~ fourth

mandibular arch Six pairs of U-shaped barsMesenchyme formed by neural crest cells, ectoderm,

and endoderm Fifth branchial arch is often so rudimentary Important structures of the face and neckHas its own developing cartilage, nerve, vascular,

and muscular components FIRST branchial arch(mandibular arch) are involved

in the formation of middle and lower face

Branchial arch formation

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Lower four pairs arches are involved in the formation of the structure of the neck.

Second branchial arch (=Hyoid arch)Reichert’s cartilage

: a middle ear bone, a process of the temporal bone, parts of the hyoid bone

Mesoderm of the hyoid arch: facial muscle, middle ear muscle, suprahyoidmuscle

Facial nerve

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Third branchial arch Parts of the hyoid bonePharyngeal muscleGlossopharyngeal nerve

Fourth and sixth branchial archMost of the laryngeal cartilageVagus nerve (+Glossopharyngeal nerve)

Table 4-2 Branchial Arches and Derivative Structures

First arches(mandibular)

Trigeminal nerve, muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani, tensor veli palatine muscles

Malleus and incus of middle ear, including anterior ligament of the malleus, sphenomandibularligament, and parts of sphenoid bone

Second arches(hyoid)

Facial nerve, stapedius muscle, muscles of facial expression, posterior belly of the digastric muscle, stylohyoid muscle

Stapes and parts of malleus and incus of middle ear, stylohyoidligament, styloid process of the temporal bone, lesser cornu of hyoid bone, upper portion of body of hyoid bone

Third arches Glossopharyngeal nerve, stylopharyngeal muscle

Greater cornu of hyoid bone, lower portion of body of hyoid bone

Fourth throughSixth arches

Superior laryngeal branch and recurrent laryngeal branch of vagusnerve, levator veli palatine muscles, pharyngeal constrictors, intrinsic muscles of the laynx

Laryngeal cartilage

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External grooves, between neighboring branchial arches

FIRST branchial groove Is located between the first and second branchial archesA mature structure of the head and neck First branchial membrane

: tympanic membrane First branchial groove

: external auditory meatus By the end of the seventh week,

: Hyoid arch enlarges and overlaps the third, fourth, and sixth arches and cover them.: the last for branchial grooves are obliterated neck formation

Branchial groove and membrane formation

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Four well-defined pairs of pharyngeal pouches

Endodermal evaginations form the lateral walls lining the pharynx

Many structures of the face and neck.

Pharyngeal pouch formation

Table 4-3 Pharyngeal Pouches and Derivative Structures

First pouches Tympanic membrane (with first branchial groove), tympanic cavity, mastoid antrum, auditory tube

Second pouches Crypts and lymphatic nodules of the palatine tonsils

Third and fourth pouches Parathyroid and thymus gland

** Developmental disturbances of the branchial apparatus• Cervical cysts or Cervical sinuses

04 Development of the Face and Neck -...

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