04 Development of the Face and Neck. Development of the Face Development of the neck

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Nickolas Webb
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1 04 Development of the Face and Neck Development of the Face Development of the neck

2 Development of the face Overview of facial development 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

3 Developing brain stomodeum

5 Table 4-1 BranchialArches and Derivative Structures First arches (mandibular) Second arches (hyoid) Third arches Fourth through Sixth arches Trigenimal nerve, muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani, tensor veli palatine muscles Facial nerve, stapedius muscle, muscles of facial expression, posterior belly of the digastric muscle, stylohyoid muscle Glossopharyngeal nerve, stylopharyngeal muscle Superior laryngeal branch and recurrent laryngeal branch of vagus nerve, levator veli palatine muscles, pharyngeal constrictors, intrinsic muscles of the laynx Malleus and incus of middle ear, including anterior ligament of the malleus, sphenomandibular ligament, and parts of sphenoid bone Stapes and parts of malleus and incus of middle ear, stylohyoid ligament, styloid process of the temporal bone, lesser cornu of hyoid bone, upper portion of body of hyoid bone Greater cornu of hyoid bone, lower portion of body of hyoid bone Laryngeal cartilage

6 Development of the face Overview of facial development 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

7 Development of the face Overview of facial development Fusion fusion of tissue on the same surface of the embryo e.g.) Most of the facial structures fusion of tissue on the different surface of the embryo e.g.) Palate

8 Development of the face Stomodeum and oral cavity formation 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

9 Embryo at third to fourth weeks of development.

10 Development of the face Mandibular 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

11 Development of the face Frontonasal process and upper face formation 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.

12 Development of the face 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.

13 Development of the face Frontonasal process and upper face formation <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

15 Development of the face Maxillary process and midface formation 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

16 Development of the face 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 intermaxillary segment

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

18 Development of the neck The fourth week of prenatal development ~ fetal period Develop from the primitive pharynx and the branchial apparatus

19 Development of the Neck 19 Primitive pharynx formation Derived from the anterior part of the foregut and will form the primitive pharynx, the future oropharynx

20 Development of the Neck 20 Branchial apparatus formation Branchial apparatus branchial arches, branchial grooves and membranes, pharyngeal pouches ARCH GROOVE or CLEFT POUCH MEMBRANE

21 Branchial arch formation The fourth week of prenatal development Stacked bilateral swellings of tissue First branchial arch(mandibular arch ) ~ fourth mandibular arch Six pairs of U-shaped bars Mesenchyme formed by neural crest cells, ectoderm, and endoderm Fifth branchial arch is often so rudimentary Important structures of the face and neck Has its own developing cartilage, nerve, vascular, and muscular components FIRST branchial arch(mandibular arch) are involved in the formation of middle and lower face

22 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, suprahyoid muscle Facial nerve

23 Third branchial arch Parts of the hyoid bone Pharyngeal muscle Glossopharyngeal nerve Fourth and sixth branchial arch Most of the laryngeal cartilage Vagus nerve (+Glossopharyngeal nerve)

24 24 Table 4-2 BranchialArches and Derivative Structures First arches (mandibular) Second arches (hyoid) Third arches Fourth through Sixth arches Trigeminal nerve, muscles of mastication, mylohyoid and anterior belly of digastric, tensor tympani, tensor veli palatine muscles Facial nerve, stapedius muscle, muscles of facial expression, posterior belly of the digastric muscle, stylohyoid muscle Glossopharyngeal nerve, stylopharyngeal muscle Superior laryngeal branch and recurrent laryngeal branch of vagus nerve, levator veli palatine muscles, pharyngeal constrictors, intrinsic muscles of the laynx Malleus and incus of middle ear, including anterior ligament of the malleus, sphenomandibular ligament, and parts of sphenoid bone Stapes and parts of malleus and incus of middle ear, stylohyoid ligament, styloid process of the temporal bone, lesser cornu of hyoid bone, upper portion of body of hyoid bone Greater cornu of hyoid bone, lower portion of body of hyoid bone Laryngeal cartilage

Branchial groove and membrane formation External grooves, between neighboring branchial arches FIRST branchial groove Is located between the first and second branchial arches A mature structure of

25 Branchial groove and membrane formation External grooves, between neighboring branchial arches FIRST branchial groove Is located between the first and second branchial arches A 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

26 Pharyngeal pouch formation Four well-defined pairs of pharyngeal pouches Endodermal evaginations form the lateral walls lining the pharynx Many structures of the face and neck. 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

Pharyngeal Apparatus. Pouches Endoderm Grooves Ectoderm Arch Neural Crest Somitomeres Aortic Arch - Vessel

Pharyngeal Apparatus. Pouches Endoderm Grooves Ectoderm Arch Neural Crest Somitomeres Aortic Arch - Vessel Pharyngeal Apparatus Pouches Endoderm Grooves Ectoderm Arch Neural Crest Somitomeres Aortic Arch - Vessel Segmental Organization Humans: Arch 1-4 prominent Arch 5 absent Arch 6 - transient First Arch Face