IBSSD Face & Neck Dev Student PDF

L24: Face & Neck Development IBSSD 1525/1513 Dr. Samuel Gutherz  Outline Review the germ layers of development Compare and contrast the developmental regions of the skull Discuss the pharyngeal apparatus development Arches & pouches (and a brief s...

L24: Face & Neck Development IBSSD 1525/1513 Dr. Samuel Gutherz  Outline Review the germ layers of development Compare and contrast the developmental regions of the skull Discuss the pharyngeal apparatus development Arches & pouches (and a brief stop at clefts) Germ Layer Review Ectoderm (outer) Central nervous system, skin, sensory organs, teeth, hair, pituitary gland, parts of skull Germ Layer Review Mesoderm (middle) Muscles, skeleton, blood vessels, connective tissues, urogenital structures Germ Layer Review Endoderm (inner) Forms portions of gut tube, respiratory system, glands Mesenchyme – CT Ectoderm Neural crest cells (NCC) Derivatives: CN ganglia, connective tissue/bones of skull, C cells of thyroid gland, odontoblasts, part of meninges Ectoderm Ectodermal placodes Form sensory organs and ganglia CN, lens placode, nasal placode, otic placode Mesoderm Paraxial mesoderm Bones of skull, skeletal muscles, dermis & connective tissue of neurocranium, part of meninges Lateral plate mesoderm Laryngeal cartilages and connective tissues Endoderm Lines pharyngeal pouches Thymus, thyroid gland, tonsils, parathyroid glands Epithelium of auditory structures Tympanic membrane Skull Development  Skull Viscerocranium – bones of the face Neural crest cells only Neurocranium – bones of braincase Neural crest cells and paraxial mesoderm Viscerocranium Pharyngeal arch 1 Maxillary process – maxilla, zygomatic, palatine, lacrimal, X vomer, nasal, inferior nasal concha, squamous temporal Mandibular process – mandible, malleus, incus Pharyngeal arch 2 Styloid process, stapes, hyoid Viscerocranium Pharyngeal arch 1 Maxillary process – maxilla, zygomatic, palatine, lacrimal, vomer, nasal, inferior nasal concha, squamous temporal Viscerocranium Pharyngeal arch 1 Maxillary process – maxilla, zygomatic, palatine, lacrimal, X vomer, nasal, inferior nasal concha, squamous temporal Mandibular process – mandible, malleus, incus Pharyngeal arch 2 Styloid process, stapes, hyoid Viscerocranium X Pharyngeal arch 1 Mandibular process – mandible, malleus, incus Viscerocranium Pharyngeal arch 2 Styloid process, stapes, hyoid Bone Dev Cartilaginous (mesenchyme → cartilage → bone) Membranous (mesenchyme → bone) Viscerocranium Bone Dev Cartilaginous Ear ossicles, styloid process, hyoid, laryngeal cartilages Membranous Everything else Neurocranium Endochondral (cartilage) ossification Base of neurocranium Neural Crest Ethmoid, sphenoid Paraxial mesoderm Parts of temporal bone, occipital base Neurocranium Intramembranous ossification Cranial vault Neural Crest Frontal, sphenoid, temporal Paraxial mesoderm Parietal, occipital Sutures & Fontanelles Sutures – where 2 bones meet Fontanelles – where 3+ bones meet Sutures & Fontanelles Allow movement of skull bones during birth Fontanelle Location Closure Date Remain open for brain Anterior Frontals & Parietals 13–24 months growth Posterior Parietals & Occipital 1–2 months Mastoid Parietal, Temporal, & Occipital 6–18 months Sphenoid Sphenoid, Parietal, Temporal, Frontal 6 months Fontanelles Bregma Anterior → Bregma Posterior → Lambda Lambda  Pterion Fontanelles Asterion Sphenoid (bilateral) → Pterion Mastoid (bilateral) → Asterion Pharyngeal Structures: Pharyngeal Arches Developing Pharynx Week 4 of development Arches – 5 outpocketings of pharynx Separators Clefts – between each arch Ectoderm Pouches – Internal to clefts Endoderm Pharyngeal Arches Ectoderm on external surface Endoderm on internal surface Mesenchyme core Mostly neural crest cells Mesoderm – muscles Lateral plate mesoderm Paraxial mesoderm Pharyngeal Arches 2 3 4&6 1 Muscles Pharyngeal Arches Cartilage Pharyngeal Arches Artery Pharyngeal Arches Cranial nerve 2 346 1 1st Pharyngeal Arch 2 prominences Maxillary Mandibular Meckel’s cartilage 1st Pharyngeal Arch Artery: Maxillary artery CN: Trigeminal (CN V) Maxillary & mandibular divisions Maxillary & Mandibular Prominence Bilateral pairs Neural crest mesenchyme Facial development 1st PA: Muscles Mastication Temporalis, masseter, medial & lateral pterygoids 1st PA: Muscles Suprahyoid Mylohyoid Anterior belly of digastric 1st PA: Muscles Palate Tensor veli palatini Tensor tympani 1st PA: Skeleton Ear ossicles Malleus Incus 1st PA: Skeleton Viscerocranium 1st PA: Skeleton Sphenomandibular ligament 2nd Pharyngeal Arch “Hyoid arch” Reichert cartilage CN: Facial nerve (CN VII) Artery: stapedial Adult – branches of ECA 2 nd PA: Muscles Muscles of facial expression Stylohyoid, posterior belly of digastric Stapedius 2 nd PA: Muscles Muscles of facial expression 2 nd PA: Muscles Stylohyoid, posterior belly of digastric 2 nd PA: Muscles Stapedius 3 rd Pharyngeal Arch Parts of hyoid bone 3 rd Pharyngeal Arch CN: glossopharyngeal nerve (CN IX) Stylopharyngeus 3 rd Pharyngeal Arch ICA and part of CCA 4 th & 6 th Pharyngeal Arches 4 Laryngeal cartilages 4 4 6 6 6 4 th & 6 th Pharyngeal Arches CN: Vagus nerve (CN X) Superior laryngeal & recurrent laryngeal nn. 4 th & 6 th Pharyngeal Arches Arteries 4th – part of arch of aorta & R subclavian a. 6th – ductus arteriosus & part of pulmonary aa. 4th & 6th PA: Muscles 4th Musculus uvulae, levator veli palatini, pharyngeal constrictors, salpingopharyngeus 4th & 6th PA: Muscles 4th Palatoglossus Cricothyroid 4th & 6th PA: Muscles 6th Laryngeal muscles Pharyngeal Pouches Overview Internal invaginations between arches 4 pairs Endoderm-lined Glands 1st Pharyngeal Pouch Forms the tubotympanic recess Middle ear cavity (ossicles) Pharyngotympanic (eustachian) tube Tympanic membrane Contact with cleft ectoderm 1st Pharyngeal Pouch Forms the tubotympanic recess Middle ear cavity (ossicles) Pharyngotympanic (eustachian) tube Tympanic membContact with cleft ectoderm rane 2nd Pharyngeal Pouch Space: tonsillar fossa Endoderm – proliferates Forms the primordium of the palatine tonsils 2nd Pharyngeal Pouch Space: tonsillar fossa Endoderm – proliferates Forms the primordium of the palatine tonsils 3rd Pharyngeal Pouch Forms dorsal and ventral extensions Lose connection with pharynx Migrate caudally Dorsal extension Inferior parathyroid gland Ventral extension Thymus Moves to thorax 3rd Pharyngeal Pouch Forms dorsal and ventral extensions Lose connection with pharynx Migrate caudally Dorsal extension Inferior parathyroid gland Ventral extension Thymus Moves to thorax 3rd Pharyngeal Pouch Forms dorsal and ventral extensions Lose connection with pharynx Migrate caudally Dorsal extension Inferior parathyroid gland Ventral extension Thymus Moves to thorax Pharyngeal Clefts Clefts 4 external clefts covered in ectoderm 1st cleft helps form tympanic membrane Tympanic membrane Other clefts form transient cervical sinus Can become issue if not closed properly