Development of head and neck Flashcards
What are pharyngeal arches derived from?
Neural crest cells from the ectoderm
When does the first pair of pharyngeal arches start to appear?
Early in week 4 to week 5
What is generally derived from the pharyngeal arches?
All bones of head and neck
What composes the pharyngeal arches?
Mesoderm and neural crest cells (ectoderm)
What lines pharyngeal pouches?
Endoderm
What lines pharyngeal clefts?
Ectoderm
Which cranial nerve supplies the first pharyngeal arch?
Trigeminal nerve - mandibular division (CNV)
Which cranial nerve supplies the second pharyngeal arch?
Facial (CNVII)
What cranial nerve supplies the third pharyngeal arch?
Glossopharyngeal (CNIX)
What cranial nerve supplies fourth pharyngeal arch?
Superior laryngeal branch of the Vagus nerve (CNX)
What cranial nerve supplies the sixth pharyngeal arch?
Recurrent laryngeal branch of Vagus nerve (CNX)
What muscles are derived from the first pharyngeal arch? MATT
Muscles of mastication (temporal, masseter, medial pterygoid, lateral pterygoid), mylohyoid, anterior belly of digastric, tensor palatine, tensor tympani
What parts of the skeleton are derived from the first pharyngeal arch?
Premaxilla, maxilla, zygomatic bone, part of temporal bone
Meckel’s cartilage, mandible, malleus, incus, anterior ligament of malleus, sphenomandibular ligament
What muscles are derived from the second pharyngeal arch?
Muscle of facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris, orbicularis oculi), posterior belly of digastric, stylohyoid, stapedius
What parts of the skeleton are derived from the second pharyngeal arch?
Stapes, styloid process, stylohyoid ligament, lesser horn of hyoid, upper body of hyoid
What muscle is derived from the third pharyngeal arch?
Stylopharyngeus
What parts of the skeleton are derived from the third pharyngeal arch?
Greater horn and lower body of hyoid bone
What muscles are derived from the fourth pharyngeal arch?
Cricothyroid
Muscles of soft palate
Pharynx muscles
What muscles are derived from the sixth pharyngeal arch?
Intrinsic muscles of larynx except cricothyroid
What skeletal structure is derived from the fourth pharyngeal arch?
Thyroid cartilage
What skeletal structures are derived from the sixth pharyngeal arch?
Laryngeal cartilages - cricoid, arytenoid, corniculate, cuneiform
What can result from first arch syndrome?
Facial anomalies -
Treacher Collins syndrome
Pierre Robin Sequence
What parts of the face are derived from the mesoderm?
Muscles and arteries
What parts of the face are derived from neural crest cells?
Bones and cartilage
What occurs for facial development in the 5th and 6th week?
Lateral nasal prominences are separated form the maxillary prominences by deep furrows called nasolacrimal groove
What occurs for facial developments between the 7th and 10th week?
Merging of 2 medial nasal prominences into intermaxillary segment
Merging of medial nasal and maxillary prominences results in continuity of the upper jaw and lip
What occurs at the end of the 4th week in nose development?
Bilateral oval thickenings of the surface ectoderm called the nasal placodes develop on the inferolateral aspects of the frontonasal prominence
What occurs from the formation of nasal pits in the 5th week?
2 lateral nasal prominences
2 medial nasal prominences
What is derived from the frontonasal prominence?
Bridge of nose
Forehead
Medial and lateral nasal prominences
What is derived from the medial nasal prominence?
Crest and tip of nose
Intermaxillary segment
What is derived from the lateral nasal prominence?
Alae of nose
What is separated from the nasolacrimal groove and what does is later form?
Maxillary from lateral nasal prominence
Nasolacrimal duct and lacrimal sac
What is derived from the intermaxillary segment? MIP
Middle part (philtrum) of upper lip
Incisors
Primary palate
What is derived from the maxillary prominence?
Cheeks
Lateral portion of upper lip
What is derived from the mandibular prominence?
Lower lip and lower face
What occurs in the 6th week of development in facial development?
Nasal pits deepen further into underlying mesenchyme and growth of nasal prominences
What originally separates nasal pits from oral cavity?
Oronasal membrane
What is formed by rupture of oronasal membrane?
Primitive choanae
What forms the palate?
Definitive choanae
What is the nasal septum formed from?
Frontal prominences fuse with definitive palate
What forms the paranasal sinuses?
Diverticula of lateral nasal wall that extend into maxilla, ethmoid, frontal, and sphenoid bones
When does palatogenesis begin?
Week 6
What is the critical period of development for the palate?
End of week 6 to beginning of week 9
What is the secondary palate derived from?
Palatine shelves from maxillary prominence fuse in midline
What forms the definitive palate?
Primary and secondary palate fuse at incisive development
What forms the hard palate?
Bone develops in anterior part of definitive palate
What causes a cleft lip?
Failure of fusion of maxillary prominence with medial nasal prominence
What causes oblique facial cleft?
Failure of fusion of maxillary prominences with lateral nasal prominence exposing nasolacrimal duct to surface
What causes cleft palate?
Failure of fusion of palatine shelves with each other or and/or primary palate
What is the effect of retinoic acid on facial deformities?
Can cause if in excess or in lack
What causes first arch syndrome?
Lack of migration of neural crest cells into first pharyngeal arch
What are two types of first arch syndrome?
Treacher Collins syndrome/mandibulofacial dysostosis
Pierre Robin syndrome/Robin sequence
What are characteristics of Treacher Collins syndrome?
Autosomal dominant
Underdeveloped zygomatic bones
Mandibular hypoplasia/micrognathia
Lower eyelid colobomas(notch)
Malformed external eears
Normal IQ
What are characteristics of Pierre Robin syndrome?
Mandible development severely affected
Triad of micrognathia, cleft palate, glossoptosis
Compression of chin against chest in oligohydramnios
What are the characteristics of holoprosencephaly?
Extensive deficiency of midline tissue
Eyes have fused - synophthalmia
Proboscis - single nasal opening
Upper lip from fusion of maxillary prominences
Narrow head
Brain with single ventricle
What causes holoprosencephaly?
Mutations in SHH
Maternal exposure to teratogens in week 3
What are characteristics of Van der Woude syndrome?
Autosomal dominant
Cleft lip with or without cleft palate
Low lip pits in 88% of cases
Cleft palate alone
Hypodontia
What is mutated in Van der Woude syndrome and its function?
Interferon regulatory factor 6
Fusing of palatal shelves
What are characteristics of oculoauriculovertebral spectrum/hemifacial microsomia/Goldenhar syndrome?
Number of craniofacial abnormalities - typically involve small and flat maxillary, temporal, and zygomatic
Eye - tumor jand dermoids
Ear - anotia, microtia
Fused and hemivertebrae - spina bifida
CVS abnormalities in 50% of cases
What arches are related to oculoauriculovertebral spectrum/hemifacial microsomia/Goldenhar syndrome?
First and second pharyngeal arches
What is derived from the first pharyngeal pouch?
Tubotympanic recess
What is derived from the second pharyngeal pouch?
Palatine tonsil
When are tonsils infiltrated with lymphatic tissue?
Month 3-5
What is derived from the ventral wing of the third pharyngeal pouch?
Thymus
What is derived from the dorsal wing of the third pharyngeal pouch?
Inferior parathyroid glands
What is derived from the dorsal wing of the fourth pharyngeal pouch?
Superior parathyroid glands
What is derived from the ventral wing of the fourth pharyngeal pouch?
Ultimobranchial body - parafollicular cells - calcitonin
What makes up the tubotympanic recess?
Primitive middle ear cavity
Tympanic membrane
Eustachian/auditory tube
What is affected to cause DiGeorge syndrome?
Third and fourth pharyngeal pouches
Deletion of long arm of chromosome 22
Disruption of neural crest cells
What are characteristics of DiGeorge syndrome?
Congenital heart defects
Mild facial dysmorphology
Learning disabilities
Recurrent infections due to thymic hypoplasia/aplasia
Hypoparathyroidism-hypocalcemia
What happens to the second, third, and fourth pharyngeal clefts?
Buried by second arch
Form cervical sinus, which obliterates
What causes pharyngeal/branchial fistulas?
When 2nd pharyngeal arch fails to grow over third and fourth arches, leaving 2nd, 3rd, and 4th clefts in contact with surface by narrow canal
Cervical cyst from remnant of cervical sinus
Where would you find pharyngeal/branchial fistulas?
Lateral neck anterior to sternocleidomastoid, often just below angle of jaw
What causes internal pharyngeal/branchial fistulas?
Cervical sinus connected to lumen of pharynx by small canal due to rupture of membrane between second pharyngeal cleft and pouch
Where do internal pharyngeal/branchial fistulas typically open?
Tonsillar region
What is formed from the first pharyngeal cleft?
Epithelial lining of external auditory meatus
