2-craniofacial development-brainscape Flashcards
Cause of Oblique facial clefts (lips into nostril)
failure of maxillary prominence to merge with the corresponding lateral nasal prominence (therefore cleft lip arises even though the lateral nasal prominence does not give rise to the lip, lip is secondary to palate)
Craniofacial aspects of Down’s Syndrome
Nasal bone is underdeveloped at week 16-20
Describe formation of the mature thyroid gland
1) Primordial thyroid descends from foramen cecum 2) Descends as bilobed diverticulum 3) Initially attached to tongue by Thyroglossal duct (disappears) 4) By week 6 it descends in front of hyoid bone 5) At final position in front of trachea by week 7
Development of the Nasal Pits
1) Deepen into surrounding NC cells & mesoderm (week 6) 2) Separated from oral cavity by oronasal membrane (week 7) 3) Oronasla membrane ruptures (midle week 7) 4) Primitive choana formed –> joins primitive nasal cavity with the oral cavity posterior to the primary palate
Effect of anticonvulsant drugs (phenobarbital) on pregnant women
increase risk of cleft palate
Facial Prominences
Two maxilary prominences Two mandibular prominences Frontonasal prominence
Facial prominences derivatives
From the first pharyngeal arch: ectoderm externally and mesoderm/neural crest cells internally
First growths of the tongue (and when)
From first pharyngeal arch at week 4: Two lateral lingual swellings and one medial tuberculum impar
Five facial prominences that give rise to the nose and what they form
1) Frontal nasal prominence (Bridge) 2) Two merged medial nasal prominences (Crest and tip) 3) Two lateral nasal prominences (form the sides)
Formation of nostrils
1) Nasal (olfactory) placodes on either side of frontal prominence form as a result of local thickening of the surface ectoderm 2) Nasal Pits form when the placodes invaginate (weeks 5-8) 3) Nasal Prominences form from the ridge of tissue overlying the nasal pits
How does the thyroid develop?
Epithelial proliferation at base of pharynx between the tuberculum impar and the hypobranchial eminence at the foramen cecum
How many dental buds in each jaw?
10
Innervation of the tongue
Anterior (arch 1) = mandibular branch of trigeminal (V) Posterior 1/3 = Glossopharyngeal (IX) Extreme posterior = Superior Laryngeal branch of Vagus (X)
Intermaxillary Segment
Caused by growth of maxillary prominence which caues fusion of medial nasal prominences, which deep to the surface leads to the intermaxillary segment which is composed of: 1) Labial component which forms the philtrum of upper lip 2) Upper jaw component (four incisor teeth here) 3) Palatal compartment (triangular primary palate)
Later medial swellings of the tongue (when)
Copula: aka hypobranchial eminence ==> 2, 3, 4th arch Development of epiglottis: from posterior of arch 4
Levothyroxine
synthetic version of thyroxine that can be presribed to obese patient if thyroxine deficiency led to obesity
Neurocranium
Bone formation primarily endochondral ossification of paraxial and prechordal mesoderm and NC cells 1) Cartilaginous neurocranium 2) Membranous neurocranium
Paranasal air surfaces (conchae)
Develop as diverticula of the lateral nasal wall and extend into maxilla, ethmoid, frontal, and spheroid bones *Increase SA to condition the air breathed in
Sensory (taste) innervation of the tongue
Anterior 2/3 = Chorda tympani branch of facial nerve (CN VII) Posterior 1/3= Glossopharyngeal
Stomodeum
Primitive oral cavity that is surrounded by the frontal prominences
Subdivisions of the cranium
Neurocranium: Surrounds the brain Viscerocranium: Bones result of pharyngeal arch development
Thyroglossal cysts
Cystic remnant of the thyroglossal duct that can lie at any point along the migratory pathway of the thyroid. If it is open to the outside byt he canal it forms a thyroglossal fistula
Tissue origin of the thyroid gland
epithelial (endoderm) ==> NOT FROM POUCHES
Viscerocranium
Bone formation primarily membrane ossification of NC cells with some mesoderm ossification 1) Cartilaginous viscerocranium 2) Membranous viscerocranium
