Head and Neck development Flashcards
Which aortic arch is vestigual?
The fifth aortic arch
What do the pharyngeal arches develop into?
Cartilage
What embryonic germ layer is the visceralcranial and neurocranial regions derived from?
Visceralcranial - neural crest cells
Neurocranial - paraxial mesoderm (somitomeres)
The laryngeals - lateral plate mesoderm
What does the first pharyngeal arch develop into?
Meckel’s cartilage
Malleus
Incus
What does the second pharyngeal arch develop into?
What does the third pharyngeal arch develop into?
What does the fourth pharyngeal and sixth arches develop into?
The laryngeal cartilages
What does the fifth pharyngeal arch develop into?
What cells migrate into the arches to provide musculature for the craniofacial region?
Paraxial mesoderm
What are the homeobox gene involved in craniofacial development?
Neural crest cells bring their genetic codes to help pattern head and neck
What patterns the pharyngeal arches and induces differentiation?
The pharyngeal pouches
BMP7, FGF8, and SHH interact with homeobox genes to pattern this tissue
Why do cervical sinuses develop?
The failure of the second arch tissue to completely occlude the other clefts
What does the endoderm of the first pharyngeal pouch form?
The auditory tube
What does the endoderm of the second pharyngeal pouch form?
The pallentine tonsils
What does the endoderm of the third pharyngeal pouch form?
Inferior parathyroid and the thymus
What does the endoderm of the fourth pharyngeal pouch form?
The superior parathyroid
Where is the thyroid derived?
Endoderm from pharynx (foramen cecum)
Tongue develops here as well
First arch forms the body of the tongue - innervated by the trigeminal nerve
The second and third arches form tissue that fuses to form first 1/3 of the tongue (including the root) - innervated by the glossopharyngeal nerve
The epiglottis and very posterior tongue is derived from the fourth pharyngeal arch
When does facial development begin?
The fourth week
What is a placode?
A sensory organ that forms when the ectoderm thickens (gets taller)
Secondary palate formation ( begins at 6.5 weeks)
Palatal shells completely fuse by 10 weeks
Secondary palate is derived from the first pharyngeal arch
Defects in the primary palate:
Cleft lip/palate
Frequency: 1 in 700 births
Boys cleft lip w/wo cleft palate = 2x girls
Girls cleft palate = 2x boys
What establishes the midline?
Notocord and prechordal plate - SHH
SHH must be bound to cholesterol to distribute properly
Mandible
Arch endoderm
The cells of the pouch endoderm communicate with the paraxial mesoderm (somites and somitomeres)
aortic arch, cranial nerve, and cartilage
Failure of the mandible to grow
Id the major embryonic prominences of the face?
