Embryology of Head and Neck Flashcards
What forms the definitive endoderm and mesoderm?
Invagination of the epiblast cells through the primitive streak
What are the three main groups of mesoderm?
Paraxial, intermediate and lateral plate
What are cervical cysts?
Remnants of the cervical sinus
What tends to cause fistulas?
When cervical cysts communicates with the external environment
Where are cervical cysts and fistulas usually located?
Typically found along the anterior border of the sternocleidomastoid
Are cervical cysts present at birth?
No = usually enlarge during childhood
How does the tongue appear in the 4th week of development?
Two lateral swellings and one midline swelling
What structures develop soon after the tongue appears in week 4 of development?
More midline swellings, copula and epiglottal
Where is the mucosa of the tongue derived from?
Anterior = derived from CN V3 Posterior = derived from CN IX
Where do myoblasts originate from?
Occipital somites
Which nerve innervates myoblasts?
CN XII
What does the inferior migration of the thyroid tissue cause?
Accessory glands or remnants
Which ventral facial structures arise from the first pharyngeal arch?
Maxilla, mandible, zygomatic and temporal (squamous part) bones, muscles of mastication
Which ventral facial features are formed from the second pharyngeal arch?
Muscles of facial expression
What forms the upper and mid-facial structures?
Proliferating mesenchyme ventral to developing brain
What are the five facial swellings present from week 5?
Frontonasal prominence (with nasal placodes), maxillary prominence (x2), mandibular prominence (x2)
What does the stomodeum surround?
The primitive oral cavity
What forms the nasal placodes?
The ectodermal thickenings on the frontonasal prominence
What are the 4 additional swellings that develop on the frontonasal prominence on week 5?
Medial nasal swelling (x2), lateral nasal swelling (x2)
What structure forms from the nasolacrimal groove?
Nasolacrimal duct = canalisation of solid epithelial cord in floor of the groove after it detaches from ectoderm
What are the components of the upper lip?
Medial nasal prominences (x2), maxillary prominences (x2)
What component makes up the lower lip?
Mandibular prominence
What are the components of the nose?
Frontonasal prominence = bridge, nasal septum
Medial nasal prominence = crest and tip
Lateral nasal prominence = alae
What forms the intermaxillary segment?
The fusion of the medial prominences of the primary palate
What does the intermaxillary segment go on to form?
Labial portion = philtrum of upper lip
Upper jaw component = carries 4 incisors
Palatal component = form primary palate
When do the uvula and incisive foramen form?
From week 10
What happens to the nasal pits as they deepen?
They penetrate into the underlying mesenchyme with forward growth of the frontonasal prominence
What does the intermaxillary segment connect to as it is forming?
The nasal fin
What causes the developing nasal sac to open?
The vacuolising and thinning of the nasal fin
How do the nasal cavities communicate with the oral cavity in the foetus?
Via the primitive choanae behind the primitive palate
What happens with the formation of the secondary plate?
Definite choanae open at the junction of the nasal cavity with the pharynx
Where do the right and left palatal shelves develop?
Parallel to the tongue
Where does the secondary palate fuse initially?
In the central region, then expands anteriorly and posteriorly
What does mandibular development facilitate?
The clearance of the tongue
What causes cleft palates?
Error in fusion of the palate
