13) Development of Face and Nose Flashcards
What are neural crest cells?
Specialised population of cells originating within neuroectoderm. Becomes displaced and enters mesoderm
What are the major facial features?
Palpebral fissures (between eyelids), oral fissure, nares, philtrum
What does the facial skeleton form from?
Neural crest of 1st pharyngeal arch
What do the muscles of mastication form from?
Mesoderm of 1st pharyngeal arch
What do the muscles of facial expression form from?
Mesoderm of 2nd pharyngeal arch
What are the 5 building blocks (prominences) of the embryological face?
Frontonasal prominence
2 maxillary prominences
2 mandibular prominences
What is the stomatodeum?
What does it go on to form?
Depression of ectoderm on ventral head
Forms buccopharyngeal membrane -> mouth
What parts of the face are derived from the frontonasal prominence?
Forehead
Bridge of nose, nose and philtrum
Upper eyelids
What parts of the face are derived from the maxillary prominence?
Cheeks
Lateral upper lip
Lateral upper jaw
What parts of the face are derived from the mandibular prominence?
Lower lip and jaw
What is the first evidence of nose formation?
Nasal placodes appear on FNP
What happens to the nasal placodes?
Invaginate and form deep pits, entrance to pit = future nostril
How does the nose form in the midline?
Maxillary prominences grow medially pushing nasal prominences (either side of pits) to midline where medial nasal prominences fuse with each other and maxillary prominences
What does fusion of the medial nasal prominences create?
Intermaxillary segment consisting of philtrum, upper jaw and primary palate
What gives rise to the palatal shelves?
Maxillary prominences
How do the palatal shelves fuse in the midline and what does this create?
When mandible has grown enough to allow tongue to drop out of the way, palatal shelves can fuse to form secondary palate
What is the pathophysiology behind cleft lip?
Failure of fusion of medial nasal prominence and maxillary prominence
What are the consequences of cleft lip on the new-born?
Difficulty suckling and with speech
Where are the eyes derived from?
Forebrain
What is the lens derived from?
Optic placode
Where are the eyes originally and how do they end up on the front of the face?
Originally on side of head but move as facial prominences grow
Where does the external auditory meatus derive from?
1st pharyngeal cleft
Where do the auricles derive from?
Proliferation of 1st and 2nd pharyngeal arches
How do the external ears ascend from neck?
Growth of mandible
Where does the inner ear derive from?
Otic placodes
What effects does alcohol have on the fetus?
Effects on neural crest migration and development of brain
What are the signs and symptoms of fetal alcohol syndrome?
Small head, short nose and flat midface
