Embryo Of Head And Neck Flashcards
Describe the cartilaginous component of the viscerocranium
First branchial arch (Meckel’s)
Second branchial arch (Reichert’s)
Third, fourth, and sixth branchial arch
Describe the membranous component of viscerocranium
Maxillary prominences of first branchial arch
Mandibular prominence of first branchial arch
Describe Apert Syndrome
Premature fusion of coronal sutures (craniosynotosis)
Causes skull deformities: acrocephalic (“tower skull”) appearance
Affects growth of brain
Describe the fontanelles
Anterior
Posterior
Anterolateral (sphenoidal)
Posterolateral (occipital)
Describe cranioschisis (acrania)
Represents failure of occipital and parietal bones to completely form or close
Usually associated with arrested brain development and rudimentary forebrain (anacephaly)
Describe microcephaly
Small cranium due to early fusion of cranial sutures
Describe macrocephaly
Enlarged cranium secondary to hydrocephaly
Early fusion of superior cranial sutures may result in a conical cranium
What is the most important event of development? Describe it
Gastrulation
Formation of trilaminar embryo
Cells come fro the epiblast
What occurs during the 4th week for primitive mouth and pharynx development?
Primitive pharynx induces evagination of ectoderm to form stomadaeum
Induced by rostral foregut entoderm
What separates the stomodeum from the endodermal foregut?
Oropharyngeal membrane (old prochordal plate)
The stomodeum is surrounded by five facial swellings which include what and what are they formed by?
Frontal (frontonasal) prominence (unpaired)
Maxillary prominences of arch I
Mandibular prominences of arch I
They are formed by mounds of mesenchyme and their overlying ectoderm
A portion of the skin ectoderm in the frontal (frontonasal prominence) thickens to form what?
Nasal placodes
What are formed by the proliferation of the mesenchyme beneath the medial and lateral edges of the nasal placodes?
Nasal prominences
What does the lateral nasal prominence form?
Alae of nose
What does the medial nasal prominence form?
Middle part of nose
Medial upper lip
Philtrum
What forms the primary palate?
Posterior (palatal) portion of intermaxillary segment
What is the nasal septum?
Midline down growth of fused medial nasal prominences
Nasal placodes invaginate to form ____, which enlarge into ____. Remaining space between this and oral cavity is ____, which ruptures to open nasopharynx to oropharynx
Nasal pits
Nasal sacs
Oronasal membrane
When does development of the face occur?
Weeks 5-10
Describe the nasolacrimal groove
Oblique furrow created between lateral nasal prominence and maxillary prominence
The ectoderm in the floor of the nasolacrimal groove thickens to form a cord. This cord separates from the surface and canalizes to form ___
Nasolacrimal duct
Describe the development of an oblique facial cleft
Due to failure of lateral nasal prominences and maxillary prominences to fuse.
Often associated with cleft chin and partial fusion of mandibular prominences
Nasolacrimal duct is exposed
What happens when the lateral nasal prominences and maxillary prominences fail to fuse?
Oblique facial cleft
What do maxillary prominences form?
Lateral parts of upper lip and jaw
Secondary palate or palatine shelves
Describe formation of muscles of facial expression (mimetic muscles)
Mesenchyme from branchial arch II invade into maxillary and mandibular swellings (arch I)
What innervates the muscles of facial expression?
Special visceral efferent (SVE) fibers from facial nerve (VII)
Special visceral efferent fibers innervate muscles of ___ origin
Branchiomeric
Pair branchial arches to their nerves
Arch I: trigeminal n
Arch II: facial n
Arch III: glossopharyngeal n
Arch IV: vagus n
What are muscles of mastication derived from?
Mesenchyme of arch I
What innervates muscles of mastication?
SVE fibers from mandibular division of trigeminal nerve
The ectoderm of facial swellings are innervated by what nerve?
Trigeminal n
The ophthalmic nerve (V1) supplies what?
GSA fibers to skin of frontonasal prominence
The maxillary nerve (V2) supplies what?
GSA fibers to skin of maxillary prominence
Mandibular nerve (V3) supplies what?
GSA fibers to skin of mandibular prominence