9. Development of nose and face (embryology) Flashcards
what does the face develop from?
most cranial part of neural tube (primitive gut tube)
what do the pharyngeal arches become?
the embryonic head and neck:
brain
CVS - heart and great vessels
special sensory organs e.g. eyes
what drives the development of the face?
expansion of cranial neural (gut) tube
appearance of complex tissue associated with outflow of developing heart
development of sense organs
need to separate resp tract from GI tract
what does each pharyngeal arch contain?
- artery (aortic arch artery), vein, cranial nerve
ectoderm covering
mesenchyme filling
endodermal lining
how are pharyngeal arches arranged?
around aortic arch vessels
what is the neural crest?
a specialised population of cells that originates within the neuroectoderm
(ectoderm classification)
what is neuroectoderm?
tissue that gives rise to CNS, fold to form neural tube
migrate around body before folding into neural tube to develop into complex nervous system
where does the neural crest stem from?
cells of lateral border of neuroectoderm
what happens to neural crest cells?
become displaced and enter the Mesoderm (outer to middle)
MIGRATE and contribute to a variety of H+N structures
what are the major features of the face?
palpebral fissures (opening of eyes)
oral fissure
nares
philtrum (groove of upper lip)
what does the facial skeleton develop from?
neural crest of 1st pharyngeal arch
what do muscles of mastication derive from?
mesoderm of 1st pharyngeal arch
what do muscles of facial expression develop from?
mesoderm of 2nd pharyngeal arch
how does the facial primordia develop?
from 1st pharyngeal arch frontonasal prominence (FNP)
how does the frontonasal prominence (FNP) develop?
surrounds ventro-lateral part of the forebrain
what does the frontonasal prominence (FNP) become?
primordia of eyes
what is significant about 1st pharyngeal arch?
largest of arches
has 2 zones of prominence (SAME arch)
what do the 2 zones of the 1st pharyngeal arch develop into?
maxillary prominence
mandibular prominence
what does the nose develop from?
nasal placode
thickening of ectoderm
what is contained within the face?
- stomatodeum
- frontonasal prominence
- maxillary + mandibular prominence (1st pharyngeal arch)
what is the stomatodeum?
buccopharyngeal membrane (within centre of stomatodeum)
small depression in the head region
(mesoderm - avascular membrane will rupture, giving opening to oral orifice)
what does the frontonasal prominence give rise to?
forehead bridge of nose nose philtrum (a letter T)
what does the maxillary prominence give rise to?
cheeks
lateral upper lip
lateral upper jaw
(like innervation of superior alveolar nerve from maxillary V2)
what does the mandibular prominence give rise to (external features of the face)?
lower lip and jaw
inferior alveolar nerve
where do nasal placodes appear?
frontonasal prominence (thickened growth of ectoderm - outer) then sinks to become nasal pit (within FNP)
what forms either side of nasal pit?
medial and lateral nasal prominences
where do maxillary prominences grow?
medially, pushing both nasal prominences closer together in the midline (ready to fuse)
what do maxillary prominences fuse with?
medial nasal prominences
where do medial nasal prominences fuse?
in the midline
what does fusion of medial nasal prominences create?
the intermaxillary segment
what does the intermaxillary segment from fusion of medial nasal prominences give rise to?
- labial component: philtrum
- upper jaw: 4 incisors
- palate: primary palate
what is the main part of definitive palate?
secondary palate
what is definitive palate derived from?
palatal shelves of maxillary prominences
initially, what separates nasal pit and oral cavity?
oronasal membrane
what happens to the oronasal membrane?
degenerates
so nasal cavity and oral cavity are continuous
(only separated by primary palate near the orifice)
how does the nasal cavity and oral cavity then separate?
the secondary palate develops from the primary palate (as an extension, until around the pharynx)
what does the maxillary prominence give rise to?
2 palatal shelves (palatine)
which grow vertically downwards into the oral cavity - either side of the developing tongue
(tongue isn’t functioning yet, oral cavity v small)
what has to happen after the 2 palatal shelves grow down vertically either side of developing tongue into the small oral cavity?
the mandible grows large enough to allow the tongue to ‘drop’ (into the oral cavity properly)
what happens after the tongue has dropped?
the palatal shelves then grow towards each other and fuse in the midline (forming the continuous palate)
what happens after the palatal shelves have fused with each other?
the nasal septum develops as a midline down-growth and ultimately fuses with palatal shelves
(nasal cavity and oral cavity both drain to middle meatus)
what is the intermaxillary segment?
medial nasal prominences
what does the intermaxillary segment (medial nasal prominences) fuse with?
maxillary process (prominences)
what does the intermaxillary esgment (medial nasal prominences) give rise to?
philtrum
primary palate
what does the maxillary process give rise to?
fused palatal (palatine) shelves
