Development of pharyngeal arches Flashcards
what are the three embryonic layers of the pharyngeal arches
mesoderm core, ectoderm and endoderm
what does the mesenchymal core of the arches derive from
mesoderm and neural crest cells
what are the three developed layers of the pharyngeal arches
Mesenchymal core from mesoderm and neural crest Internal endodermal pouch External cleft (ectoderm)
what is the name for the precursor of the mouth
stomodeum
closed by the oropharyngeal membrane which later ruptures
what bony structures does the first arch form
maxilliary prominence
mandibular prominence
what are somitomeres
ill defined segments of paraxial mesoderm in the head region rostral to the somites
what does paraxial mesoderm form
migrates in to the pharyngeal arches to form muscle in the head and some connective tissue
what skeletal structures does paraxial mesoderm form
parietal, occipital, petrous temporal bone
what structures does the lateral plate mesoderm form
laryngeal cartilage and connective tissue
what skeletal structures does the neural crest form
frontal bone, sphenoid bone, squamous temporal, nasal, lamcrimal, maxilla, mandible
what muscles does the first arch form
muscles of mastication, ant belly digastric, mylohyoid, tensor tympani, tensor veli palatini
what skeletal elements does the first arch form
maxilla, zygomatic bone, mandible, malleus, incus
what muscles are formed from the second arch
muscles of facial expression, stylohyoid, stapedius, posterior belly of digastric
what skeletal elements are formed from the second/ hyoid arch
stapes, styloid process, lesser horn of the hyoid and upper body of hyoid
what muscle is made from the third arch
stylopharyngeus
what skeletal structurs are made from the third arch
greater horn of the hyoid, lower part of body of hyoid
what nerve is associated with the third arch
glossopharyngeal
what muscles are derived from the 4th and 6th arches
all the muscles of the pharynx except stylopharyngeus
all the muscles of the palate except tensor veli palatini
cricothyroid
all the muscles of the larynx `
what skeletal structures are made from the 4th and 6th arches
epiglottis, laryngeal cartilages, thyroid, cuneiform , coniculate, arytenoids
what artery does the 4th right arch give
subclavian artery
what artery does the 6th arch give
pulmonary arteries
Paraxial mesoderm
All voluntary muscles, arteries,
neurocranium, meninges, dorsal skin
Lateral plate mesoderm
Laryngeal car1lages; regional connec1ve 1ssue
what does Neural crest form
Pharyngeal arch skeleton,
Also viscerocranium,
glandular connective tissue,
parts of the neurocranium, teeth, interact with
ectodermal placodes for ganglia/sensory nerve forma1on
what do Ectodermal placodes form
with neural crest to form neurones of sensory ganglia
(V,VII, IX and X) also sensory apparatus (eyes/nose not shown)
what is an ectopic thymus
thymus remains in the neck
what is treacher collins sydrome
autosomal dominant
first/ second arch
defective treacle protein
failure of apoptosis of neural crest cells and migration
abnormal eye shape micrognathia hearing loss underdeveloped zygoma malformed ears
what are the features of digeorge syndrome
3rd and 4th pouches fail to develop and thymus and parathyroids are defective
CATCH-22 cardiac abnormality abnormal facies thymic aplasia cleft palate hypocalcaemia
deletion in chromosome 22- de novo
what is the role of sonic hedghog protein in craniofacial patterning
governs the width of facial features
inadequate function- narrowing and fusion, cyclopia
excessive SHH widening and structures duplicated
