embryology of head and neck Flashcards
when does the face form
weeks 4-14
when does the thyroid, thymus and parathyroid form
weeks 4-7
what are the bones around the brain called
the neurocranium (8 bones)
what are the facial bones called
the viscerocranium (15 bones)
what are the flat bones of the neurocranium and what is this group called
frontal and parietal bones
calvaria
what are the bones of neurocranium that make up the base of the skull
the chondrocranium
what is the cellular origin of the facial bones and frontal bone
neural crest cells from the dorsal part of neural tube
what is the cellular origin of the skull bones (minus the frontal)
the paraxial mesoderm, cells that are cranial to the somites
called: unsegmented, somitic, somitomeric or pre-otic
what is the cellular origin of the laryngeal bones
the lateral plate mesoderm
what is endochondral ossification
formation of a cartilage template and then formation of bone
what is intramembranous ossification
direct formation of bone
what skull bones form via endochondral ossification
occipital bone (chondrocranium)
what skull bones form via intramembranous ossification
the parietal and frontal bones
what are sutures important for
molding at birth
where do sutures arise from
sagital: neural crest
coronal: paraxial mesoderm
When do the anterior and mastoid fontanelles close?
around 2 years
when do the posterior and sphenoidal fontanelles close
after 6 months
what is craniosynostosis
premature fusion of sutures
scaphocephaly is what
a long AP skull due to early fusion of sagittal suture
bradycephaly is what
a short square shaped skull due to early coronal fusion
Crouzon syndrome
AD
FGFR2 gain of function mutation
craniosynostosis, ocular proptosis, mandibular prognathism, progressive hydrocephaly
Apert syndrome
AD
FGFR2 gain of function mutation
craniosynostosis, syndactyly of hands and feet, mental retardation
Pfeiffer syndrome
AD
FGFR2 gain of function mutation
craniosynostosis, syndactly of hands and feet
when do pharyngeal arches form
in the 4th week
what are pharyngeal pouches
evaginations of the endoderm between arches
what are pharyngeal clefts
invaginations of ectoderm between arches
how many arches, pouches and clefts
5 arches, 4 pouches and clefts
what does each arch contain
cartilage, muscles, artery and nerve
where does the muscle of pharyngeal arches come from
somitic mesoderm
where does the artery of pharyngeal arches come from
somitic mesoderm
where does the cartilage of pharyngeal arches come from
lateral plate neural crest cells
where does the nerve of pharyngeal arches come from
neural tube (ectoderm)
how does the mandible form
intramembranous ossification
what is and does meckels cartilage form
It is the first pharyngeal arch
the mandible, incus and malleus
what is and does Reicherts cartilage form
It is the 2nd pharyngeal arch
the lesser horn of hyoid, styloid process, stapes
what does the 3rd pharyngeal arch form
the greater horn of hyoid bone
what is the origin of the 1, 2 and 3rd pharyngeal arches
the neural crest cells
what is the origin of the IV and VI pharyngeal arches
lateral plate mesoderm
what do the 4th and 6th pharyngeal arches form
thyroid cartilage, cricoid cartilage and arytenoid cartilage
what nerve innervates the 1st arch
trigeminal nerve (CN V)
what nerve innervates the 2nd arch
facial nerve (CN VII)
What nerve innervates the 3rd arch
glossopharyngeal nerve (CN IX)
what nerve innervates the 4th and 6th arch
the superior laryngeal branch and the recurrent branch of the vagus (CN X)
what does cleft 1 form
the external auditory meatus and the external part of the tympanic membrane
what forms the cervical sinus
cleft 2 migrates and 3 and 4 curl up
what does pouch 1 form
the tubotympanic recess that becomes the Eustachian tubes
what does pouch 4 form
the ultimobranchial body and superior paraythyroid
what does pouch 2 form
the tonsil
what does pouch 3 form
the inferior parathyroid and the thymus
when is the thymus active
during perinatal period and childhood and then involutes after puberty
what does PTH do
increases Ca2+ levels in the blood
where is the thyroid gland derived from
not from a pouch
from the floor of pharynx between pouch 1 and 2 (endoderm)
what are the hypoglossal ducts
they connect the foramen cecum to the thyroid gland
when does thyroid function begin
week 10-12
what does the ultimobranchial body do
fuses with thyroid gland and creates calcitonin producing ‘C’ cells
what is the derivative of C cells
endoderm
what does calcitonin do
reduces calcium levels in the blood
first arch syndromes
insufficient migration of neural crest cells into pharyngeal arch 1
- treacher-collin syndrome
- Pierre robin syndrome
treacher collins syndrome
AD
TCOF1 gene mutation, treacle protein mutation
causes: hypoplasia of mandible, external ear abnormalities
Pierre robin syndrome
SOX9 gene associated
u shaped cleft palate, glossoptosis and airway obstruction
DiGeorge syndrome cause
failure of pouches 3 and 4 to differentiate into thymus and parathyroid glands
- micro deletion of chromosome q22
- abnormal neural crest migration
DiGeorge syndrome symptoms
facial anomalies
immunosuppression (thymus)
hypocalcemia (parathyroid)
Pharyngeal fistula
persistence of pouch 2 or cleft 2
anterior border of SCM
pharyngeal cyst
persistence of clefts 2, 3, 4
along angle of mandible
drainage in palatine tonsil
thyroglossal cysts and sinuses
if the thyroglossal duct persists and forms a cyst
- located in midline near hyoid
thyroglossal cyst under the tongue
lingual cyst
derivative of frontal nasal prominance
forehead, dorsal and apex of nose
derivative of lateral nasal prominance
alae (sides) of nose
derivative of medial nasal prominance
nasal septum, ethmoid bone, cribriform plate
derivative of intermaxillary segment
philtrum and primary plate
derivative of maxillary prominance
upper cheek region and lip
derivative of mandibular prominance
chin, lower lip and cheek
derivative of fusion of Fr. nasal and max pr
nasolacrimal duct
what is the name of the opening form the nasal cavity to the mouth
choana
how does that hard palate form
intramembranous ossification
what is in the soft palate
muscles
vagus and trigeminal nerves
what is choanal atresia
cyclical period of cyanosis due to a closed choana
the anterior 2/3 of the tongue is formed by what
the first arch
the posterior 1/3 of the tongue is formed by the what
the third arch
what forms the epiglottis
the 4th arch
what is ankyloglossia
tongue tied
innervation of anterior 2/3 of tongue
trigeminal ganglion
innervation of taste buds
facial nerve
innervation of posterior tongue and epiglottis
vagus nerve
innervation of posterior 1/3 of tongue and vallate apillae
glossopharyngeal nerves
tongue musculature innervation
hypoglossal nerve cranial nerve XII
what is the dental papilla
a transient signalling structure that signals to form the enamel knot
precursor of enamel
ameloblasts
precursor of predentin
odontoblasts
morphogen means
dose dependent signalling
defect resulting in loss of Shh defects
severe midline defects
low Shh activity
cyclopia
very high Shh activity
facial duplications
holoprosencephaly
cyclopia
what is the cause of cleft lip
failure of maxillary prominance and medial nasal prominance joining
cleft palate cause
failure of palatal shelves (primary and secondary) fusing together along midline
cleft lip is where in relation to incisive foramen
anterior
cleft palate is where in relation to incisive foramen
posterior
clefts distribution among sexes
lip more common in men
palate more common in females
