Pharyngeal arches Flashcards
cysts
sealed cavity filled with air, pus, fluid
sinus
cavity within a tissue, can open externally
fistula
abnormal connection between 2 structures
migration
cells move (or don’t) during development
Proliferation
growth in cell number thru cell division
Genetics
mutations change patterns in migration, proliferation, etc..
how many pharyngeal arches are there?
5
when do pharyngeal arches emerge?
at neural tube closure
about 4 weeks of development
what is unique about the first arch
shows two prominences
- maxillary prominence
- mandibular promnence
what are the components found in each arch?
nerve, artery, cartilage, and muscular component
aortic arches
arise from mesoderm and bridge between the truncus arteriosus and the dorsal aorta
aortic arch 1
maxillary and external carotid
aortic arch 2
stapedial
aortic arch 3
common and internal carotid
aortic arch 4
aortic and subclavian
aortic arch 6
pulmonary
cartilage arch 1
meckel’s cartilage, maxilla, mandible, malleus, incus
cartilage arch 2
stapes, styloid process, lesser horn and upper portion of body of hyoid bone
cartilage arch 3
greater horn and lower portion of body of hyoid bone
cartilage arch 4-6
laryngeal cartilages
muscles arch 1
muscles of mastication
eg: temporalis, masseter, medial and lateral pterygoids
muscles arch 2
all muscles of facial expression
muscles arch 3
stylopharyngeus
muscles arch 4
constrictors of pharynx
muscles arch 6
intrinsic muscles of larynx
nerves of arch 1
trigeminal
nerves of arch 2
facial nerve
nerves of arch 3
glossopharyngeal (IX)
nerves of arch 4
vagus superior laryngeal
nerves of arch 6
recurrent laryngeal
mandibular process of arch 1 forms:
lower lip, lower face, lower cheek regions, chin, mandible, body of the tongue
maxillary process of arch 1 forms:
midface, upper cheek regions, upper lip sides, secondary palate, maxilla, and zygomatic bone
treacher collins syndrome mutation
Treachle gene mutation
1st arch syndrome
Pierre Robin sequence
hypoplasia of mandible, misplacement of tongue, cleft palate, defects of eye and ear, airway obstruction
*cause is unknown
How many pharyngeal grooves are there?
4
pharyngeal grooves/clefts are made of what origin?
ectoderm
which cleft is the only cleft not obliterated in development?
the 1st one
what does the 1st cleft give rise to?
the external auditory meatus
Preauricular sinus and cysts
often unilateral 1st or 2nd arch defect
Branchial sinuses, cysts, and fistulas
Lateral cervical
uncommon, open to external(to neck), failure of second groove or cervical sinus to obliterate
*if it is continuous with skin of neck it is a fistula
Branchial sinuses, cysts, and fistulas
Internal branchial
rare, persistent second pouch, open into intratonsillar cleft (into pharynx)
2nd pouch defect
how many pharyngeal pouches do you have?
4 or 5 pairs
pouches are of what origin?
endodermal origin
1st pharyngeal pouch gives to what structure?
distal portion- forms middle ear and makes the inner portion of tympanic membrane
proximal: forms eustachian tube
second pharyngeal pouch gives to what structure?
the lining of the crypts in the palatine tonsils and tonsillar fossa
third pharyngeal pouch gives rise to what?
inferior parathyroid gland(dorsal wing) and the thymus(ventral wing)
Fourth pharyngeal pouch gives rise to what?
superior parathyroid gland(dorsal) and the ultimobranchial body aka C cells of thyroid (ventral wing)
migration defects:
cervical thymus
cord of thymus persists in neck on path of descent
migration defects:
accessory thymus
piece of thymus remaining in path of descent
DiGeorge syndrome
failure of 3rd and 4th pouches to differentiate into thymus, parathyroid
-neural crest defects
DiGeorge syndrome CATCH 22
C: cardiac abnormality (tetralogy of Fallot) A: abnormal faces T: thymic aplasia C: cleft palate H: hypocalcemia/hypoparathyroidism
tetralogy of Fallot
overriding aorta
pulmonic stenosis
ventricular septal defect
right ventricular hypertrophy
Hox genes regulate what?
anterior to posterior identity
up and down rostral to caudal
T/F neural crest cells, with different anterior to posterior identities as determined by Hox expression, migrate form the Rhombomeres into the pharyngeal arches
true
Loss of Hox expression causes arch 2 to do what?
lose it anterior to posterior identity and gives a duplicate arch 1 structure
-so no lesser horn or upper body of hyoid, but will have two malleus, incus, and tympanic ring
what does the Dlx code
proximal - distal or ventral -dorsal of the arches
development of the tongue (floor of the arches)
arch 1 forms anterior 2/3 epithelium
arch 2 is covered up as arch 3 grows
arch 3 forms most of posterior 1/3 epithelium
arch 4 forms the bit of tongue at very back of throat
arch 1 in tongue formation
median tongue bud
distal tongue buds
-these become anterior 2/3 of tongue
arch 2 in tongue formation
forms middle swelling called copula
arches 3 and 4 in tongue formation
- hypopharyngeal eminence over grows copula(arch 2) and gives rise to posterior 1/3
- epiglottis arises posterior to hypopharyngeal eminence
where do tongue muscles come from?
occipital somites
what is the dividing line between oral tongue and pharyngeal tongue
terminal sulcus groove
what is the foramen cecum
at the midline and is the site of thyroid primordium
thyroid gland developement
forms from an endodermal diverticulum(pouch) just posterior to the floor of the 1st arch
**this not a pharyngeal pouch!!
not bilateral
-diverticulum elongates into the thyroglossal duct.
development of the pituitary gland
forms from the upward invagination of the oral ectoderm in the stomodeum (Rathke’s pouch)
-separates from oral epithelium, moves into contact with diencephalon.
neurohypophysis(posterior pituitary)
develops from the developing brain (neural ectoderm)
adenohypophysis (anterior pituitary)
develops from the stomodeum roof (oral ectoderm).
