pharyngeal arches Flashcards
pharyngeal arch 1 CN
CN V
pharyngeal arch 2 CN
CN VII
pharyngeal arch 3 CN
CN IX
pharyngeal arch 4 CN
CN X
pharyngeal arch 1 aortic arch, gives rise to?
Aortic arch I: becomes maxillary aa
pharyngeal arch 2 aortic arch, gives rise to?
aortic arch 2; gives rise to hyoid and stapedial aa which normally go away with development
pharyngeal arch 3 aortic arch, gives rise to?
aortic arch 3; common cartoid and proximal internal carotid aa
pharyngeal arch 4 aortic arch, gives rise to?
aortic arch 4; right subclavian and the aorta
mm dereived from pharyngeal arch 1
masticory tensor tympani mylohyoid tensor palatini veli anterior digastric
mm dereived from pharyngeal arch 2
facial expression mm stylohyoid platysma post digastric stapedius
mm dereived from pharyngeal arch 3
stylopharyngeus
mm dereived from pharyngeal arch 4
pahrygeal and laryngeal mm
skeletal derivatives of arch 1
malleus incus sphenoman ligament meckel's cartilage-mandible tympanic ring
skeletal derivatives of arch 2
stapes
styloid
lesser horn of hyoid
stylohyoid ligament
skeletal derivatives of arch 3
greater horn
body of hyoid
skeletal derivatives of arch 4
laryngeal cartilages
pharyngeal groove/cleft vs pouch
groove/cleft: outside of where two arches meet
pouch: inside of where two arches meet
first pharyngeal groove (where arches 1 and 2 meet) becomes?
external ear/ external auditory meatus
2nd, 3rd, 4th pharyngeal grooves become?
cervical sinuses: temporary, pathology if not resorbed
1st pharyngeal pouch becomes (where arches 1 and 2 meet)?
middle ear and eutaschian tube
2nd pharyngeal pouch becomes (where arches 2 and 3 meet)?
supratonsilar fossa
3rd pharyngeal pouch becomes (where arches 3 and 4 meet)?
thymus and inf PTG
4th pharyngeal pouch becomes (where arches 4 and 5 meet)?
sup PTG
post brachial body
when does the pharyngeal region form
around the 4th week
pharyngeal complexes
Blocks of mesenchymal tissue separated externally by
pharyngeal clefs (grooves) and internally by pharyngeal pouches.
The pharyngeal complexes are crucial for normal
formation of the neck & face.
components of pharyngeal arches
Pharyngeal arch (skeletal, muscular, nerve & artery components) Pharyngeal clefts (external) Pharyngeal pouches (internal)
processes and names of the first arch
the first (mandibular) arch has two processes - the
maxillary and the mandibular (really 3 if you include the
frontonasal).
which arches form face/neck? can be observed externally?
The first two pharyngeal arches develop into facial
and neck structures that can be observed externally, the other
arches do not.
neural crest migration to the arches
Neural-crest migrates into the arches
The migrating neural crest cells differentiate into the skeletal element of each arch,
Branches of specific cranial nerves, which are derived from neuroectoderm, migrate into each pharyngeal arch.
Development of the Arterial System
6 pair of aortic arches, one for each arch
Connect aortic sac/TA to dorsal aortae
heart developing ventricle and atria
structures found in each pharyngeal arch
Skeletal element
Muscles
A branch of a specific cranial nerve
Artery
skeletal elements of arch 1
The migrating neural crest in the first arch induce the formation of a cartilaginous rod
(Meckel’s cartilage).
The more posterior portion differentiates and becomes ossified into the malleus and the incus.
The more anterior portion of Meckel’s cartilage serves as a scaffolding for intramembranous bone formation of the mandible.
In between the two middle ear bones and the mandible, the sphenomandibular ligament forms, connecting the first arch skeletal elements.
In addition, the maxilla, zygoma and part of the temporal bone form in the maxillary portion of the first arch.
skeletal elements of arch 2
The skeletal elements of the second arch initially appear as a bar of cartilage (Reichert’s).
The posterior portion differentiates into the stapes & the styloid process of the temporal bone.
The anterior portion differentiates into the lesser horns (cornu) and the superior portion of the hyoid bone. In between these elements, the stylohyoid ligament is formed.
Skeletal elements –
Arches 3,4 & 6
The skeletal elements of the third pharyngeal arch are the greater horns (cornu) and inferior portion of the hyoid bone.
Skeletal elements of the fourth-sixth pharyngeal arches differentiate into all the laryngeal cartilages (thyroid, arytenoid, corniculate, cuneiform, and cricoid), except the epiglottis (comes from the laryngeotracheal diverticulum)
general rule for what mm come from each arch?
mm inn by nerve of that arch
1: CNV
2: CNVII
3: CNIX
4: CNX
Terminal branches of maxillary artery are associated with?
the first pharyngeal arch.
Tissues of the second pharyngeal arch are supplied by? (aa)
the stapedial artery, which regresses.
The common carotid artery and root of internal carotid artery are associated with?
with the third pharyngeal arch.
The ductus arteriosus and roots of pulmonary arteries are associated with which arches?
the fourth-sixth pharyngeal arches.
treacher-collins
Mandibulo-facial dysostosis
Underdevelopment of structures associated with Arch 1.
Pierre Robin Sequence
Micro-/Retrognathia=glossoptosis (pushes tongue back) to cause airway obstruction
pharyngeal clefts become?
The first pharyngeal cleft deepens and forms the external auditory
meatus and canal. This is the only cleft that gives rise to an adult
structure. The second-fourth clefts become overgrown by the
second pharyngeal arch and, thus, become enclosed as a cervical
sinus. Normally, this cervical sinus regresses.
ectopic thyroid
thyroid develops at the foramen cecum and will migrate to its adult position
may have misplaced thyroid tissues along this route or still present on the tongue=lingual thyroid
formation of the eustachian tube
The first pouch increases in size and migrates towards the first pharyngeal cleft. As the pouch and cleft
approach each other, the auditory (pharyngotympanic or eustachian) tube is formed and the endoderm of the first pouch forms the lining of the middle ear (tympanic cavity).
tympanic membrane formation
At its most distal end, endoderm of the first pouch becomes approximate to the ectoderm of the first pharyngeal cleft with only a small amount of mesoderm separating them. This is the site of the tympanic membrane.
second pharyngeal pouch becomes? what forms beneath it?
site of the tonsillar fossa in the adult
Underneath the endoderm of the second pouch develops pit-like depressions (tonsillar crypts) mesoderm differentiates into lymphoid tissue that is called the palatine tonsils.
Pharyngeal Pouch 3 develops?
Dorsally, the posterior endodermal region develops into bilateral inferior parathyroid glands (III), which
migrate toward the posterior aspect of the inferior pole of the thyroid gland.
Ventrally, the anterior endodermal region of the third pouch differentiates bilaterally into thymus gland tissue.
Each part migrates inferiorly and fuses with its counterpart in the midline, and the united gland migrates inferiorly to the superior mediastinum of the thorax.
how can the inferior PTG form more superior than the superior PTG?
inf will migrate further down and eventually be inf to the sup PTG
Pharyngeal Pouches 4-5 develop?
The posterior endoderm develops into superior parathyroid glands that migrate to the posterior aspect of the thyroid gland.
The anterior endoderm of the fourth pouch develops an ultimobranchial body that migrates to the thyroid gland. Cells from the ultimobranchial body differentiate into parafollicular cells (C cells) that produce calcitonin.
The endoderm of the fifth pharyngeal pouch contributes to the formation of the ultimobranchial body
Digeorge syndrome
failure of the thymus gland to develop from the third pharyngeal pouch
adult derivatives of pharyngeal pouch 1
Auditory (pharyngotympanic, eustachian) tube, middle ear (tympanic
cavity), part of the eardrum (tympanic membrane)
adult derivatives of pharyngeal pouch 2
Tonsillar crypts
adult derivatives of pharyngeal pouch 3
Inferior parathyroid glands
Thymus gland
adult derivatives of pharyngeal pouch 4
Superior parathyroid glands
Ultimobranchial body
adult derivatives of pharyngeal pouch 5
Ultimobranchial body
anterior 2/3 of the tongue development
Median tongue bud; overgrown by lateral lingual swellings, fusion indicated by the median sulcus
posterior third of the tongue development
Mesoderm of the second pharyngeal arch forms a central process (copula)
It is overgrown by a central process from the third and fourth pharyngeal arches, the hypopharyngeal (hypobranchial) eminence, which develops into the posterior one-third of the tongue.
between the anterior and posterior tongue?
terminal sulcus
mm of the tongue development and inn
Muscles of the tongue develop from the mesoderm of the occipital myotomes that migrate into the developing tongue. Branches of the hypoglossal nerve (CN XII) follow the migrating occipital myoblasts and thus innervate the intrinsic muscles of the tongue
formation of the thyroid gland
The endodermal mass of cells invaginates into the underlying mesoderm, creating the thyroid diverticulum that is positioned between the anterior two-thirds and posterior one-third of the developing tongue.
The thyroid diverticulum grows inferiorly, often between the skeletal elements of the second and third pharyngeal arches.
It then migrates to a position anterior to the upper portion of the developing trachea.
connection between origin of thyroid diverticulum and the thyroid gland is called the thyroglossal duct and normally regresses over time, if not thyroglossal duct cyst