SM_08b: Branchial Arches Flashcards
Pharyngeal / branchial arches are ____
Pharyngeal / branchial arches are series of paired swellings flanking the developing oropharynx
- Appear early in 4th week
- Differentiate into terminal structures by end of 7th week
- Composed of endoderm, mesoderm, neural crest ectomesenchyme, and ectoderm
- Fundamental aspect of vertebrates: musculoskeletal structures of the pharynx serving dual roles of feeding and respiration, new ectomesenchyme-based features
- Reflect common vertebrate embryological foundations
- Give rise to important structures
Describe the basic gross structure of the pharyngeal arches
Basic gross structure of the pharyngeal arches
- 6 pairs but the 5th disappears and 4th and 6th fuse
- Bars of mesoderm lined externally with ectoderm, internally with endoderm
- Separated externally by grooves (clefts) and internally by puches
- Composed of cartilaginous supportive rod, musculature, blood supply (aortic arch system) and a nerve supplying these structures
Arch 1
- Aortic arch:
- Cranial nerve:
- Branchiometric muscles:
Arch 1 (mandibular)
- Aortic arch: maxillary artery
- Cranial nerve: trigeminal (V)
- Branchiometric muscles: muscles of mastication, tensor tympani, mylohyoid, tensor veli palatini, anterior digastric
Arch 2
- Aortic arch:
- Cranial nerve:
- Branchiometric muscles:
Arch 2 (hyoid)
- Aortic arch: hyoid artery, stapedial artery
- Cranial nerve: facial (VII)
- Branchiometric muscles: muscles of facial expression, stapedius, stylohyoid, posterior digastric
Arch 3
- Aortic arch:
- Cranial nerve:
- Branchiometric muscles:
Arch 3
- Aortic arch: internal carotid artery
- Cranial nerve: glossopharyngeal (IX)
- Branchiometric muscles: stylopharyngeus
Arch 4 + 6
- Aortic arch:
- Cranial nerve:
- Branchiometric muscles:
Arch 4 + 6
- Aortic arch: right subclavian artery and aorta
- Cranial nerve: vagus (X)
- Branchiometric muscles: pharyngeal and laryngeal muscles
Describe the developmental timetable and dynamic events of pharyngeal arches
Developmental timetable and dynamic events of pharyngeal arches
- All during weeks 4-7
- Six arches develop, but #5 disappears, #6 merges with #4, and only 1-4/6 have adult derivatives
- First four arches are well-formed and externally obvious by the end of week 4 (#6 is too small to see externally)
- Arch structures are fully differentiated by end of week 7
- Development proceeds cranially to caudally (#1 is differentiated by the time #6 appears)
Development of pharyngeal arches involves ___ migration
Development of pharyngeal arches involves neural crest cell migration
- At beginning of week 4, neural crest cells migrate into the developing arches, forming the cartilaginous rods and developing into the skeleton and connective tissue of much of the face etc
- Congenital anomalies result from problems with this complex migration of neural crest cells
Endodermal-ectodermal membranes ___
Endodermal-ectodermal membranes never disintegrate
(mesoderm secondarily invades the borders between external ectodermal grooves and internal endodermal pouches)
Describe the terminal fate of arches
Terminal fate of arches
- During week 5: arch #2 enlarges and overgrows the posterior arches, closing off the grooves posterior to arches #2, #3, and #4/6
- Forms cervical sinus, which typically obliterates by week 7
In the pharyngeal arches, ectoderm gives rise to ____ and ____
In the pharyngeal arches, ectoderm gives rise to epidermis and sensory neurons of the epibranchial ganglia
In the pharyngeal arches, endoderm generates the ____, forming the ____, ____, ____, and ____
In the pharyngeal arches, endoderm generates the epithelial lining of the pharynx, forming the taste buds, thyroid, parathyroid, and thymus
In the pharyngeal arches, neural crest ectomesenchyme forms ____ and ____
In the pharyngeal arches, neural crest ectomesenchyme forms skeletal and connective tissue of the arches
In the pharyngeal arches, mesoderm generates ____ and ____
In the pharyngeal arches, mesoderm generates musculature and endothelial cells
Arch 1 mesenchyme gives rise via ____ to ____, ____, ____, ____, ____, and ____
Arch 1 mesenchyme gives rise via intramembranous ossification to mandible, maxilla, zygoma, palatine, pterygoid plates of spheoid, and squamous and tympanic temporal
(nasal, lacrimal, vomer ossify intramembranously from neighboring ectomesenchyme)
Mandible (fused dentary bones) develops via ____ of ____ around the first arch cartilaginous rod
Mandible (fused dentary bones) develops via intramembranous ossification of branchial arch I (mandibular arch) mesenchyme around the first arch cartilaginous rod
- Meckel’s cartilage mostly disappears, persisting as sphenomandibular ligament (other derivatives of Meckel’s cartilage are malleus, anterior ligament of malleus, and incus)
- Secondary cartilaginous condensations from arch I mesoderm contribute to the condyle, coronoid process, and mandibular symphysis
Derivatives of arch cartilage of Arch 1 (Maeckel’s cartilage) are ____, ____, ____, and ____
Derivatives of arch cartilage of Arch 1 (Maeckel’s cartilage) are malleus, incus, anterior ligament of malleus, and sphenomandibular ligament
Derivatives of arch cartilage of Arch II (Reichert’s cartilage) are ____, ____, ____, and ____
Derivatives of arch cartilage of Arch II (Reichert’s cartilage) are stapes, styloid process, lesser cornu and upper body of hyoid bone, and stylohyoid ligament
Derivatives of arch cartilage of Arch III are ____
Derivatives of arch cartilage of Arch III are greater cornu and lower body of hyoid bone
Derivatives of arch cartilage of Arch IV/VI are ___
Derivatives of arch cartilage of Arch IV/VI are laryngeal cartilages
Muscles derived from branchial arch mesoderm of Arch 1 include ____, ____, ____, ____, and ____
Muscles derived from branchial arch mesoderm of Arch 1 include muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, and tensor veli palatini
Muscles derived from branchial arch mesoderm of Arch 2 include ____, ____, ____, and ____
Muscles derived from branchial arch mesoderm of Arch 2 include muscles of facila expression, stapedius, stylohyoid, and posterior belly of digastric
Muscles derived from branchial arch mesoderm of Arch 3 include ___
Muscles derived from branchial arch mesoderm of Arch 3 include stylopharyngeus
Muscles derived from branchial arch mesoderm of Arch 4/6 include ____, ____, ____, ____, ____, and ____
Muscles derived from branchial arch mesoderm of Arch 4/6 include intrinsic laryngeal muscles, pharyngeal constrictors, striated muscles of esophagus, cricothyroid, levator veli palatini, and palatoglossus
Arch 1 mostly disappears but forms part of the ___
Arch 1 mostly disappears but forms part of the maxillary arteries
Arch 2 mostly ____
Arch 2 mostly disappears (stapedial arteries in embryo)
Arch 3 contributes to the ___ and ___ arteries
Arch 3 contributex to the common and internal carotid arteries
Arch 4 becomes the ____ artery and part of the ____
Arch 4 becomes the proximal right subclavian artery and part of the arch of the aorta
Arch 5 has ___ arterial derivatives
Arch 5 has no arterial derivatives
Arch 6 becomes the ____ and ____ artery
Arch 6 becomes the ductus arteriosus and proximal portions of the pulmonary artery
Describe what happens to Arch 6’s artery
Arch 6’s artery
- Right side: degenerates -> right recurrent laryngeal nerve hooks under the derivative of arch 4’s artery (subclavian proximal portion)
- Left side: persists -> forms ductus arteriosus and part of pulmonary trunk -> left recurrent laryngeal nerve hooks under the ligamentum arteriosum
The first external groove persists as the ____
The first external groove persists as the external acoustic meatus
(subsequent grooves are obliterated with the overgrowth of Arch II and the closure of the cervical sinus)
1-3 come from the ____, while 4-6 come from the ____
1-3 come from the lower part of Arch I, while 4-6 come from the cephalic portion of Arch II
Derivatives of internal pouch of Arch 1 include ___, ___, ___, and ___
Derivatives of internal pouch of Arch 1 include inner layer of tympanic membrane, auditory tube epithelial lining, middle ear, and mastoid air cells
Derivatives of internal pouch of Arch 2 include ___
Derivatives of internal pouch of Arch 2 include crypt and clefts of palatine tonsil
Derivatives of internal pouch of Arch 3 include ____ and ____
Derivatives of internal pouch of Arch 3 include inferior parathyroid gland and epithelium of thymus
Derivatives of internal pouch of Arch 4 include ___ and ___
Derivatives of internal pouch of Arch 4 include superior parathyroid gland and ultimobranchial body (eventually incorporated into thyroid)
Nerve for Arch 1 is ___
Nerve for Arch 1 is trigeminal (CN V)
Nerve for Arch II is ____
Nerve for Arch II is facial nerve (CN VII)
Nerve for Arch III is ____
Nerve for Arch III is glossopharyngeal (CN IX)
Nerve for Arch IV-VI is ___
Nerve for Arch IV-VI is vagus (CN X)
Pretrematic nerve for Arch 1 is ___
Pretrematic nerve for Arch 1 is ophthalmic division of trigeminal (V)
Pretrematic nerve for Arch 2 is ____
Pretrematic nerve for Arch 2 is chorda tympani of facial nerve (VII)
Pretrematic nerve for Arch 3 is ____
Pretrematic nerve for Arch 3 is tympanic nerve of glossopharyngeal (IX)
Branchial cysts are ___ that are remnants of the ___ developing along the ___ muscle
Branchial cysts are spherical / elongated cysts that are remnants of the 2nd pharyngeal groove developing along the anterior border of the sternocleidomastoid muscle
(often associated with branchial sinuses)
Branchial sinuses are openings along the ____ due to failure of the ____ and ____ to obliterate
Branchial sinuses are openings along the anterior border of the sternocleidomastoid due to failure of the 2nd pharyngeal groove and cervical sinus to obliterate
Branchial fistulas are ____ resulting from persistence of the ____
Branchial fistulas are canal openings internally into tonsillar sinus and externally onto the side of the neck resulting from the persistence of the 2nd pharyngeal groove and pouch
Branchial vestiges are ____ and are typically found ____
Branchial vestiges are cartilaginous or bony remnants of branchial arch cartilages which do not fully transform / disappear and are typically found anterior to the inferior third of the sternocleidomastoid muscle
Preauricular pits, dimples, cysts, and sinuses are common developmental abnormalities that likely result from ____
Preauricular pits, dimples, cysts, and sinuses are common developmental abnormalities that likely result from abnormal transformtion of the auricular hillocks
(unrelated to 1st cleft sinuses)
Pouch transformation anomaly is ___ and occurs in ____
Pouch transformation anomaly is failure of the 3rd and 4th arch pouches to differentiate into thymus and parathyroid gland and occurs in DiGeorge syndrome
(DiGeorge syndrome also involves abnormal development of first arch elements)
First (Mandibular) Arch syndrome results from ____ and leads to ____
First (Mandibular) Arch syndrome results from insufficient migration of neural crest cells into the 1st arch around week 4 of development and leads to various malformations of the mandible, palate, and ears
Treacher-Collins syndrome results from ____ and presents as ____
Treacher-Collins syndrome results from failure of neural crest cells to properly migrate in the first place and presents as zygomatic underdevelopment, downward slanting palpebral fissures, defects of lower eyelids, deformed external ears, and abnormalities of middle and internal ears
Pierre-Robin syndrome results from ____ and presents as ____
Pierre-Robin syndrome results failure of neural crest cells to properly migrate in the first place and presents as mandibular underdevelopment, cleft palate, and defects of eye and ear
Fetal alcohol syndrome affects ____, and ethanol teratogenicity may act in part by promoting ____
Fetal alcohol syndrome affects facial primordia, and ethanol teratogenicity may act in part by promoting spontaneous cartilage formation
