Branchial Arches Flashcards
What are branchial sinuses?
Openings along anterior border of sternomastoid due to failure of 2nd pharyngeal groove and cervical sinus to obliterate
What is the terminal fate of the posterior branchial arches?
Arch 2 enlarges and grows over the posterior arches, forming a sinus (cervical sinus) that typically goes away by week 7
What nerve(s) derive from branchial arch I?
Trigeminal (V)
branchial arch I has a maxillary and mandibular component and the ophthalmic component is a pretrematic branch
What is Pierre-Robin Syndrome?
Mandibular underdevelopment + cleft palate + defects of eyes and ear
What arteries derive from branchial arch I?
Part of maxillary artery
What muscles form from branchial arch IV/VI?
Levator veli palatini
Pharyngeal constrictors
Intrinsic laryngeal muscles
Cricothyroid
Esophageal striated muscles
What is the terminal structure that ectoderm forms?
Epidermis and sensory neurons of the epibranchial ganglia
What structures form from the floor of branchial arch II?
Foramen cecum, thyroid gland
What cranial nerve forms from branchial arch III?
Glossopharyngeal (IX) nerve
pretrematic branch: tympanic
What structure forms from the groove/cleft of branchial arch I?
External auditory meatus
What structure forms from the pouch of branchial arch I?
Middle ear chamber + eustachian tube
What cartilaginous bones form from branchial arch II rods?
Stapes, styloid process, lesser horn of hyoid and upper part of the body
What cartilaginous bones derive from arch rods of branchial arch I?
Malleus, incus
What arteries are associated with branchial arch III?
Internal carotid
What ligaments derive from arch rods of branchial arch I?
Anterior ligament of the malleus, sphenomandibular ligament
What muscles derive from branchial arch I?
Muscles of mastication
anterior belly of digastric, myohyoid, tensor veli palatini, tensor tympani
What cartilaginous bones form from branchial arch IV/VI rods?
Thyroid, cricoid, arytenoid cartilages
Corniculate, cuneiform cartilages
What arteries form from branchial arch IV/VI?
Right subclavian, left aorta, ductus arteriosus
What are branchial cysts?
Spherical or elongate cysts that are (usually) remnants of the 2nd pharyngeal groove and develop along the anterior border of the sternomastoid muscle
What ligaments form from branchial arch II rods?
Stylohyoid ligament
What muscles derive from branchial arch II?
Muscles of facial expression
posterior belly of digastric, stylohyoid, stapedius, auricular muscles
What is the terminal structure that mesoderm forms?
Musculature and endothelial cells
What is a pouch transformation anomaly?
Failure of 3rd and 4th arch pouches to differentiate into thymus and parathyroid glands (ex. DiGeorge Syndrome)
What is first (mandibular) arch syndrome?
A syndrome that leads to various malformations in mandible, palate, ears that results from insufficient migration of neural crest cells into the 1st arch around week 4
What cranial nerves are associated with branchial arch IV/VI?
Vagus nerve (superior laryngeal and recurrent laryngeal)
What are the external features of branchial arch 1?
Maxilla, mandible, pinna of ear
What structures form from the puch of branchial arch III?
Tymus, inferior parathyroid
What membrane forms from branchial arch I?
Tympanic membrane
What structure forms from the floor of branchial arch I?
Distal tongue buds
What is the importance of neural crest cell migration?
Wk 4 - neural crest cells migrate into developping arches and form cartilaginous rods that develop into the skeleton and connective tissue of much of the face
What structure forms from the pouch of branchial arch II?
Palatine tonsil
What structures form from the floor of branchial arch III?
Hypobranchial eminence
What arteries form from branchial arch II?
Stapedial (degenerates before birth)
What is the terminal structure that endoderm forms?
Epithelial lining of the pharynx, forming taste buds + thyroid + parathyroid + thymus
What cartilaginous bones are formed from branchial arch III rods?
Greater horn of hyoid and lower part of body
What structures form from the pouch of branchial arch IV/VI?
Superior parathyroid, postbranchial body
What are branchial fistulas?
Canal opening internally into tonsillar sinus and externally onto side of neck resulting from persistence of 2nd pharyngeal groove and puch
What structures form from the floor of branchial arch IV/VI?
Hypobranchial eminence
What external features form from branchial arch II?
Pinna of ear, side of neck
What are branchial vestiges?
Cartilaginous or bony remnants of branchial arch cartilages which do not fully transform/disappear
typically anterior to inferior third of sternocleidomastoid muscle
What is treacher-collins syndrome?
Zygomatic underdevelopment + downward slanting palpebral fissures + defects of lower eyelids + deformed external ears + abnormalities of middle and internal ears
What is the terminal structure that neural crest ectomesenchyme forms?
Skeletal and connective tissues of the arches
What is the basic structure of the branchial arches?
Externally lined with ectoderm, internally lined with endoderm
Arches separated by grooves externally and internally by pouches
Each arch has a cartilaginous supportive rod, musculature, blood supply, and a nerve
What muscles form from branchial arch III?
Stylopharyngeus
What cranial nerve is associated with branchial arch II?
Facial nerve (VII)
pretrematic branch = chorda tympani
What bones derive from the migrated ectomesenchyme of branchial arch I?
Mandible, maxilla, zygomatic, palatine, pterygoid plates of sphenoid, squamous and tympanic temporal
