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57 terms

Devo Branchial Arches I

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The branchial arches are also referred to as ____.
Pharyngeal arches
What are the four components of the pharyngeal apparatus?
arches, puches, grooves/clefts, membranes
What tissue are the arches formed from?
mesenchyme, from paraxial and lateral plate mesoderm
What causes differentiation of the mesenchyme into the branchial arches?
neural crest cells
True or false: each arch is covered by ectoderm and lined by endoderm.
True
Which structure separates the arches externally?
pharyngeal groove
Which structure separates the arches internally?
pharyngeal pouch
What does the stomodeum come from, and what does it become?
surface ectoderm, lining of oral cavity
What structures form the oropharyngeal membrane? When does it rupture, and what structures are then linked?
ectoderm and endoderm, 26 days, foregut and pharynx with the amniotic cavity
When do the nasal placodes appear?
28 days
When do each of the arches appear?
23, 24, 26, 28 days
What does arch one become? What is its letter?
jaw and face, maxilla and mandible, "m"
Which nerve innervates the muscles of arch 1?
CN V, particularly V3
What muscles come from arch 1?
muscles of mastication, mylohyoid, and the two tensors
What does the cartilage of arch 1 become, and what is its name?
malleus and incus, Meckel's cartilage
What does the ligament of arch 1 become?
anterior ligament of malleus, sphenomandibular ligament
What is arch 2's letter?
S
What nerve is associated with arch 2?
CN VII
What muscles come from arch 2?
stylohyoid, stapedius, muscles of facial expression
What is the name of arch 2's cartilage, and what does it become?
Reichert's, stapes, styloid process, stylohoid ligament, lesser horn and upper body of hyoid
What ectodermal depression is formed by the enlargement of arch 2, and what does it contain?
cervical sinus, arches 3 and 4
When does the neck first appear smooth?
7th week
What nerve is associated with arch 3?
CN IX
what muscle is associated with arch 3?
stylopharyngeus
What structures are derived from the cartilage of arch 3?
greater horn lower body of hyoid
What nerve is associated with arch 4?
superior laryngeal branch of CN X
What muscles are derived from arch 4?
cricothyroid, levator veil palatini, and the pharyngeal constrictors
What do the cartilages of arches 4-6 become?
laryngeal cartilages
What does the pouch of arch 1 become?
pharygnotympanic tube, tympanic cavity, mastoid antrum
What does the pouch of arch 2 become?
tonsillar sinus/fossa, endoderm-> crypts, mesenchyme -> lymphatic nodules of palatine tonsil
What does the dorsal aspect of the pouch of arch 3 become?
inferior parathyroid gland
What does the dorsal aspect of the 4th pharyngeal pouch become?
superior parathyroid gland
What does the groove of arch 1 become?
external acoustic meatus
What dos the membrane of arch 1 become?
tympanic membrane
What does the first aortic arch become? What does it supply?
maxillary arteries, ears, teeth, muscles of eye and face
What do the stapedial arteries come from?
dorsal part of 2nd aortic arch
What does the 3rd aortic arch become?
common carotid, internal carotid (after joining with dorsal aortae)
What does the 4th aortic arch become?
arch of aorta (left), right subclavian (right)
What does the proximal part of left aortic arch 6 become?
left pulmonary artery
What does the distal part of left aortic arch 6 become?
ductus arteriosus
What does the right aortic arch 6 become?
pulmonary artery
What does the ventral aspect of the pouch of arch 3 become?
thymus
What does the ventral aspect of the 4th pharyngeal pouch become?
ultimopharyngeal body, which becomes the parafollicular cells of the thymus. These secrete calcitonin.
What is a branchial fistula?
abnormal passage with two open ends, extending between two mucosal surfaces
What does a fistula of arch 1 do? What usually causes it?
open to tonsillar sinus and external side of neck, results from persistence of second pharyngeal groove and pouch
What does a fistula of the second arch do?
runs b/w IX, XII, stylohyoid, and hyoid, through carotids, opens to platysma
What does a fistula of the third arch do?
pierces thyrohyoid membrane superior to CN X, passes caudal to IX, rostral to XII, posterior to carotid
What is a branhial sinus?
blind pit, only one opening
What causes an external sinus, and where is it located?
persistence of 2nd pharyngeal groove and cervical sinus, anterior border of SCM
What causes an internal sinus, and where is it located?
Persistence of proximal 2nd pharyngeal pouch, tonsillar sinus
What is a branchial cyst?
cavity with no openings
Where are branchial cysts most often found? What causes them?
inferior to angle of mandible or anterior border of SCM, persistence of cervical sinus or 2nd pharyngeal groove
Which syndromes are associated with the first arch?
Treacher-Collins, Pierre Robin
What are the symptoms of Treacher-Collins syndrome? What causes it?
malar hypoplasia, dow-slanting palpebral fissures, defects of lower eyelids, deformed auricles of ears, caused by autosomal dominant defect
What are the symptoms of Pierre Robin syndrome?
micrognathia, cleft palate, defects of eye and ear
What causes DiGeorge syndrome?
microdeletion in chromosome 22, failure of 3rd and 4th pharygneal pouches to develop into thymus and parathyroid
What are the symptoms of DiGeorge syndrome?
infection, congenital hypoparathyroidism, fish-mouth, low/notched ears, nasal clefts, thyroid hypoplasia, cardiac anomalies