Aortic Arch/Branchial Apparatus EC

Question 1

1st Aortic arch derivaties

Answer 1

Maxillary artery

Question 2

2nd Aortic arch derivatives

Answer 2

Stapedial artery

Hyoid artery

Question 3

3rd Aortic arch derivatives

Answer 3

Common carotid artery

Internal Carotid artery (proximal part)

Question 4

4th Aortic arch derivatives

Answer 4

Aortic arch

Right subclavian artery (proximal)

Question 5

6th Aortic arch derivatives

Answer 5

Pulmonary arteries

Ductus arteriosus

Question 6

Branchial apparatus organization (Clefts, Arches, and Pouches)

Answer 6

“CAP from outside to in”

Clefts=Ectoderm
Arches=Mesoderm and Neural crest
Pouches=Endoderm

Question 7

Branchial cleft cyst

Answer 7

2nd-4th branchial clefts form cervical sinuses which are usually obliterated by proliferation of 2nd arch mesenchyme

Failure of obliteration of cervical sinuses results in branchial cleft cyst within lateral neck

Question 8

1st Branchial arch derivatives (cartilage, muscles, nerves)

Answer 8

Meckel’s cartilage:
Mandible, Malleus-incus and sphenoid, Mandibular ligament

Muscles of Mastication:
Masseter, temporalis, lateral and Medial pterygoids, ant. belly of digastric, tensor tympani, tensor veli palatini

V2 and V3 (chew)

Question 9

Mandibular hypoplasia, facial abnormalities (syndrome and mechanism)

Answer 9

Treacher Collins syndrome

1st branchial arch fails to migrate

Question 10

2nd Branchial arch derivatives (cartilage, muscles, nerves)

Answer 10

Reighert’s cartilage:
Stapes, Styloid process, Lesser horn of hyoid, Stylohyoid ligament

Muscles of facial expression, Stapedius, Stylohyoid, Posterior belly of digastric

CN VII

Question 11

3rd Branchial arch derivatives (cartilage, muscles, nerves)

Answer 11

Greater horn of hyoid

Stylopharyngeus

CN IX

Question 12

Fistula between tonsillar area and cleft in lateral neck (syndrome and mechanism)

Answer 12

Congenital pharyngo-cutaneous fistula

Persistence of 3rd cleft and pouch

Question 13

4th Branchial arch derivatives (cartilage, muscles, nerves)

Answer 13

Thyroid cartilage

Pharyngeal constrictors, Cricothyroid, Levator veli palatini

CN X (superior laryngeal branch)

Question 14

6th Branchial arch derivatives (cartilage, muscles, nerves)

Answer 14

Cricoid, Arytenoids, Corniculate, Cuneiform cartilage (all laryngeal except thyroid)

Intrinsic muscles of larynx except cricothyroid

CN X (recurrent laryngeal branch)

Question 15

Arches forming posterior 1/3 of tongue

Answer 15

Arches 3 and 4

Question 16

1st Branchial pouch derivatives

Answer 16

Middle ear cavity, eustachian tube, mastoid air cells

Ears

Question 17

2nd Branchial pouch derivatives

Answer 17

Epithelial lining of palatine tonsil

Tonsils

Question 18

3rd Branchial pouch derivatives

Answer 18

Dorsal wings –> Inferior parathyroids

Ventral wings –> Thymus

Question 19

4th Branchial pouch derivatives

Answer 19

Dorsal wings –> Superior parathyroids

Question 20

Mutation of germline RET (neural crest cells)
~adrenal medulla (pheochromocytoma)
~Parathyroid (3/4th pharyngeal pouch)
~Parafollicular cells (Medullary thyroid cancer -4/5th pharyngeal pouches)

Answer 20

MEN2A

Question 21

Failure of fusion of the maxillary and medial nasal processes

Answer 21

Cleft lip

failure in formation of primary palate

Question 22

Failure of fusion of the lateral palatine processes, the nasal septum, and median palatine process

Answer 22

Cleft palate

failure in formation of secondary palate