Branchial arch derivatives

Question 1

1st arch

Answer 1

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

Muscles: Muscles of Mastication (temporalis, Masseter, lateral and Medial pterygoids), Mylohoid, anterior belly of digastric, tensor tympani, tensor veli palatini

Nerves: CNV2, V3

Abnormalities: Treacher Collins syndrome: 1st arch neural crest fails to migrate –> mandibular hypoplasia, facial abnormalities

Question 2

2nd arch

Answer 2

Cartilage: Reichert’s cartilage: Stapes, Styloid process, lesser horn of hyoid, Stylohyoid ligament

Muscles: muscles of facial expression–Stapedius, Stylohyoid, posterior belly of digastric

Nerves: CN VII

Question 3

3rd arch

Answer 3

Cartilage: greater horn of hyoid

Muscles: stylopharyngeus

Nerve: CN IX

Abnormalities: congenital pharyngocutaneous fistula: persistence of cleft and pouch –> fistula between tonsillar area, cleft in lateral neck

Question 4

4th-6th arches

Answer 4

Cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform

4th arch: CN X (superior laryngeal branch)

6th arch: CN X (recurrent laryngeal branch)

Arches 3 and 4 form posterior 1/3 of tongue; arch 5 makes no major contributions