Branchial apparatus (arches, clefts, pouches)

Question 1

Aortic arch derivatives

Answer 1

1-6

develop into arterial system

Question 2

1st aortic arch

Answer 2

part of maxillary artery (branch of external carotid)

1st arch is MAXimal

Question 3

2nd aortic arch

Answer 3

stapedial artery and hyoid artery

second=stapedial

Question 4

3rd aortic arch

Answer 4

common carotid artery and proximal part of internal carotid

C is 3rd letter of alphabet

Question 5

4th aortic arch

Answer 5

left - aortic arch
right- proximal part of right subclavian artery
4th arch = 4 limbs

Question 6

5th aortic arch

Answer 6

degenerates

Question 7

6th aortic arch

Answer 7

proximal part of pulmonary arteries and (on left only) ductus arteriosus

Question 8

nerve that gets caught in aortic arches

Answer 8

recurrent laryngeal nerve
right- loops under right subclavian (4th arch)
left - loops under aortic arch, distal to ductus arteriosus

Question 9

branchial clefts

Answer 9

derived from ectoderm

aka branchial grooves

Question 10

branchial arches

Answer 10

derived from mesoderm (muscle, arteries) and neural crest (bones and cartilage

Question 11

branchial pouches

Answer 11

derived from endoderm

Question 12

order of branchial apparatus

Answer 12

CAP covers outside to inside
branchial clefts - ectoderm
branchial arches - mesoderm
branchial pouches - endoderm

Question 13

1st cleft

Answer 13

external auditory meatus

Question 14

2nd-4th clefts

Answer 14

temporary cervical sinuses

obliterated by proliferation of 2nd arch mesenchyme

Question 15

persistent 2nd-4th clefts

Answer 15

persistent cervical sinus
branchial cleft cyst within lateral neck, doesn’t move
versus thyroglossal cysts - midline and moves with swallowing

Question 16

branchial 1st arch

Answer 16

M+T+chew
CARTILAGE - meckel cartilage: mandible, malleus, incus, spheno-mandibular ligament
MUSCLE - muscles of mastication (temporalis, massester, lateral and medial pterygoids), mylohyoid, anterior belly of digastric, tensor tympani, tensor veli palatini
NERVES - CN V2 and V3

Question 17

branchial 2nd arch

Answer 17

S+smile
CARTILAGE - reichert cartilage: stapes, styloid process, lesser horn of hyoid, stylohyoid ligament
MUSCLE - muscles of facial expression, stapedius, stylohyoid, platysma, posterior belly of digastric
NERVES - CN VII (facial expression)

Question 18

branchial 3rd arch

Answer 18

pharynx+ swallow stylishly
CARTILAGE - greater horn of hyoid
MUSCLE - stylopharyngeus (innervated by glossopharyngeal nerve)
NERVES - CN IX

Question 19

branchial 4+6th arch

Answer 19

cricothyroid+ larynx+ simply swallow + speak
CARTILAGE - thyroid, cricoid, arytenoids, corniculate, cuneiform
MUSCLE - 4th: most pharyngeal constrictors, cricothyroid, levator veli palatini; 6th: all intrinsic muscles of larynx except cricothyroid
NERVES - 4th: CN X (superior laryngeal branch); 6th: CN X (recurrent laryngeal branch)

Question 20

Treacher Collins syndrome

Answer 20

1st arch neural crest fails to migrate -> mandibular hypoplasia, facial abnormalities

Question 21

Congential pharyngocutaneous fistula

Answer 21

persistence of cleft (2nd/3rd) and pouch -> fistula between tonsilar area and lateral neck

Question 22

posterior third tongue make up

Answer 22

arches 3 and 4

Question 23

branchial 5th arch

Answer 23

no major developmental contributions

Question 24

branchial 1st pouch

Answer 24

develops into middle ear cavity, eustachian tube, mastoid air cells
contributes to endoderm lined structures of ear

Question 25

branchial 2nd pouch

Answer 25

develops into epithelial lining of palatine tonsil

Question 26

branchial 3rd pouch

Answer 26

dorsal wings - develop into inferior parathyroids
ventral wings - develop into thymus
3rd pouch contributes to 3 structures

Question 27

branchial 4th pouch

Answer 27

dorsal wings - develop into superior parathyroids

Question 28

mnemonic for branchial pouches

Answer 28

ears, tonsils, bottom to top

1) ear
2) tonsils
3) dorsal bottom for inferior parathyroids
3) ventral (to=thymus)
4) top=superior parathyroids)