Development of the Branchial Arches or Pharyngeal Arches

Question 1

what does folding of the embryonic disc allow

Answer 1

part of the yolk sac gets absorbed within the embryo and leaves a part outside the embryo which disintegrates

Question 2

what does the absorbed part of the yolk sac develop into

Answer 2

the digestive tract and the respiratory tract

Question 3

what does the endoderm lining the yolk sac form

Answer 3

the lining epithelium of these two tracts

Question 4

cephalic part of the primitive gut

Answer 4

pharynx
extends from oropharyngeal membrane to tracheobronchial diverticulum

Question 5

adult pharynx is a common passage for both

Answer 5

air and food

Question 6

pharyngeal arches

Answer 6

4th week
neural crest cells migrate to future head
first pair appears lateral to developing pharynx
4 pharyngeal arches are visible, 5th and 6th are still rudimentary

Question 7

formation and patterning of pharyngeal arches is from

Answer 7

sonic hedge hog gene and the homeobox gene

Question 8

pharyngeal (branchial) apparatus

Answer 8

composed of branchial clefts, arches, and pouches
clefts: from ectoderm
arches: from mesoderm and neural crests
pouches: from endoderm

Question 9

CAP covers

Answer 9

outside form inside

Question 10

branchial arches

Answer 10

six pairs of arches
5th pair disappear
responsible for:
face, neck, definitive mouth, pharynx, larynx

Question 11

what is in each branchial arch

Answer 11

a cartilaginous rod
a nerve
muscle tissue
an artery

Question 12

aortic arch artery within each arch runs

Answer 12

from the aortic sac ventrally to the dorsal aorta on the left and right sides

Question 13

branchial arch 1 (mandibular) arch derivatives

Answer 13

meckel’s cartilage
muscles
nerves

Question 14

branchial arch 1 (mandibular) arch derivatives: meckel’s cartilage

Answer 14

mandible, middle ear ossicles - malleus, incus, sphenomandibular

Question 15

branchial arch 1 (mandibular) arch derivatives: muscles

Answer 15

muscles of mastication (temporalis, massester, lateral and medial pterygoids
floor of the mouth muscles: myelohyoid, anterior belly of digastric
tensor tympani, tensor palati and anterior 2/3 of tongue

Question 16

branchial arch 1 (mandibular) arch derivatives: nerve

Answer 16

mandibular N (third division of the trigeminal nerve or cranial nerve V)

Question 17

derivatives of the 2nd pharyngeal arch

Answer 17

reichert’s cartilage: stapes, styloid process of the temporal bone, lesser horn of hyoid, stylohyoid ligament

muscles: muscles of facial expression, stapedius, stylohyoid ligament, posterior belly of digastric

nerve: CN VII (facial)

Question 18

derivatives of the 3rd pharyngeal

Answer 18

ventral part: greater cornua and lower part of the body of the hyoid bone
stylopharyngeus muscle
nerve - CN-IX

Question 19

derivatives of 4th and 6th arches

Answer 19

laryngeal cartilages: thyroid, cricoid, arytenoids, corniculate, cuneiform
muscles (4th arch): 3 constrictors of the pharynx (superior, middle and inferior), cricothyroid, levator palati
muscles (6th arch): all intrinsic muscles of larynx except cricothyroid
nerves: 4th - CN X (superior laryngeal branch) 6th - CN X (recurrent laryngeal branch)

Question 20

what arches form posterior 1/3 of tongue

Answer 20

3 and 4

Question 21

derivatives of the pouches

Answer 21

first pouch: mastoid air cells, auditory tube, middle ear cavity
second pouch: palatine tonsil
third pouch: dorsal - parathyroid gland III (inferior), ventral - thymus
fourth pouch: parathyroid IV (superior)

Question 22

pharyngeal clefts (grooves)

Answer 22

first cleft: dorsal part - forms the external auditory meatus
second, third, fourth clefts: loose contact with the surface, form a cavity called cervical sinus and later disappears

Question 23

what forms the tympanic membrane

Answer 23

a membrane in the first pharyngeal pouch between the endoderm of the pouch and the ectoderm of the groove

Question 24

cervical sinus, cyst & fistula formation

Answer 24

failure of obliteration of the pharyngeal grooves

Question 25

sinus

Answer 25

small opening with mucoid discharge

opens anterior to sternocleidomastoid, common in lower third

Question 26

cyst

Answer 26

painless swelling
lies anterior to the sternocleidomastoid
sometimes close to the angle of the mandible

Question 27

fistula

Answer 27

canal opens internally to the tonsillar sinus and externally in the side of the neck