Development of the Branchial Arches or Pharyngeal Arches Flashcards
what does folding of the embryonic disc allow
part of the yolk sac gets absorbed within the embryo and leaves a part outside the embryo which disintegrates
what does the absorbed part of the yolk sac develop into
the digestive tract and the respiratory tract
what does the endoderm lining the yolk sac form
the lining epithelium of these two tracts
cephalic part of the primitive gut
pharynx
extends from oropharyngeal membrane to tracheobronchial diverticulum
adult pharynx is a common passage for both
air and food
pharyngeal arches
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
formation and patterning of pharyngeal arches is from
sonic hedge hog gene and the homeobox gene
pharyngeal (branchial) apparatus
composed of branchial clefts, arches, and pouches
clefts: from ectoderm
arches: from mesoderm and neural crests
pouches: from endoderm
CAP covers
outside form inside
branchial arches
six pairs of arches
5th pair disappear
responsible for:
face, neck, definitive mouth, pharynx, larynx
what is in each branchial arch
a cartilaginous rod
a nerve
muscle tissue
an artery
aortic arch artery within each arch runs
from the aortic sac ventrally to the dorsal aorta on the left and right sides
branchial arch 1 (mandibular) arch derivatives
meckel’s cartilage
muscles
nerves
branchial arch 1 (mandibular) arch derivatives: meckel’s cartilage
mandible, middle ear ossicles - malleus, incus, sphenomandibular
branchial arch 1 (mandibular) arch derivatives: muscles
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
branchial arch 1 (mandibular) arch derivatives: nerve
mandibular N (third division of the trigeminal nerve or cranial nerve V)
derivatives of the 2nd pharyngeal arch
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)
derivatives of the 3rd pharyngeal
ventral part: greater cornua and lower part of the body of the hyoid bone
stylopharyngeus muscle
nerve - CN-IX
derivatives of 4th and 6th arches
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)
what arches form posterior 1/3 of tongue
3 and 4
derivatives of the pouches
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)
pharyngeal clefts (grooves)
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
what forms the tympanic membrane
a membrane in the first pharyngeal pouch between the endoderm of the pouch and the ectoderm of the groove
cervical sinus, cyst & fistula formation
failure of obliteration of the pharyngeal grooves
sinus
small opening with mucoid discharge
opens anterior to sternocleidomastoid, common in lower third
cyst
painless swelling
lies anterior to the sternocleidomastoid
sometimes close to the angle of the mandible
fistula
canal opens internally to the tonsillar sinus and externally in the side of the neck
