head and neck development

Question 1

three layers of embryo at day 17

Answer 1

ectoderm, mesoderm, endoderm going from the outside to the inside

Question 2

prosencephalic organizing center and rhombencephalic organizing center

Answer 2

they are important signaling centers to tell how to form the brain and face and ear

Question 3

olfactory plactodes and the frontonasal process (frontal) prominence

Answer 3

they are paired thickening of ectoderm and associatex with the telencephalon, forebrain
frontonasal process (frontal) prominence- condensed mesenchyme

Question 4

pharyngeal arches and grooves (clefts)

Answer 4

they are the ridges that form behind the frontonasal prominence
*mesenchyme condensations
*5 pairs
*usually 3 pairs are actually visible
*only the first arch has subdivisions
they make the outside of the pharynx
the grooves are the indentations between each of the arches there are usually only 2-3 that are visible. The floor of the groove is the pharyngeal membrane (closing plate) what ends the pharynx

Question 5

pharyngeal pouches

Answer 5

they are little lateral dilations of the pharynx that are between the pharyngeal arches and on the opposite side of the pharyngeal grooves
interface between the groove and the pouch is the pharyngeal membrane
so groove is on the outside and pouches are on the inside

Question 6

oral cavity

Answer 6

boundaries: Caudal- cardiac bulge
cranial-frontonasal prominence
lateral- first phayrngeal arch
posterior-oropharyngeal membrane

Question 7

origin of the pharyngeal arch mesenchyme

Answer 7

paraxial mesoderm: head mesoderm or occipital somites

neural crest: ectoderm majority

Question 8

pharyngeal arch basic components

Answer 8

core of condensed mesenchyme-becomes cartilage
loose mesenchyme-becomes connective tissue
head mesoderm-becomes skeletal muscle
a pharyngeal arch artery- aortic arch
a cranial nerve-becomes a cranial nerve

Question 9

what the pharyngeal arches 1234and6 become

Answer 9

1- malleus and incus, anterior ligament of malleus and sphenomandibular ligament
2- stapes, styloid process and stylohyoid ligament
3-hyoid bone
4 and 6-thyrod and circoid cartilage

they also become bones and muscles in the skull and face
1- muscles of mastication
2- facial expression and sup strap
3-stylopharyngeus
4+6- pharyngeal/ larynx muscles

Question 10

arches- cranial nerves

Answer 10

1- V
2-VII
3-IX
4-X sup laryngeal
6-X inf laryngeal (recurrent laryngeal)

Question 11

first groove remains as the…

Answer 11

external autidory meatus

Question 12

pharyngeal grooves incomplete

Answer 12

causes a hole that leaks in childhood or a really large lump

Question 13

persistence of pharyngeal groove findings

Answer 13

1st cleft duplication
persistent cervical sinus (blind pouch)
cervical fistula- just an epitheleal tube that goes all the way to pharynx
cervical cyst

the openings are always lateral

Question 14

derivatives of pharyngeal endoderm

Answer 14

thyroid gland, thymus gland, parathyroid gland, lining of middle ear, epithelia of palatine tonsil, epithelium of pharynx

Question 15

fate of the pharyngeal pouches

Answer 15

1- middle ear cavity and inner tympanic mem
2- palatine tonsil
3+4= parathyroid glands
thymus and thyroid

Question 16

chromosome 22q11.2, digeorge syndrome

Answer 16

mandible and ear issues

Question 17

stromodeum

Answer 17

opening of the mouth

Question 18

three parts of the developing face

Answer 18

frontonasal prominence, maxillary prominence, mandibular prominence

Question 19

during 5-7 weeks what happens to the frontonasal prominence

Answer 19

there is a formation of the lateral and medial nasal prominences and the lateral nasal prominence merges with the maxillary prominence and frontonasal prominence. The two medial nasal prominences come together to form a intermaxillary segment- this forms the middle part of the upper lip, the incisor bridge of maxilla and the primary palate

Question 20

choanal atresia

Answer 20

absence of nasal choanae- the hole that connects the primitive nostril to the nasopharynx

Question 21

the human palate has two parts

Answer 21

primary- triangle
secondary-the actual palate
the tongue has to move down to get out of the way for the palate to fuse correctly