Friday 5 - Ach - Embryology of head and neck

Question 1

Where, embryologically, do the maxillary prominence and the mandibular prominence come from?

Answer 1

The first pharyneal arches

Question 2

what pharyndeal arch never developes and dissapears

Answer 2

5 (pouch 5 disappears too)

Question 3

what are the pharyngeal pouches made of?

Answer 3

endoderm. (epithelial endoderm……..)

they are part of the developing gut

Question 4

where does the only permanent pharyngeal membrane form in human development

Answer 4

between the 1st and 2nd arch

Question 5

do the pharyngeal arches develope to form neurocranium or viscerocranium?

Answer 5

viscerocranium.

Question 6

where does the mesoderm come from that goes into the pharyngeal arches

Answer 6

the somites and somitomeres

Question 7

Tounge precursor mesoderm comes from what somite

Answer 7

occipital somites

Question 8

Do neural crest cells move in to the phar. arches?

what do they become

Answer 8

yup

become mesenchyme

Question 9

somite and somitomere migration to the pharyngeal arches

vs

neural crest cell migration to phar. arches

Answer 9

somites and somitomeres-

more nonspecific migration
from mesoderm

NCC-

very specific migration to form mesenchyme (this mesenchyme is special because it is not formed from mesoderm, but rather ectoderm, because neural crest cells are formed from ectoderm)

Question 10

*arches and the cranial nerves assoc.

1
2
3
4
6

Answer 10

1. CN V - trigem
2. CN VII - facial
3. CN IX - glossopharyngeal
4. CN X - vagus
5. CN X - vagus

Question 11

what is the muscle derived from the 3rd pharyngeal arch

Answer 11

stylopharygeus

Question 12

bones derived from the first phar. arch

Answer 12

maxilla
zygomatic
squamous part of temporal bone

(intramembranous ossification)

Question 13

Meckel’s cartilage

where
what does it become

Answer 13

Developes within the first pharyngeal arch,

posterior portion becomes malleus and incus

anterior part becomes the ligament of the malleus, spine of the sphenoid bone, and the spheno-mandibular ligament (attaches at the lingula) AND the cartilaginous core of the mandible

Question 14

Muscles supplied by V3

come from which arch

Answer 14

Tense tense chew chew

tensor tympani
tensor veli palatini

all muscles of mastication

frist pharyngeal arch

Question 15

Treacher collins syndrome general

Answer 15

definiency of neural crest cells migrating into the first arch

mandibulofacial dysostosis

eyelid malformation, hypoplastic (flat) cheek and jaw, “fish mouth” appearence

Question 16

pierre robin syndrome general

Answer 16

deficiency of neural crest cells migrating into the arch

small jaw (micrognathia), large, posteriorly placed tounge leading to cleft pallate (soft palate)

Question 17

skeletal derivs from second arch

Answer 17

Reichert’s cartilage-

stapes
styloid process
stylohyoid ligament
lesser cornu of the hyoid bone
upper body of the hyoid bone

Question 18

nerves of second arch and what muscles they innervate

Answer 18

facial nerve

muscles of facial expression
posterior belly of digastric
stylohyoid
stapedius

Question 19

Goldenhar syndrome

Answer 19

1st and 2nd arch syndrome

hypoplastic maxilla, mandible, and temporal bone usually unilaterally

Question 20

skeletal derivs of the third arch

Answer 20

lower body of hyoid

greater cornu of the hyoid bone

Question 21

nerve of third arch, what muscle(s) does it innervate?

Answer 21

glossopharyngeal

only muscle it goes to is the stylopharyngeus

Question 22

skeletal derivatives of the fourth and sixth arches

Answer 22

thyroid cartilage
cricoid cartilatge
arytenoid cartilage

other small laryngeal cartilages

Question 23

what branch of the vagus nerve comes out of the fourth phary. arch

what does it do

Answer 23

superior laryngeal,

carries sensation from the above the vocal folds

supplies muscles of the soft palate (except for tensor veli palatini (V3))

supplies muscles of the pharynx (except stylopharyngeus (glossopharyngeal))

Question 24

sixth arch what branch of vagus comes out of it

what does it do

Answer 24

recurrent laryngeal branch of vagus

innervates intrinsic muscles of larynx (except cricothyroid)

sensation for larynx below the vocal folds

Question 25

First pharyngeal pouch

becomes

Answer 25

tubotympanic recess becomes epithelial lining of:

auditory tube

tympanic or middle ear cavity

mastoid air cells

Question 26

second pharyngeal pouch

becomes

Answer 26

epithelial component of the palatine tonsils

Question 27

Third pharyngeal pouch

becomes

Answer 27

Thymus (ventral part of third pouch)

inferior parathyroid glands (dorsal part of third arch)

Question 28

fourth pharyngeal pouch becomes

Answer 28

parafollicular cells of thyroid (c cells)

superior parathyroid glands (dorsal)

Question 29

the parathyroid glands from the third pouch develop and move _________ to the parathyroid glands of the fourth pouch

Answer 29

caudally (this makes there position variable apparently…)

Question 30

ectopic

Answer 30

somewhere where something is not normally found

Question 31

DiGeorge Syndrome

Answer 31

no thymus or parathyroids resulting in diminished immunity, hypocalcemia

Question 32

What does the first pharyngeal membrane become

Answer 32

tympanic membrane

Question 33

how does the cervical sinus come about?

what is it lined with

what happens if it doesn’t dissapear

Answer 33

overgrowth of 2nd arch across the 3rd and 4th clefts leads to this sinus

lined with endothelial cells

lateral cervical cists if it doesn’t disappear

Question 34

how does the thyroid develop

Answer 34

evagination of the the endoderm from the floor of the pharynx between 1st and 2nd pouch (call thyroid diverticulum)

Question 35

two things that come together to form the thyroid

Answer 35

thyroid diverticulum -> follicular cells of thyroid

4th pharyngeal pouch -> ultimobranchial body -> parafollicular (C) cells

Question 36

if you see an adult with a mass in their neck it is what until proven otherwise

in a child?

Answer 36

adult - cancer

child - developmental abnormality

Question 37

branchial vs thyroglossal cyst

Answer 37

branchial - lateral neck

thyroglossal cyrst - middle neck

Question 38

anterior 2/3rds of toung come from

posterior

Answer 38

1st pharyngeal arch

3rd pharyngeal arch

Question 39

what forms the intrinsic muscles of the tounge

Answer 39

occipital myotomes

Question 40

what muscle of the tounge is not supplied by the hypoglossal nerve

Answer 40

palatoglossal (vagus)

Question 41

ankyloglossia

Answer 41

tounge tied (lingual frenulum is still attached)