Embryology of head and neck

Question 0

Paraxial mesoderm (somites and somitomeres) forms the majority of what 4 things?

Answer 0

Membranous and cartilaginous parts of the neurocranium
All voluntary muscles of the craniofacial region
Dermis and CTs in dorsal region of head
Meninges caudal to the prosencephalon (forebrain)

Question 1

Mesenchyme for formation of the head region is derived from what 4 things?

Answer 1

neural crest cells
ectodermal placddes
paraxial mesoderm
lateral plate mesoderm

Question 2

Lateral plate mesoderm forms what?

Answer 2

Laryngeal cartilages and CT in this region

Question 3

Neural crest cells form what million things?

Answer 3

entire viscerocranium, part of neurocranium, bone, cartilage, tendons, dermis, pia mater, arachnoid mater, sensory neurons, glandular CT, dentin

Question 4

Ectodermal placodes form what?

Answer 4

neurons of the 5th, 7th, 9th, 10th cranial sensory ganglia

Question 5

When do the pharyngeal arches appear?

Answer 5

In the 4th and 5th weeks of development

Question 6

Pharyngeal arches begin to develop as _____________ and migrate from ___________

Answer 6

neural crest cells

hindbrain

Question 7

The pharyngeal arches support the lateral walls of the _________

Answer 7

primordial pharynx

Question 8

which arch completely regresses and forms nothing?

Answer 8

5th

Question 9

The pharyngeal arches have what 4 components?

Answer 9

1 Pharyngeal arch artery that arises from the truncus arteriosus and runs around the pharynx to enter the dorsal aorta
2 Cartilaginous rod that forms the skeleton
3 Muscular component
4 Cranial nerve that supplies the mucosa and muscles derived from the arch

Question 10

Cartilage/bones and ligaments from 1st arch?

Answer 10

Meckel’s cartilage (provides template for mandible development)
Malleus and Incus (also from Meckel’s)
Anterior ligament of the malleus
Sphenomandibular ligaments

Question 11

Cartilage/bones and ligaments by 2nd arch?

Answer 11

Reichert cartilage provides a template for:

Stapes, styloid process, lesser cornu of hyoid, upper part of body of hyoid, stylohyoid ligament

Question 12

Cartilage/bones and ligaments by 3rd arch?

Answer 12

Greater cornu of hyoid

Lower part of body of hyoid

Question 13

Bones/cartilage and ligaments of 4th and 6th?

Answer 13

Thyroid cartilage
Cricoid cartilage
Arytenoid cartilage
Corniculate cartilage
Cuneiform cartilage

Question 14

Muscles and cranial nerves 1st arch

Answer 14

V2 & V3
Muscles of mastication
Anterior belly of digastric
Mylohyoid
Tensor tympani
Tensor veli palatini

Question 15

Muscles and nerves of 2nd arch?

Answer 15

CN VII
Mimetic
Stapedius
Posterior belly of digastric
Stylohyoid

Question 16

Muscles/nerves in 3rd arch?

Answer 16

CN IX

stylopharyngeus

Question 17

Muscles/nerves from 4th arch?

Answer 17

Superior laryngeal branch of X
Muscles of soft palate (except tensor veli palatini)
Muscles of pharynx (except stylopharyngeus)
Cricothyroid and cricopharyngeus

Question 18

Muscles/nerves from 6th arch?

Answer 18

Recurrent laryngeal nerve from X
Intrinsic muscles of larynx (except cricothyroid)
Striated muscles of esophagus

Question 19

1st arch arteries?

Answer 19

disappear but remnants form

maxillary arteries

Question 20

2nd arch arteries

Answer 20

disappear but remnants form

Hyoid and stapedial arteries

Question 21

3rd arch arteries

Answer 21

common carotid arteries

1st part of internal carotid arteries

Question 22

left 4th arch arteries

Answer 22

arch of aorta from left common carotid to left subclavian

Question 23

right 4th arch arteries

Answer 23

right subclavian (proximal portion)

Question 24

Remainder of internal carotid arteries?

Answer 24

dorsal aorta

Question 25

external carotid arteries

Answer 25

sprout from 3rd aortic arch

Question 26

Proximal arch of aorta and brachiocephalic artery?

Answer 26

aortic sac

Question 27

Distal right subclavian and left subclavian

Answer 27

7th intersegmental arteries

Question 28

There are ___ paired pharyngeal pouches that develop in a _________ sequence between the arches

Answer 28

4 | craniocaudal

Question 29

Pharyngeal membranes are formed by what?

Answer 29

Endoderm of pouches and ectoderm of pharyngeal grooves

Question 30

The 1st pharyngeal pouch gives rise to what

Answer 30

Tubotympanic recess - tympanic cavity and mastoid antrum

Question 31

Connection of tubotympanic and pharynx forms what?

Answer 31

Auditory tube

Question 32

2nd pharyngeal pouch

Answer 32

palatine tonsil | portion will remain as tonsilar fossa

Question 33

3rd pharyngeal pouch

Answer 33

``` Inferior parathyroid glands (solid dorsal portion) Thymus gland (hollow ventral portion) ```

Question 34

4th pharyngeal pouch

Answer 34

``` Superior parathyroid gland (each bulbar dorsal portion) Ultimopharyngeal body (hollow ventral portion) ```

Question 35

Fusion of the ultimopharyngeal body and thyroid gland gives rise to

Answer 35

``` parafollicular cells (C cells) of thyroid gland calcitonin producing ```

Question 36

5th pharyngeal pouch

Answer 36

rudimentary and becomes part of 4th

Question 37

There are ____ pharyngeal grooves that from during the _____________ weeks

Answer 37

4 | 4th and 5th

Question 38

The pharyngeal grooves separate what? Are invaginations of what?

Answer 38

Pharyngeal arches externally | Ectoderm

Question 39

Which is the only groove that persists? What does it give rise to?

Answer 39

Pharyngeal groove 1 | external acoustic meatus

Question 40

What happens to the other grooves?

Answer 40

lie in slit like depression known as the cervical sinus

Question 41

Pharyngeal membranes form where? Which one survives and what does it become?

Answer 41

Found between pharyngeal arches | Pharyngeal membrane 1 becomes the tympanic membrane

Question 42

Mandibulofacial dystostosis ?

Answer 42

Defective migration or proliferation of neural crest cells | caused by underdevelopment of 1st and 2nd pharyngeal arches

Question 43

Treacher-Collins and Pierre Robin syndromes?

Answer 43

Congenital malformations of eyes, ears, mandible and palate | 1st arch

Question 44

DiGeorge syndrome

Answer 44

Caused by abnormalities of neural crest cell migration and proliferation while 3rd & 4th pharyngeal arches develop. (1) minor craniofacial defects including micrognathia, low set ears, auricular abnormalities, and cleft palate (2) total or partial agenesis of the derivatives of the 3rd & 4th pharyngeal pouches (thymus & parathyroid glands) (3) cardiovascular defects. This syndrome is associated with partial monosomy of chromosome 22 but is also seen with children of alcoholic women

Question 45

Which glands are highly variable in number and location?

Answer 45

parathyroid (2-6)

Question 46

A remnant of the thyroglossal duct may persist and form the

Answer 46

Thyroglossal duct cyst in the tongue or even the anterior portion of the neck usually just below the hyoid infection = thyroglossal duct sinus

Question 47

ankyloglossia

Answer 47

tongue tie | frenulum is too short but will stretch with time

Question 48

Clefts of the anterior palate

Answer 48

Lateral palatine processes don't meet and fuse with the primary palate

Question 49

Clefts of posterior palate

Answer 49

lateral palatine processes don't meet and fuse with each other and with the nasal septum

Question 50

Clefts of the anterior and posterior parts of the palate

Answer 50

lateral palatine processes don't meet with primary palate, each other, or nasal septum

Question 51

Coloboma of the iris

Answer 51

Defect in the inferior sector of the iris or the pupillary margin gives the pupil a keyhole appearance Failure of closure of the retinal fissure during the 6th week