Embryology of the head and neck

Question 1

Describe the differences in the mesoderm found in the Trunk and in the head.

Answer 1

T:
Segmental nature
somites
derivatives

H:
Occipital somites
Pre-otic/auricular/orbital mesoderm
mesoderm brachial arches

Question 2

Which structures do the neural crest cells produce?

Answer 2

Cranial and sensory ganglia and nerves
Adrenal medulla
Melanocytes
Phyrangeal pouch cartilage
meninges
bulbar and conal ridges
cranial mesenchyme

Question 3

Which gene controls the neural crest migration to the pharyngeal pouches?

Answer 3

Hox

Question 4

Which structures make up the pharyngeal arches?

Answer 4

Striated muscle
cartilage
artery
nerve

Question 5

Which structures arise from pharyngeal arch 1?

Answer 5

maxilla
mandible
squamous temporal
malleus and incus

mastication
mylohyoid
anterior digastric
Tensor tympani
Tensor veli palatini

Trigenimal nerve
External carotid artery, maxillary artery.

Question 6

Which structures arise from pharyngeal arch 2?

Answer 6

Stapes
styloid process
lesser horn and body of hyoid

facial expression
stapedius
stylohyoid
posterior digastric

facial nerve and stapedial aa

Question 7

Which structures arise from the pharyngeal arch 3?

Answer 7

greater horn and body of hyoid
stylopharyngeus

Glossophyrangeal
Common carotid

Question 8

Which structures arise from pharyngeal arch 4 and 6?

Answer 8

larynx
pharynx
levator of palate
oesophagus
Vagus
Right subclavian

Question 9

Which structures arise from pharyngeal arch 5?

Answer 9

Rudimentary, haha!

Question 10

What is form by pouch 1?

Answer 10

Eustachian tube

Question 11

What form by pouch 2?

Answer 11

palatine tonsils

Question 12

What form by pouch 3?

Answer 12

upper derivative forms thymus
and lower forms inferior parathyroid

Question 13

What form by pouch 4?

Answer 13

Superior parathyroid
C cells of thyroid

Question 14

What form by pouch 5?

Answer 14

c cells of the thyroid gland

Question 15

Explain the development of the 2nd cleft.

Answer 15

Downward growth covering arches 2-4.
Forms the platysma muscle.

initially forms the sinus of his when the arch combines with the third and fourth cleft.
Eventually forms the cervical sinus

Question 16

Describe the development of the thyroid gland.

Answer 16

originates between the 1st and 2nd pharyngeal pouches near the base of the tongue.
it then descends through the foramen cecum of the tongue to its position by the larynx forming a thyroglossal duct.
The duct will close.

Question 17

Describe the development of the parathyroid gland.

Answer 17

3rd pouch gives rise to the inferior parathyroid and the 4th pouch gives rise to the superior parathyroid.
Both of them descend from to the thyroid, however, the inferior parathyroid descends further hence it is lower than the superior parathyroid pouch

Question 18

Describe the development of the tongue.

Answer 18

Anterior part 2/3 develops from the first arch
There is lateral and medial (tuberculum impar) lingual swelling
the lateral swelling fuses and forms the median sulcus.
forming the fungiform posterior and the filiform and foliate more anteriorly

posterior part 1/3 from the 3rd arch
A hypopharyngeal eminence component forms
this grows up forming a terminal sulcus, which is prominent after fusion.
There is an outgrowth of circumvallate papillae.
they migrate forward into the fungiform region, which drags the nerve supply with them.

Question 19

Describe the development of the face.

Answer 19

Frontonasal prominence
- nasal placode- gives rise to the nasolateral process and nasomedial process. This then undergoes merging. A nasolacrimal groove also forms that houses the tear ducts.

Maxillary and mandibular prominences
the processes fuse across the midlines.
then it approaches the frontonasal process (ascends)

the external acoustic meatus also develops inferior and then ascends to its position.

Question 20

Describe the development of the hard palate.

Answer 20

Primary palate- median palatine process from the intermaxillary segment of the maxilla
Secondary- 2 lateral palatine process- maxillary prominences
Elevates
horizontal growth
once the tongue becomes smaller and moves inferiorly there is midline contact and eventually fusion.