Pharyngeal and Craniofacial Development

Question 1

Pharyngeal arches

Answer 1

Appear between weeks 4 and 5
Consist of bars of mesenchymal tissues surrounded by endoderm on the inside, and ectoderm on the outside
The bars are separated by deep clefts

Question 2

Pharyngeal cleft

Answer 2

Separates the pharyngeal arches

Question 3

Otic placode

Answer 3

Forms part of the external ear

Question 4

Cranial neuropore

Answer 4

Open neural tube at the anterior end of the embryo

Question 5

4 components of the pharyngeal arches

Answer 5

Aortic arch
Cartilaginous rod
Muscular element (forms muscles of head/neck region)
Nerves (innervate the mucosa and muscles of the arch - crest cell derived)

Question 6

Aortic arch

Answer 6

Artery that arises from the truncus arteriosus (primordial heart structure) and runs around the (primordial) pharynx to enter the dorsal aorta

Question 7

Cartilaginous rod of the pharyngeal arch

Answer 7

Gives rise to the skeleton of the arch

From the migrating crainal crest

Question 8

4 components of the pharyngeal apparatus

Answer 8

Pharyngeal arches
Pouches
Grooves
Membranes (endoderm and ectoderm)

Question 9

Stomadeum

Answer 9

Primitive mouth

Question 10

How many arches are there?

Answer 10

5
But they are names 1, 2, 3, 4, and 6
“5th” one is part of thyroid

Question 11

Mesenchyme for the pharyngeal apparatus comes from…

Answer 11

Paraxial (mostly) and lateral plate mesoderm

Gives rise to muscular component of the face

Question 12

The core of each arch receives ___ which contributes to ___

Answer 12

Neural crest

Skeletal components of the face, including the cartilage components

Question 13

Somatic mesoderm is also called….

Answer 13

Paraxial mesoderm

Question 14

Each pharyngeal arch consists of a core of ___ mesoderm and ___ mesenchyme. What do each of them give rise to?

Answer 14

Somatic mesoderm core: arch artery and skeletal muscle tissue
Neural crest mesenchyme: develops into bone, cartilage, and/or connective tissue in each arch

Question 15

What cranial nerve is associated with each different arch?

Answer 15

1. Trigeminal (V)
2. Facial (VII)
3. Glossopharyngeal (IX)
4. Superior laryngeal branch of the vagus (X)
5. Recurrent laryngeal branch of the vagus (X)

Question 16

Since there are 5 pharyngeal arches, there are __ pouches

Answer 16

4

Technically 5, but the last one is atypical and considered part of the 4th pair

Question 17

Skeletal/Cartilage Elements of the arches:
1.
2.
3.
4.
6.

Answer 17

1. Meckel’s cartilage, incus, malleus, zygomatic bone and process, maxilla
2. Styloid process, stapes
3. Hyoid bone
4. Thyroid cartilage
5. Cricoid cartilage

Question 18

Pharyngeal pouches create what

Answer 18

Epithelial endodermal lining of the craniofacial region

Contribute to the formation of glands

Question 19

Pouch derivatives
1.
2.
4.
5.

Answer 19

1. External auditory meatus, primitive tympanic/middle ear cavity, Eustachian tube, eardrum
2. Palantine tonsil and tonsilar fossa
3. Superior parathyroid gland
4. Ultimobranchial body that incorporates into the thyroid gland

Question 20

1st cleft derivatives

Answer 20

Dorsal part of first cleft penetrates underlying mesenchyme and gives rise to external auditory meatus

Question 21

4 mesenchymal prominences you can see at 42 days

Answer 21

1. Mandibular prominence (distal part of 1st arch)
2. Maxillary prominence (proximal potion of 1st arch)
3. Frontonasal prominence
4. Nasal prominences (contain nasal placode)

Question 22

Philtrum

Answer 22

Upper lip

Result of the intermaxillary process from the fusion of the face