H&N Development of the Nose & Face

Question 1

What are the pharyngeal (branchial) arches?

Answer 1

Sequence of ridges
Form in lateral walls of embryonic pharynx
Bulge into lumen of pharynx & onto outside of future face & neck regions

Question 2

What are the pharyngeal arches covered by?

Answer 2

Externally - ectoderm

Internally - endoderm

Question 3

How many pharnygeal arches are there?

Answer 3

5

1-6 but the 5th disappears & merges with the 4th

Question 4

What are the pharnygeal clefts (grooves) and pouches?

Answer 4

Pharyngeal clefts separate the pharyngeal arches on the outside (ectoderm)
Pharyngeal pouches separate them on the inside (endoderm)

Question 5

What is the cervical sinus?

Answer 5

1st & 2nd Ph arch are largest
2nd grows down to cover arches 3-6 creating a space - cervical sinus
Usually obliterated, remnants are branchial cysts

Question 6

What does each pharyngeal arch contain?

Answer 6

Artery
Vein
Cranial nerve
Mesenchyme

Question 7

The mesenchyme in each Ph arch is of mixed origin. What are these origins and what will they become?

Answer 7

Some mesodermal origin
Most from neural crest cells (migrate into arches from developing nervous system)
Mesoderm becomes muscles
Neural crest cells becomes bone & cartilage

Question 8

Which part of the neural tube forms the brain?

Answer 8

Anterior end
Prosencephalon - Forebrain
Mesencephalon - Midbrain
Rhombencephalon - Hindbrain

Question 9

What are the nerves of the pharyngeal arches?

Answer 9

1st Ph Arch - CN V Trigeminal
2nd Ph Arch - CN VII Facial
3rd Ph Arch - CN IX Glossopharyngeal
4th & 6th Ph Arches - CN X Vagus
 - 4th - Superior Laryngeal 
 - 6th - Recurrent Laryngeal

Question 10

What muscles arise from the 1st Ph Arch?

Answer 10

Muscles of mastication

Muscles of mandibular process - digastric, mylohyoid

Question 11

What muscles arise from the 2nd Ph Arch?

Answer 11

Muscles of facial expression

Stapedius

Question 12

What muscle arises from the 3rd Ph Arch?

Answer 12

Stylopharyngeus

Question 13

What muscles arise from the 4th Ph Arch?

Answer 13

Cricothyroid

Constrictors of pharynx

Question 14

What muscles arise from the 6th Ph Arch?

Answer 14

Intrinsic muscles of larynx

Question 15

What arteries arise from the branchial arches?

Answer 15

1st & 2nd aortic arch disappear
3rd - ICA
4th - Arch of aorta & R Brachiocephalic
6th - Pulmonary arteries

Question 16

Where does the facial skeleton arise from?

Answer 16

FNP

1st Ph Arch

Question 17

What skeletal elements arise from the 1st Ph Arch?

Answer 17

Meckel’s cartilage
Mandibular prominence (Meckel’s)
Malleus & Incus
Template for mandible (membranous ossification)

Question 18

What skeletal elements arise from the 2nd Ph Arch?

Answer 18

Reichert’s cartilage
Stapes
Styloid process of skull
Hyoid bone (upper)

Question 19

What skeletal elements arise from the 3rd Ph Arch?

Answer 19

Hyoid bone (lower)

Question 20

What skeletal elements arise from the 4th-6th Ph Arches?

Answer 20

Epiglottis

Laryngeal cartilages - Thyroid, Cricoid, Arytenoid

Question 21

How many Ph pouches are there?

Answer 21

4 pairs

Question 22

What does the 1st Ph pouch become?

Answer 22

Eustachian tube

Middle ear cavity

Question 23

What does the 2nd Ph pouch become?

Answer 23

Crypts of palatine tonsil

Question 24

What does the 3rd Ph pouch become?

Answer 24

Dorsal part - Inferior parathyroid

Ventral part - Thymus

Question 25

What does the 4th Ph pouch become?

Answer 25

Dorsal part - Superior parathyroid

Ventral part - Thyroid C cells

Question 26

How is the middle ear developed?

Answer 26

Ossicles
- Cartilage bar derivatives (Meckel’s/Reichert’s)
Tympanic cavity & Auditory tube
- 1st Ph pouch derivatives

Question 27

Which Ph clefts remain?

Answer 27

1st cleft only

2nd arch grows down to cover others

Question 28

What are branchial cysts?

Answer 28

Remnants of cervical sinus (not fully obliterated)
Cysts/fistulae can occur
Anywhere along ant border of SCM