Lecture 1 - Development of the H&N

Question 1

What are the pharyngeal arches covered by?

Answer 1

Externally the arches are covered by ectoderm, internally by endoderm.

Question 2

How many branchial arches are there?

Answer 2

Six branchial arches, but fifth is rudimentary and merges with the fourth

Question 3

What are branchial arches separated by on the outside?

Answer 3

Branchial clefs

Question 4

What are branchial arches separated by on the inside?

Answer 4

Branchial pouches

Question 5

What are the largest branchial arches?

Answer 5

1st & 2nd

Question 6

What is inside each branchial arch?

Answer 6

Artery
Vein
Cranial nerve
Mesenchyme (mesodermal/neural crest)

Question 7

What are the three main parts of the brain?

Answer 7

o Prosencephalon – Forebrain
o Mesencephalon – Midbrain
o Rhombencephalon – Hindbrain

Question 8

What are the three main roles of cranial nerves?

Answer 8

Somatic efferent
Special sensory
Nerves of the pharyngeal arches
- Somatic and visceral afferent from skin and mucous membranes
- Visceral motor
- Special visceral motor or branchial motor to striated muscles

Question 9

What are the five cranial nerves of the pharyngeal arches?

Answer 9

Trigeminal nerve (1st)
Facial nerve (2nd)
Glossopharyngeal nerve (3rd)
Vagus nerve (4th and 6th)

Question 10

What arteries are derived from the first three branchial arches?

Answer 10

Common, external and internal carotid arteries and branches

Question 11

What arteries are derived from the fourth branchial arch

Answer 11

Aortic arch

Part of right subclavian artery

Question 12

What arteries are dervived from 6th branchial arch?

Answer 12

Pulmonary arteries

Question 13

What happens to 1st and 2nd arch arteries?

Answer 13

They disappear

Question 14

What happens to the third arch artery?

Answer 14

Becomes internal carotid

Question 15

What happens to 4th arch artery?

Answer 15

Arch of aorta (L) and brachiocephalic (R)

Question 16

What happens to 6th arch artery?

Answer 16

Becomes pulmonary artery

Question 17

What muscles are derived from the first arch?

Innervated by?

Answer 17

Muscles of mastication 
Anterior belly of digastrics
Mylohyoid
Tensor tympani
Tensor palatini

Mandibular branch of the trigeminal nerve

Question 18

What muscles are derived from the 2nd branchial arch?

Innervated by?

Answer 18

Muscles of facial expression
Posterior belly of digastrics
Stylohyoid
Stapedius 
Auricular

Facial nerve

Question 19

What muscles are derived from the 3rd branchial arch?

Answer 19

Stylopharyngeus

Glossopharyngeal nerve

Question 20

What muscles are derived from arches 4-6?

Answer 20

Striated muscle of upper oesophagus 
Cricothyroid
Levator palatini
Constrictors of the pharynx
Intrinsic muscles of the larynx

Superior laryngeal branch of vagus
Recurrent laryngeal branch of vagus

Question 21

What is the facial skeleton made from embryologically speaking, and what arch is it derived from?

Answer 21

The frontal nasal skeleton

1st pharyngeal arch

Question 22

What are the muscles of mastication derived from?

Answer 22

1st pharyngeal arch

Question 23

What are the muscles of facial expression derived from?

Answer 23

2nd pharyngeal arch

Question 24

What skeletal elements are derived from 1st pharyngeal arch

Answer 24

Meckels cartilage

• Mandibular prominence
• Malleus and incus

Question 25

What skeletal elements are derived from 2nd pharyngeal arch?

Answer 25

Rechert’s cartilage

• Stapes
• Styloid process
• Hyoid bone (less comu and upper body)

Question 26

What skeletal elements are derivdd from 3rd arch?

Answer 26

Hyoid bone (greater cornu and lower body)

Question 27

What skeletal elements are derived from 4th arch?

Answer 27

Hypobranchial eminence (becomes epiglottis)

Question 28

What skeletal elements are derived from 4-6th branchial arch?

Answer 28

Cartilages of the larynx

Question 29

What is found in 1st pharyngeal pouch?

Answer 29

Eustachian tube and middle ear cavity

Question 30

What is found in 2nd pharyngeal pouch?

Answer 30

Crypts of palatine tonsil

Question 31

What is found in 3rd pharyngeal pouch?

Answer 31

Dorsal part – Inferior Parathyroid

Ventral part – Thymus

Question 32

What is found in 4th pharyngeal pouch?

Answer 32

Dorsal Part – Superior Parathyroid
Ventral Part (ultimobranchial body) – Thyroid C cells

Question 33

What does the middle ear develop from?

Answer 33

o Ossicles
 Cartilage bar derivatives (Meckel’s/Reichert’s)
o Tympanic Cavity and Auditory Tube
 1st Pharyngeal pouch derivatives

Question 34

What happens to the pharyngeal clefts

Answer 34

The 1st cleft is the only one that remains, as the 2nd arch grows down to cover the others. However, there can be remnants.

Question 35

How are branchial cysts formed?

Answer 35

If the cervical sinus is not obliterated, cysts or fistulae can occur. These can occur anywhere along the anterior border of sternocleidomastoid.