Embryology- Head and Neck, Cranial Nerves

Question 1

What tissues are the pharyngeal arches derived from?

What do they interact with

Answer 1

General Mesoderm; they interact with neural crest cells

Question 2

Glands and mucosae, original tissue and what they interact with

Answer 2

Endoderm, interact with neural crest ectoderm

Question 3

Brain, embryologic origin tissue

Answer 3

Ectoderm

Question 4

Cranial nerves, origin

Answer 4

ectoderm

Question 5

Placodes

What are they? What tissue are they derived from?

Answer 5

• Discs that appear on ectoderm, sensory specialization occurs here
• Later form eye lens, ear spaces, nasal cavity, neurogenic structures
• All derived from ectoderm

Question 6

Head somites
What are they (specific m.m.)?
What tissue are they derived from?

Answer 6

Derived from head mesoderm

• eg. eye muscles, tongue, SCM, trapezius

Question 7

What tissues make up the skull? What to they become? What is the embryologic tissue they are derived from?

Answer 7

All derived from mesoderm. Different precursors eventually become bone.

Endochondral cartilages (later bone replaces it)- make up anterior and posterior neurocranium- vertebrae, ethmoid, nasal conchae, central sphenoid

Intramembranous ossification desmocranium (dermal bones)- interact with neural crest cells- make frontal, parietal, occipital, and zygomatic bones

Notochord (makes basisphenoid and basioccipital bones), vertebrae, endochondral cartilages mix

Question 8

How does endochondral cartilage in skull become bone?

Answer 8

Bone tissue comes above and below it, later bone fills in

Question 9

The notochord makes part of which bones?

Answer 9

Basisphenoid and basioccipital bones

• Neurocranium is also involved with formation of these bones

Question 10

Which cranial nerves are associated with placodes?

Answer 10

I- Olfactory
II- Optic
VII- Vestibulocochlear

-They are all sensory nerves–> “special afferent”

Question 11

Which cranial nerves are associated with head somites and somitomeres?

Answer 11

III- Oculomotor
IV- Trochlear
VI- Abducens
XI- Accessory
XII- Hypoglossal

-They are all motor nerves–> all are general somatic efferent AND CN III is also general visceral efferent

Question 12

Which cranial nerves are associated with pharyngeal arches?

Answer 12

V- Trigeminal
VII- Facial
IX- Glossopharyngeal
X- Vagus

• These are “mixed” nerves, sensory and motor component
• -> All are special afferent (SA), General somatic afferent (GSA), General visceral afferent (GVA), , General visceral efferent (GVE), Special visceral efferent (SVE)

Question 13

What does the nasal placode form?

Answer 13

Mucosa of nasal capsule

Question 14

What does the lens placode form?

Answer 14

Lens of the eye

Question 15

What does the otic placode form?

Answer 15

Vestibular and cochlear parts of the ear?

Question 16

What do the neurogenic placodes form?

Answer 16

Parts of the cranial nerves

Question 17

What embryologic precursor are the pharnygeal pouches derived from?

Answer 17

Paraxial mesoderm

Question 18

What is cranial nerve zero?

Answer 18

the Vomeronasal organ

Question 19

Which pharnygeal arches are associated with what cranial nerve?

Answer 19

Arch 1 (Meckel’s Cartilage): Trigeminal nerve (V)

Arch 2 (Reichert’s Cartilage): Facial nerve (VII)

Arch 3 (Carotid arch): Glossopharyngeal nerve (IX)

Arch 4 (Systemic arch): Vagus nerve (X), ONLY superior laryngeal branch

Arch 6 (Pulmonary arch): Vagus nerve (X), ONLY recurrent laryngeal branch

Question 20

Which pharnygeal arches are associated with what arteries?

Answer 20

Arch 1 (Meckel’s Cartilage): Artery mainly gone- remnants of maxillary and part of external carotid

Arch 2 (Reichert’s Cartilage): Stapedial artery

Arch 3 (Carotid arch): Internal and external carotid arteries

Arch 4 (Systemic arch): Parts of aorta and right subclavian artery

Arch 6 (Pulmonary arch): Proximal part of pulmonary arteries

Question 21

Which cranial nerves are associated with which muscles?

Answer 21

III, IV, VI- Eye muscles

XI- SCM, Trapezius

XII- Intrinsic tongue muscles

Question 22

What main structures are derived from pharyngeal arch 1?

Answer 22

• Incus and malleus bones of middle ear

- Some muscles of mastication

Question 23

What main structures are derived from pharyngeal arch 2?

Answer 23

• Stapes (ear bone)
• Stylohyoid ligament
• Some muscles of facial expression

Question 24

What main structures are derived from pharyngeal arch 3?

Answer 24

• Main part of hyoid bone (greater horn, lower part of body) and cartilage
• Stylopharyngeus (pharyngeal muscle)

Question 25

What main structures are derived from pharyngeal arch 4?

Answer 25

• Laryngeal cartilages, e.g. cricoid cartilage

- Laryngeal m.m., cricothyroid m., constrictors of pharynx

Question 26

What main structures are derived from pharyngeal arch 6?

Answer 26

Same as arch 4

• Laryngeal cartilages, e.g. cricoid cartilage
• Laryngeal m.m., cricothyroid m., constrictors of pharynx

Question 27

What structures do the pharyngeal grooves become?

Answer 27

1st- External auditory canal

2nd, 3rd, 4th- Often closed up, occasionally replaced by cervical sinus

Question 28

What structures do the pharyngeal pouches form?

Answer 28

The glands! Generally

1st- Auditory canal, middle ear

2nd- Palatine tonsil

3rd- Inferior parathyroid (and Thymus per Dr. Solunias)

4th- Superior parathyroid

Question 29

How does thyroid migrate during development?

Answer 29

-Starts in tongue, specifically in foramen cecum, cells migrate down to where pharyngeal pouch 3,4 are developing into parathyroid glands