Craniofacial Development

Question 1

What are the pharyngeal arches?

Answer 1

Bars of paraxial mesoderm between the pouches and clefts.

Question 2

When do the pharyngeal arches appear in humans?

Answer 2

In the 4th and 5th weeks of development.

Question 3

What does the paraxial mesoderm of the arches go on to make?

Answer 3

Muscles.

Question 4

Which muscles are derived from the 1st pharyngeal arch? Which nerve are they innervated by?

Answer 4

MUSCLES OF MASTICATION + anterior belly of digastric, mylohyoid

Vc

Question 5

Which muscles are derived from the 2nd pharyngeal arch? What are they innervated by?

Answer 5

Muscles of facial expression, VII

Question 6

Which muscle is derived from the 3rd pharyngeal arch? What supplies it?

Answer 6

Stylopharyngeus, IX

Question 7

Which muscles are derived from the 4th pharyngeal arch? Which nerve are they innervated by?

Answer 7

Muscles of vocalisation and swallowing, superior laryngeal branch of vagus X

Question 8

Which muscles are derived from the 6th pharyngeal arch? Which nerve are they innervated by?

Answer 8

Internal muscles of larynx, recurrent laryngeal branch of vagus.

Question 9

What do the arch cartilages arise from?

Answer 9

Neural crest cells.

Question 10

What is the origin of neural crest cells?

Answer 10

Ectoderm

Question 11

Where do the neural crest cells emigrate into the arches from?

Answer 11

The dorsal region/crest of the embryonic neural tube. From the hindbrain and midbrain in the head.

Question 12

What kind of cell are neural crest cells?

Answer 12

Stem cells

Question 13

Which cartilages do neural crest cells form from the 1st arch?

Answer 13

Palatopterygoquadrate cartilage

Meckel’s cartilage

Question 14

Which cartilages do neural crest cells form form the 2nd arch?

Answer 14

Reichert’s cartilage

Question 15

Which bones are formed from the 1st arch?

Answer 15

Allisphenoid
Malleus
Incus

Question 16

Which bones and ligaments are formed from the 2nd arch?

Answer 16

Stapes
Styloid process
Stylohyoid ligament
Lesser cornu of hyoid

Question 17

Which bones are formed from the 3rd arch?

Answer 17

Body of hyoid

Greater cornu of hyoid

Question 18

Which cartilages are formed from the 4th arch?

Answer 18

Thyroid cartilage

Cricoid cartilage

Question 19

Which arches do cardiac neural crest cells migrate through? What do they go on to form?

Answer 19

4th and 6th arches, aorticopulmoary septum

Question 20

Name 3 ways of fate mapping.

Answer 20

1) chimeric quail-chick grafting (replace chick neural tube + crest with quail, identify quail cells with quail specific antibody)
2) labelling neural tube with fluorescent dye
3) genetic lineage tracing in mice

Question 21

What do cranial neural crest cells form? (13)

Answer 21

Many cartilages+bones of the skull
Tooth pulp+odontoblasts
Pericytes, connective tissue, smooth muscle of arteries
Thymus+parotid gland mesenchyme
Melanocytes
Parasympathetic ganglia
Olfactory ensheathing cells
Schwann cells
Dermis
Meninges of forebrain
Peripheral somatosensory neurons

Question 22

What do nerve-dwelling neural crest cell progenitors give rise to? (neural crest cells colonising peripheral nerves)

Answer 22

Melanocytes

Post-ganglionic parasympathetics

Question 23

Where are the cell bodies of peripheral somatosensory neurons?

Answer 23

Trunk dorsal root ganglia
Trigeminal ganglion
Superior ganglia of VII, IX and X

Question 24

Where do vagal neural crest cells come from?

Answer 24

Caudal hindbrain

Question 25

Where do peripheral special sensory and viscerosensory neurons come from?

Answer 25

Cranial neural placodes

Question 26

Which cranial nerves contain viscerosensory fibres? Which ganglia of these nerves do they arise from?

Answer 26

VII, IX, X, inferior ganglia

Question 27

What are cranial neural placodes?

Answer 27

Bilateral patches of thickened neurogenic surface ectoderm, paired on either side of the head.

Question 28

What does the otic placode form? (VIII)

Answer 28

The entire inner ear, special sensory neurons of the ear, cranial nerve VIII

Question 29

What does the olfactory placode form?

Answer 29

The entire olfactory epithelium, including olfactory receptor cells

Question 30

What does the lens placode form? (II)

Answer 30

The lens of the eye.

Question 31

Is the trigeminal nerve mainly made up of cranial neurogenic placode or neural crest cells?

Answer 31

Neural crest cells

Question 32

What does the geniculate ganglion form? (VII)

Answer 32

Some of the viscerosensory neurons in the geniculate ganglion (inf ganglion VII). Their axons transmit information from taste buds in the ant 2/3 tongue to the nucleus of the solitary tract in the medulla.

Question 33

What does the petrosal placode form? (IX)

Answer 33

Viscerosensory neurons in the petrosal ganglion (inf ganglion IX). Their axons transmit information from the nucleus of the solitary tract to:
Taste buds from post 1/3 tongue
General visceral information from pharynx
Chemoreceptors and mechanoreceptors in the carotid body and sinus.

Question 34

Where do neural crest derived cells in the superior ganglion IX transmit information? What information

Answer 34

Somatosensory information from the post 1/3 tongue, pharynx, auditory tube and middle ear to trigeminal sensory nucleus.

Question 35

What does the nodose placode form? Where do their fibres transmit information to and from?

Answer 35

Viscerosensory neurons in the nodose ganglion (inferior ganglion of X). Information to the nucleus of the solitary tract from the
Taste buds in the epiglottic vallecula
General visceral info from pharynx, larynx
Chemoreceptors and mechanoreceptors in the aortic bodies and aortic arch

Question 36

What does the first pharyngeal cleft form?

Answer 36

The EAM

Question 37

What does the first pharyngeal pouch form?

Answer 37

The middle ear and Eustachian tube.