Lecture 34: Development of Pharynx

Question 1

What is the main organizer for pharyngeal arch development?

Answer 1

Foregut endoderm

Question 2

What determines craniocaudal segmentation of the pharyngeal arches?

Answer 2

Hox genes

Question 3

List the aortic arch, cranial nerve, muscle and skeletal derivatives of the 1st pharyngeal arch

Answer 3

Aortic arch: Mandibular
CN: Cranial
Derivatives: Meckel’s cartilage, malleus (articular cartilage), incus (quadrate cartilage)

Question 4

List the aortic arch, cranial nerve, muscle and skeletal derivatives of the 2nd pharyngeal arch

Answer 4

Aortic arch: Hyoid
CN: Facial
Derivatives: Reicher’s cartilage, hyoid, stapes, styloid process, muscles of facial expression

Question 5

What gene influences development of the second pharyngeal arch?

Answer 5

Hoxa-2

Question 6

List the cranial nerve and derivatives of the 3rd pharyngeal arch

Answer 6

CN: Glossopharyngeal
Derivatives: hyoid, upper pharynx, stylopharyngeus

Question 7

List the cranial nerve and derivatives of the 4th pharyngeal arch

Answer 7

CN: Vagus
Derivatives: muscles and cartilages of the larynx and pharynx

Question 8

List the derivative of the 1st pharyngeal groove

Answer 8

External auditory meatus

Question 9

List the derivative of the 2nd and 3rd pharyngeal grooves

Answer 9

Cervical sinus (temporary structure)

Question 10

List the derivatives of the first pharyngeal pouch

Answer 10

Auditory tube, tympanic cavity of middle ear

Question 11

List the derivatives of the second pharyngeal pouch

Answer 11

Fossa for palatine tonsils

Question 12

List the derivatives of the third pharyngeal pouch

Answer 12

Inferior parathyroids, thymus

Question 13

List the derivatives of the fourth pharyngeal pouch

Answer 13

Superior paraythyroids, ultimobranchial body

Question 14

Which cells secrete calcitonin?

Answer 14

Parafollicular C cells of the thyroid (from ultimobranchial body)

Question 15

Foramen cecum

Answer 15

Opening of thyroglossal duct as a small pit at the base of the tongue

Question 16

What forms Rathke’s pouch?

Answer 16

Midline upgrowth from roof of ectodermal stomodeum

Question 17

List the primordia of the tongue

Answer 17

Lateral lingual swellings (paired), tuberculum impar, copula

Question 18

Micrognathia

Answer 18

Small mandible/jaw

Question 19

Agnathia

Answer 19

No jaw

Question 20

Treacher Collins Syndrome

Answer 20

Mutation of TCOF1 gene that disrupts neural crest cells of the 1st pharyngeal arch; facial abnormalities

Question 21

Pharyngeal cysts/sinuses/fistulas

Answer 21

Cysts: Completely enclosed cavity
Sinus: closed at one end, open at other end to pharynx
Fistula: Tube open at both ends outside pharynx

Question 22

Ankyloglossia

Answer 22

Subnormal regression of frenulum by mutation in Tbx-22

Question 23

DiGeorge’s Syndrome

Answer 23

Cranial neural crest deficiency; malformation of 1st arch structures/outflow tract; abnormalities in parathyroids, thymus, thyroid, immune systel