Question 1

Which signaling molecule patterns the cranial-caudal axis of the hindbrain?

Accepted Answer

Retinoic acid is responsible for patterning the cranial-caudal axis of the hindbrain. Its gradient concentration correlates with the identity of different rhombomeres, which are labeled segments along the hindbrain.

Question 2

Van der Woude syndrome is predominantly characterized by which defect?

Accepted Answer

Van der Woude syndrome is a genetic condition characterized by cleft lip and/or cleft palate. While other abnormalities can occur with this syndrome, the primary defect is the defective outgrowth of the facial processes which leads to the formation of a cleft.

Question 3

The third pharyngeal arch artery gives rise to which adult blood vessel(s)?

Accepted Answer

The third pharyngeal arch artery gives rise to the common carotids and roots of internal carotids.

Question 4

The muscles of mastication,excluding the tongue muscles,arise from the mesoderm of which structure(s)?

Accepted Answer

The muscles of mastication arise from the mesoderm of the first pharyngeal arches.

Question 5

The stylopharyngeus muscle is innervated by which nerve?

Accepted Answer

The stylopharyngeus muscle is innervated by the glossopharyngeal nerve (CN IX).

Question 6

The muscles of facial expression arise from the mesoderm of which structure(s)

Accepted Answer

The muscles of facial expression develop from the mesoderm of the second pharyngeal arches.

Question 7

Researchers have shown that the Hox genes are important for patterning the pharyngeal arches.Which of the Hox genes is essential for the specification of the second pharyngeal arch and when genetically inactivated in mice,result in the homeotic transformation of the second pharyngeal arch into one with first pharyngeal arch identity?

Accepted Answer

Hoxa2 is essential for the specification of the second pharyngeal arch. When genetically inactivated in mice, it results in the transformation of the second pharyngeal arch into one with first pharyngeal arch identity.

Question 8

Researchers have shown that the mandibular prominence can be transformed into the maxillary prominence by the genetic inactivation of two homeobox transcription factors in mice.What are these two factors?

Accepted Answer

The two homeobox transcription factors whose genetic inactivation can transform the mandibular prominence into the maxillary prominence in mice are Dlx5 and Dlx6.

Question 9

Mutations in the growth factor SONIC HEDGEHOG would be expected to result in which birth defect?

Accepted Answer

Mutations in the growth factor SONIC HEDGEHOG are known to cause the birth defect holoprosencephaly, which is a disorder of forebrain development that can result in a range of facial and brain abnormalities. Cleft lip and cleft palate are typically caused by a combination of genetic and environmental factors, while craniosynostosis and mandibulofacial dysostosis are caused by mutations in other genes.

Question 10

Neural crest cells migrate from the hindbrain in distinct streams.How many neural crest cells streams are there in the hindbrain?

Accepted Answer

There are three distinct streams of neural crest cells that migrate from the hindbrain: the cranial, cardiac, and vagal streams.

Question 11

The oropharyngeal membrane ruptures to create the continuity between the developing gut and oral cavity during which week of gestation?

Accepted Answer

The oropharyngeal membrane ruptures to create the continuity between the developing gut and oral cavity during the 5th week of gestation.

Question 12

At birth what is the approximate ratio of the facial skeleton to the cranial vault?

Accepted Answer

The answer of At birth what is the approximate ratio...

Question 13

The developing hindbrain is segmented into rhombomeres,which are characterized by the differential expression of members of the Hox family of transcription factors.Researchers have shown that some members of the Hox family are crucial for the specification of the rhombomeres.When Hoxa1 is genetically inactivated in mice,which rhombomeres are affected?

Accepted Answer

Hoxa1 is crucial for the development of rhombomeres 4 and 5, and its inactivation affects these segments.

Question 14

Both cleft lip and palate have a genetic component,which results in differences in the frequency of cleft lip and palate in females and males.Does cleft lip occur more often in females or males?

Accepted Answer

Cleft lip occurs more often in males than females, with a male to female ratio of approximately 2:1.

Question 15

Fate mapping studies of neural crest cell migration have been carried out in chicks,quails,and mice.These studies have shown that the neural crest cells that populate the second pharyngeal arch arise from which level(s)of the brain?

Accepted Answer

The answer of Fate mapping studies of neural crest cell...

Quiz 18: Development of the Pharyngeal Apparatus and Face