Question 1

The muscles of the larynx are derived from which pharyngeal arches?

Accepted Answer

The muscles of the larynx are derived from the third, fourth, and sixth pharyngeal arches. The third arch gives rise to the stylopharyngeus muscle, the fourth arch gives rise to the cricothyroid muscle, and the sixth arch gives rise to the intrinsic muscles of the larynx (except for the cricothyroid muscle). Therefore, option E is the correct answer.

Question 2

The cheeks are formed from which prominences?

Accepted Answer

The cheeks are formed from the maxillary prominences.

Question 3

Which of the craniosynostosis syndromes is unusual in that it is X-linked,with females,but not males,being symptomatic?

Accepted Answer

Craniofrontonasal dysplasia is X-linked and has a pattern of inheritance that results in females being more affected than males. The other craniosynostosis syndromes listed (Apert's syndrome, Pfeiffer syndrome, Muenke syndrome, and Saethre-Chotzen syndrome) have an autosomal dominant pattern of inheritance, meaning that either males or females can be affected.

Question 4

A child is diagnosed with DiGeorge syndrome due to a 22q11.2.1 deletion encompassing approximately 30 to 40 genes.Researchers have genetically inactivated these genes in mice to identify which are essential for pharyngeal arch development.Which two genes in the deleted area are now thought to be the key players in DiGeorge syndrome?

Accepted Answer

According to the given information, researchers inactivated genes in mice to identify the key players in DiGeorge syndrome. The deleted area encompasses approximately 30-40 genes, but only two genes are mentioned as key players in the syndrome. These genes are TBX1 and CRKl, which are both located within the deleted area. Therefore, option B is the correct answer.

Question 5

A premature infant is examined by a neonatologist at University hospital.Based on its facial features and a maternal history,the child is diagnosed with fetal alcohol syndrome.Fetal alcohol syndrome most dramatically affects derivatives of which pharyngeal arches?

Accepted Answer

Fetal alcohol syndrome can lead to a range of developmental abnormalities, including those affecting structures derived from the first pharyngeal arch. This arch gives rise to structures such as the maxilla, mandible, and associated facial features, which are often notably affected in individuals with this syndrome.

Question 6

The third pharyngeal pouches lie between which pharyngeal arches?

Accepted Answer

The third pharyngeal pouches are located between the third and fourth pharyngeal arches.

Question 7

The first pharyngeal arch forms on which day of gestation?

Accepted Answer

The first pharyngeal arch forms on day 22 of gestation.

Question 8

Craniosynostosis,the premature closure of the sutures,is usually due to increased signaling of which pathway?

Accepted Answer

Craniosynostosis is often associated with increased signaling in the FGF (Fibroblast Growth Factor) pathway, which plays a crucial role in the development and growth of bones, including the skull.

Question 9

The secondary palate forms by fusion of which processes?

Accepted Answer

The secondary palate forms from the fusion of the paired lateral palatine processes, which grow downwards from the maxillary prominences. This process is crucial for separating the nasal and oral cavities.

Question 10

The thyroid gland starts to produce circulating hormones during which weeks of gestation?

Accepted Answer

The thyroid gland starts to produce circulating hormones during weeks 10-12 of gestation, making choice B the correct answer.

Question 11

The superior parathyroid gland arises from which structure?

Accepted Answer

The answer of The superior parathyroid gland arises from which...

Question 12

The third aortic arches lie between which pharyngeal grooves/clefts?

Accepted Answer

The third aortic arches lie between the second and third pharyngeal grooves/clefts.

Question 13

A teenage boy who is taking Accutane® for severe acne meets a new girl at school and begins dating her.She too has acne,although mild,and asks her boyfriend to share his medicine with her.After a few weeks of dating they begin to have unprotected intercourse.Which embryonic cell population will be most endangered by Accutane® exposure if the girl becomes pregnant?

Accepted Answer

Accutane® (isotretinoin) is known to cause severe birth defects due to its teratogenic effects, particularly affecting the neural crest cells, which are crucial for the development of many structures in the embryo, including the face, heart, and nervous system.

Question 14

A new mom takes her baby son on an airplane trip.On descent,the child begins to cry vociferously,and does not quiet down until a few minutes after landing.At the next well-baby visit,the pediatrician explains that the eustachian tube in infants is very short and horizontally oriented,resulting in difficulty in clearing pressure from the middle ear.The eustachian tube forms from a persisting portion of a pharyngeal pouch that remains connected to the pharynx.Which pharyngeal pouch forms the eustachian tube?

Accepted Answer

The answer of A new mom takes her baby son...

Question 15

The mesoderm forms which derivative of the pharyngeal apparatus?

Accepted Answer

The answer of The mesoderm forms which derivative of the...

Question 16

A researcher discovers a gene that when knocked out causes the most common form of cleft lip seen in humans.Examination of the expression of this gene in embryos shows that it is expressed in the facial prominences that flank the area of cleft lip formation.What are these flanking prominences?

Accepted Answer

The flanking prominences mentioned in the question are the ones that are located on either side of the area where cleft lip forms. According to the answer options, the only pairing of prominences that flank the area of cleft lip formation are maxillary and medial nasal prominences (option B). The other options either include prominences that are not located in the correct position or do not form a pair on either side.

Question 17

A child is diagnosed with Treacher Collins syndrome,which results from a mutation in the gene TCOF1 encoding the protein TREACLE.What embryonic tissue is the most affected by this mutation?

Accepted Answer

Treacher Collins syndrome results from a mutation in the TCOF1 gene, which encodes the protein TREACLE. This protein is important in the development of neural crest cells, which give rise to many tissues in the head and face. Therefore, the most affected embryonic tissue in this syndrome is the neural crest cells.

Question 18

A baby boy presents with Treacher Collins syndrome.A medical geneticist evaluates the boy and meets with both parents.She notices that the mother has mild Treacher Collins-like features.Which pharyngeal arch derivatives are most dramatically affected in this syndrome?

Accepted Answer

Treacher Collins syndrome primarily affects the derivatives of the first pharyngeal arch, leading to abnormalities in the development of the face, including the cheekbones, jaw, and external ears.

Question 19

Derivatives of the second pharyngeal arches are innervated by which nerves?

Accepted Answer

The structures derived from the second pharyngeal arch (also known as the hyoid arch) are innervated by the facial nerve (cranial nerve VII). This includes muscles such as the stapedius, stylohyoid, and muscles of facial expression.

Question 20

Fontanelles allow deformation of the skull during birth.How many fontanelles are present at birth?

Accepted Answer

At birth, there are typically six fontanelles present: two major ones (the anterior and posterior fontanelles) and four minor ones (two sphenoidal or anterolateral fontanelles and two mastoid or posterolateral fontanelles). These soft spots allow for the deformation of the skull during birth and provide space for brain growth during infancy.

Quiz 17: Development of the Pharyngeal Apparatus and Face