Week 3 - The Development of the Pharyngeal Arches

Question 1

What is the Pharyngeal Apparatus?

Answer 1

Segmental series of paired swellings surrounding the developing pharynx

Some textbooks may refer to them as the Branchial Apparatus

Question 2

What are Pharyngeal Arches?

Answer 2

Paired swellings located between developing forebrain and heart, consisting of mesenchymal tissue covered by ectoderm and endoderm

Question 3

How are Pharyngeal Arches numbered?

Answer 3

In a cranio-caudal sequence

Question 4

What does a typical Pharyngeal Arch contain?

Answer 4

• Mesenchyme
• Cartilaginous bar
• Artery
• Cranial nerve

Question 5

What is Meckel’s cartilage?

Answer 5

Cartilaginous component of the 1st pharyngeal arch

Question 6

What does the dorsal end of Meckel’s cartilage form?

Answer 6

Malleus and incus of the middle ear

Question 7

What is the role of mesenchyme surrounding Meckel’s cartilage?

Answer 7

Guides the formation of the mandible

Question 8

What does the 2nd pharyngeal arch cartilage become?

Answer 8

Reichert’s cartilage

Question 9

What does the dorsal end of Reichert’s cartilage form?

Answer 9

Stapes of the middle ear and styloid process of temporal bone

Question 10

What muscles are derived from the 1st pharyngeal arch?

Answer 10

• Muscles of mastication
• Anterior belly of digastric
• Tensor tympani
• Tensor veli palatini
• Medial and lateral pterygoid
• Temporalis
• Masseter
• Mylohyoid

Question 11

Which cranial nerve is associated with the 1st pharyngeal arch?

Answer 11

Trigeminal (V)

Question 12

What are the derivatives of the 3rd pharyngeal arch?

Answer 12

• Greater horn of hyoid bone
• Lower ½ body of hyoid bone
• Stylopharyngeus muscle

Question 13

What cranial nerve is associated with the 3rd pharyngeal arch?

Answer 13

Glossopharyngeal (IX)

Question 14

What cartilages are derived from the 4th and 6th pharyngeal arches?

Answer 14

• Thyroid cartilage
• Cricoid cartilage
• Arytenoid
• Corniculate
• Cuneiform

Question 15

What is Treacher Collins Syndrome?

Answer 15

Inherited condition characterized by underdevelopment of maxilla, mandible, and zygomatic bones

Question 16

What genetic mutation causes Treacher Collins Syndrome?

Answer 16

Mutation in the TCOF1 gene

Question 17

What is the first pouch derivative?

Answer 17

Tympanic cavity and auditory tube

Question 18

What does the second pouch develop into?

Answer 18

Palatine tonsil

Question 19

What do the dorsal and ventral wings of the 3rd pouch differentiate into?

Answer 19

• Dorsal wing: inferior parathyroid gland
• Ventral wing: thymus

Question 20

What is the developmental origin of the tongue?

Answer 20

Two lateral lingual swellings and one medial swelling (tuberculum impar) from the first pharyngeal arch

Question 21

What is the innervation of the anterior 2/3 of the tongue?

Answer 21

• General sensory: mandibular division of trigeminal nerve (CN V)
• Special sensory: chorda tympani (CN VII)

Question 22

What is the innervation of the posterior 1/3 of the tongue?

Answer 22

• Glossopharyngeal nerve (CN IX)
• Vagus nerve (CN X)

Question 23

Fill in the blank: The 2nd pharyngeal arch is also known as the ______.

Answer 23

Hyoid arch

Question 24

True or False: The 5th pharyngeal arch is always visible on the external surface.

Answer 24

False

Question 25

What is the general sensory innervation of the tongue?

Answer 25

Mandibular division of trigeminal nerve (CN V) - lingual branch ## Footnote This innervation is primarily responsible for the sensation in the anterior two-thirds of the tongue.

Question 26

What provides special sensory innervation (taste) to the anterior two-thirds of the tongue?

Answer 26

Chorda tympani (branch of facial nerve - CN VII) ## Footnote The chorda tympani carries taste sensations from the anterior part of the tongue.

Question 27

Which nerves provide sensory innervation to the posterior one-third of the tongue?

Answer 27

Glossopharyngeal nerve (CN IX) and Vagus nerve (CN X) ## Footnote CN IX innervates the majority of the posterior tongue while CN X innervates the epiglottis.

Question 28

What is the primary nerve for motor innervation of the tongue muscles?

Answer 28

Hypoglossal nerve (CN XII) ## Footnote The hypoglossal nerve is responsible for the movement of the majority of the tongue muscles.

Question 29

What structures contribute to facial development during Week 4?

Answer 29

Frontonasal prominence, Nasal placode, Maxillary prominence, Mandibular prominence ## Footnote These structures are crucial in the initial formation of the face.

Question 30

What occurs during facial development in Weeks 5-6?

Answer 30

Nasal placodes invaginate to form nasal pits, lateral and medial nasal prominences develop, maxillary prominences merge with medial nasal prominences to form upper lip, and mandibular prominences merge to form lower lip and jaw ## Footnote This period is essential for the shaping of the facial structure.

Question 31

During Weeks 6-7 of facial development, what is formed between the lateral nasal prominence and maxillary prominence?

Answer 31

Nasolacrimal groove ## Footnote This groove eventually leads to the formation of the nasolacrimal duct.

Question 32

What is the intermaxillary segment composed of?

Answer 32

Labial component, Upper jaw component, Palatal component ## Footnote The intermaxillary segment is vital for the development of the upper lip and palate.

Question 33

What are the two parts that compose the palate?

Answer 33

Primary palate and Secondary palate ## Footnote The primary palate is part of the intermaxillary segment, while the secondary palate forms the definitive hard and soft palates.

Question 34

What is the clinical significance of cleft lip and/or palate?

Answer 34

Affects 1/700 babies in the UK, causes defective speech, breathing, feeding, and dental problems ## Footnote Clefts can be anterior or posterior and are often related to environmental factors during pregnancy.

Question 35

What defines anterior cleft deformities?

Answer 35

Clefts anterior to the incisive foramen, involving cleft lip and/or primary palate ## Footnote These deformities result from a lack of fusion of the maxillary prominence with the medial nasal prominence.

Question 36

What defines posterior cleft deformities?

Answer 36

Clefts posterior to the incisive foramen, involving the secondary palate and cleft uvula ## Footnote These deformities are due to failure of fusion of palatine shelves.

Question 37

What is the surgical intervention timeline for cleft lip and cleft palate?

Answer 37

Cleft lip surgery: 3-6 months; Cleft palate surgery: 6-12 months ## Footnote Timely surgical intervention is crucial for improving outcomes in affected individuals.

Question 38

Fill in the blank: The primary palate is part of the _______.

Answer 38

intermaxillary segment

Question 39

True or False: The nasolacrimal duct forms from a thickened cord that undergoes apoptosis.

Answer 39

True ## Footnote This process is crucial for the proper formation of the nasolacrimal system.