Face And Palate

Question 1

When do pharyngeal arches start to form

Answer 1

4th week as neural crest cells start to migrate

Question 2

What does the pharyngeal arch contain

Answer 2

Mesenchyme, myoblast, nerve, artery, cartilage

Question 3

First pharyngeal arch

Answer 3

Trigeminal nerve. Muscles of mastication. Tensor palatini and tensor tympani. Anterior digastric. Mylohyoid. Meckel’s cartilage. Malleus and incus. Pouch gives rise to external auditory canal and tympanic membrane

Question 4

Second pharyngeal arch

Answer 4

Facial nerve. Muscles of facial expression. Posterior digastric. Stylohyoid. Stapedius. Reichert’s cartilage. Hyoid bone lesser horn and upper body. Pouch form palatine tonsil crypt.

Question 5

Third pharyngeal arch

Answer 5

Stylopharyngeus. Glossopharyngeal nerve. Hyoid bone greater horn, inferior body. Pouch give rise to thymus and inferior parathyroid

Question 6

Fourth pharyngeal arch

Answer 6

Vagus nerve. Muscles of soft palate (tensor palatini, levator palatini, palatoglossus, palatopharyngeus, uvula muscle), pharynx and larynx. Thyroid, cricoid, arytenoid cartilage. Pouch is thyroid c cells (Calcitonin) and superior parathyroid

Question 7

Sixth pharyngeal arch

Answer 7

Scm and trapezius. Accessory nerve.

Question 8

Boundaries of stomodeum

Answer 8

Developing heart at the bottom. Buccopharyngeal membrane at posterior. Frontal prominence on top. First pharyngeal arch on lateral walls

Question 9

Buccopharyngeal membrane composed of what 2 layers of tissue

Answer 9

Ectoderm and endoderm

Question 10

What forms the external tissues of the face

Answer 10

Frontonasal prominence and first pharyngeal arch.

Frontonasal prominence is of neural crest origin.
First pharyngeal arch is mesoderm and neural crest in origin

Question 11

Describe the whole development of the face

Answer 11

4th week:
Nasal placode: bilateral oval shape thickening of ectoderm, lower part of frontonasal prominence. Medial and lateral nasal prominences proliferate, invagination, nasal pit

6th week:
Medial nasal prominence start to fuse towards midline.
Mandibular prominences merge.
Maxillary prominence start to emerge from mandibular prominence.

7th week: (everything else happens)

• medial nasal prominence merge to form intermaxillary segment and filtrum and incisors
• maxillary and medial nasal prominence merge
• maxillary and lateral nasal prominence merge
• medial and lateral nasal prominence merge

Question 12

Hare lip is

Answer 12

Bilateral cleft lip. Medial and maxillary prominences don’t fuse

Question 13

Extrinsic factors of elevation of palatal shelf

Answer 13

Nasal septum. Mandible growth spurt. Fetal mouth opening reflex.

Question 14

Intrinsic forces for movement of palatal shelf

Answer 14

GAGs. Hyaluronic acid. These result in hydration of ECM.

Contraction of mesenchymal cells. Differential proliferation of mesenchymal cells. Change in vascularity