Embryo - Cranialfacial

Question 1

Describe the embryological development of face from first pharyngeal arch.

Answer 1

1st Pharyngeal Arch

• Mandibular & Maxillary prominences are derived
  
  • Maxillary prominences = arise as triangular projections from DORSAL part of mandibular process
• Nasal pit
  
  • becomes nasal cavity
• Medial nasal process
  
  • becomes side of nose

Question 2

Describe fronto-nasal, maxillary and mandibular prominences and their role in the development of face.

Answer 2

Frontalnasal process becomes:

• forehead & dorsum of nose

Lateral nasal process becomes:

• Ala (sides) of nose

Medial nasal process (intermaxillary segment) becomes:

• Deep philtrum
• Nasal septum
• Primary Palate + Premaxilla

Maxillary process becomes:

• Superficial philtrum
• Lateral parts of upper lip
• Secondary palate
• Maxilla (minus premaxilla)
• Zygomatic
• Squamous temporal

Mandibular processes become:

• Lower jaw
• Lower lip
• Chin

Question 3

Describe nasal placode, medial and lateral nasal prominences and formation of intermaxillary segment.

Answer 3

Formation of Nasolacrimal duct + sac

• Nasolacrimal groove
  
  • groove btw the maxillary process & lateral nasal process
  • from eyeball –> nasal cavity
• Maxillary + lateral nasal processes fuse
  
  • ectoderm gets buried –> ectodermal column of cells
    
    • forms NASOLACRIMAL DUCT + SAC
• Derivatives of laternal nasal processes:
  
  • Ala (sides) of nose

Formation of Intermaxillary process:

• Maxillary processes grow MEDIALLY
  
  • pushing the medial nasal processes toward each other
• 2 Medial Nasal Processes
  
  • fuse to form the INTERMAXILLARY SEGMENT

Question 4

Describe derivatives of intermaxillary segment.

Answer 4

Derivatives of intermaxillay segment:

1. Deep part of philtrum
   
   • vertical groove from the lose to upper lip
2. Primary palate
   
   • small projection grows backwards in oral cavity
   • forms free maxillary part of maxilla
3. Nasal septum
4. Premaxillary part of maxilla

Notes:

• Maxillary processes grow MEDIALLY
  
  • pushing the medial nasal processes toward each other
• 2 Medial Nasal Processes
  
  • fuse to form the INTERMAXILLARY SEGMENT

Question 5

Describe formation of lower lip and jaw.

Question 6

Describe the formation of nasolacrimal duct and sac.

Question 7

List the derivatives of maxillary prominence.

Answer 7

Derivatives of the maxillary processes:

1. Superficial philtrum
2. Lateral parts of upper lip
3. Maxilla (minus the premaxilla)
4. Zygomatic
5. Secondary palate
6. Squamous temporal

Note:

• Maxillary processes fuse w/ intermaxillary segment
  
  • form the superficial part of philtrum of upper lip

Question 8

Describe the embryological basis of cleft lip, cleft palate and oblique facial clefts.

Answer 8

Cleft lip

• Median cleft upper lip (Hare lip)
  
  • Failure of fusion of 2 MEDIAL NASAL PROCESSES to form intermaxillary segment
    
    • Cleft in MIDLINE
• Unilateral cleft upper lip
  
  • Failure of fusion of LEFT maxillary process w/ intermaxillary segment
    
    • Cleft on left side
• Bilateral cleft upper lip
  
  • Failure of MAXILLARY PROCESS TO FUSE w/ intermaxillary segment
    
    • fusion not complete on either side

Cleft palate:

• Anterior cleft anomalies (anterior to fossa)
  
  • include cleft upper lip + gum
  • Failure of fusion btw PRIMARY & SECONDARY palate
• Posterior cleft anomalies (posterior to fossa)
  
  • cleft extends behind the incisive fossa into posterior part of hard & soft palate
  • Failaure of fusion btw LATERAL PALATINE processes

Oblique facial clefts:

• Nasolacrimal duct is OPEN on the surface
  
  • Failure of MAXILLARY PROCESS to fuse w/ LATERAL nasal process & MEDIAL nasal process on the right side
    
    • from angle of eye –> upper lip = open

Question 9

Describe the embryology of the formation of hard and soft palate.

Answer 9

Basics:

• Critical period for dev of palate = 6-9 weeks

2 Embryological parts:

• Primary palate
  
  • ​formed as triangular backward projection (median palatal process)
    
    • ​from INTERMAXILLARY SEGMENT
  • forms the:
    
    • anterior part of HARD PALATE
• Secondary palate
  
  • formed from 2 palatine shelves (lateral palatal processes)
    
    • projecting from inner aspects of the MAXILLARY PROCESSES
      
      • eventually shelves fuse together in midline w/ nasal septum + primary palate in front
  • forms the:
    
    • GREATER part of HARD PALATE (posterior part)
    • entire SOFT PALATE

Junction of 2 palates:

• Incisive foramen (fossa)

Question 10

Describe the formation of nasal cavity and paranasal sinuses.

Question 11

Describe the stages in the formation of the teeth and related embryological anomalies.

Question 12

Describe the constituents of the pharyngeal apparatus.

Question 13

Describe the formation and fate of pharyngeal arches, pharyngeal grooves, pharyngeal pouches and pharyngeal membranes.

Question 14

Describe the embryological basis of branchial cysts, Treacher Collin’s syndrome, Robin sequence and DiGeorge anomaly.

Question 15

Describe the embryological development of the Thyroid gland and related anamolies.