Development of Face and Palate Question And Answers

Question 1. Development of face.
Answer:

Development of face:

• Around 4th week of intrauterine life, a prominent bulge develops on the ventral aspect of the embryo.
• Below it there is a depression called stomadeum.
• The mesoderm covering the developing forebrain proliferates and forms a downward projection called frontonasal process.
• The pharyngeal arches are laid down.
• The first branchial arch helps in the development of nasomaxillary complex.

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• It forms lateral border of stomadeum.
• It gives off a bud from its dorsal end called maxillary process.
• Localized thickenings occur above stomadeum called nasal placodes
• These placodes soon sink to form nasal pits.
• At this stage stomadeum is surrounded
  • Above- frontonasal process
  • Sides maxillary process
  • Below mandibular process.
• The resultant nasal pit divides into medial nasal process and lateral nasal process.
• The maxillary process fuses with lateral nasal process and forms nasolacrimal duct.

Lower lip:

• The mandibular processes of the two sides grow towards each other and fuses in the midline to form lower lip and lower jaw.

Upper lip:

It is formed by the two medial nasal prominences and the two maxillary prominences.

Nose:

• The maxillary process fuses with the medial nasal process, as a result nasal pits are cut off from the stomadeum
• The frontonasal process becomes narrower to form nasal septum.
• The merged medial nasal prominences provide the crest and tip and the lateral nasal prominences form alae.

Cheek:

• It is formed by the fusion of maxillary and mandibular process.

Question 2. Development of palate and its anomalies.
Answer:

Development of palate  :

• Palatal shelves are given out from maxillary process.
• These shelves grow medially.
• Initially these grows down to the tongue vertically.
• Lateral during 7th week, shelves turns upwards
• These shelves fuses with each other in the midline their fusion begins anteriorly and proceeds backwards.
• Mesial edges fuse with lower end of nasal septum.
• Thus, palate is formed alongwith the separation of two nasal cavities with that of oral cavity.
• Intramembranous ossification occurs of mesoderm of the palate to form hard palate.
• This ossification doesnot extend into the most posterior portion, which remains as soft palate.

Anomalies:

• Cleft palate: causes.
• Lack of fusion of the palatine shelves.
• Failure of the tongue to drop down.
• Anticonvulsant drugs – given during pregnancy

Question 3. Development of face and its anomalies. (or) Development anomalies of face.
Answer:

Anomalies:

1. Harelip – causes.
   • Non fusion of maxillary processes and medial nasal process.
   • Defective development of the frontonasal process.
   • Non fusion of two mandibular process.
2. Oblique facial cleft.
   • Arise due to non-fusion of the maxillary and lateral nasal process.
3. Macrostomia.
   • Due to inadequate fusion of maxillary and mandibular process.
4. Microstomia – Due to too much fusion.
5. Bifid nose.
   • Due to bifurcation of frontonasal process.
6. Mandibulofacial dysostosis.
7. Retrognathia or agnathia.
8. Hypertelorism – widely separated eyes.

Question 4. Frontonasal process
Answer:

• During the third week of embryonic development, two areas of thickened ectoderm, the olfactory areas appear immediately under the forebrain in the anterior wall of the stomodeum
• This is termed as frontonasal process
• It is the midline unpaired structure that develops into the forehead
• It is situated between the telencephalon, the stomodeum and the nasal pits
• The nasal pits indent the frontonasal process and divide into a medial and lateral nasal processes.

Question 5. Development of upper lip and its anomalies
Answer:

Development of upper lip:

• Each maxillary process grows medially
• It fuses first with the lateral nasal process and then the medial nasal process
• The mesodermal basis of the lateral part of the lip is formed from the maxillary process
• The overlying skin is derived from ectoderm covering the process
• The mesodermal basis of the medial part of the lip is formed from the frontonasal process
• The ectoderm of the maxillary process overgrows the mesoderm to meet the opposite maxillary process in the midline
• Thus entire upper lip is formed
• Muscles of upper lip are derived from mesoderm of the second branchial arch

Anomalies:

• Harelip/ Cleft lip-occurs due to
  • Non fusion of maxillary processes with medial nasal process
  • Defective development of frontonasal process
  • Non fusion of two mandibular processes

Question 6. Harelip.

Answer:

• It is used to describe defects of lip.

Harelip Causes:

• Non fusion of maxillary processes with medial nasal process-leads to defect in upper lip.
• Defective development of frontonasal process. Leads to midline defect of upper lip.
• Non-fusion of two mandibular processes – leads to
  midline defect of lower lip.

Question 7. Oblique facial cleft.
Answer:

Oblique facial cleft Causes:

• Non-fusion of the maxillary and lateral nasal processes.

Oblique facial cleft Effects:

• Cleft from medial angle of the eye to mouth.
• Absence of nasolacrimal duct.

Question 8. Cleft palate.
Answer:

Cleft palate Causes:

• Lack of fusion of the palatine shelves.
• Failure of tongue to drop down between shelves.
• Anticonvulsant drug-s phenobarbital given during pregnancy.

Cleft palate Effects:

• Cleft may extends anteriorly and results in cleft lip also.
• Defective speech
• Difficulty in swallowing.
• Dental problems.
• Esthetic problems.
• Due to unesthetic look-psychological problems.

Question 9. Development of upper lip.
Answer:

• Each maxillary process grows medially.
• It fuses first with the lateral nasal process and then the medial nasal process.
• The mesodermal basis of the lateral part of the lip is formed from the maxillary process.
• The overlying skin is derived from ectoderm covering the process.
• The mesodermal basis of the median part of the lip is formed from the frontonasal process.
• The ectoderm of the maxillary process overgrows the mesoderm to meet the opposite maxillary process in the midline.
• Thus the entire upper lip is formed.
• The muscles of the lip are derived from mesoderm of the second bronchial arch.

Question 10. Cleft lip/ Harelip

Answer:

Cleft lip Causes:

• Non fusion of maxillary processes with medial nasal process
• Defective development of frontonasal process
• Non fusion of two mandibular processes

Question 11. Development of palate
Answer:

• Palatal shelves are given out from maxillary process
• These shelves grow medially
• Initially they grow down to the tongue vertically
• Later during 7th week, shelves turn upwards
• These shelves fuses with each other in midline
• Fusion occurs anteriorly and proceeds backwards
• Mesial edges fuses with lower border of nasal septum
• Thus, palate is formed along with the separation of two nasal cavities with that of oral cavity
• Intramembranous ossification occurs of the mesoderm of the plate to form hard palate
• This ossification does not extend into the most posterior portion, which remains as soft palate