Preclinical Paediatrics · MU Sofia

2. Chronology in the development of the maxillofacial region by weeks.

Traces the development of the face, lip, nose and palate week by week, from the face primordia and frontonasal, maxillary and mandibular processes in week 4 through fusion in weeks 5 to 7. It includes a day-by-day list for days 24 to 28, then covers palatal development in weeks 7 to 9, including palatal shelf elevation and closure, and finishes with a brief outline of tongue development from week 4.

Inside: 2 sections · 13 labelled pictures · 12 flashcards · 7 min

Topic 2 of 40 in the MU Sofia syllabus for Preclinical Paediatrics (Dental Medicine, Year 3). The free AceMed note covers it in 2 sections, about 987 words (7 min of reading), with 12 flashcards.

In this note

  1. CHRONOLOGY IN DEVELOPMENT OF MAXILLOFACIAL REGION BY WEEKS
  2. Development of Tongue

CHRONOLOGY IN DEVELOPMENT OF MAXILLOFACIAL REGION BY WEEKS

Development of the Face:

Face and oral structures formed between the 4th and 7th week

  • Face forms from the fusion of 5 face primordia which develop during week 4 and fuse during weeks 5 through to 8
  • Primordia: ectodermal swellings or prominences that are filled with mesodermal and neural crest cells:
  • Frontonasal prominence
  • Mandibular prominence (2): from branchial arch Left + Right
  • Maxillary prominence (2): from branchial arch Left + Right.

Facial Development

Between weeks 4 to 7, there are migratory flows of neural crests which perform a series of symmetrical spatial processes. Processes are swelling of mesenchyme that causes grooves between processes that appear

  • Formation of grooves and channels
  • Approaching of symmetrical processes to medial line and fusion of processes

4th Week of Development

  • Oral pit surrounded by several masses of tissues
  • Face develops primarily from tissues surrounding the oral pit
  • Above the oral pit is covering of brain termed the frontal process from which the forehead develops
  • Lateral to oral pit are right and left maxillary processes from which develop the maxilla
  • Below the oral pit is mandibular arch (called mandibular process) which forms the lower jaw
  • In 4th week, when facial tissues have just begun to organize, they measure only a few millimetres in height and width and are only as thick as a sheet of paper

Day 24→ starts development of frontal prominence, mandibular and maxillary processes from 1st branchial arch

Day 26→ well-formed maxillary and mandibular processes

Day 27→ starts the appearance of nasal placode and odontogenic epithelium

Day 28→ localised thickenings develop within frontal prominence forming olfactory placodes

Formed with help of two maxillary and one frontal nasal Processes. Maxillary processes grow forward and upward And form the upper lateral edge of mouth. Frontal nasal Process grows downwards towards the maxillary processes Fusion between the maxillary and frontal nasal processes

take place in 7th week.

Development of Lower Face

  • Occurs within the 4th week, with 2 bulges forming inferior to stomodeum
  • Formation of lower jaw is from the two mandibular prominences which arise from the mandibular arch and grow forward and out
  • Meet in midline at 30 to 35 days and joined by fusion (called the symphysis)
  • Lower lip formed by merging of the two streams of ectomesenchyme of mandibular processes

Formation of Upper Jaw

  • About 28 days, localized thickenings develop with the ectoderm of the frontal prominence called the olfactory placodes

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