[PART 1] MODULE 12: HOW DO CLEFTS DEVELOP

3 TO 4 WEEKS

→ undifferentiated structures 

→ most distinguishable structures: neuropore and primitive brain

→ underdeveloped eyes are seen as bulges on the side of the head

→ stomodeum → oral and nasal cavities 

→ neural crest cells: develop the neural features of the face

neural crest cells

develop the neural features of the face

23-24 DAYS

→ rostral (anterior) neuropore → mandibular (1st) arch  → 1st pharyngeal groove → otic placode → level of section H										→ stomodeum → heart prominence  → pharyngeal (branchial) arches: 1st and 2nd → heart begins to pump

24 days

 heart begins to pump

23 DAYS

→ orophrayngeal membrane 

→ maxillary prominence

→ mandibular prominence

26 DAYS

→ ruptured orophrayngeal membrane

→ heart prominence

→ maxillary prominence

→ mandibular prominence

26 DAYS

→ hyoid arch 

→ otic pit

→ upper limb bud

28 DAYS

→ 2nd pharyngeal groove

→ stomodeum 

→ level of section

28 DAYS

→ stomodeum → nasal placode → mandibular (1st) pharyngeal arch  → hyoid (2nd) arch	→ cartilages: 1st arch (meckel) and 2nd arch (reichert)  → nerve → muscle → mandibular (1st) arch → 1st pharyngeal (branchial) membrane → hyoid (2nd) arch → 2nd pharyngeal pouch → 3rd aortic arch → 3rd pharyngeal pouch  → mesodermal core of 4th arch
→ midbrain → 1st pharyngeal pouch  → aortic arches (1st to 4th) → esophagus → lung bud → dorsal aorta → esophagus → truncus arteriosus (common arterial trunk from heart) → heart → thyroid diverticulum	→ lens placode → nasal placode → stomodeum → hyoid arch

5-6 WEEKS

→ face begins to become apparent

→ 1st brachial arch fuses at midline to form mandible; the anterior ⅔ of the tongue will come 

→ 2nd branchial arch gives rise to structures in the mid and lower face 

→ 3rd branchial arch forms the base of the tongue

→ nasal pits (at the side of the face)

6TH WEEK

→ nasomedial process has developed into globular process

→ all nasal, facial, and oral structures are present in rudimentary forms

→ the nasomedial process becomes the bridge of the nose, nasal septum

→ nasolateral process forms alaes of the nose

→ globular process forms the prolabium and premaxilla

→ maxillary process unites with the globular process to form parts of the upper lip, alveolar ridge and maxilla

→ developmental of palatal plates

31-35 DAYS

→ nasal pit 

→ eye

→ nasolacrimal groove

33 DAYS

→ nasal pit

→ median lateral: nasal prominences

→ nasolacrimal groove

→ external acoustic meatus (first pharyngeal groove)

35 DAYS

→ medial nasal prominence

→ lateral nasal prominence 

→ external acoustic meatus and external ear

7TH WEEK

• the nose, eyes, and mouth become fully recognizabe 

→ eyes will move further apart as the head continues to grow

→ a disturbance at this stage may cause hypertelorism

8TH WEEK

→ emergence of 2 shelves from inner side of maxillary process = from palatine process

→ large tongue is in between the palatine process and small mandible

→ nasal septum develops from frontonasal process and mesoderm of maxillary process

40 DAYS

→ forehead

→ eyelid

→ nostril

→ lower jaw

48 DAYS

→ eyelid

→ medial nasal prominences merging with each other and the maxillary prominences

9TH WEEK

→ premaxilla begins to ossify 

→ fusion of the palatine process begins from premaxilla backwards

→ from the lateral process the soft palate begins to develop

→ palatal shelves remain vertically oriented in the stomodeum on either side of the tongue 

→ tongue is positioned high in the stomodeum filling the area that will become nasal and oral cavities

70 DAYS

→ eyelids closed

→ nasolacrimal groove

→ intermaxillary segment

12TH WEEK

→ complete orofacial development

→ 86 days