Wmbryologyy

1. Done by /Mahmoud elsabagh
supervision of prof DR /Ahmed
Ali

2. 4th to 8th week from 5 Swellings
(Ectoderm
)
1st Arch
Ectodermal
thickenings(5th
week)

3. 6th week : ectoderm from Nasal placode invaginates to form oval nasal pits

4. 12.5 mm Enbryo stage : Maxillary prominence grows medially

5. Nasal pits separate from stomodeum

6. Intermaxillary process (fusion of medial nasal process) central tissues pushed up to
form nasal prominence

7. Globular process forms the philtrum (lateral angles of medial nasal process)
By 7th week invaginates to form nasolacrimal duct
Canalisation may not complete till after birth

8. • Nasal Septum Development – 13.5 mm embryo stage (6th week)
• Fusion of maxillary to frontonasal process.
• Midline ridge from posterior end of frontonasal process forms
septum
• 6th week
• 15mm stage

9. Nasal pits deepen and coalesce (end of 6th week)

10. Primitive Choanae formed at 7th week

11. Primitive nasal septum is completely Cartilagenous
2 centres
Groove on which septal catilage sits

12. Lateral nasal processes – nasal alae and lateral nasal wall
Hard palate formed by around 8th and 9th week
Palatine shelf – Medial extensions of maxillary process

14. Fuses with septum forming 2 passages which opens into defintive choanae

15. Paraseptal Jacobsons cartilage invagination of ectoderm leads to
Vomeronasal Organ

16. Disappears leaving a blind tubular pouch 2 – 6mm long

17. Jacobsons cartilage involutes leaving small cartilagenous bulge

18. VNO / Jacobsons organ is first stage of the accessory olfactory system,
and contains sensory neurons that detect chemical stimuli mainly used to
detect pheromones found in many animals

20. Processes
Structures
Formed
 Frontonasal Forehead, Bridge of nose,
medial and lateral nasal
prominences
 Maxillary Cheeks, Lateral portion of
upper lip
 Medial Nasal Philtrum of upper lip, Crest
and tip of nose
 Lateral Nasal Alae of nose, lateral nasal
wall
 Mandibular Lower lip and jaw