Embryology - Development of mouth and face Flashcards
(42 cards)
When is the stomadeum present?
Third week:
- SOmites appear and the buccopharyngeal membrane breaks down.
When the embryo is 3mm long and in its 4th week what happens?
The frontonasal process and the beginning of mandibular and hyoid arches appear.
When do teeth start forming?
Six weeks.
How big is the embryo at 6 weeks?
12mm long.
When does calcification of the first dentine occur?
In the 5th month, followed closely by enamel.
What bounds the stomodeum?
Mandibular arch.
What does the mandibular arch produce?
- Floor of the mouth.
- Lower jaw.
- Lower lip.
- Two maxillary processes.
What is the mandibular arch’s cranial boundary?
Forebrain capsule.
What does the forebrain capsule develop into?
Frontonasal processes.
How is the frontonasal processes identified?
Two nasal pits:
1. Median processes.
2. Two lateral nasal processes.
How is the median process characterised?
By a pair of convex globular processes.
What happens to the lateral nasal processes?
They unite with the globular processes to encircle the nostril.
What does the maxillary and lateral nasal processes encircle?
The eye - they meet together alon the line of nasolacrimal duct.
Where on the facade does the maxillary process unite?
In the midline below the nostril. To produce the whole of the upper lip and the maxillae.
What does the frontonasal processes produce?
Pre-maxilla - which is covered over by medial extensions of the maxilla in man.
How is the upper part of the face formed?
By fusion of the frontonasal and maxillary processes. However, it’s just a mask at first, as the nasal septum and palate have yet to be completed.
Where does the developing tongue lay?
Against the floor of the cranium.
How does the nasal septum form?
A midline flange grows down from the base of the forebrain capsule (mesenchymal precursor of the skull).
What grows from each maxillary process?
Flange - palatial process grows medically across the dorsum of the tongue.
What happens when the nasal septum and the two palatal processes meet?
They unite from before backwards, they separate the nasal cavities from each other and also separate the cavities from the mouth.
What forms the nasal capsule?
Mesoderm.
When does chondrification of the nasal capsule occur?
By the 6th week.
What also occurs at the 6th week?
THe nasal walls and hard palate are outlines by a thin layer of hyaline cartilage.
When does ossification of the hyaline cartilage in the nasal capsule begin?
After 6 weeks.
