Oral Embryology Flashcards
(29 cards)
Where does fertilisation occur?
Within the oviduct
How long is tubal transport of the fertilised ova?
7-10 days
At what stage does the embryo enter the uterus?
The morula or early blastocyst
When does the blastocyst implant?
By day 17
What is the internal cavity of the blastocyst called?
A blastocoele
In what direction does general embryologic development occur?
Cephal-caudal direction
What is the sequence of embryological development?
- Head folds
- Neural tube closure
- Somite formation
- Development of the brachial clefts
- Development of the lens placode
- Development of the otic placode
- Development of the cardiac bulg
- Development of the limb buds
Define gastrulation?
The formation of the embryo’s germ layers
What is the Rauber’s layer?
The area that gives rise to the proliferation of the inner cell mass during gastrulation
What develops from the inner cell mass?
The endodermal layer, then the embryonic disc
How are mesodermal tissues and the notochord formed?
From infolding of the embroynic disc in a cephalon-caudal direction
How are pharyngeal clefts formed?
By invaginations of the surface ectoderm
What do the pharyngeal clefts define?
Pharyngeal arches
What are the pharyngeal arches composed of?
Mesenchyme and neural crest cells; aortic arch artery and an associated cranial nerve
What does facial formation depend on?
The correct formation, development and fusion of five primordial structures:
- Single fronto-nasal prominence
- Paired maxillary prominences
- Paired mandibular prominences
How are the nasal cavities formed?
An ectodermal thickening forms the nasal placodes; then mesenchymal thickenings alongside this form the medial and lateral nasal prominences
How is the primary palate formed?
A thin membrane separates the nasal pits from the oral cavity. The caudal portion of this later atrophies to form a common oro-nasal opening (the choana); and the remaining rostral portion of the membrane forms the incisive process and the primary palate
How does the tongue develop?
From the proliferation of mesenchymal tissues on the floor of the primordial pharynx.
What part of the tongue develops from the first pharyngeal arch?
Two lateral lingual swellings and one medial lingual swelling
What part of the tongue develops from the second and third pharyngeal arch?
A midline swelling known as the Copula
What part of the tongue develops from the third and fourth pharyngeal arch?
The hypopharyngeal eminence
How does the rostral 2/3 of the tongue form?
The fusion of the two lateral lingual swellings and the medial lingual swelling
How does the caudal 1/3 of the tongue form?
From the expansion of the Copula with some contribution from the hypopharyngeal eminence
What forms the lung bud?
The laryngo-tracheal groove at the caudal portion of the pharyngeal arches forms the primordial trachea
