E - Development of face Flashcards
When does the external human face develop in gestation?
Between the 4th and 6th week
When is the face completed?
6th week gestation
When does the palate begin to develop?
Between the 6th and 8th week
What does the development of the palate cause?
Distinction between the oral and nasal cavities
What’re the two important tissues involved in face and nose development?
Pharyngeal arches and neural crest cells
How many pharyngeal arches are there? Position? When do they form?
Six - out-pocketings of the mesoderm - fourth week of gestation
What does each pharyngeal arch have?
A branch of the aorta, a cranial nerve and a cartilage bar.
What’re neural crest cells?
A specialised cell lineage which originate from the neuroectoderm
Where do neural crest cells go?
As the neural tube forms, cells from the lateral border of the neuroectoderm are displaced through the mesoderm
How do neural crest cells help face and palate development?
They enter the mesoderm where they enter the pharyngeal arches and contribute towards their derivatives
When does the oropharyngeal membrane appear?
Week 3 of gestation
What does the oropharyngeal membrane consist of?
Ectoderm and endoderm - externally and internally respectively
What happens to the oropharyngeal membrane in the fourth week of gestation?
It breaks down to become the future oral cavity and sits at the beginning of the digestive tract
What do structures of the external face originate from?
Frontonasal prominence and the mandibular and maxillary prominences
From what does the frontonasal prominence originate from?
Proliferation of mesenchymal neural crest cells ventral to the forebrain
Originations of the mandibular and maxillary prominences
The 1st pharyngeal arch
Space between the maxillary prominences and its derivatives
Stomatodeum - mouth and pituitary gland
Outline Nasal development
Bumps called nasal placodes appear on the frontonasal prominence. These invaginate to form nasal pits. The nasal pits have medial and lateral prominences on each side
How is a central structure of the face formed in gestation?
As the maxillary prominences develop laterally, the nasal prominences push inwards medially. The maxillary prominences then fuse with the nasal prominences
Derivatives of frontonasal prominence
Forehead, bridge of nose, medial and lateral nasal prominences
Derivatives of medial nasal prominences
Philtrum (the groove between the mouth and nose), primary palate, upper 4 incisors and associated jaw
Derivatives of lateral nasal prominences
Side of nose
Derivatives of maxillary prominences
Cheeks, lateral upper lip, secondary palate, lateral upper jaw
Derivatives of mandibular prominences
Lower lip and jaw
