3.1 Development of the head & neck Flashcards
The face is formed between the 4th and 10th weeks by the fusion of five facial prominences (processes) derived from _________________
Derivatives of ___________: Forehead, nose (including nasal septum), middle portion of upper lip, primary palate (internal part of FNP)
Derivatives of ____________: Lateral portion of upper lip, most of cheek and upper jaw, secondary palate
Derivatives of ________: Inferior lip, cheek, and lower jaw
neural crest-derived mesenchyme & 1st pharyngeal arches;
Frontonasal prominence (FNP);
Maxillary (1 pair)
Mandibular (1pair)
The secondary palate (on each side) fuses in the midline with the __________ and anteriorly with the _____________:
• Hard palate separates the oral cavity from the nasal cavity
• Any defects in fusion of these prominences cause defects like cleft palate and cleft lip
nasal septum;
primary palate
During the 4th week of embryonic development, the 5 facial prominences develop around the __________________:
• Stomodeum is still temporarily closed by the oropharyngeal membrane at this point; membrane later ruptures → stomodeum becomes oral cavity
During the 5th week, a pair of _______________ develop on the frontonasal prominence (future nasal cavities):
• Nasal placodes invaginate to form nasal pits → simultaneously divide part of the FNP into the medial and lateral nasal prominences
• _________________ is the furrow separates the lateral nasal prominence and the maxillary prominence
stomodeum (future mouth);
thickened ectodermal nasal (olfactory) placodes;
Nasolacrimal groove
In the 6th – 7th weeks, the maxillary prominence grows rapidly (increases in size) towards midline:
• Growth of maxillary prominence and regression of FNP pushes medial nasal prominence towards midline
- Medial nasal: Fuse to form the ___________________
- Lateral nasal: _____________
- Maxillary: Enlarges to form most of the cheek and maxillae
• Fuses with medial nasal prominence: lateral portion of upper lip
• Fuses with lateral nasal prominence after the nasolacrimal duct has formed in the nasolacrimal groove - Mandibular: Fuse to form the ______________
bridge of the nose (midline portion) and the philtrum (middle portion of upper lip);
Sides (ala) of the nose ;
lower lip, chin and lower jaw
DEVELOPMENT OF THE PALATE
The intermaxillary segment is formed by the fusion of the _______________:
• Gives rise to the philtrum of upper lip, median part of upper jaw (with the 4 incisor teeth) and the primary palate
Primary palate forms only the small anterior part of the hard palate, while the remaining main part of the definitive palate is formed by the secondary palate:
• Secondary palate is formed by the _______________ growing out of the maxillary swellings (directed downwards and obliquely on each side of the tongue) • During the 7th week, the mandible grows and expands → tongue moves ______________
→ allows palatine shelves to move horizontally and fuse to form secondary palate
• Secondary palate fuses with primary palate anteriorly to form the definitive palate (____________ is the junction between the two)
medial nasal prominences;
palatine shelves;
downwards;
incisive foramen
FACIAL DEVELOPMENTAL DEFECTS
The defects of facial formation occur due to a failure of fusion between any of the facial prominences (resulting in various combinations of defects)
Cleft lip:
- unilateral: Failure of maxillary prominence to fuse with its corresponding ______________
- bilateral: Same as unilateral cleft lip (but occurs bilaterally)
- median: Failure of two _____________ to fuse in the midline
Cleft palate: Failure of ______________ to fuse to form the secondary palate
Oblique facial cleft: Failure of maxillary prominences to merge with their corresponding lateral nasal prominences
• Usually causes an exposed _____________
medial nasal prominence;
medial nasal prominences;
palatine shelves;
nasolacrimal duct
DEVELOPMENT OF THE EAR
The ear consists of the external ear, middle ear, and internal ear, which have different origins but function as one unit:
• Middle ear (tympanic cavity) is surrounded by the tympanic membrane/eardrum (separates the external and middle ear)
• __________________ connects the tympanic cavity with nasopharynx
Auditory (pharyngotympanic) tube
The inner ear begins to develop on the 22nd day of development from the thickening of _____________ on either side of the hindbrain (otic placodes):
• Otic placodes invaginate to form ______________, which further divide into dorsal and ventral components
• Collectively known as the ________________ (involved in equilibrium except for the cochlea forming the organ of Corti involved in hearing)
Vesicle Derivatives
- Ventral: ______, _________
- Dorsal: ___, ______, ________
ectoderm;
otic (auditory) vesicles;
membranous labyrinth;
Saccule, cochlear duct;
Utricle, semicircular canals, endolymphatic duct
The middle ear cavity develops from the _______________along with the auditory tube (which connects middle ear to nasopharynx):
• Ossicles (bones) of the middle ear develop from the mesoderm of the 1st and 2nd pharyngeal arches including the following:
- 1st pharyngeal arch: ________
- 2nd pharyngeal outch: ___________
tubotympanic recess (1st pharyngeal pouch)
inceus, malleus;
stapes
The outer ear (external auditory meatus) develops from the 1st pharyngeal cleft:
• Tympanic membrane (lying between the external and middle ear) is derived from the 1st pharyngeal cleft, arch, and pouch
- _______________: Ectoderm of 1st pharyngeal cleft
- ___________: Mesoderm of 1st pharyngeal arch
- __________: Endoderm of 1st pharyngeal pouch
Outer epithelial lining;
Middle fibrous part;
Inner lining
During the 5th week, there are six mesenchymal proliferations (auricular hillocks) which develop at the ____________________:
• Auricular hillocks begin to enlarge, differentiate and eventually fuse to produce the definitive form of the auricle during the 7th week
• Auricle is gradually translocated from its original location low on the side of the neck to a more ____________ site as the face develops
dorsal aspect of the 1st and 2nd pharyngeal arches;
lateral and cranial
