Formation of the Face
Terms
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- The face is derived from what 5 primordia:
-
FP = frontal process
MNP = medial nasal process
LNP = lateral nasal process
MaxP = maxillary process
ManP = mandibular process - What is FUSION?
- Joining of FREE processes; involves epithelial disintegraion.
- What is MERGING?
- Joining of incompletely separated processes b removing the intervening groove between them.
- Which of the face primordia has already joined prior to face formation?
- Mandibular processes
- What are the lateral/medial nasal processes?
- Elevations that surround the olfactory placodes; caused by growth of the Frontal Process.
- What are the 5 steps in face formation?
-
1. MaxP fuses with LNP
2. MAXP merges with FP
3. 2 MNPs merge
4. MAXP fuses with MNP
5. Maxp merges with ManP - Where do the MNP and LNP arise from?
- Olfactory placodes on FP
- Where do MaxP and ManP arise from (what arch)?
- Arch 1
- What is dacryostenosis?
- Failure of the nasolacrimal duct to canalize
- What happens to the olfactory placode when the MNP/LNP form?
- It becomes the NASAL PIT floor
- What develops as a result of MaxP fusing with LNP and merging with FP? (steps 1/2)
- The nasolacrimal duct and sac.
- What is dacryostenosis again?
- Failure of canalization of the nasolacrimal duct.
- What happens after MaxP fuses w/ LNP and merges w/ FP? (Step 3) What is the result?
- The 2 MNP's merge to form the Intermaxillary segment
- What 3 things make up the intermaxillary segment?
-
1. Middle upper lip (philtrum)
2. Incisor bridge of upper jaw
3. Primary Palate - What happens after forming the intermaxillary segment? (Step 4)
- MNP fuses w/ Max P to create the Nasal Fin
- What is the purpose of the nasal fin?
- It separates the nasal pit from the oral cavity.
- What is the last step of face formation?
- MaxP merges with ManP to form the CHEEKS.
- How does the nose develop?
-
1. LNP makes the Nose Ala
2. MNP + FP make the bridge, top, and between external nares - Define Choanae:
- the openings between the nasal cavity and pharynx
- What direction does the nasal cavity enlarge in?
- Anterior-posterior
- How do the primitive choanae form?
-
1. Oronasal membrane stretches
2. Membrane ruptures
3. Forms Primitive Choanae - What is Choanal atresia?
- Absence of one or both primitive choanae due to obstruction (usually bone)
- What does bone obstruction to choanae development result in?
- Failure of oronasal membrane to rupture by 38 days.
- What type of situation results in bilateral choanal atresia?
- Emergency! Respiratory distress immediately.
- What is the Ethmoid Bone responsible for?
- Orbital separation and nasal cavity growth.
- What 2 conditions can result from abnormal ethmoid devo?
-
1. Hypotelorism
2. Hypertelorism - What causes hypotelorism? what is it?
- Small ethmoid - eyes too close
- What causes hypertelorism? What is it?
- Big ethmoid - eyes too wide
- By what week is human facial form achieved?
- Weke 8
- What does elongation and hypertrophy of Arch 1 accomplish?
-
-Ears moving superdorsally
-Eyes moving toward midline -
What is the ratio of cranium:face size in
-Newborn
-Adult -
Newbie = 8:1
Acult = 3:1 - What do the 1' and 2' palates form together?
- The hard palate
- What causes the formation of the primary palate?
- The merging of the MNP's
- What forms the secondary palate?
- -Palatine processes - of the maxillary and palatine bones.
- What drives the apposition and fusion of the palatine plates?
- Shelf force - directed force that elevates the palatal processes to a horizontal pos.
- What is essential for proper palate fusion?
- Inferior movement of the tongue as the mandibular arch grows ant-posteriorly.
- What cell process allows fusion of the palatine processes?
- Apoptosis
- What is the last part of the palate to develop?
- Soft palate - from mesenchymal proliferation of the caudal 2' palate; LASTLY = uvula
- What causes a Lateral Cleft Lip?
- Failure of 1' and 2' palates to fuse
- What causes a median cleft lip?
- Failure of the MNPs to merge (to form the 1' palate)
- What causes an Oblique Facial Cleft?
- Failure of the MaxP and ManP to merge
- What causes a Cleft Palate?
- Failure of the 2' palate to fuse
- What is the most common type of cleft LIP?
- Lateral (uni or bi)
- What are the common characteristics of lateral cleft lip?
-
-Left side
-Boys - What are the common qualities of cleft PALATE?
-
-Seen w/ Cleft LIP
-Females 2x as often
-Specific factors lead to it - What 3 morphogenic factors lead to cleft palate?
-
1. Abnormal tongue devo (fails to move down during 2' fusion)
2. Cysts - remnants of fusion
3. Impediment of shelf force - What can impede the shelf force?
- Glucocorticoids at pharmocologic levels
- What is cleft palate by itself NOT influenced by?
- Race
- What is Cleft lip by itself not influenced by?
-
Maternal Age
Parity - What are Cleft lip AND palate together not influenced by?
- Nothing
- What are 3 types of First Arch Syndromes?
-
1. Mandibulofacial Dysostasis
2. Maxillary hypoplasia
3. Mandibular hypoplasia -
What is another name for Mandib dysostasis?
What symptoms? -
Treacher Collins Syndrome
-Slanting eye crease
-Clefts of arch 1 structures
-Deaf, lower lid coloboma -
What is another name for maxillary hypoplasia?
Symptoms: -
Crouzon
-Hypoplastic midface
-Hypertelorism
-Coronal suture synostosis
-Malocclusion -
What is another name for mandibular hypoplasia?
Symptoms: -
Pierre Robin Sequence
-Small jaw
-Glossoptosis
-Difficulty breathing
-Cleft palate - What is CHARGE association?
- A set of anomalies that are often seen together.
- What does CHARGE stand for?
-
-Coloboma of the eye
-Heart Defects
-Atresia (of choana)
-Retardation
-Genital Hypoplasia
-Ear anomalies - What determines if a patient has charge?
- 4/6 anomalies must be present
- What is holoprosencephaly?
- All midline defects of forebrain and face.
- What are 3 associated "faces" assoc w/ holoprosencephaly?
-
1. Cyclopia (maybe proboscis)
2. Ethmocephaly (Hypotelorism+)
3. Cebocephaly (Hypotelorism + single nostril + proboscis) - What is the mildest form of holoprosencephaly?
- Single maxillary incisor
- What 4 factors are associated with holoprosencephaly?
-
1. Toluene inhalation
2. Maternal diabetes
3. Fetal alcohol syndrome
4. Trisomy conditions -
What is Apert's syndrome?
Symptoms: -
Towering skull
-Flat midface area
-Syndactyly
-Cleft palate
-Variable intelligence - Symptoms of Accutane induced facial dysplasia:
-
-First arch defects
-Ear anomalies
-Skin problems
-Cleft lip and palate - What is Lateral Facial Dysplasia?
- Syndrome of the 1st/2nd arches; Affects one side only.
- What are the symptoms of lateral facial dysplasia?
-
-Small mouth
-One side of face small
-Microtia (small ear)
-Hemivertebrae/hypoplastic vert. - What is a Proboscis?
- A blind end tube-like structure.