Embryology, Surgical and Applied Anatomy of the Palate .ppt

Introduction

The palate forms the roof of the oral cavity.
Development begins during week 5 IU.
Fusion of its component parts is not complete until week 12 IU.
The palate forms from 2 major parts: the primary and secondary palates.
The palate is important for:

  • Phonation
  • Deglutition
  • Mechanical partition
  • Salivation
  • Ruggae

Embryology of the Palate

Third Week

  • Development of the palate is traced from the embryology of the face.
  • A chronological event from week 3 to 12 IU.
  • First evidence is seen in week 3 IU.

Structures evident at week 3:

  • Enlarging brain primordium
  • Oropharyngeal membrane
  • Pericardial swelling (heart primordium)

Facial prominences around the mouth:

  • Frontonasal prominence
  • Paired maxillary prominences
  • Paired mandibular prominences

Cranial neural crest cells populate these prominences.
Palatogenesis starts in week 6 and completes by week 12.

Buccopharyngeal (Oropharyngeal) Membrane

  • Found between the brain and heart primordia
  • Made of ectoderm and endoderm
  • Breaks down in week 4 to connect mouth and foregut

Fourth Week

  • Breakdown of the oropharyngeal membrane
  • Emergence of frontonasal and mandibular arches
  • Appearance of otic, lens, and nasal placodes
  • Maxillary process appears at stomodeum corners

Nasal Placodes (Week 4–5)

  • Become olfactory epithelium
  • Surrounded by medial and lateral nasal swellings
  • Form nasal pits and begin nasal cavity development

Sixth Week

  • Merging of medial nasal processes forms the intermaxillary process
  • Develops into the primary palate
  • Gives rise to the premaxilla (carrying the upper incisors)

Nasal Cavity and Primitive Choana

  • Nasal pits become cavities
  • Nasal fin forms then thins to oronasal membrane
  • Oronasal membrane breaks to form primitive choana

Secondary Palate Development

  • Occurs because the primary palate is too short
  • Develops from lateral palatal shelves of maxillary processes
  • Palatal fusion completes by week 12

Palatal Shelf Outgrowth (Weeks 7–8)

  • Palatal processes grow vertically beside the tongue
  • By week 8, tongue drops and shelves elevate horizontally
  • Fusion with each other, primary palate, and nasal septum follows

Mechanisms of Palatal Shelf Elevation

  • Rapid shelf rotation
  • Tissue growth dynamics
  • Tongue movement and jaw growth

Fusion Process

  • Medial edge epithelium (MEE) cells undergo apoptosis
  • A midline epithelial seam (MES) forms then disintegrates
  • Secondary palate becomes continuous and fuses with nasal septum

Membrane Bone Formation

  • Forms in primary palate to make premaxilla
  • Bone grows into lateral shelves to form hard palate
  • Posterior shelves remain unossified, forming soft palate and uvula

Centers of Ossification

  • One in each maxilla and palatine bone
  • Appear in week 8
  • Incomplete ossification defines palatine sutures

Facial Malformations: Clefts

  • Caused by failed fusion or merging
  • Can be unilateral or bilateral
  • Complete or incomplete clefts of lip, palate, or both

Applied Anatomy of the Palate
Skeletal framework includes:

  • Sphenoid
  • Temporal
  • Premaxilla
  • Maxilla proper
  • Palatine bone

These serve as muscle attachments and passageways for nerves/vessels.

Hard Palate Anatomy

  • Bony plate separating oral and nasal cavities
  • Covered above by respiratory mucosa and below by oral mucosa
  • Includes premaxilla, incisive foramen, palatine processes, horizontal plates

Soft Palate (Velum)

  • Fibromuscular structure attached to hard palate
  • Contains mucosa, palatine aponeurosis, and muscle
  • Uvula hangs from its midline
  • Oral surface: median palatine raphe
  • Nasal surface: ciliated epithelium (anterior), oral-like (posterior)

Muscles of the Soft Palate

  • Tensor veli palatini: opens Eustachian tube
  • Levator veli palatini: elevates soft palate
  • Palatoglossus: pulls tongue root upward
  • Palatopharyngeus: raises pharyngeal wall
  • Musculus uvulae: lifts uvula

Velopharyngeal Mechanism

  • Ensures oral-nasal cavity separation
  • Crucial for speech, swallowing, and blowing
  • Involves velum, lateral and posterior pharyngeal walls

Velopharyngeal Closure

  • Achieved by muscles like:
    • Levator veli palatini
    • Musculus uvulae
    • Superior pharyngeal constrictor
    • Palatoglossus
    • Palatopharyngeus
    • Salpingopharyngeus

Pharyngotympanic Tube

  • Cartilaginous and osseous parts
  • Opens during swallowing and sneezing
  • Maintains ear pressure and drains fluid
  • Can allow spread of infections

Cleft Palate Anatomy

  • Abnormal muscle orientation and aponeurosis
  • Muscles like tensor/levator veli palatini insert abnormally
  • Leads to speech issues and middle ear problems


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