PALATE DEVELOPMENT

developed palate

initially the nasal cavity and oral cavity are continuous

when developed, the palate separates the nasal cavity from the oral cavity

developed palate comprised of

hard bony portion

soft (soft tissue) portion

hard palate

anterior aspect of palate

bony portion (maxilla and palatine bones)

soft palate

posterior aspect of palate

mobile and comprised of muscle fibers covered by mucous membrane

posteriorly has a central process that is the uvula

primary palate begins to

develop early in week 6

1. first, medial nasal prominences merge to form intermaxillary segment

intermaxillary segment gives rise to

labial component

upper jaw component

palatal component

labial component

forms the philtrum of the upper lib

upper jaw component

carries the 4 incisors

palatal component

forms the triangular primary palate

primary palate

portion of palate that is anterior and midline (premaxillary portion of the maxilla)

1. small portion that is anterior to incisive foramen

also early in week 6, the secondary palate

begins to develop

max prominences expand medially and give rise to

projections called palatal shelves (or lateral palatine processes)

at first, palatal shelves are directed

obliquely inferior

after palatal shelves are directed obliquely inferior, they advance

medially and fuse at midline to form the secondary palate

secondary palate

develops into the majority (remaining portions) of the hard and all of soft palate

of the secondary palate, the palatal shelves (lateral palatine processes) initially project

infero-medially on each side of the tongue

during week 7 and 8, the palatal shelves

ascend and assume a horizontal position

after palatal shelves have ascended, tongue is

now inferior to palate

orofacial clefts

cleft lip

cleft palate

cleft lip and palate

most common oromaxillofacial anomalies

cleft lip

when portions of the lip fail to fusec

cleft palate

when portions of the palate fail to fuse

1. soft palate only

2. hard and soft palate, but secondary palate only

3. primary and secondary palates, includes lip

cleft lip and palate

when these clefts occur together, rather than in isolation

classified as anterior vs posterior cleft defects

incisive foramen is dividing landmark

cleft can occur

unilaterally or bilaterally

median cleft lip

medial nasal prominences fail to fuse in midline to form the philtrum portion of the IM segment

unilateral or bilateral cleft lip

max prominence fails to fuse with medial nasal prominence

unilateral or bilateral oblique facial cleft

max prominence fails to fuse with medial and lateral nasal prominences

1. cleft extends onto face

anterior cleft defect

cleft in palate and/or lip structures anterior to the incisive foramen (unilateral or bilateral)

1. cleft lip only

2. cleft primary palate and cleft lip

posterior cleft defect

clefts in palate posterior to incisive foramen

1. clefts of the secondary palate

complete cleft defect

combination of anterior and posterior cleft defects

orofacial cleft repair

surgery improves the ability to eat/drink, breathe, hear, and speak

cleft lip surgery (cheiloplasty)

to close the lip and improve symmetry of lip/nose

cleft palate surgery (palatoplasty)

to close the opening between the nasal and oral cavity

create a palate that works well for speech

orofacial clefts and dentistry

developed nose portions

external nose

nasal cavity

developed nose boundaries

anterior - nares (nostrils)

posterior - choanae (opening/doorway between the nasal cavity and nasopharynx)

divide at midline by nasal septum

by the end of embryo week 4, nasal placodes develop on

each side of the frontonasal prominence

margins of the placodes proliferate

producing a horseshoe shaped elevation surrounding the nasal placode

1. lateral nasal prominence

2. medial nasal prominence

after proliferation of placode margins, nasal placodes now in a depression called

nasal pits

5 facial prominences that give rise to the external nose continue to grow and shape nose

frontal prominence - gives rise to the root

merged medial nasal prominences - form the crest and apex (tip)

lateral nasal prominences - form the alae (sides)

during the embryo 6th week, the nasal pits deepen considerably

partly due to growth of the surrounding medial and lateral nasal prominences

partly due to nasal pits penetration into the underlying mesenchyme and formation of primordial nasal sacs

each nasal sac grows dorsally (ventral to developing forebrain)

at first, the oronasal membrane separates the

nasal sacs from the oral cavity

by the end of embryo week 6, oronasal membrane ruptures

nasal and oral cavities are in communication by way of primitive choanae

choanae lie on each side of midline, posterior to primary palate

later, the choanae are pushed posteriorly with further development of secondary palate

1. will then be located at junction of nasal cavity and pharynx

nasal septum (midline structure separating nasal cavity into L and R cavities) grows

inferiorly

by embryo week 12, the nasal septum fuses

with the newly formed palate

choanal atresia

failure of the oronasal membrane to rupture

1. results in congenital narrowing of the back of the nasal cavity

2. causes difficulty breathing

3. unilateral or bilateral

   1. unilateral - mild symptoms, can go unidentified at birth

   2. bilateral - emergency, requires surgery

choanal atresia also often associated with other developmental anomalies including CHARGE syndrome

genetic syndrome (autosomal dominant) that affects many areas of the body

CHARGE

coloboma (iris defect(

heart defects

atresia (choanal)

slowed growth

genital anomalies

ear anomalies

developed paranasal sinuses

air filled cavities within the bones of the skull

1. frontal sinuses

2. maxillary sinuses

3. ethmoid air cells (sinuses)

4. sphenoid sinus

role in humidifying and heating air, speech sounds, reduce weight of skull

paranasal sinuses develop

as outgrowths from the walls of the nasal cavities

independently on differing timelines

paranasal sinuses extend into bones of same name to become

pneumatic (air-filled) extensions of the nasal cavities

paranasal sinus growth

alters shape of face during infancy/childhood

adds resonance to voice during adolescence

maxillary sinuses begin to develop as

spaces during late fetal life

1. very small at birth (pea-sized)

2. grows slowly until puberty

3. may continue to increase in size throughout lifetime

frontal, sphenoid, and ethmoid air cells (sinuses) develop as

spaces soon after birth

ethmoid air cells (sinuses)

small before the age of 2 yrs

begin to grow more rapidly at 6-8 yrs

frontal sinuses

rapid growth between puberty and adulthood

typically stops growing around 25 years of age

sphenoid sinus

rapid growth in childhood

majority of growth has occurred by puberty