Palate Development

Notice - Mark Hill

Currently this page is only a template and will be updated (this notice removed when completed).

Introduction

File:Stage18-19 Cleft Primary Palate.jpg

Stage 18-19 Cleft Primary Palate

The palate has two key stages of development during embryonic and an early fetal involving the fusion of structures (epithelia to mesenchymal).

Historic Head Embryology
1910 Skull \| 1910 Skull Images \| 1912 Nasolacrimal Duct \| 1921 Human Brain Vascular \| 1923 Head Subcutaneous Plexus \| 1919 21mm Embryo Skull \| 1920 Human Embryo Head Size \| 1921 43 mm Fetal Skull \| Historic Disclaimer

Some Recent Findings

A genome-wide association study of cleft lip with and without cleft palate identifies risk variants near MAFB and ABCA4^[1] "Case-parent trios were used in a genome-wide association study of cleft lip with and without cleft palate. SNPs near two genes not previously associated with cleft lip with and without cleft palate (MAFB, most significant SNP rs13041247, with odds ratio (OR) per minor allele = 0.704, 95% CI 0.635-0.778, P = 1.44 x 10(-11); and ABCA4, most significant SNP rs560426, with OR = 1.432, 95% CI 1.292-1.587, P = 5.01 x 10(-12)) and two previously identified regions (at chromosome 8q24 and IRF6) attained genome-wide significance."
A dosage-dependent role for Spry2 in growth and patterning during palate development^[2] "The formation of the palate involves the coordinated outgrowth, elevation and midline fusion of bilateral shelves leading to the separation of the oral and nasal cavities. Reciprocal signaling between adjacent fields of epithelial and mesenchymal cells directs palatal shelf growth and morphogenesis. Loss of function mutations in genes encoding FGF ligands and receptors have demonstrated a critical role for FGF signaling in mediating these epithelial-mesenchymal interactions. The Sprouty family of genes encode modulators of FGF signaling. We have established that mice carrying a deletion that removes the FGF signaling antagonist Spry2 have cleft palate."

Textbooks

The Developing Human: Clinically Oriented Embryology (8th Edition) by Keith L. Moore and T.V.N Persaud - Moore & Persaud Chapter Chapter 10 The Pharyngeal Apparatus pp201 - 240.
Larsen’s Human Embryology by GC. Schoenwolf, SB. Bleyl, PR. Brauer and PH. Francis-West - Chapter 12 Development of the Head, the Neck, the Eyes, and the Ears pp349 - 418.

Movies


Face Development	Palate 1	Palate 2	Tongue	Ultrasound - Cleft Lip
Quicktime \| Flash	Quicktime \| Flash	Quicktime \| Flash	Quicktime \| Flash	Quicktime \| Flash

Links: Quicktime Movies | Flash Movies | Ultrasound

Development Overview

Pharyngeal Arch Components

Major features to identify for each: arch, pouch, groove and membrane. Contribute to the formation of head and neck and in the human appear at the 4th week. The first arch contributes the majority of upper and lower jaw structures.

Early Face and Pharynx

Pharynx - begins at the buccopharyngeal membrane (oral membrane), apposition of ectoderm with endoderm (no mesoderm between)

Pharyngeal Arch Development

branchial arch (Gk. branchia= gill)
arch consists of all 3 trilaminar embryo layers
ectoderm- outside
mesoderm- core of mesenchyme
endoderm- inside

Neural Crest

Mesenchyme invaded by neural crest generating connective tissue components
cartilage, bone, ligaments
arises from midbrain and hindbrain region

Face Development

Begins week 4 centered around stomodeum, external depression at oral membrane

5 initial primordia from neural crest mesenchyme

single frontonasal prominence (FNP) - forms forehead, nose dorsum and apex
nasal placodes develop later bilateral, pushed medially
paired maxillary prominences - form upper cheek and upper lip
paired mandibular prominences - lower cheek, chin and lower lip

Frontonasal Process

The frontonasal process (FNP) forms the majority of the superior part of the early face primordia. It later fuses with the maxillary component of the first pharyngeal arch to form the upper jaw. Failure of this fusion event during the embryonic period leads to cleft lip. Under the surface ectoderm the process mesenchyme consists of two cell populations; neural crest cells, forming the connective tissues; and the mesoderm forming the endothelium of the vascular network.

A chicken developmental model study has identified a specific surface region, the Frontonasal Ectodermal Zone (FEZ), initially induced by bone morphogenetic proteins that appears to regulate the future growth and patterning of the frontonasal process. The specific frontonasal ectodermal zone was located in the frontonasal process ectoderm flanking a boundary between Sonic hedgehog (Shh) and Fibroblast growth factor 8 (Fgf8) expression domains.^[3]

Head Growth

continues postnatally - fontanelle allow head distortion on birth and early growth
bone plates remain unfused to allow growth, puberty growth of face

Embryonic Palate

Primary palate, fusion in the human embryo between stage 17 and 18, from an epithelial seam to the mesenchymal bridge.

Fetal Palate

Secondary palate, fusion in the human embryo in week 9. This requires the early palatal shelves growth, elevation and fusion during the early embryonic period. The fusion event is to both each other and the primary palate. palatal shelf elevation | secondary palate

Abnormalities

Cleft Palate - Australia (1981-1992)^[4]

The way in which the upper jaw forms from fusion of the smaller upper prominence of the first pharyngeal arch leads to a common congenital defect in this region called "clefting", which may involve either the upper lip, the palate or both structures.

Ten most frequently reported birth anomalies

Hypospadias (More? Development Animation - Genital Male External | Genital Abnormalities - Hypospadia)
Obstructive Defects of the Renal Pelvis (More? Renal System - Abnormalities)
Ventricular Septal Defect (More? Cardiovascular Abnormalities - Ventricular Septal Defect)
Congenital Dislocated Hip (More? Musculoskelal Abnormalities - Congenital Dislocation of the Hip (CDH))
Trisomy 21 or Down syndrome - (More? Trisomy 21)
Hydrocephalus
Cleft Palate
Trisomy 18 or Edward Syndrome - multiple abnormalities of the heart, diaphragm, lungs, kidneys, ureters and palate 86% discontinued (More? (More? Trisomy 18)
Renal Agenesis/Dysgenesis- reduction in neonatal death and stillbirth since 1993 may be due to the more severe cases being identified in utero and being represented amongst the increased proportion of terminations (approximately 31%).
Cleft Lip and Palate - occur with another defect in 33.7% of cases.

From the Victorian Perinatal Data Collection Unit in Victoria between 2003-2004.

Embryonic Human Cleft Palate

	File:Stage18 cleft palate.jpg	File:Stage19 cleft palate.jpg
Stage16	Stage18	Stage19

Cleft Lip

International Classification of Diseases code 749.1 for isolated cleft lip and 749.2 for cleft lip with cleft palate.
Australian national rate (1982-1992) 8.1 - 9.9 /10,000 births.
Of 2,465 infants 6.2% were stillborn and 7.8% liveborn died during neonatal period.
rate similar in singleton and twin births.

Cleft Palate

International Classification of Diseases code 749.0
Australian national rate (1982-1992) 4.8 - 6 /10,000 births.
Of 1,530 infants 5.5% were stillborn and 11.5% liveborn died during neonatal period.
slightly more common in twin births than singleton.

(Data: Congenital Malformations Australia 1981-1992 P. Lancaster and E. Pedisich ISSN 1321-8352)

Links: Development Animation - Palate 1 | Development Animation - Palate 2 | Orofacial Cleft with or without cleft palate

Search Pubmed Now: cleft lip | cleft palate

References

↑ <pubmed>17693063</pubmed>
↑ <pubmed>17693063</pubmed>
↑ <pubmed>18028903</pubmed>
↑ P. Lancaster and E. Pedisich, Congenital Malformations Australia 1981-1992, ISSN 1321-835.