PRENATAL GROWTH OF MAXILLA

BY- ANUBHUTI SABHLOK

THE PRENATAL LIFE ARBITRARILY IS DIVIDED INTO THREE PERIODS:

1) PERIOD OF OVUM2) EMBRYONAL PERIOD3) FETAL PERIOD

The period of ovum is of 2 weeks,in this period there is cleavage of ovum and its attachment to the uterine wall.

The embryonal period starts from the third week to the eighth week of IUL, during this period major development of facial and cranial region occurs.

The fetal period extends between the eighth week and the birth,during this period increase in growth rate and size of craniofacial structures occurs.

Growth of maxilla

Around the fourth week of IUL, a prominent bulge appears on the ventral aspect of the embryo corresponding to the developing brain. Below the bulge is a shallow depression corresponding to the primitive mouth called the stomodeum. Floor of mouth-buccopharangeal membrane.

By around 4th week of IUL,5 branchial arches form in of future head and neck.The first branchial arch is called the mandibular arch forms the lateral wall of the stomodium and it plays an important role in development of the naso-maxillary region.

Pharyngeal arches

The mesoderm covering the developing brain proliferates in a downward direction and forms a downward projection called the frontonasal process.

The stomodeum is thus overlapped a) Superiorly by the frontonasal process b) Laterally by the mandibular arches.

The mandibular arch gives off a bud from its dorsal end called THE MAXILLARY PROCES, which grows ventro-medio-cranially and is called as the mandibular process.

Thus at this stage the stomodium is overlapped Above by frontonasal process Below by mandibular processOn either side by maxillary process

The ectoderm overlying the frontonasal process shows bilateral localised thickenings called as Nasal placodes, which soon sinks and form nasal pits.The formation of these nasal pits divides the frontonasal process into:- ( A)The medial nasal process ( B)The lateral nasal processAs the maxillary process undergoes growth the fronto nasal process becomes narrow so that the 2 nasal pits come closer.

The depression present in the midline of fusion of the maxillary process and the medial nasal process is called the philtrum. The line of fusion of the maxillary process and the lateral nasal process corresponds to the nasolacrimal duct. The two mandibular process grow medially, and fuse to form the lower lip and lower jaw.

DEVELOPMENT OF PALATE

The palate is formed by contributions of the:-(a)Maxillary process(b)Palatal shelves given off by the maxillary process(c)Fronto nasal processThe fronto nasal process gives rise to the premaxillary region while the palatal shelves form the rest of the palate.

As the palatal shelves grow medially, their union is prevented by the presence of tongue initially. In the seventh week(47th and 54th day)a transformation in the position of the palatal shelves occurs from vertical to horizontal.As the proliferation of nasal septum takes place during the mandibular growth it allows the tongue to drop down.

The two palatal shelves, by 81/2 weeks are in a close approximation. After joining of the palatal shelves, the epithelial lining sheds off. The connective tissue intermingle s resulting in their fusion.

The medial edges of the palatal processes fuse with the free lower end of the nasal septum separating the 2 nasal cavities from each other and from the oral cavity.

Failure of fusion of palatine processes with each other and the nasal septum gives rise to defect CLEFT PALATE

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