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EMBRYLOGY8 Dr.Ban A.Ghani EMBRYOLOGY8 Dr.Ban A.Ghani EMBRYLOGY8 Dr.Ban A.Ghani Palatogenesis involves the initiation, growth, morphogenesis, and fusion of the primary and secondary palatal shelves from initially separate facial prominences during embryogenesis to form the intact palate separating the oral cavity from the nostrils. Palatal formation: Tissue intervening between nasal and oral cavities is known as the palate. By the 6th week the primary palate, formed by the two maxillary and two medial nasal processes, separates the developing oral and nasal cavities. Subsequently, between 6th and 8th weeks, the secondary palate is formed from two palatal processes (outgrowths of the maxillary processes).Primary and secondary palates together form the definitive palate. Development of the primary palate:Around the 5th week, the intermaxillary segment arises as a result of fusion of the two medial nasal processes and the frontonasal process within the embryo. The intermaxillary segment gives rise to the primary palate. The primary palate will form the premaxillary portion of the 1 EMBRYOLOGY8 Dr.Ban A.Ghani maxilla (anterior one-third of the final palate). This small portion is anterior to the incisive foramen and will contain the maxillary incisors. The secondary palate: is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates ,it consists anteriorly of the bony hard palate and posteriorly of the muscular soft palate. The hard palate is crucial for normal feeding and speech, whereas the soft palate is movable and closes off the nasal airway during swallowing. The development of the secondary palate commences in the 6th week of human embryological development, as paired outgrowths, which initially grow vertically flanking the developing tongue and subsequently reorient to the horizontal position above the dorsum of the tongue in a process known as palatal shelf elevation . With growth and expansion of the mandible the tongue moves down, allowing the palatine shelves to grow toward the midline where they meet and fuse with each other.The secondary palate fuses anteriorly with the primary palate with the incisive foramen being the landmark between the primary palate and secondary palate,and anterodorsally with the nasal septum, to form the intact roof of the oral cavity. Complete fusion of the primary and secondary palate is a complex process involving growth of the component tissues, epithelial to mesenchymal 2 EMBRYOLOGY8 Dr.Ban A.Ghani transformation, cell migration, and programmed cell death at fusion sites – disruption of any part of this process can result in cleft palate. Cleft palate is often (but NOT always) accompanied by cleft lip. 3 EMBRYOLOGY8 Dr.Ban A.Ghani The palatine uvula: is a conic projection from the posterior edge of the middle of the soft palate, composed of connective tissue containing a number of racemose glands (A gland that has the appearance of a bunch of grapes if viewed as a three-dimensional reconstruction), and some muscular fibers. It also contains a large number of serous glands that produce a lot of thin saliva ,during swallowing, the soft palate and the uvula move together to close off the nasopharynx, and prevent food from entering the nasal cavity. Cleft lip and cleft palate:Cleft lip and cleft palate are facial and oral malformations that occur very early in pregnancy, while the baby is developing inside it’s mother. Clefting results when there is not enough tissue in the mouth or lip area, and the tissue that is available does not join together properly. A cleft palate is a split or opening in the roof of the mouth. A cleft palate can involve the hard palate, and/or the soft palate Cleft lip and cleft palate can occur on one or both sides of the mouth. Because the lip and the palate develop separately, it is possible to have a cleft lip without a cleft palate, a cleft palate without a cleft lip, or both a cleft lip and cleft palate together. 4 EMBRYOLOGY8 Dr.Ban A.Ghani Cleft lip is a physical split or separation of the two sides of the upper lip and appears as a narrow opening or gap in the skin of the upper lip. This separation often extends beyond the base of the nose and includes the bones of the upper jaw and/or upper gum. Hare lip: A congenital cleft or fissure in the midline of the upper lip, resembling the cleft upper lip of a hare, often occurring with cleft palate .Result from bilateral failure of fusion of maxillary and medial nasal prominences to fuse. Oblique facial cleft :unilateral failure of maxillary and lateral nasal prominences to fuse. Macrostomia:incomplete lateral merging of maxillary and mandibular processes. Frontonasal dysplasia: hyperplasia of inferior frontonasal prominence,thus preventing fusion of the medial nasal prominenses. 5 EMBRYOLOGY8 Dr.Ban A.Ghani Bilateral macrostomia Hypertelorism associated with frontonasal dysplasia and encephalocele. 6 EMBRYOLOGY8 Dr.Ban A.Ghani 7 .
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