palate, roof of the mouth. The front part, known as the hard palate, formed by the upper maxillary bones and the palatine bones, separates the mouth from the nasal cavity. It is composed of a bone plate covered with a layer of mucous membrane tissue. The back portion, or soft palate, consists of muscular tissue and mucous membrane forming a partial partition between the mouth and the throat. A small conelike projection, the uvula, hangs from the middle of the soft palate in humans. The soft palate and uvula move upward during swallowing or sucking, preventing food from entering the nasopharynx. In mammals other than humans, the soft palate overlaps the larynx during swallowing so as to prevent entry of foreign substances into the respiratory tract. Both the hard and soft portions of the palate are lined with mucous membrane containing numerous glands that lubricate the mouth and throat. If the sides of the bony palate fail to come together during embryonic development an opening, or cleft, remains along the midline. This condition, known as cleft palate, can be repaired surgically in early infancy. See digestive system.

cleft palate, incomplete fusion of bones of the palate. The cleft may be confined to the soft palate at the back of the mouth; it may include the hard palate, or roof of the mouth; or it may extend through the gum and lip, producing a gap in the teeth and a cleft lip, which is cosmetically difficult to repair but is not disabling. The condition appears to be hereditary but not under the control of a single pair of genes. A cleft palate causes separation between the oral and nasal cavities. An infant cannot develop proper suction for drinking, and there is the danger of milk entering the nasal cavity and being aspirated into the lungs. Formula must be carefully placed at the back of the tongue for normal swallowing to take place. Ear infection may result from food or fluid passing from the nasal cavity to the middle ear by way of the Eustachian tubes. Proper speech articulation is difficult unless the cleft is surgically closed, with a prosthesis. The proper time for such an operation is in dispute; some authorities prefer early closure, before the cleft interferes with development of normal speech habits, while others prefer to wait for several years until facial growth has been completed. Dental, orthodontic, psychiatric, and speech therapy may be required.

Roof of the mouth, separating the oral and nasal cavities. The front two-thirds, the hard palate, is a plate of bone covered by mucous membrane. It gives the tongue a surface against which to make speech sounds and shape food during chewing and keeps pressures in the mouth from closing off the nasal passage. The flexible soft palate behind it is made of muscle and connective tissue and ends in the uvula, a fleshy projection. It rises to block the nasal cavity (see nose) and upper pharynx off from the mouth and lower pharynx for swallowing or to create a vacuum for drinking. Cleft palate, a congenital disorder involving a gap in the palate, can be corrected surgically.

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Fairly common congenital disorder in which a fissure forms in the roof of the mouth. It may affect only the soft palate or extend through the hard palate, so that the nasal cavity opens into the mouth. The septum (dividing wall) between the nostrils is often absent. Cleft lip, a fissure in the lip beneath the nostril, or other abnormalities may accompany it. Cleft palate limits the ability of an infant to suck, which may lead to malnutrition, and causes speech problems in childhood. Surgical repair, usually at about 18 months of age, forms an airtight separation between nose and mouth. Speech training is still needed, and patients may have a high risk of nose, ear, and sinus infections.

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