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Soft Palate in Male Dromedary
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History
There is no doubt that the most impressive aspect of the rutting behavior of the male dromedary is the frequent exteriorization of the soft palate (also known as Dulaa or Dulla) accompanied by the characteristic gurgling sound. The soft palate is also exteriorized whenever the animal is irritated and this behavior has been associated with aggressiveness and danger in popular literature and tales (Figure 1.33). This phenomenon, known in different parts of the world where the dromedary is reared, has attracted a lot of interest from scientists and lay people to try to understand the anatomical structure and mechanism of distention of the soft palate.(26, 40)

Figure 1.33: Exteriorized soft palate (dulla) in the dromedary.
Exteriorization of the soft palate is not seen in either the Bactrian camel or the llama. The majority of researchers agree as to the non-functioning diverticulum of the female dromedary and that this is an anatomic peculiarity of the male.(33)
An attempt to scientifically describe this anatomical feature of the dromedary was made in the early part of the 19th century (Savi cited by Dorandi20). This author described the dulaa as a loose extension, corresponding to the uvula in man and other domestic animals, over 1 foot in length, hanging from the lower surface of the soft palate. Exteriorization of the soft palate was explained by the mechanical action of gas eructed from the stomach. A more comprehensive review was offered by Dorandi(20) who described the structure as "A vesica buccal is". Others have given this structure the name of 'vesica palatina' because it arises from the oroventral part of the soft palate and is located immediately behind the isthmus faucium.(7)
Morphology
According to Lesbre(41) the soft palate measures 25 cm although other authors reported values ranging from 30 to 35 cm.(40) From either side of the free end of the soft palate, a well developed posterior pillar extends to the beginning of the esophagus, where they meet on its dorsal surface. The soft palate is attached dorsally and is free in its ventral aspect with its surface folded when it is not distended. The position of the muscles of the soft palate is similar to that in other domestic animals. These are well-developed, especially the palatinus muscle.
The lateral surfaces are in contact with the anterior part of the pharynx. The oral part is free and situated against the posterior part of the dorsum and the root of the tongue. From the posterior part of the dulaa a fold of mucous membrane extends backwards along the median line of the soft palate.(7)
The fixed part of the soft palate lies on the horizontal palatine bone and is loosely attached to the underlying sub-mucous tissue. The root of the tongue is connected to the soft palate by the anterior pillars. The palatine surface is then folded onto itself and proceeds posteriorly to reach the palatinus muscle and is closely attached to the ventral surface of this muscle along its length. Small pink glands are found between the layers of the mucous membrane of the diverticulum of the soft palate. These glands open on both surfaces of the diverticulum by very small, short ducts.(33)
Microscopic examination of the dromedary soft palate shows a different structure from that of other domestic animals. On both surfaces of the wall of the diverticulum, stratified epithelium is present separated by a thick layer of areolar tissue containing small areas of mucous glands.(33)
Mechanism of distention
Many authors have attempted to study the mechanism of distention and exteriorization of the soft palate in the dromedary. It was stated that the soft palate is pushed upward to approach the nasal membrane (transverse septum) which forms a valve. Simultaneously, air is forced out from the lungs and enters the 'cul de sac'. The air which is trapped in the 'cul de sac' extends the septum to reach the soft palate and complete plugging of the posterior nares. Thus, air can only pass through the isthmus faucium where it becomes concentrated in the middle part of the dulaa. The latter becomes twisted, forming with the tongue and the anterior pillars a structure resembling an inflated sac which projects outside the mouth. On the other hand, Lombardini(42) stated that the soft palate is first raised when air issuing from the glottis forces the soft palate upward and anteriorly toward the pharynx, thus closing the passage between the latter and the guttural cavities (posterior nares). He also suggested that, even if this narrow passage remains free, most of the air will still be directed toward the mouth, and consequently, the soft palate. The most complete study of the mechanism of distention of the soft palate was offered by Arnautovic and Abdel Magid.(7) These authors showed that attempts to blow air through natural openings - esophagus, anterior and posterior nares, opening of mouth, Eustachian tube - and the openings of the glandular projections on the surface of the dulaa, fail to distend it. It is only when the anterior nares are tightly closed and air is blown through the trachea, that the dulaa is distended.(7) The soft palate should first be raised to prevent access of air to the posterior nares.(7, 42) This is done by contraction of its muscles, which pushes the soft palate upward so that the folds of mucous membrane on the respiratory surface of the former, together with the transverse septum, form a closing valve. Escape of air from the diverticulum into the buccal cavity is prevented by crossing of the folds of mucous membrane of the dulaa and the anterior pillars of the tongue. Therefore, the soft palate is distended merely by air forced from the lungs.
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