الفهرس 
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Abstract
The current study carried out on the oropharyngeal cavity of clinically healthy two types of adult turtles (the Greek tortoise and the red-eared slider turtle) due to their overspread as pet animals in Egypt as they have a unique body shape and attractive colors, beside their calmness and ease of handling.
The Greek tortoises are herbivorous land tortoises with total carapace length ranging from 20.7:22.1 cm and body weight 1.18:1.28 kg, while the red-eared sliders are omnivorous semiaquatic with carapace length about 23.4:25.1 cm and body wight 1.41:1.73 kg. Both species were used to study and describe the anatomical structures of the oropharyngeal cavities in relation to their different feeding behavior and ecological habitats, the description of the anatomical features and differences between two species were done by using the scanning electron microscopic examination (SEM) and light microscopy for the most important part beside the close gross morphological examination.
The oropharyngeal cavities of both examined species were divided into upper roof and lower floor by cutting through the oral commissures at both sides, the roofs include the following anatomical parts from anterior to posterior (upper rhamphotheca, peri-palatine region, rostral palatine region, middle palatine region, caudal palatine region, and pharynx), while the floors include the following anatomical parts (lower rhamphotheca, peri-lingual region, lingual region, post lingual region).
In Greek tortoise
The upper rhamphotheca is a convex hard keratinized structure with three anterior teeth like projections (tomiums), these tomiums are involved as prosthetic structures for the loss of teeth since Greek tortoise is edentulous.
The peri-palatine region includes 2 wavy pointed upper alveolar ridges, one on each side (7.6 mm in length) that act as a chewing surface inside the mouth to compensate the tooth loss.
The rostral palatine region includes two peripheral palatine ridges (25.3 mm in length &0.4 mm in width), one median palatine ridge (5.8 mm in length &0.4 mm in width) and two palatine folds (6 mm in length &2.4 mm in width), the rostral palatine region is lined with highly keratinized stratified squamous epithelium.
The middle palatine region is occupied by two choanal openings that separated by vomer and limited laterally by two choanal folds. The choanal openings are pine nut in shape (6.65 mm in length &1.99 mm in width) that are lined with respiratory epithelium. While the vomer (5.58mm in length &1.34mm in width) is a longitudinal septum that has a longitudinal vomer cleft.
The caudal palatine mucosa shows a single pair of circumvallate papillae with multiple openings of palatine glands. At higher magnification, the circumvallate papillae has multiple taste pores.
The pharyngeal mucosa is lined with keratinized stratified epithelium and the lamina propria has multiple mucus acini.
The lower rhamphotheca guards the floor of the mouth and appears as a keratinized V-shape structure with one median tomium.
The peri-lingual area that surrounds the tongue has two main structures: the lower alveolar ridge and the para lingual ridge. The lower alveolar ridge (6.4 mm in length) shows the same pattern and function as the upper one except it is shorter in length. The para lingual ridge is a V-shaped structure that surrounds the anterior half of the tongue.
The lingual region is fully occupied by an elongated heart-shape tongue (19.93 mm in length) composed of apex rostrally, body at the middle, and root posteriorly. The tongue appears as a muscular mass that can protrude outside the mouth for food capture (lingual prehension) and the dorsal surface of the tongue is fully occupied by well-developed papillae with clear interpapillary spaces, the papillae arranged in different directions and shapes such as conical, rectangular, filamentous, bifurcated papillae. Moreover, these papillae have both mechanical role in food manipulation and gustatory roles through the surface taste pores.
The mucus glands and acini are common features in the oropharyngeal mucosa of Greek tortoise since the mucus is an important lubricating substance for moistening and swallowing the food.
The post lingual region is occupied by laryngeal mound, this laryngeal mound is separated from the tongue by small peri-glottic space. The laryngeal mound is an elongated structure (7.85 mm in length &5.49 mm in width) that has an anterior slit-like opening (glottis) and numerous glandular openings.
In red-eared slider
The upper rhamphotheca is a keratinized U- shaped structure with sharp blade edge and one median premaxillary notch.
The peri-palatine region is area of interest in our study that shows multiple teeth like projections (not real teeth) that act as a rough chewing surface to squeeze and mash the food, these projections represented into two types : type1 are large pointed cone shape projections arranged in one line (upper alveolar ridge) on each side, this line is 10.33 mm in length while type2 shows multiple shapes (pimple like, artichoke like, small cone shape with a surrounding groove and small cone shape without groove) that scattered around the upper alveolar ridge.
Generally, the palate of red-eared slider tends to simplicity compared to the palate of Greek tortoise as it shows no folds and less ridges. The rostral palatine region shows only two peripheral palatine ridges (9.9 mm in length &0.56 mm in width) and there isn’t a median palatine ridge. Microscopically, this region is lined with slightly keratinized stratified squamous epithelium.
The middle palatine region is fully occupied by two choanal openings separated by vomer. The choanal openings are elliptical in shape (7.4 mm in length &2.67 mm in width) and are lined with respiratory epithelium. The vomer (4.58 mm in length &0.48 mm in width) is a very narrow septum without cleft.
The caudal palatine region is lined with poorly keratinized epithelium with a mix of taste pores and glandular openings. In the same line, the pharyngeal mucosa is lined with a slightly keratinized epithelium.
The lower rhamphotheca is a keratinized structure guards the floor of the oropharyngeal cavity from rostral and lateral and has a sharp edge with one median tomium.
The peri-lingual region shows the same features of the upper peri-palatine region except the lower alveolar ridge (4.86 mm in length) is shorter than the upper one and an extra structure appears; the para lingual ridge that encircles the entire length of the tongue.
The lingual region is fully occupied by a small arrowhead shaped tongue (16.96 mm in length) with a median longitudinal fissure. The tongue is composed of apex, body, and root. The tongue is not movable due to its strong fixation by the lingual frenulum and ligament of the root of the tongue, thus red-eared slider depends on suction feeding mechanism through creating a negative pressure inside the oropharyngeal cavity instead of lingual prehension.
The dorsal surface of the tongue is covered with lingual papillae, mostly ridge in shape with less distinct interpapillary spaces especially at the lingual apex. The papillary surface is lined with non-keratinized epithelium showing numerous microvilli and taste pores.
The post lingual region includes a diamond shape laryngeal mound (4.9 mm in length & 5.1 mm in width) that has a median Y-shape opening of glottis with numerous glandular openings.