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Mouth
Lips - Lizards have moveable lips composed of flexible skin.
Teeth
Lizard teeth are used for grasping, piercing and breaking food or, in the case of monitors, slicing and cutting. Mollusk-eating Caiman lizards (Dracaena guianensis) and adult Nile monitors (Varanus niloticus) have broad rounded cheek teeth for crushing shells.
The teeth are generally pleurodont (attached to the sides of the mandible without sockets) but in some families, such as agamids (Agamidae) and chameleons (Chamaeleonidae), they are acrodont (attached to the biting edges of the jaws without sockets). The teeth of the venomous Gila monster and the Mexican beaded lizard are grooved to allow the flow of venom; however they have no direct connection to the sublingual venom glands. Venom is injected with the chewing action as it flows along the dental grooves.
Pleurodont teeth are shed and replaced whereas acrodont teeth are only replaced in very young specimens. For agamids and chameleons, special care should be taken to avoid damaging the acrodont teeth when opening a lizard's mouth with a rigid speculum as these teeth are irreplaceable. Furthermore, acrodont dentition is reportedly susceptible to periodontal disease.
Tongue
The tongue is generally mobile and protrusible. In the green iguana, the tip is darker than the rest and could be mistaken for a lesion. Lizards such as monitors and tegus have deeply forked tongues and chameleons have a projectile tongue for gathering food.
Gastrointestinal Tract
The organs and divisions of the gastrointestinal tract are similar to those of mammals. The lizard has a simple, elongated stomach. The liver may contain melanin and have black spots - all lizards have a gall bladder. A caecum is present in many species and herbivorous lizards have a sacculated colon to aid fermentation.
Cloaca
A cloaca is present and is divided into coprodeum (collects faeces), ureodeum (collects urinary wastage) and proctodeum (final chamber prior to elimination)
References
- Mader, D.R. (2005). Reptile Medicine and Surgery. Saunders. pp. 1264. ISBN 072169327X