Mouth (aka Oral Cavity or Buccal Cavity)
The digestive system begins with the mouth or oral cavity. It is bounded laterally by the cheeks, dorsally by the hard palate, ventrally by the mandible and caudally by the soft palate. The oral cavity is covered with mucus membranes and lymphatic follicles to provide immunity.
Lips & Teeth
The horse uses his lips to sort food and direct it into the mouth. **Disadvantage: very selective grazers and can sift through vitamin/mineral pellets, oral meds or dewormers. An accessory digestive organ located in the sockets of the alveolar processes of the incisive bone, mandible and maxillae. The front teeth or incisors are used to tear forage grasses from the pasture. From there the tongue helps push the food back to the rear molars for grinding.
Tongue
An accessory digestive organ composed of skeletal muscle covered with mucous membrane. Many papillae contain taste buds which are the receptors for Gustation (taste). Some papillae lack taste buds but have receptors for touch. Lingual Glands in the lamina propria of the tongue secrete both mucus and a watery serous fluid. Helps to move food to the back of the mouth in preparation for swallowing.
Salivary Glands
release a secretion called Saliva (10-12L per day) into the oral cavity. This cleanses the mouth and teeth and keeps the mucus membranes of the mouth and pharynx moist. Secretion increases when food enters the mouth and it lubricates, dissolves and begins chemical breakdown of the food. 4 major pairs of salivary glands: Parotid, Submandibular, Sublingual and Buccal. Saliva is 99.5% water and 0.5% ions such as sodium, potassium, chloride, buffers such as bicarbonate and phosphate. Also present are some dissolved gases and various organic substances including urea and uric acid, mucus, IgA, bacteriolytic enzyme lysozyme. Virtually no digestive enzymes are present in the saliva of a horse. pH is more alkaline of saliva Salivary glands help remove waste molecules from the body. Mucus lubricates food. IgA prevents attachment of microbes so they cannot penetrate the epithelium Lysozyme kills bacteria (however, they are not present in large enough amounts to kill all oral bacteria).
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