Figure 1. (a) Lateral view of the movement of the mandible during propalinal mastication in a rodent, during propalinal gnawing in a rodent, and a rodent cranium (note the large and procumbent incisors). In this and subsequent figures, the approximate directions of pull of the masseter and medial pterygoid muscles (MP) are shown by the green arrow, and the direction of pull of the temporalis muscle is shown by the blue arrow. The arrows on the movement orbits indicate the direction of mandibular movement. As the arrow approaches the horizontal line, the mandibular teeth approach the maxillary teeth and the power stroke occurs. (b) Frontal view of the movement of the mandible during mastication in a carnivore and a carnivore cranium. Note the large and sharp canines, and the vertical orientation of mandibular movement during the power stroke. (c) Frontal view of the movement of the mandible during mastication in a herbivore and a herbivore cranium. Note the large transverse component to the power stroke, and the large diastemata between the anterior and cheek teeth. Po, posterior; An, anterior; mx, maxilla; ma, mandible; MP; masseter and medial pterygoid muscles; Te, temporalis muscle; B, buccal; L, lingual; z, zygomatic arch. Adapted from Hiiemae K (2000).

Figure 2. Lateral view of a mid-sagittal section through the oral cavity and pharynx of a human showing the different parts of the pharynx (nasal part, oral part and laryngeal part).

Figure 3. Swallowing. (a) The soft palate has contracted to cover the entrance to the nasal part of the pharynx and the tongue is pushing the food bolus (red) toward the oral part of the pharynx. (b) The tongue reaches its maximal posterior and superior position as the food bolus passes through the oral part of the pharynx and into the laryngeal part of the pharynx. The epiglottis is folded over the opening to the larynx and trachea, and the pharyngeal elevator muscles are contracting. (c) The food bolus is in the laryngeal part of the pharynx, which has elevated and is now constricted as a result of contraction of the pharyngeal constrictor muscles.