The Mandible hangs off the skull suspended by a sling formed of muscles attached to the ramus of each side of the bone. The ramus is the vertical part of the mandible. The Masseter muscle, forms the sling on the outside of the ramus; the lateral and medial pterygoid muscles on the inside. The masseter can be felt by placing a hand just in front of you ear and then clenching your jaw. To feel the pterygoids, you must place your fingers inside your mouth.
From the front, the mandible is a parabola. From the side, the shape of the ramus a bit more clearly defined a 'hockey stick'. The lateral pterygoid will attach to the inside to the condyle, the bump at the top back of the mandible and to the skull just under the cheekbone. Its contraction pulls the jaw forward. The medial pterygoid muscle attaches to the bottom corner of the mandible and connects to the skull up behind the upper molars at back of the mouth.
From above, the thickness of the condyle of the mandible can be appreciated. This hooks into the capsule of the jaw hinge and works in a very subtle manner to rotate and drop as the jaw opens. The narrowness of the ramus allows plenty of space for the masseter on the outside and the pterygoids on the inside.
- The mandible consists of:
- a curved, horizontal portion, the body. (See body of mandible).
- two perpendicular portions, the rami, which unite with the ends of the body nearly at right angles. (See ramus mandibulae)
- Alveolar process, the tooth bearing area of the mandible (upper part of the body of the mandible)
- Condyle, superior (upper) and posterior projection from the ramus, which makes the temporomandibular joint with the temporal bone
- Coronoid process, superior and anterior projection from the ramus. This provides attachment to the temporalis muscle
- Foramina (singular = foramen)
- Mandibular foramen, paired, in the inner (medial) aspect of the mandible, superior to the mandibular angle in the middle of the ramus.
- Mental foramen, paired, lateral to the mental protuberance on the body of mandible.
- Nerves
- Inferior alveolar nerve, branch of the mandibular division of Trigeminal (V) nerve, enters the mandibular foramen and runs forward in the mandibular canal, supplying sensation to the teeth. At the mental foramen the nerve divides into two terminal branches: incisive and mental nerves. The incisive nerve runs forward in the mandible and supplies the anterior teeth. The mental nerve exits the mental foramen and supplies sensation to the lower lip.
- Articulations
- The mandible articulates with the two temporal bones at the temporomandibular joints.