Which of the following statements are true concerning the adult mandible? (1) The mandibular foramen lies in the centre of the mandibular ramus both in the vertical and horizontal planes. (2) The angle formed by the junction of the ramus and the body of the mandible is an acute one. (3) The genial tubercles are attachments for the anterior bellies of the digastric muscles. (4) The temporalis muscle attaches to the lateral surface of the coronoid process.
(1) and (3)
(1) and (2)
(1) and (4)
(1) (3) (4)
1 explanations
oneguy
(1) The mandibular foramen is located below the occlusal plane at the age of 3. It subsequently moved upward with age. By the age of 9 to 10, it reaches approximately the same level as the occlusal plane. The foramen continued to move upward to 4-5mm above the occlusal plane in the adult. And the position of mandibular foramen in adult is about halfway between the anterior and posterior border of the ramus.
(2) The mandibular angle is the angle formed by junction of the posterior edge of the ramus of the mandible and the inferior surfaces of the body of the mandible. At birth, the angle is obtuse (175°), and the condyloid portion is nearly in line with the body. In the adult, the mandibular ramus is almost vertical in direction, the mandibular angle normally is from 110° to 120°.
(3) The anterior belly of the digastric muscle arises from a depression on the inner side of the lower border of the mandible called the Digastric Fossa, close to the symphysis and passes downward and backward and is attached to the hyoid bone.
(4) Temporalis muscle origins from the temporal fossa of the temporal bone, passes medial to the zygomatic arch and inserts into the coronoid process of the mandible. Contraction of the Temporalis muscle elevates and retracts mandible.
oneguy