External oblique ridge
- Continuation of anterior border of mandibular ramus.
- Arises lateral to alveolar process from 3rd molar to 1st molar area.
- Thick in posterior areas, thinner anteriorly.
- Appears as linear radiopaque structure running obliquely downward and forward from 3rd molar area.
- Internal oblique ridge: attachment of mylohyoid muscle, which supports the floor of oral cavity – it is LOWER (like a floor).
- External oblique ridge: arises on the ascending ramus, so it is HIGHER (ascending).