This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Elastic fibres of periodontal ligament which regulate the vascular flow: 
Select and explain. 
A. Oxytalan, B. Elaunin, C. Both, D. Elastin
A: Oxytalan
Answer: A: Oxytalan 
Explanation: Periodontal ligament consists of principal fibres and elastic fibres. Principal fibres are made up of collagen type I. They are purely collagenous.
The elastic fibres are present in two immature forms called oxytalan and elaunin (AIIMS-07). Oxytalan fibres run parallel to the root surface and are attached to the blood vessels thus they regulate the vascular flow.