Which tissue gives rise to the periodontal ligament?

• A. Dental pulp.
• B. Fibroblasts from the dental follicle.
• C. Odontoblasts.
• D. Chondrocytes.

Answer: (B)

The periodontal ligament arises from fibroblasts that come from the dental follicle (the dental sac) surrounding the developing tooth. As the tooth forms, the mesenchymal cells of the follicle differentiate into PDL fibroblasts, which synthesize the collagen-rich extracellular matrix of the ligament and organize into the fiber bundles (including Sharpey's fibers) that anchor cementum to the alveolar bone. This connective tissue is what provides tooth support and the ability to absorb loads.

Dental pulp is derived from the dental papilla and contains odontoblasts that form dentin, not the ligament. Odontoblasts specifically lay down dentin; chondrocytes form cartilage, which isn’t part of the periodontium. So the tissue giving rise to the periodontal ligament is the fibroblasts from the dental follicle.