Critical anatomy of the osseocartilaginous junction at the K-area demonstrated on a 75-year-old male cadaver. (A, B) Histological sections demonstrating the chondro-osseous junction between the bony and cartilaginous vault with fused layers of perichondrium and periosteum. (C, D) Cephalic continuation of the quadrangular cartilage from the osseocartilaginous junction upward toward the nasion.