Rupture of small perforating vessels is a result of a “stress-riser” effect, at the junction of the vessel and the semi-rigid pinnal cartilage. Small vascular channels perforate the conjoined layers, allowing small vessels originated from the lateral pinnal vasculature to supply the medial cartilage layer and overlying cutaneous surface. The pinna assumes a flattened appearance as growth of the dog and cat continues.
As each bud enlarges and elongates, the lateral and medial layers contact and laminate together with connective tissue.
During embryologic development, the pinna begins as a small triangular bud.
The lateral sheet of cartilage is thinner than the medial sheet of cartilage comprising the scapha.