what causes an orca's dorsal fin to collapse
Captive killer whales Scientists from the National Marine Fisheries Service (NMFS) have reported that "the collapsed dorsal fins commonly seen in captive killer whales do not result from a pathogenic condition, but are instead thought to most likely originate from an irreversible structural change in the fin's collagen over time. Possible explanations for this include: (1) alterations in water balance caused by the stresses of captivity dietary changes, (2) lowered blood pressure due to reduced activity patterns, or (3) overheating of the collagen brought on by greater exposure of the fin to the ambient air."[65] According to SeaWorld's website, another reason for the fin to bend may be the greater amount of time that captive whales spend at the surface, where the fin is not supported by water pressure.[66] The Whale and Dolphin Conservation Society says that dorsal fin collapse is largely explained by captive killer whales swimming in small circles due to the inadequate space in which they have to swim.[67] SeaWorld, however, claims that "Neither the shape nor the droop of a whale's dorsal fin are indicators of a killer whale's health or well-being."[66]
Dorsalis pedis artery In human anatomy, the dorsalis pedis artery (dorsal artery of foot), is a blood vessel of the lower limb that carries oxygenated blood to the dorsal surface of the foot. It arises at the anterior aspect of the ankle joint and is a continuation of the anterior tibial artery. It terminates at the proximal part of the first intermetatarsal space, where it divides into two branches, the first dorsal metatarsal artery and the deep plantar artery. The dorsalis pedis communicates with the plantar blood supply of the foot through the deep plantar artery.