In lungfishes, bowfin and bichirs, the swim bladder is supplied with blood by paired pulmonary arteries branching off from the hindmost (6th) aortic arch.
Reduced lysyl oxidase activity results in defective collagen and elastin polymerization and corresponding connective-tissue abnormalities including aortic aneurisms, loose skin, and fragile bones.
Other causes of aortic stenosis include calcification of a congenital bicuspid aortic valve (30-40% of cases) and acute rheumatic fever post-inflammatory (less than 10% of cases).
