I don't mean to be blunt or dismissive, but the pressure in the veins/arteries has nothing to do with (a) the thickness/elasticity of the wall tissue, (b) the diameter of the arteries/veins, or (c) the number of (branches of) arteries/veins.
This can either be caused by a more prominent maxilla (upper jaw) or a retruded mandible (lower jaw further back than it should be). This causes a discrepancy in how all teeth contact, and can manifest as an increased overjet. An increased overjet can also be caused by a discrepancy in the number of teeth, or the length of the arch.
Mitral valve disease has many causes. Some forms of mitral valve disease can be present at birth (congenital heart defect). Mitral valve regurgitation can be caused by problems with the mitral valve, also called primary mitral valve regurgitation. Mitral valve regurgitation is often caused by mitral valve prolapse, in which the mitral valve flaps (leaflets) bulge back into the left atrium.