Originally posted by Mudge
Sub Q fat loss with skin exposed to sunlight? Happens in the face.
True, loss of subcutaneous fat and thinning of the skin but another process plays a role in the gradual appearance of veins with time and age......
First and foremost, we are all born with all the superficial veins we will have. So why do they appear gradually over time! With regards to BB, as Mudge pointed out, loss of subcutaneous fat is a main one but the other is a form of venous insufficiency.
Superficial veins can be catagorized as "normal", or varicosities or telangiectasia (spider veins), (the latter two are the visible surface manifestations of an underlying venous insufficiency syndrome.) Venous insufficiency is when venous blood escapes from a normal flow path and flow in a backward manner or retrograde manner.Thus, varicose veins and spider veins are normal veins that have dilated under the influence of increased venous pressure.
In healthy veins, one-way valves direct the flow of venous blood upward and inward. Blood is collected in superficial venous capillaries, flows into larger superficial veins, and eventually passes through valves into the deep veins and then centrally to the heart and lungs. Superficial veins are suprafascial, while deep veins are within the muscle fascia. Perforating veins allow blood to pass from the superficial veins into the deep system.
Within muscle compartments, muscular contraction compresses deep veins and causes a pumping action that can produce transient deep venous pressures as high as 5 atmospheres. Deep veins can withstand this pressure because of their construction and because their confining fascia prevents them from becoming excessively distended. In contrast to deep veins, the venous pressure in superficial veins normally is very low. Exposure to high pressures causes superficial veins of any size to become dilated and tortuous.
Perfectly normal veins will dilate and become tortuous in response to continued high pressure, as is seen in patients with dialysis shunts or with spontaneous arteriovenous malformations or lifting weights.
Elevated venous pressure most often is the result of venous insufficiency due to valve incompetence in the deep or superficial veins. Varicose veins are the undesirable pathways by which venous blood refluxes back into the congested extremity.
Chronically increased venous pressure also can be caused by outflow obstruction, either from intravascular thrombosis (blood clot) or from extrinsic compression, such as an overdeveloped or hypertrophied tendon, an extra or malformed rib, muscle etc. .
As for how these superficial venous valves fail, it may result from direct trauma or from thrombotic valve injury, but most commonly simply is due to the effects of high pressure within the superficial venous system. (When exposed to high pressure for a long enough period of time, superficial veins dilate so much that their diameter increaes in size.)
This could be why some BBs are seeing "new" veins in areas that they were not apparent