Hello Good Evening, You describe about veins but you did not tell that these are present in both elbows or in single, because this is important to identify any abnormality or define a anatomical appearance. If it is present similar in both elbows that nothing to worry, because it can a anatomical appearance of your veins in you, which can be present with little variation in everyone, but if it present in only one side than it might be indicate that these are peripherals collateral s or anastomosis, due to some obstruction in blood flow, which can be of any type, like pathological (any thrombus or infarct at that site) or positional (if you use a particular position of upper limb which can cause obstruction in the flow of veins). So go through your self examination and if you find anything abnormal or significant, than go to your GP. Regards.