Veins can collapse if too much negative pressure is used when withdrawing blood as the walls are rather thin.
The superficial veins of the legs connect to the deep veins through "penetrating veins" which run perpendicular to the skin from one to the other. The deep veins are essentially a column of blood running from your head to you feet and so when one is standing are under high pressure. In order to keep this pressure away from the frail superficial veins the penetrating veins have valves. When one of these valves goes bad the high pressure is allowed to go back to the superficial veins which blow up like balloons and become visible as what we call varicose veins (or "spider veins").
It is brought back to the heart to be pumped through the lungs to be exhaled.
There are three major categories of veins: superficial veins, deep veins, and perforating veins. All varicose veins are superficial veins; they lie between the skin and a layer of fibrous connective tissue called fascia.
There are three types of veins, superficial veins that are just beneath the surface of the skin, deep veins that are large blood vessels found deep inside muscles, and perforator veins that connect the superficial veins to the deep veins.
Pulmonary veins
Varicose veins are called dialated veins
Varicose veins.
Veins
Yes they do have veins because when i eat them have black veins :/
The deep veins that drain the forearm are the radial veins and ulnar veins. These veins run alongside the radial and ulnar arteries respectively, and eventually join to form the brachial veins. The brachial veins then merge to form the axillary vein, which continues the drainage pathway.
A grapevine has netted veins.
shark veins?