After blood delivers oxygen to the tissues and picks up carbon dioxide, it returns to the heart through a system of veins. The capillaries, where the gaseous exchange occurs, merge into venules and these converge to form larger and larger veins until the blood reaches either the superior vena cava or inferior vena cava, which drain into the right atrium.
There are four types of veins:
*Deep veins are located within muscle tissue
*Superficial veins are closer to the skin’s surface
*Pulmonary veins transport blood that’s been filled with oxygen by the lungs to the heart
*Systemic veins
Systemic veins are located throughout the body from the legs up to the neck, including the arms and trunk. Systemic veins transport blood from the body tissue to the right atrium of the heart. This blood has a reduced oxygen content because the oxygen has been used for metabolic activities in the tissue cells.
The systemic veins may be arranged into three groups:
(1) The veins of the heart.
(2) The veins of the upper extremities, head, neck, and thorax, which end in the superior vena cava.
(3) The veins of the lower extremities, abdomen, and pelvis, which end in the inferior vena cava.
The inferior vena cava, also referred to as the posterior vena cava, is the largest vein in the human body. The superior vena cava is a large vein located in the upper anterior mediastinum. It is responsible for carrying deoxygenated blood from the upper body (head, neck, upper limbs, and some organs of the chest) to the heart.
Systemic veins
