Veins serve a critical function within our bodies. When blood has been pumped by the heart to various parts of the body, it must return back to the heart. In a metaphorical sense, veins are the return portion of a round-trip plane ticket. The veins serve the purpose of delivering the blood, now bluish in color, back to the right atrium (chamber) of our heart. In the heart, blood will collect more oxygen and prepare to be pumped back out through arteries. This is a cycle that continues as long as a person is living.
Veins can vary greatly in size. The largest vein in the body is called the vena cava, which is Latin for 'hollow vein.' There are two sections of the vena cava, one below the heart and one above it. The section above the heart is called the superior vena cava, and it returns blood from the head, neck, chest, and upper limbs back to the heart. You can remember this term by associating the word 'superior' with 'above.'
The lower section is called the inferior vena cava, and it returns blood from all other parts of the body back to the heart. Similar to the aforementioned example, 'inferior' can be associated with 'below.' As we get farther away from the heart and toward extremities, veins branch out and get smaller and smaller. The internal network of veins that are not visible drain directly into the vena cave. The superficial network of veins that are visible drain into the groin or axillae before draining in the the deeper vena cava veins.