In certain cities, too, traditional farms and other forms of urban farming - such as crops grown on rooftops or vacant lots - may only be 60 to 100 miles away, close enough to compete with vertical farms. Vertical-farming projects have sprouted up in several North American cities as well as in the Netherlands, Scandinavia, Germany, Korea, Japan, Abu Dhabi and Singapore among others.
Deoxygenated blood enters the right atrium through three major veins: the superior and inferior vena cava and the coronary sinus. The superior vena cava returns all of the blood to the heart from tissues superior to the heart in the head, neck, arms and upper thorax. Likewise, the inferior vena cava returns blood to the heart from tissues inferior to the heart, including the legs, abdomen and lower thorax.
NOTE The function of veins is to return blood to the heart. Veins have thinner walls and have one way valves in them. 1  those that take blood from the heart to the lungs to be re-oxygenated; known as the pulmonary arteries. 2  These are the only arteries that transport de-oxygenated blood.