Please read earlier post (by one) before reading this one.

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So... how is this like the human heart.

The Blood is like a river, traveling in vessels it deposits its nutrients into the organs and musculature of the landscape.

The landscape in turn holds water, and this water travels through from the drenched areas (near the rivers and lakes) to dryer places.  Zion being a dry and high place has much water passing towards it.  It reaches maximum here and pours out again.

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In the human body blood travels from the heart, to the large vessels and then to the smaller, until it disperses in the organs and musculature.

Once in the musculature and organs, it is changed (sometimes nourished and purified -as in the liver) and then returns pouring back into the veins, but also draining into the lymphatics (which is closer to the desert, the musculature and the spleen) The veinous flow returns to the heart from below, while the lymphatic drains into the heart from above.  This is close to what happens in Zion.