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" The Human Heart CONSIDER, FOR example, the human heart and its accompanying circulatory system. The human heart is vastly superior to any human artifact. Every second it undergoes a cycle of contraction and expansion, and beats continually and faithfully for the duration of a human lifetime. It starts beating in the womb and in eighty years will beat about two billion times. The cardiac muscle itself consists of an interconnected syncytium of billions of muscle cells specially adapted to resist fatigue and contract autonomously without external activation or control. Within the cardiac muscle cells there are trillions of tightly packed molecular arrays of contractile filaments whose regular rhythmic lengthening and shortening generate the cardiac cycle. At rest each of us needs about a fourth a liter of oxygen per minute to satisfy our energy needs.30 This involves the movement every minute of one hundred trillion oxygen molecules across every square millimeter of the alveolar surface of the lungs. And with every contraction the heart pumps one hundred billion red blood cells through hundreds of kilometers of tiny capillaries.31 Coursing through the capillaries in the lungs, each of these tiny nano-machines carries one billion molecules of oxygen (O2) from the lungs to the tissues, each loosely bound to an iron atom in the hemoglobin. By the heart’s unceasing activity it ensures a bountiful supply of oxygen to provide us with the vital energy of life. The red cells themselves, no less than the heart, are also miracles of bioengineering. During its 120-day lifetime in the circulatory system, each red cell makes hundreds of thousands of circuits, covering hundreds of miles. It is only because the red cell membranes are uniquely soft and strong—one hundred times softer than a latex membrane of comparable thickness but stronger than steel32—that they can withstand these repeated deformations as they squeeze though the smallest capillaries, which in many cases have a diameter of five microns, almost half the diameter of the average red blood cell. "

― Michael Denton , The Miracle of Man: The Fine Tuning of Nature for Human Existence

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Michael Denton quote : The Human Heart CONSIDER, FOR example, the human heart and its accompanying circulatory system. The human heart is vastly superior to any human artifact. Every second it undergoes a cycle of contraction and expansion, and beats continually and faithfully for the duration of a human lifetime. It starts beating in the womb and in eighty years will beat about two billion times. The cardiac muscle itself consists of an interconnected syncytium of billions of muscle cells specially adapted to resist fatigue and contract autonomously without external activation or control. Within the cardiac muscle cells there are trillions of tightly packed molecular arrays of contractile filaments whose regular rhythmic lengthening and shortening generate the cardiac cycle. At rest each of us needs about a fourth a liter of oxygen per minute to satisfy our energy needs.30 This involves the movement every minute of one hundred trillion oxygen molecules across every square millimeter of the alveolar surface of the lungs. And with every contraction the heart pumps one hundred billion red blood cells through hundreds of kilometers of tiny capillaries.31 Coursing through the capillaries in the lungs, each of these tiny nano-machines carries one billion molecules of oxygen (O2) from the lungs to the tissues, each loosely bound to an iron atom in the hemoglobin. By the heart’s unceasing activity it ensures a bountiful supply of oxygen to provide us with the vital energy of life. The red cells themselves, no less than the heart, are also miracles of bioengineering. During its 120-day lifetime in the circulatory system, each red cell makes hundreds of thousands of circuits, covering hundreds of miles. It is only because the red cell membranes are uniquely soft and strong—one hundred times softer than a latex membrane of comparable thickness but stronger than steel32—that they can withstand these repeated deformations as they squeeze though the smallest capillaries, which in many cases have a diameter of five microns, almost half the diameter of the average red blood cell.
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