Wilderness Underfoot: Nature's hardest working organ

StoryImage( ‘/Images/Story//Auto-img-112490531732401.jpg’, ”, ”);
StoryImage( ‘/Images/Story//Auto-img-112490542932697.jpg’, ”, ‘The human heart – Your heart is just a bit larger than your fist. Many people mistakenly believe the heart is on the left side of the chest. It is actually located in the center, but part of a lobe is touching the left wall of your chest, so that’s where a doctor places a stethoscope to listen for the most clear sound of the beat. Human hearts have four chambers – a trait shared by other mammals and birds. Reptiles have three-chambered hearts, and fish have simpler two-chambered hearts. Humans and other animals owe their complexity to the origination of the heart in a flatworm that evolved about 700 million years ago. The earliest, most primitive hearts were simple tubes that contracted, causing blood to flow. As animal bodies became larger, and increasingly complex and demanding, hearts evolved additional chambers to better deliver oxygen-rich blood and nutrients.’);

The heart is so vital that only a few minutes without its pulsing can result in death

Just larger than a clenched fist, the heart is perhaps the most incredible muscle in the human body. Unlike other muscles, it works endlessly without fatigue, beating about 70 times per minute. Each year, this powerful pump will pulse about 35 to 40 million times, and over a lifetime it will pump more than a million barrels of blood through the human body.

Pushing blood around isn’t an easy task, either. The heart must contract with the same amount of pressure it takes you to squeeze a firm rubber ball with your hand. Blood is first pumped out to the lungs, returning to the heart with fresh oxygen. Some of this oxygen is used by the heart, itself. With another push through the heart, oxygen-rich blood is then sent through the human body. The blood travels through flexible tubes called vessels. These vessels can range in size from the diameter of a kitchen faucet in large arteries, to one-tenth the diameter of a human hair in tiny capillaries. About 12,000 miles of blood vessels are woven throughout your body.

Within the blood is the fuel for all of the other organs, as well as nutrients, disease fighting antibodies, and oxygen. Blood also helps carry away waste materials and gases such as carbon dioxide so they can be eliminated from the body.

When a hearts stops beating (cardiac arrest), the most immediate threat to the human body is the sudden loss of fresh oxygen – and the organ that is most at risk is the brain. A brain can begin to suffer damage within about four minutes after the supply of oxygen is stopped, and after about six minutes it begins to die. Any time a brain suffers injury due to loss of oxygen, it is referred to as anoxic brain injury. The goal of cardiopulmonary resuscitation (CPR) is to revive somebody whose heart has stopped beating before the onset of brain damageinjury and death.

From the Aug. 24-30, 2005, issue

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