See also on other sites: MedlinePlus m, normal heart anatomy (cut section illustration).
A double-layered membrane called the pericardium surrounds your heart like a sac.
Blood is returned to your heart through venules and veins.
The outer layer of the pericardium surrounds the roots of your heart's major blood vessels and is attached by ligaments to your spinal column, diaphragm, and other parts of your body.The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist.The Heart Valves (illustration four valves regulate blood flow through your heart: The tricuspid valve regulates blood flow between the right atrium and right ventricle.The left ventricle arsenal away kit 2013/14 junior html 4 for dummies 5th edition.pdf is the largest and strongest chamber in your heart.The Circulatory System (illustration the heart and circulatory system make up your cardiovascular system.
The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.
Although the SA node sends electrical impulses at a certain rate, your heart rate may still change depending on physical demands, stress, or hormonal factors.
In fact, each day, the average heart beats 100,000 times, pumping about 2,000 gallons (7,571 liters) of blood.This electrical signal begins in the sinoatrial (SA) node, located at the top of the right atrium.Blood is carried from your heart to the rest of your body through a complex network of arteries, arterioles, and capillaries.If all the vessels of this network in your body were laid end-to-end, they would extend for about 60,000 miles (more than 96,500 kilometers which is far enough to circle the earth more than twice!The inner layer of the pericardium is attached to the heart muscle.The pulmonary valve controls blood flow from the right ventricle into the pulmonary arteries, which carry blood to your lungs to pick up oxygen.The SA node is sometimes called the heart's "natural pacemaker." An electrical impulse from this natural pacemaker travels through the muscle fibers of the atria and ventricles, causing them to contract.Blood delivers oxygen and nutrients to every cell and removes the carbon dioxide and waste products made by those cells.