Centuries ago, scholars believed that the heart was the seat of thoughts and emotions. They believed this mainly because when you think of something, and become emotional, your heart rate speeds up. William Harvey, an English Physician, first described blood circulation in 1628, and although great strides had been made toward understanding the cardiovascular system, it was not until the middle to last part of the twentieth century that scientists came to understand its functions. Ellen White said, much earlier, “The more active the circulation the more free from obstructions and impurities will be the blood. The blood nourishes the body. The health of the body depends upon the healthful circulation of the blood.” Healthful Living, 178.
Your heart is about the size of your fist, no matter what age or size you are. Its duty is to pump blood through blood vessels (arteries) and to receive the blood again from the veins and repeat the process.
Blood circulation has two main purposes. First, it delivers oxygen, nutrients, water, hormones, and other essentials to each cell of the body. Second, it transports all the carbon dioxide and other waste products of the cells to the lungs to be expired or to the kidneys to be excreted. The adult heart beats approximately 70 times per minute and pumps 2,000 gallons (7,570 liters) of blood each day. There are about 60,000 miles (96,560 km) of blood vessels in the human body, or enough to encircle the Earth more than twice over.
The heart is a muscle, made by God as a different kind of muscle than those that move the skeleton. It has four chambers, the two atria and the two ventricles. It is really like two pumps in one. The right side of the heart receives circulated blood from the body. Blood drains from veins into the right atrium and then flows through a valve (tricuspid valve) into the right ventricle when the valve is opened. The blood then is shunted through another valve (pulmonary semilunar) to the lungs where it will drop off its carbon dioxide load and pick up inhaled oxygen. Blood and inspired air do not directly mix. Oxygen and carbon dioxide are transported across a special thin membrane in the lungs. When the blood is oxygenated, it becomes bright red. It then continues its journey back to the heart where its first stop is the left atrium. As the valve (bicuspid or mitral) opens, blood flows into the left ventricle. The left ventricle is the largest chamber in the heart and has a large portion of muscle surrounding it.
Only when a blood vessel is damaged, such as in a cut, is blood ever not contained within the circulatory system. Even when it flows through organs, such as the brain or liver, blood is always inside a blood vessel. Arteries are the vessels that carry blood away from the heart to the body. Blood is highly pressurized as it travels away from the heart, so arteries do not need valves. Arteries get smaller and smaller the farther they are from the heart, becoming arterioles. As blood arrives at the tissues, the vessels become so small that only one blood cell can fit through at a time. These tiny vessels are called capillaries. This is where the oxygen/carbon dioxide and nutrient/waste exchange takes place. The oxygen and nutrients are dropped off, and the blood picks up its load of carbon dioxide and other waste and continues its journey back to the heart. As the blood vessels start to get bigger, nearer the heart, they are called venules and then veins. Blood is much less pressurized by now, and its journey to the heart is assisted through skeletal muscle contraction and the use of valves. One-fifth of the blood goes to the kidneys to drop off its waste load and then continues to the right side of the heart.
Why do you hear your heart beating but you cannot hear your other muscles when they contract? It is not the muscle contraction that you are hearing. The sound that is heard when the heart beats, lub-dub, comes from the heart valves. The first sound, the “lub,” occurs when the tricuspid and mitral valves shut after the blood has gone through. The “dub” occurs when the pulmonic and aortic valves close. The lub-dub can be heard through a stethoscope or if you put your ear to someone’s chest.
Prior to 1900, heart disease was rare. Before machines made life easier, people plowed their fields, milked cows and did laundry by hand. The main method of transportation was walking. Rich meats were available only to the wealthy on a regular basis, and refined grains were unheard of. As the Industrial Age brought new methods to improve life, it also brought new ways to eat. Meats, refined foods, and high-fat foods became a staple of daily life, and the common people developed and died of rich man’s diseases. Between 1940 and 1967, the rate of heart disease increased so sharply that the World Health Organization called it the world’s most serious epidemic. The role of diet and exercise in heart disease prevention and treatment was finally discovered. Much earlier, Ellen White noted that “The more we exercise, the better will be the circulation of the blood. . . . Those who accustom themselves to proper exercise in the open air will generally have a good and vigorous circulation.” Healthful Living, 186.
God is not only the architect of your heart, but He maintains every beat that sends blood through your body and every breath that fills your lungs with oxygen. The daily care of this system lies in your hands.
“Be of good courage, and he shall strengthen your heart, all ye that hope in the LORD.” Psalm 31:24.
Relationship between the Cardiovascular System and Other Systems
Integumentary: skin cell stimulation produces local changes in blood flow; delivers immune system cells to injury; clotting seals breaks in skin; removes toxins; provides heat.
Skeletal: provides calcium needed for normal heart muscle contraction; protects blood cells developing in bone marrow; provides calcium and phosphorous for bone maintenance; delivers hormones and nutrition to bone cells.
Muscular: skeletal muscle contractions help move blood through veins; protects superficial blood vessels; muscles make up most of the heart organ; delivers oxygen and nutrients, removes carbon dioxide, lactic acid, and heat during muscle activity.
Nervous: controls patterns of circulation; modifies heart rate and regulates blood pressure; certain cells in blood vessels maintain blood-brain barrier; helps to make cerebrospinal fluid.
Endocrine: helps regulate production of red blood cells; involved in elevating blood pressure; adrenaline stimulates cardiac muscle, elevating heart rate and contraction force; distributes hormones throughout the body; heart secretes hormone ANP.
Lymphatic: defends against pathogens or toxins in blood; fights infections of cardiovascular organs; returns tissue fluid to circulation; distributes white blood cells; carries antibodies; clotting response aids in slowing spread of disease-causing germs.
Respiratory: provides oxygen and removes carbon dioxide; transports oxygen and carbon dioxide between lungs and other body tissues.
Digestive: provides nutrients; absorbs water and ions essential to maintenance of normal blood volume; distributes digestive tract hormones; carries nutrients, water, and ions away from sites of absorption; delivers nutrients and toxins to liver.
Urinary: releases hormones to elevate blood pressure and accelerate red blood cell production; removes waste products delivers blood to capillaries where filtration occurs; accepts fluids and solutes reabsorbed during urine production.
Reproductive: estrogens may maintain healthy vessels and slow development of hardening of the arteries with age; distributes reproductive hormones; provides nutrients, oxygen, and waste removal for developing fetus.
Sheryle Beaudry, a certified teletriage nurse, writes from Estacada, Oregon where she lives with her husband and twin daughters.