Topic Resources To support the absorption of oxygen and release of carbon dioxide, about 5 to 8 liters (about 1.3 to 2.1 gallons) of air per minute are brought in and out of the lungs, and about three tenths of a liter (about three tenths of a quart) of oxygen is transferred from the alveoli to the blood each minute, even when
the person is at rest. At the same time, a similar volume of carbon dioxide moves from the blood to the alveoli and is exhaled. During exercise, it is possible to breathe in and out more than 100 liters (about 26 gallons) of air per minute and extract 3 liters (a little less than 1 gallon) of oxygen from this air per minute. The rate at which oxygen is used by the body is one measure of the rate of energy expended by the body. Breathing in and out is accomplished by
respiratory muscles
Control of Breathing Breathing is usually automatic, controlled subconsciously by the respiratory center at the base of the brain. Breathing continues during sleep and usually even when a person is unconscious.... read more .
The function of the respiratory system is to move two gases: oxygen and carbon dioxide. Gas exchange takes place in the millions of alveoli in the lungs and the capillaries that envelop them. As shown below, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli.Gas
Exchange Between Alveolar Spaces and Capillaries
Three processes are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs: ventilation, diffusion, and perfusion.
Ventilation is the process by which air moves in and out of the lungs.
Diffusion is the spontaneous movement of gases, without the use of any energy or effort by the body, between the alveoli and the capillaries in the lungs.
Perfusion is the process by which the cardiovascular system pumps blood throughout the lungs.
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The heart is an amazing organ. It pumps oxygen and nutrient-rich blood throughout your body to sustain life. This fist-sized powerhouse beats (expands and contracts) 100,000 times per day, pumping five or six quarts of
blood each minute, or about 2,000 gallons per day. Your heart is a key part of your cardiovascular system, which also includes all your blood vessels that carry blood from the heart to the body and then back to the heart. As the heart beats, it pumps blood through a system
of blood vessels, called the circulatory system. The vessels are elastic, muscular tubes that carry blood to every part of the body. Blood is essential. In addition to carrying fresh oxygen from the lungs and nutrients to the body's tissues, it also takes the body's waste products, including carbon dioxide, away from the tissues. This is necessary to sustain life and promote the
health of all parts of the body. There are three main types of blood vessels: This vast system of blood vessels -- arteries, veins, and capillaries -- is over 60,000 miles long. That's long enough to go around the world more than twice!How Does Blood Travel Through the Heart?
The heart is located under the rib
cage, slightly to the left of your breastbone (sternum) and between your lungs. Looking at the outside of the heart, you can see that the heart is made of muscle. The strong muscular walls contract (squeeze), pumping blood to the rest of the body. On the surface of the heart, there are coronary arteries, which supply oxygen-rich blood to the heart muscle itself. The major blood vessels that enter the heart are the superior vena cava, the inferior vena cava, and the pulmonary veins. The
pulmonary artery exits the heart and carries oxygen-poor blood to the lungs. The aorta exits and carries oxygen-rich blood to the rest of the body. On the inside, the heart is a four-chambered, hollow organ. It is divided into the left and right side by a muscular wall called the septum. The right and left sides of the heart are further divided into two top chambers called the atria, which receive blood from the veins, and two bottom chambers called ventricles, which pump blood into
the arteries. The atria and ventricles work together, contracting and relaxing to pump blood out of the heart. As blood leaves each chamber of the heart, it passes through a valve. There are four heart valves within the heart: The tricuspid and mitral valves lie between the atria and ventricles. The aortic and pulmonic valves lie between the ventricles and
the major blood vessels leaving the heart. The heart valves work the same way as one-way valves in the plumbing of your home. They prevent blood from flowing in the wrong direction. Each valve has a set of flaps, called leaflets or cusps. The mitral valve has two leaflets; the others have three. The leaflets are attached to and supported by a ring of tough, fibrous tissue called the annulus. The annulus helps to maintain the proper shape of the valve. The leaflets of the mitral
and tricuspid valves are also supported by tough, fibrous strings called chordae tendineae. These are similar to the strings supporting a parachute. They extend from the valve leaflets to small muscles, called papillary muscles, which are part of the inside walls of the ventricles.Where Is Your Heart and What Does It Look Like?
The right and left sides of the heart work together. The pattern described below
is repeated over and over, causing blood to flow continuously to the heart, lungs, and body. Once blood travels through the pulmonic valve, it enters your lungs. This is called the pulmonary circulation. From your pulmonic valve, blood travels to the pulmonary artery to tiny capillary vessels in the lungs. Here, oxygen travels from the tiny air sacs in the lungs, through the walls of the capillaries, into the blood. At the same time, carbon dioxide, a waste product of
metabolism, passes from the blood into the air sacs. Carbon dioxide leaves the body when you exhale. Once the blood is oxygenated, it travels back to the left atrium through the pulmonary veins. Like all organs, your heart is made of tissue that requires a
supply of oxygen and nutrients. Although its chambers are full of blood, the heart receives no nourishment from this blood. The heart receives its own supply of blood from a network of arteries, called the coronary arteries.How Does Blood Flow Through the Heart?
Right Side of the Heart
Left Side of the Heart
How Does Blood Flow Through
Your Lungs?
What Are the Coronary Arteries of the Heart?
Two major coronary arteries branch off from the aorta near the point where the aorta and the left ventricle meet: These arteries
and their branches supply all parts of the heart muscle with blood. Coronary artery disease occurs when plaque builds up in the coronary arteries and prevents the heart from getting the enriched blood it needs. If this happens, a network of tiny blood vessels in the heart that aren't usually open called collateral vessels may enlarge and become active. This
allows blood to flow around the blocked artery to the heart muscle, protecting the heart tissue from injury. The atria and ventricles work together, alternately contracting and relaxing to pump blood through your heart. The electrical system of the heart is the power source that makes this possible. Your heartbeat is triggered by electrical impulses that travel down a special pathway through the heart. At rest, a normal heart beats around 50 to 90 times a minute. Exercise, emotions, fever, and some
medications can cause your heart to beat faster, sometimes to well over 100 beats per minute.How Does the Heart Beat?