The structure of the heart: 4 chambers
The heart is divided into four chambers: the left atrium, left ventricle, right atrium, and right ventricle. Between each chamber are valves (such as the mitral and tricuspid valves) that prevent blood from flowing backward. As the heart muscle contracts and relaxes rhythmically, it acts as a pump pushing blood throughout the body.
Pulmonary circulation (the lesser circulation)
The circuit in which oxygen-poor blood leaving the right ventricle travels to the lungs, picks up oxygen, and returns to the left atrium. Blood carried to the lungs through the pulmonary artery releases carbon dioxide and takes in oxygen at the alveoli, then returns to the heart's left atrium through the pulmonary veins. Thanks to this process, the blood circulating through our body can continue to be supplied with oxygen.
Systemic circulation (the greater circulation)
The circuit in which oxygen-rich blood leaving the left ventricle delivers oxygen and nutrients to tissues throughout the body and returns to the right atrium. Blood pumped out through the aorta travels through large and small blood vessels throughout the body, delivering oxygen and nutrients to each tissue and cell, and in exchange picks up carbon dioxide and waste products, returning to the heart's right atrium through the venae cavae.
The difference between arteries and veins
Arteries carry blood away from the heart, while veins carry blood back to the heart, and their structures also differ. Arteries have thick, elastic walls able to withstand high pressure, whereas veins typically have relatively thin walls and often contain valves that prevent blood from flowing backward. As an exception, the pulmonary artery carries oxygen-poor blood, while the pulmonary vein carries oxygen-rich blood.
Capillaries: the site of exchange
Oxygen, carbon dioxide, nutrients, and waste products are actually exchanged with cells through the thin walls of extremely narrow capillaries. If arteries and veins are the routes that "transport" blood, capillaries are the actual site where substances are exchanged with tissue cells. Their walls are thin enough to consist of a single layer of cells, which allows substance exchange to occur easily.
The components of blood
Blood is made up of plasma, its liquid component, and cellular components such as red blood cells, white blood cells, and platelets. Red blood cells carry oxygen using hemoglobin, white blood cells are responsible for the body's immune defense, and platelets carry out the clotting function that stops bleeding when there's a wound. Plasma contains a variety of dissolved substances, including water, nutrients, and hormones.
Blood pressure and heart rate
Blood pressure is expressed as two numbers β systolic and diastolic β while heart rate refers to the number of times the heart beats per minute. An adult's resting heart rate is generally known to fall in the range of 60β100 beats per minute, though it is common for athletes and others to have a lower rate than this. Blood pressure and heart rate vary considerably between individuals depending on age, health status, and activity level, so regular measurement and management are recommended.
Habits for keeping your cardiovascular system healthy
Regular aerobic exercise, not smoking, managing sodium intake, and getting regular checkups are known to help maintain cardiovascular health. These lifestyle habits are general recommendations that can help support vascular health and blood pressure management; if you already have a cardiovascular condition or risk factors, it's important to consult a healthcare professional and follow a management approach tailored to you.