Circulatory System in Humans

The heart is a muscular organ with four chambers and valves that pump blood throughout the body. It has a double-layered sac called pericardium.

Blood vessels are tubes that carry blood. Arteries carry blood away from the heart, veins carry blood toward it, and capillaries connect arteries to veins.

The human circulatory system has two circuits: pulmonary and systemic. Blood flows through the heart twice to complete one full trip.

Blood is made up of plasma and different blood cells (like red blood cells, white blood cells, and platelets).

Blood groups (like A, B, AB, and O) are based on the presence or absence of certain proteins on the red blood cells.

The heart has four chambers: two upper chambers called auricles (atria) and two lower chambers called ventricles. The auricles receive blood, while the ventricles pump blood out.

A thick muscular wall that divides the heart into left and right sides, preventing mixing of oxygenated and deoxygenated blood.

Valves in the heart act like doors that open in one direction, controlling the flow of blood between chambers.

Located between the left auricle and left ventricle, the bicuspid valve allows blood to flow from the left auricle to the left ventricle.

The tricuspid valve is present between the right auricle and right ventricle, controlling blood flow from the right auricle to the right ventricle.

Located at the base of the pulmonary artery, this valve allows blood flow from the right ventricle to the pulmonary artery.

Found at the origin of the aorta, this valve controls blood flow from the left ventricle to the aorta.

A group of cells in the upper right auricle of the heart that initiates heartbeats by generating electrical impulses.

The heart's rhythm becomes abnormal, potentially beating too fast, too slow, or a combination of both.

The blood vessels that enter or leave the heart. These include the vena cavae, coronary arteries and veins, pulmonary arteries, and pulmonary veins.

A large vein that carries deoxygenated blood from the upper body to the heart.

A large vein that carries deoxygenated blood from the lower body to the heart.

These carry deoxygenated blood from the right ventricle to the lungs for oxygenation.

These carry freshly oxygenated blood from the lungs back to the left auricle.

The main artery that arises from the left ventricle and carries oxygenated blood to all parts of the body except the lungs.

The heart constantly pumps blood. Deoxygenated blood is received in the right auricle via the superior and inferior vena cavae, then pumped to the lungs. Oxygenated blood returns to the heart and is pumped out to the body through the aorta.

A feeling of the heart beating too fast, skipping a beat, or fluttering, often caused by anxiety or heart conditions.

A sudden, complete stop of the heart's contractions, caused by narrowed blood vessels in the coronary arteries, preventing blood flow to the heart.

High blood pressure, a condition where blood vessels constrict, making it harder for blood to flow. It increases the risk of heart disease, kidney disease, diabetes and blindness.

Cardiac arrest is caused by a blockage of the coronary arteries, usually due to cholesterol and calcium buildup, reducing blood flow to the heart.

An antigen is a protein molecule found on cells, bacteria, and other substances, that triggers the body to produce antibodies.

An antibody is a chemical substance produced by the body in response to antigens. Each antibody binds to a specific antigen.

The transfer of blood from one person (donor) to another (receiver).

Mixing incompatible blood groups (e.g., antigen A and antibody A) causes clumping of red blood cells because the antibodies bind to the antigens.

Blood transfusions are necessary to replace lost blood due to severe injury, surgery, or illness, restoring blood volume and oxygen carrying capacity.