Circulatory System – Basic Heart Anatomy, Cardiac Cycle & Blood Components

Vocabulary flashcards covering heart conduction system, cardiac cycle terms, blood typing concepts, major heart valves, circulatory circuits, vessel hierarchy, and primary blood components.

Sinoatrial (SA) Node

Pacemaker of the heart located in the upper right atrium; initiates each cardiac impulse and atrial contraction.

Atrioventricular (AV) Node

Electrical relay station between atria and ventricles; delays impulse before passing it to the Bundle of His.

Bundle of His

Bundle of specialized fibers in the interventricular septum that conducts impulses from the AV node to Purkinje fibers.

Purkinje Fibers

Network of fibers that distribute the electrical impulse through ventricular myocardium, triggering ventricular contraction.

Cardiac Cycle

Complete sequence of events in one heartbeat, including systole (contraction) and diastole (relaxation) of atria and ventricles.

Systole

Phase of the cardiac cycle when heart chambers contract and eject blood.

Diastole

Phase of the cardiac cycle when heart chambers relax and fill with blood.

Autonomic Nervous System (ANS) Regulation

Sympathetic and parasympathetic nerves that modify heart rate and force of contraction.

Antigen (Blood Typing)

Surface protein on erythrocytes that determines ABO and Rh blood groups.

Antibody (Blood Typing)

Plasma protein that targets and binds foreign antigens not present on an individual’s own red blood cells.

Agglutination

Clumping of erythrocytes when antibodies bind incompatible antigens, leading to transfusion reactions.

Universal Recipient (AB+)

Blood type possessing A, B, and Rh antigens, therefore produces no ABO or Rh antibodies and can receive any blood type.

Universal Donor (O−)

Blood type lacking A, B, and Rh antigens; its red cells rarely trigger antibody formation, making it suitable for most recipients.

Rhesus (Rh) Factor

Additional blood cell antigen denoted as positive (+) or negative (−); important in transfusions and pregnancy.

Tricuspid Valve

Right atrioventricular valve separating right atrium from right ventricle.

Bicuspid (Mitral) Valve

Left atrioventricular valve separating left atrium from left ventricle.

Pulmonary Semilunar Valve

Valve between right ventricle and pulmonary artery preventing backflow into the ventricle.

Aortic Semilunar Valve

Valve between left ventricle and aorta preventing backflow into the ventricle.

Pulmonary Circuit

Circulatory route carrying deoxygenated blood from right heart to lungs and returning oxygenated blood to left heart.

Systemic Circuit

Circulatory route transporting oxygenated blood from left heart to body tissues and returning deoxygenated blood to right heart.

Artery

Blood vessel that carries blood away from the heart; usually oxygenated except pulmonary artery.

Vein

Blood vessel that carries blood toward the heart; usually deoxygenated except pulmonary vein.

Arteriole

Small artery encircled by smooth muscle; key regulator of blood pressure and blood flow into capillaries.

Venule

Small vein that collects blood from capillaries and drains into larger veins.

Capillary

Microscopic vessel with single-cell endothelial wall enabling exchange of gases, nutrients, and wastes with tissues.

Precapillary Sphincter

Ring of smooth muscle controlling blood entry into capillary beds, adjusting tissue perfusion.

Pulmonary Artery

Only artery carrying deoxygenated blood; transports blood from right ventricle to lungs.

Pulmonary Vein

Only vein carrying oxygenated blood; returns blood from lungs to left atrium.

Plasma

Liquid portion of blood containing proteins, salts, gases, and nutrients.

Serum

Plasma devoid of clotting proteins, obtained after blood coagulation.

Platelet (Thrombocyte)

Cell fragment essential for blood clotting (hemostasis).

Erythrocyte (Red Blood Cell)

Biconcave cell that transports oxygen via hemoglobin.

Leukocyte (White Blood Cell)

Immune cell that defends the body by phagocytosis or antibody production.