circulatory system
The organ system that transports materials such as nutrients, O2, and hormones to body cells and transports CO2 and other wastes from body cells.
closed circulatory system
- A circulatory system in which blood is confined to vessels and is kept separate from the interstitial fluid.
open circulatory system
A circulatory system in which blood is pumped through open-ended vessels and bathes the tissues and organs directly. In an animal with an open circulatory system, blood and interstitial fluid are one and the same.
cardiovascular system
A closed circulatory system with a heart and branching network of arteries, capillaries, and veins.
atrium
(plural, atria) A heart chamber that receives blood from the veins.
vein
(1) In animals, a vessel that returns blood to the heart. (2) In plants, a vascular bundle in a leaf, composed of xylem and phloem.
capillary
A microscopic blood vessel that conveys blood between an arteriole and a venule; enables the exchange of nutrients and dissolved gases between the blood and interstitial fluid.
pulmonary artery
A large blood vessel that conveys blood from the heart to a lung.
pulmonary vein
A blood vessel that conveys blood from a lung to the heart.
ventricle
(1) A heart chamber that pumps blood out of a heart. (2) A space in the vertebrate brain, filled with cerebrospinal fluid.
aorta
An artery that conveys blood directly from the left ventricle of the heart to other arteries.
arteriole
A vessel that conveys blood between an artery and a capillary bed.
artery
A vessel that carries blood away from the heart to other parts of the body.
superior vena cava
A large vein that returns O2-poor blood to the heart from the upper body and head.
inferior vena cava
A large vein that returns O2-poor blood to the heart from the lower, or posterior, part of the body
cardiac cycle
The alternating contractions and relaxations of the heart.
diastole
The stage of the heart cycle in which the heart muscle is relaxed, allowing the chambers to fill with blood.
systole
The contraction stage of the heart cycle, when the heart chambers actively pump blood.
atrioventricular (AV) node
A region of specialized heart muscle tissue between the left and right atria where electrical impulses are delayed for about 0.1 second before spreading to both ventricles and causing them to contract.
sinoatrial (SA) node
The pacemaker of the heart, located in the wall of the right atrium, that sets the rate and timing at which all cardiac muscle cells contract.
pacemaker
The SA (sinoatrial) node; a specialized region of cardiac muscle in the right atrium that maintains the heart's pumping rhythm (heartbeat) by setting the rate at which the heart contracts.
systemic circuit
One of two main blood circuits in terrestrial vertebrates; conveys blood between the heart and the rest of the body.
pulmonary circuit
One of two main blood circuits in terrestrial vertebrates; conveys blood between the heart and the lungs.
double circulation
Circulation with separate pulmonary and systemic circuits, in which blood passes through the heart after completing each circuit; ensures vigorous blood flow to all organs
blood
A type of connective tissue with a fluid matrix called plasma in which blood cells are suspended.
blood pressure
The force that blood exerts against the walls of blood vessels.
hypertension
Abnormally high blood pressure; a persistent blood pressure above 140/90.
erythrocyte
A blood cell containing hemoglobin, which transports O2. Also called red blood cell.
anemia
A condition in which an abnormally low amount of hemoglobin or a low number of red blood cells results in the body cells receiving too little oxygen
Erythropoietin (EPO)
A hormone that stimulates the production of erythrocytes. It is secreted by the kidney when tissues of the body do not receive enough oxygen.
leukocyte
A blood cell that functions in defending the body against infections and cancer cells. Also called white blood cell.
phagocyte
A white blood cell (for example, a neutrophil or a monocyte) that engulfs bacteria, foreign proteins, and the remains of dead body cells.
leukemia
A type of cancer of the blood-forming tissues, characterized by an excessive production of white blood cells and an abnormally high number of them in the blood; cancer of the bone marrow cells that produce leukocytes.
plasma
The liquid matrix of the blood in which the blood cells are suspended.
platelet
A pinched-off cytoplasmic fragment of a bone marrow cell; platelets circulate in the blood and are important in blood clotting.
heart
A muscular pump that propels a circulatory fluid (blood) through vessels to the body.
heart attack
The damage or death of cardiac muscle cells and the resulting failure of the heart to deliver enough blood to the body.
heart murmur
A hissing sound that most often results from blood squirting backward through a leaky valve in the heart.
heart rate
The frequency of heart contraction.
atherosclerosis
A cardiovascular disease in which fatty deposits called plaques develop on the inner walls of the arteries, narrowing their inner diameters
cardiac output
The volume of blood pumped per minute by each ventricle of the heart.
capillary bed
One of the networks of capillaries that infiltrate every organ and tissue in the body.
venule
A vessel that conveys blood between a capillary bed and a vein.
cardiovascular disease
Diseases of the heart and blood vessels.
fibrin
The activated form of the blood-clotting protein fibrinogen, which aggregates into threads that form the fabric of a blood clot.
fibrinogen
The plasma protein that is activated to form a clot when a blood vessel is injured.
stem cell
An unspecialized cell that can divide to produce an identical daughter cell and a more specialized daughter cell, which undergoes differentiation.
stroke
The death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head.