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Circulatory System

The system responsible for transporting materials throughout an animal’s body.

Open Circulatory System

A circulatory system where fluid (hemolymph) bathes organs directly and has no distinction between blood and interstitial fluid.

Closed Circulatory System

A circulatory system where blood and interstitial fluid are physically separated, with blood contained within vessels.

Single Circulation

A type of circulation found in fish, where blood flows through the heart and is then pumped to the gills and body.

Double Circulation

A more complex circulatory system in crocodiles, birds, and mammals where oxygenated and deoxygenated blood are separated into two circuits.

Hemolymph

The fluid that circulates in an open circulatory system, which is a mixture of blood and interstitial fluid.

Erythrocytes

Red blood cells responsible for oxygen transport in the blood.

Leukocytes

White blood cells that defend the body against infection and disease.

Plasma

The liquid component of blood containing water, nutrients, hormones, and waste products.

Cardiac Cycle

The sequence of events that occur during a single heartbeat, consisting of diastole and systole.

Diastole

The phase of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood.

Systole

The phase of the cardiac cycle when the heart muscle contracts and blood is ejected from the chambers.

Arteries

Blood vessels that carry oxygenated blood away from the heart.

Veins

Blood vessels that carry deoxygenated blood back to the heart.

Capillaries

Thin-walled blood vessels where gas and nutrient exchange occurs.

Atria

The upper chambers of the heart that receive blood from the veins.

Ventricles

The lower chambers of the heart that pump blood out to the body and lungs.

Atrioventricular (AV) Valves

Valves that prevent backflow of blood from ventricles to atria.

Semilunar Valves

Valves that prevent backflow of blood from the aorta and pulmonary arteries into the ventricles.

Sinoatrial (SA) Node

The pacemaker of the heart that initiates electrical impulses for heartbeats.

Atrioventricular (AV) Node

The node that receives electrical impulses from the atria and transmits them to the ventricles.

Pacemaker

A group of cells in the heart that regulate the heartbeat by generating electrical signals.

Blood Pressure

The force exerted by circulating blood on the walls of blood vessels.

Cardiac Output (CO)

The amount of blood the heart pumps in liters per minute.

Vasodilation

The widening of blood vessels, which increases blood flow.

Vasoconstriction

The narrowing of blood vessels, which decreases blood flow.

Baroreceptors

Specialized sensors in the arteries that detect changes in blood pressure.

Osmotic Pressure

The pressure that draws fluid back into the blood from interstitial fluid.

Thrombocytes (Platelets)

Cell fragments involved in blood clotting.

Endothelium

The thin layer of cells lining the blood vessels.

Lymphatic System

System that collects fluid that is not recaptured from interstitial space and returns it to the blood.

Interstitium

The fluid-filled space between cells, important in nutrient and waste exchange.

Septum

The wall dividing the right and left sides of the heart.

Pulmonary Circulation

The part of the circulatory system that carries deoxygenated blood from the heart to the lungs and back to the heart.

Systemic Circulation

The part of the circulatory system that carries oxygenated blood from the heart to the body and returns deoxygenated blood back to the heart.

Coronary Circulation

The circulation of blood in the blood vessels that supply the heart muscle itself.

Aneurysm

An abnormal bulge in a blood vessel caused by weak vessel walls.

Plaque

A fatty deposit in the arteries that can lead to atherosclerosis.

Cardiomyopathy

A disease of the heart muscle affecting its size, shape, and ability to pump blood.

Arrhythmia

An irregular heartbeat caused by problems with the heart's electrical system.

Hypertension

Abnormally high blood pressure, often requiring medical management.

Ischemia

Insufficient blood flow to an organ or part of the body, especially the heart.

Myocardial Infarction (Heart Attack)

Damage to the heart muscle due to blocked blood flow, often caused by a blood clot.

Stent

A small mesh tube used to treat narrowed or blocked arteries.

Angioplasty

A medical procedure that uses a balloon to open up narrowed or blocked blood vessels.