Cardiovascular System

Epicardium

The outermost layer of the heart wall, serving as the innermost layer of the pericardium.

Myocardium

The middle layer of the heart wall, composed of thick cardiac muscle responsible for the heart's contracting function.

Endocardium

The innermost layer lining the interior structures of the heart, including chambers and valves.

Atria

Receiving chambers of the heart, consisting of the right atrium and left atrium.

Ventricles

Thicker muscular chambers of the heart that pump blood, comprising the right and left ventricles.

Pulmonary Arteries

Vessels carrying deoxygenated blood from the right ventricle to the lungs for gas exchange.

Pulmonary Veins

Vessels carrying oxygenated blood from the lungs back to the left atrium.

Atrioventricular (AV) Valves

Valves situated between the atria and ventricles to prevent backflow during ventricular contraction.

Tricuspid Valve

The three-cusped valve located between the right atrium and right ventricle.

Mitral Valve

The two-cusped valve located between the left atrium and left ventricle.

Chambers of the Heart

The four internal hollow spaces of the heart, including two atria and two ventricles.

Coronary Circulation

The circulation that supplies blood to the myocardium, separate from blood flow in heart chambers.

Myocardial Infarction

A condition caused by the blockage of blood flow to the heart muscle, often due to plaque formation.

Cardiac Cycle

The sequence of events in one complete heartbeat, including systole and diastole.

Sinoatrial (SA) Node

The primary pacemaker of the heart, initiating electrical impulses for heart contractions.

Atrioventricular (AV) Node

The node that receives impulses from the SA node and introduces a delay to allow for atrial contraction.

Baroreceptors

Receptors that monitor blood pressure and send information to the cardiovascular centers in the brain.

Plasma

The liquid component of blood, making up approximately 55% of total blood volume.

Erythrocytes

Red blood cells that transport oxygen within the body.

Cholesterol Plaques

Deposits in arteries that can lead to atherosclerosis and increase the risk for myocardial infarction.

Hemoglobin

A protein in red blood cells responsible for transporting oxygen from the lungs to the tissues.

Aortic Semilunar Valve

The valve located at the exit of the left ventricle leading into the aorta.

Pulmonary Semilunar Valve

The valve located at the exit of the right ventricle leading into the pulmonary trunk.

Chordae Tendineae

Fibrous strands that anchor the cusps of the AV valves and prevent backflow.

Blood Viscosity

The thickness of blood, which affects flow resistance; blood is more viscous than water.

Capillaries

Microscopic vessels where gas and nutrient exchange occurs between blood and tissues.

Heart Murmur

An abnormal sound caused by turbulent blood flow within the heart.

Thrombus

A blood clot that can form on a plaque and obstruct blood flow.

Tissue Ischemia

Reduced blood flow to a tissue, often leading to necrosis or damage.

Defibrillation

A medical treatment using electrical shocks to reset the heart's rhythm.

Hyperlipidemia

Elevated levels of lipids in the blood, often linked to heart disease.

Mediastinum

The central compartment of the thoracic cavity between the pleural cavities that contains the heart, aorta, esophagus, and trachea.

Fibrous Pericardium

The tough, superficial layer of the pericardial sac composed of dense connective tissue that anchors the heart and prevents overfilling.

Pericardial Cavity

The fluid-filled space situated between the parietal and visceral layers of the serous pericardium that reduces friction during contractions.

Moderator Band

A muscular ridge located in the right ventricle that carries conducting system fibers to coordinate muscle contractions.

Trabeculae Carneae

A series of muscular ridges lining the internal myocardial surfaces of both ventricles.

Coronary Sinus

The large venous channel on the posterior surface of the heart that collects deoxygenated blood from cardiac veins and delivers it to the right atrium.

Purkinje Fibers

Specialized conducting cells that rapidly distribute electrical impulses throughout the ventricular myocardium to trigger contraction.

Cardioacceleratory Center

A regulatory center located in the medulla oblongata that activates sympathetic pathways and releases norepinephrine to increase heart rate.

Cardioinhibitory Center

A regulatory center located in the medulla oblongata that activates parasympathetic pathways and releases acetylcholine to decrease heart rate.

Tunica Intima

The innermost layer of a blood vessel wall, consisting of an endothelial lining and an internal elastic membrane in arteries.

Tunica Media

The middle layer of a blood vessel wall composed of concentric sheets of smooth muscle that regulate vessel diameter.

Tunica Externa

The outermost connective tissue layer of a blood vessel that stabilizes and anchors the vessel to adjacent structures.

Elastic Arteries

Large conducting vessels, such as the aorta and pulmonary trunk, that contain high amounts of elastic fibers to absorb systolic pressure waves.

Arterioles

Small arterial vessels known as resistance vessels that regulate blood flow into capillary beds via vasoconstriction and vasodilation.

Venous Reserve

The volume of blood held within large venous networks ($60\text{--}65\%$ of total blood volume) that can be redirected to critical organs during physiological demand.

Diapedesis

The process by which leukocytes squeeze between endothelial cells of capillary walls to migrate into surrounding connective tissues.

Positive Chemotaxis

The directional movement of white blood cells toward specific chemical signals released by damaged tissues or invading pathogens.

Red Bone Marrow

The specialized tissue responsible for the production of all formed elements in circulating blood.

Normal Blood pH

The slightly alkaline homeostatic pH range of blood, maintained between $7.35$ and $7.45$.

Capillary Hydrostatic Pressure Range

The blood pressure gradient across a capillary bed, which typically declines from approximately $35\,\text{mm Hg}$ to $18\,\text{mm Hg}$.