Structure of the Heart and Cardiovascular System

A series of vocabulary flashcards to assist in studying the structure and functions of the heart and cardiovascular system.

Cardiovascular System

The system composed of the heart, blood vessels, and blood.

Apex of the Heart

The tip of the heart, the narrowest area, resting on the diaphragm.

Mediastinum

The central area in the thoracic cavity where the heart is located.

Atria

Plural form of atrium; the two upper chambers of the heart that receive blood.

Pericardium

The membrane surrounding the heart that protects and anchors it.

Fibrous Pericardium

The tough outer layer of the pericardium made of dense connective tissue.

Serous Pericardium

The inner layer of the pericardium, which is fluid-filled to reduce friction.

Epicardium

The visceral layer of the serous pericardium that is fused to the heart surface.

Myocardium

The thick muscular layer of the heart responsible for pumping blood.

Endocardium

The innermost layer of the heart made of a smooth layer of endothelial tissue.

Atria vs. Ventricles

Atria receive blood; ventricles pump blood out of the heart.

Tricuspid Valve

The valve between the right atrium and right ventricle; has three cusps.

Bicuspid Valve

Also known as the mitral valve; the valve between the left atrium and left ventricle; has two cusps.

Pulmonary Valve

The valve that controls blood flow from the right ventricle to the pulmonary trunk.

Aortic Valve

The valve that controls blood flow from the left ventricle to the aorta.

Coronary Circulation

The circulation of blood supply to the heart muscle itself.

Gap Junctions

Connections between cardiac muscle fibers allowing for rapid spread of electrical impulses.

SA Node

The sinoatrial node; the natural pacemaker of the heart located in the right atrium.

AV Node

The atrioventricular node; it transmits signals from the atria to the ventricles.

ECG (Electrocardiogram)

A test that measures the electrical activity of the heart and records its rhythm.

Systole

The phase of the heartbeat when the heart muscle contracts and pumps blood.

Diastole

The phase of the heartbeat when the heart muscle relaxes and fills with blood.

Collateral Circulation

Connections between blood vessels that provide alternative routes of blood flow.

Capillaries

The smallest blood vessels, where the exchange of gases, nutrients, and wastes occurs.

Venules

Small veins that collect blood from capillaries.

Veins

Blood vessels that carry blood back to the heart.

Arteries

Blood vessels that carry blood away from the heart.

Tunica Interna

The inner layer of blood vessels, continuous with the endocardium.

Tunica Media

The middle layer of blood vessels, primarily composed of smooth muscle.

Tunica Externa

The outer layer of blood vessels made of connective tissue.

Aorta

The largest artery in the body, carrying oxygenated blood from the heart to the body.

Coronary Sinus

A collection of veins that merge to form a large vessel that carries blood to the right atrium.

Size, Shape, and Location of the Heart

Approximately the size of a fist, cone-shaped, located in the mediastinum (central thoracic cavity) between the lungs, with its apex pointing inferiorly and to the left.

Layers of the Serous Pericardium

The serous pericardium consists of two layers: the outer parietal pericardium and the inner visceral pericardium (also known as the epicardium), separated by pericardial fluid.

Layers of the Heart Wall

From superficial to deep, the three layers are the epicardium, myocardium, and endocardium.

Myocardium (Structure and Function)

The thickest middle layer of the heart wall, composed of cardiac muscle cells; responsible for the heart's pumping action.

Endocardium (Structure and Function)

The innermost layer of the heart, made of a smooth sheet of endothelial tissue, lining the heart chambers and valves to reduce friction for blood flow.

Right Atrium (Structure and Function)

Receives deoxygenated blood from the body via the superior vena cava, inferior vena cava, and coronary sinus.

Left Atrium (Structure and Function)

Receives oxygenated blood from the lungs via the four pulmonary veins.

Right Ventricle (Structure and Function)

Pumps deoxygenated blood to the lungs via the pulmonary trunk.

Left Ventricle (Structure and Function)

Pumps oxygenated blood to the rest of the body via the aorta; has the thickest muscular wall.

Superior Vena Cava (SVC)

A large vein that carries deoxygenated blood from the upper body (head, arms, chest) to the right atrium.

Inferior Vena Cava (IVC)

A large vein that carries deoxygenated blood from the lower body (legs, abdomen) to the right atrium.

Pulmonary Trunk and Arteries

The pulmonary trunk emerges from the right ventricle, splits into left and right pulmonary arteries, carrying deoxygenated blood to the lungs.

Pulmonary Veins

Four veins (two from each lung) that carry oxygenated blood from the lungs to the left atrium.

Aorta (Great Vessel Role)

The largest artery, originating from the left ventricle and extending down to the abdomen, distributing oxygenated blood to the body.

Pathway of Blood Flow through the Heart

1. Deoxygenated blood enters Right Atrium (SVC, IVC, Coronary Sinus) {\rightarrow} 2. Tricuspid Valve {\rightarrow} 3. Right Ventricle {\rightarrow} 4. Pulmonary Valve {\rightarrow} 5. Pulmonary Trunk/Arteries (to lungs) {\rightarrow} (gas exchange in lungs) {\rightarrow} 6. Oxygenated blood enters Left Atrium (Pulmonary Veins) {\rightarrow} 7. Bicuspid/Mitral Valve {\rightarrow} 8. Left Ventricle {\rightarrow} 9. Aortic Valve {\rightarrow} 10. Aorta (to body).

Left Coronary Artery (LCA)

Originates from the aorta and quickly branches into the anterior interventricular artery (LAD) and circumflex artery, supplying the left side of the heart.

Right Coronary Artery (RCA)

Originates from the aorta and supplies the right atrium, most of the right ventricle, and parts of the interventricular septum and left ventricle; gives off the marginal and posterior interventricular arteries.

Coronary Venous Return

Deoxygenated blood from the myocardium is collected by cardiac veins (great cardiac vein, middle cardiac vein, small cardiac vein) and drains into the coronary sinus, which empties into the right atrium.

Atrioventricular (AV) Valves Function

The tricuspid (right) and bicuspid/mitral (left) valves prevent backflow into the atria during ventricular contraction; they open when atrial pressure exceeds ventricular pressure and close when ventricles contract, forcing cusps shut.

Semilunar (SL) Valves Function

The pulmonary (right) and aortic (left) valves prevent backflow into the ventricles during ventricular diastole; they open when ventricular pressure exceeds arterial pressure and passively close when ventricles relax and arterial blood pressure pushes them shut.

Cardiac vs. Skeletal Muscle Action Potential (AP)

Cardiac muscle AP has a prolonged plateau phase (due to slow Ca^{2+} influx) not present in skeletal muscle; this extends the refractory period to prevent tetany and allow for ventricular filling.

Functional Relevance of Cardiac Muscle AP Plateau

The long refractory period caused by the plateau prevents summation and tetany, ensuring that the heart has time to relax and fill with blood before the next contraction, which is essential for efficient pumping.

Events of Cardiac Muscle Cell Contraction

1. Depolarization (Na^{+} influx). 2. Plateau phase (Ca^{2+} influx through L-type channels, K^{+} efflux). 3. Repolarization (Ca^{2+} channels close, K^{+} efflux continues). 4. Ca^{2+} binds to troponin, initiating cross-bridge cycling and muscle contraction.

Parts of the Heart's Conduction System

Includes the SA Node, AV Node, Bundle of His (atrioventricular bundle), right and left Bundle Branches, and Purkinje fibers.

Conduction Pathway of the Heart

1. SA Node (pacemaker) {\rightarrow} 2. Atrial muscle (contraction) {\rightarrow} 3. AV Node (delay) {\rightarrow} 4. Bundle of His {\rightarrow} 5. Bundle Branches {\rightarrow} 6. Purkinje Fibers (ventricular muscle contraction).

Autonomic Nerve Supply to the Heart

The heart is innervated by both sympathetic nerves (increase heart rate and contractility) and parasympathetic nerves (decrease heart rate via the vagus nerve).

Normal ECG Tracing Components

• P wave: Atrial depolarization (contraction). - QRS complex: Ventricular depolarization (contraction) and atrial repolarization. - T wave: Ventricular repolarization (relaxation). - PR interval: Time from atrial excitation to start of ventricular excitation. - QT interval: Time from ventricular depolarization to repolarization.