Chapter 20: The Heart

Comprehensive vocabulary flashcards covering the organization, anatomy, physiology, heartbeat mechanics, and cardiodynamics of the human heart.

Pulmonary circuit

The circuit that carries blood to and from the gas exchange surfaces of the lungs.

Systemic circuit

The circuit that carries blood to and from the rest of the body.

Arteries

Blood vessels that carry blood away from the heart.

Veins

Blood vessels that carry blood to the heart.

Capillaries

Also known as exchange vessels, these are networks of small, thin-walled vessels between arteries and veins where dissolved gases, nutrients, and wastes are exchanged.

Right atrium

The chamber of the heart that collects blood from the systemic circuit.

Right ventricle

The chamber of the heart that pumps blood to the pulmonary circuit.

Left atrium

The chamber of the heart that collects blood from the pulmonary circuit.

Left ventricle

The chamber of the heart that pumps blood to the systemic circuit.

Base

The top part of the heart where the great veins and arteries attach.

Apex

The pointed tip of the heart.

Mediastinum

The region between the 2 pleural cavities which contains the heart, great vessels, thymus, esophagus, and trachea.

Pericardium

The double lining of the pericardial cavity, consisting of the outer parietal pericardium and the inner visceral pericardium.

Pericardial cavity

The space between the parietal and visceral pericardium which contains lubricating pericardial fluid.

Auricle

The expandable outer portion of the thin-walled atria.

Coronary sulcus

A groove that divides the atria and the ventricles.

Interventricular sulci

The anterior and posterior grooves that separate the left and right ventricles.

Epicardium

The outer layer of the heart wall, which is also the visceral pericardium.

Myocardium

The middle, muscular wall of the heart consisting of concentric layers of cardiac muscle tissue.

Endocardium

The inner layer of the heart wall.

Intercalated discs

Interconnections between cardiac muscle cells that convey the force of contraction and propagate action potentials.

Atrioventricular (AV) valves

Valves that permit blood to flow in only 1 direction: from the atria to the ventricles.

Superior vena cava

The vessel that delivers systemic blood from the head, neck, upper limbs, and chest to the right atrium.

Inferior vena cava

The vessel that delivers systemic blood from the trunk, viscera, and lower limbs to the right atrium.

Coronary sinus

An opening in the right atrium into which the cardiac veins return blood.

Pectinate muscles

Prominent muscular ridges found on the anterior atrial wall and the inner surfaces of the right auricle.

Tricuspid valve

The right atrioventricular (AV) valve which has 3 fibrous flaps or cusps.

Chordae tendineae

Connective tissue fibers that attach the free edges of AV valve cusps to the papillary muscles.

Papillary muscles

Muscles in the ventricles that tense the chordae tendineae to prevent valves from opening backward.

Trabeculae carneae

Muscular ridges on the internal surface of the right and left ventricles.

Moderator band

A ridge in the right ventricle containing part of the conducting system that coordinates the contractions of cardiac muscle cells.

Mitral valve

The left atrioventricular (AV) valve, also known as the bicuspid valve.

Aortic valve

The valve through which blood leaves the left ventricle to enter the ascending aorta.

Aortic sinuses

Sac-like dilations at the base of the ascending aorta that prevent valve cusps from sticking and are the origin sites for the left and right coronary arteries.

Fibrous skeleton

Four bands of connective tissue around the heart valves and great vessel bases that stabilize valves and electrically insulate ventricular cells from atrial cells.

Coronary circulation

The supply of blood to the muscle tissue of the heart provided by the coronary arteries and cardiac veins.

Sinoatrial (SA) node

Located in the posterior wall of the right atrium, it contains pacemaker cells and begins atrial activation.

Atrioventricular (AV) node

Located in the floor of the right atrium, it receives the impulse from the SA node and delays it before atrial contraction begins.

Purkinje fibers

Part of the conducting system that distributes the electrical impulse through the ventricles to stimulate contraction.

Bradycardia

An abnormally slow heart rate.

Tachycardia

An abnormally fast heart rate.

Electrocardiogram (ECG or EKG)

A recording of the electrical events in the heart obtained by placing electrodes on the body.

P wave

The ECG feature produced when the atria depolarize.

QRS complex

The ECG signal produced when the ventricles depolarize.

T wave

The ECG feature produced when the ventricles repolarize.

P-R interval

The time measured from the start of atrial depolarization to the start of the QRS complex.

Q-T interval

The time measured from ventricular depolarization to ventricular repolarization.

Resting potential

The electrical potential of a cell at rest, which is about $-90\,mV$ for a ventricular cell and $-80\,mV$ for an atrial cell.

Absolute refractory period

The period during which cardiac muscle cells cannot respond to further stimulation.

Systole

The phase of the cardiac cycle involving contraction and rising pressure.

Diastole

The phase of the cardiac cycle involving relaxation and falling pressure.

Heart murmur

The sound produced by regurgitation of blood through the heart valves.

Cardiodynamics

The study of the movement and force generated by cardiac contractions.

End-diastolic volume (EDV)

The amount of blood in a ventricle at the end of its relaxation phase.

End-systolic volume (ESV)

The amount of blood remaining in a ventricle at the end of its contraction phase.

Stroke volume (SV)

The volume of blood ejected per beat, calculated as $SV = EDV - ESV$.

Cardiac output (CO)

The volume of blood pumped by each ventricle in 1 minute, calculated as $CO = HR \times SV$.

Cardiac reserve

The difference between resting cardiac output and maximal cardiac output.