Chapter 18: The Cardiovascular System - The Heart

Comprehensive vocabulary flashcards covering the anatomy, physiology, circulation, and clinical correlations of the heart as presented in Chapter 18.

Pulmonary circuit

The transport system of the right side of the heart that pumps oxygen-poor blood to the lungs to get rid of $CO_2$ and pick up $O_2$.

Systemic circuit

The transport system of the left side of the heart that pumps oxygenated blood to body tissues.

Mediastinum

The anatomical region between the second rib and fifth intercostal space where the heart is located.

Apex

The inferior tip of the heart that points toward the left hip.

Apical impulse

The heartbeat palpated between the fifth and sixth ribs, just below the left nipple.

Pericardium

A double-walled sac surrounding the heart consisting of a superficial fibrous layer and a deep two-layered serous layer.

Epicardium

The visceral layer of the serous pericardium that forms the external surface of the heart.

Myocardium

The middle layer of the heart wall composed of circular or spiral bundles of contractile cardiac muscle cells.

Cardiac skeleton

A crisscrossing, interlacing layer of connective tissue that anchors muscle fibers, supports vessels and valves, and limits the spread of action potentials.

Endocardium

The innermost layer of the heart wall that is continuous with the endothelial lining of blood vessels.

Interatrial septum

The internal partition that separates the superior receiving chambers of the heart.

Fossa ovalis

A depression in the interatrial septum that is a remnant of the fetal foramen ovale.

Coronary sulcus

Also known as the atrioventricular groove, it encircles the junction of the atria and ventricles.

Auricles

Appendages on the atria that increase atrial volume.

Pectinate muscles

Muscle ridges found in the anterior portion of the right atrium and only in the auricles of the left atrium.

Crista terminalis

The region that separates the posterior smooth-walled region from the anterior region of the right atrium.

Superior vena cava

The vein that returns blood to the right atrium from body regions above the diaphragm.

Inferior vena cava

The vein that returns blood to the right atrium from body regions below the diaphragm.

Coronary sinus

The vessel that returns blood from the coronary veins to the right atrium.

Trabeculae carneae

Irregular ridges of muscle found on the internal walls of the ventricles.

Papillary muscles

Ventricular muscles that project into the cavity and anchor the chordae tendineae.

Chordae tendineae

Collagen cords that anchor the cusps of the atrioventricular valves to the papillary muscles.

Tricuspid valve

The right atrioventricular (AV) valve consisting of three cusps located between the right atrium and ventricle.

Mitral valve

Also known as the bicuspid valve, it is the left AV valve located between the left atrium and ventricle.

Semilunar (SL) valves

The two valves (aortic and pulmonary) that prevent backflow from major arteries into the ventricles.

Angina pectoris

Thoracic pain caused by a fleeting deficiency in blood delivery to the myocardium, resulting in weakened cells.

Myocardial infarction

A heart attack caused by prolonged coronary blockage, leading to cell death and repair with noncontractile scar tissue.

Intercalated discs

The connecting junctions between cardiac cells containing desmosomes for structural integrity and gap junctions for electrical coupling.

Functional syncytium

The term describing the heart's behavior as a single coordinated unit due to electrical coupling via gap junctions.

Pacemaker cells

Noncontractile cardiac cells that spontaneously depolarize to initiate the depolarization of the entire heart.

Pacemaker potential

The unstable resting membrane potential where $K^+$ channels are closed and slow $Na^+$ channels are open, causing gradual depolarization.

Sinoatrial (SA) node

Known as the pacemaker of the heart, it generates impulses at approximately 75 times per minute.

Atrioventricular (AV) node

Located in the inferior interatrial septum, it delays impulses by 0.1 second to allow for atrial contraction.

Atrioventricular (AV) bundle

Also called the bundle of His; the only electrical connection between the atria and the ventricles.

Subendocardial conducting network

Also known as Purkinje fibers; the network that completes the impulse pathway into the apex and ventricular walls.

Cardioacceleratory center

A center in the medulla oblongata that uses the sympathetic trunk to increase heart rate and force.

Cardioinhibitory center

A center in the medulla oblongata that uses the vagus nerve to decrease heart rate.

P wave

The ECG wave representing the depolarization of the SA node and the atria.

QRS complex

The ECG feature representing ventricular depolarization and masking atrial repolarization.

T wave

The ECG wave representing ventricular repolarization.

Systole

The period of heart contraction.

Diastole

The period of heart relaxation.

End diastolic volume (EDV)

The volume of blood in each ventricle at the end of ventricular diastole.

End systolic volume (ESV)

The volume of blood remaining in each ventricle after systole.

Dicrotic notch

A brief rise in aortic pressure caused by the backflow of blood rebounding off the closed aortic semilunar valve.

Cardiac output (CO)

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

Stroke volume (SV)

The volume of blood pumped out by one ventricle with each beat, calculated as $SV = EDV - ESV$.

Preload

The degree to which cardiac muscle cells are stretched just before they contract, related to the Frank-Starling law of the heart.

Frank-Starling law of the heart

The relationship stating that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (EDV).

Contractility

Contractile strength at a given muscle length, independent of muscle stretch and EDV.

Afterload

The back pressure exerted by arterial blood that the ventricles must overcome to eject blood.

Tachycardia

An abnormally fast heart rate, defined as greater than $100\text{ beats/min}$.

Bradycardia

A heart rate slower than $60\text{ beats/min}$.

Congestive heart failure (CHF)

A condition where the heart is an inefficient pump such that blood circulation is inadequate to meet tissue needs.

Foramen ovale

A fetal heart structure that connects the atria to bypass the pulmonary circulation; its remnant is the fossa ovalis.

Ductus arteriosus

A fetal structure connecting the pulmonary trunk to the aorta; its remnant is the ligamentum arteriosum.