Chapter 19: Cardiovascular System: Heart

Comprehensive vocabulary flashcards covering anatomical structures, histological features, electrophysiology, cardiac cycle events, hemodynamics, and embryological development of the heart from Chapter 19.

Perfusion

The delivery of blood per unit time per gram of tissue, expressed in units of $\text{mL/min/g}$.

Arteries

Blood vessels that transport blood away from the heart; most carry oxygenated blood.

Veins

Blood vessels that transport blood toward the heart; most carry deoxygenated blood.

Capillaries

Microscopic blood vessels that serve as sites of exchange for respiratory gases, nutrients, and wastes between blood and body cells or alveoli.

Atria

The superior receiving chambers of the heart that gather incoming blood and pass it to the ventricles.

Ventricles

The inferior pumping chambers of the heart that contract to force blood out into the great arterial trunks.

Great Vessels

The large arteries and veins directly attached to the base of the heart, including the venae cavae, pulmonary trunk, pulmonary veins, and aorta.

Pulmonary Circulation

The circuit that conveys deoxygenated blood from the right side of the heart to the lungs for gas exchange and returns oxygenated blood to the left atrium.

Systemic Circulation

The circuit that carries oxygenated blood from the left side of the heart to systemic tissues throughout the body and returns deoxygenated blood to the right atrium.

Cardiomegaly

An abnormal enlargement of the heart that can reach up to twice typical size, commonly resulting from the heart working harder to compensate for congestive heart failure.

Pulmonary Edema

Swelling and fluid accumulation within the lungs that results from impaired left ventricular pumping, leading to impaired gas exchange and breathing difficulties.

Pericardium

A multi-layered fibroserous covering enclosing the heart that restricts overfilling, anchors the heart, and lubricates its movements.

Fibrous Pericardium

The tough, outer layer of dense connective tissue that attaches to the diaphragm and great vessels, anchoring the heart and preventing overfilling.

Epicardium

The visceral layer of the serous pericardium and outermost layer of the heart wall, composed of simple squamous epithelium and areolar connective tissue with adipose tissue.

Pericardial Cavity

The potential space between the parietal and visceral layers of serous pericardium that contains lubricating serous fluid.

Cardiac Tamponade

A clinical condition resulting from fluid accumulation in the pericardial cavity that compresses the heart and prevents its chambers from filling and pumping.

Ligamentum Arteriosum

A fibrous remnant of the fetal ductus arteriosus located between the pulmonary trunk and the aortic arch.

Coronary Sulcus

A surface groove extending around the circumference of the heart that demarcates the external boundary between the atria and the ventricles.

Myocardium

The middle and thickest layer of the heart wall, composed of cardiac muscle tissue that contracts to pump blood.

Endocardium

The innermost layer of the heart wall made of simple squamous epithelium (endothelium) and areolar connective tissue; lines the internal chambers and covers heart valves.

Fossa Ovalis

An oval depression on the interatrial septum representing the former location of the fetal foramen ovale.

Trabeculae Carneae

Irregular muscular ridges located on the internal walls of the right and left ventricles.

Papillary Muscles

Cone-shaped muscular projections extending from internal ventricular walls that anchor tendinous cords (chordae tendineae).

Tendinous Cords

Thin strands of collagen fibers (chordae tendineae) connecting papillary muscles to atrioventricular valve cusps to prevent cusp inversion into the atria.

Atrioventricular (AV) Valves

Heart valves situated between an atrium and a ventricle (the right AV/tricuspid valve and left AV/bicuspid or mitral valve) that close during ventricular contraction to prevent backflow into the atria.

Semilunar Valves

Heart valves positioned at the boundaries between ventricles and arterial trunks (pulmonary and aortic semilunar valves) that prevent backflow of blood into relaxing ventricles.

Fibrous Skeleton

A structural framework of dense irregular connective tissue that provides anchor rings for valves, attachments for muscle bundles, and electrical insulation between atria and ventricles.

Functional End Arteries

Arteries (such as the coronary arteries) whose anatomical anastomoses are too minute to provide an effective alternate route of blood supply in the event of an occlusion.

Coronary Sinus

A large venous vessel situated in the posterior coronary sulcus that collects deoxygenated blood from cardiac veins and empties directly into the right atrium.

Intercalated Discs

Specialized cell-to-cell junctions between cardiac muscle cells containing mechanical desmosomes and electrical gap junctions, permitting the myocardium to act as a functional syncytium.

Sinuatrial (SA) Node

The primary pacemaker of the heart, located in the posterior wall of the right atrium, that spontaneously initiates action potentials to establish heart rhythm.

Atrioventricular (AV) Node

A cluster of specialized conduction cells in the floor of the right atrium that delays the electrical action potential to ensure ventricles fill prior to contracting.

Vagal Tone

Continuous parasympathetic inhibitory input transmitted along the vagus nerves (CN X) that holds the resting heart rate around $75\,\text{beats/min}$, well below the inherent SA node firing rate of $100\,\text{beats/min}$.

Pacemaker Potential

The progressive spontaneous depolarization of SA nodal cells from $-60\,\text{mV}$ to threshold ($-40\,\text{mV}$) without external stimulation, driven by inward $\text{Na}^+$ flux through slow voltage-gated cation channels.

Electrocardiogram (ECG)

A composite clinical tracing of the electrical activity produced by all myocardial cells during each heart cycle, recorded using skin electrodes.

P Wave

The ECG deflection that reflects atrial depolarization initiated by the SA node.

QRS Complex

The ECG waveform representing ventricular depolarization, during which atrial repolarization also occurs simultaneously.

T Wave

The ECG deflection indicating electrical repolarization of the ventricles.

End-Diastolic Volume (EDV)

The maximal volume of blood contained within a single ventricle at the end of ventricular diastole (rest), typically averaging $130\,\text{mL}$.

End-Systolic Volume (ESV)

The remaining volume of blood within a ventricle at the conclusion of ventricular contraction (systole), typically averaging $60\,\text{mL}$.

Stroke Volume (SV)

The volume of blood pumped out by a single ventricle during one contraction, defined by the relationship $\text{SV} = \text{EDV} - \text{ESV}$ (typically $70\,\text{mL}$ at rest).

Cardiac Output (CO)

The volume of blood pumped by a single ventricle in one minute, determined by the formula $\text{CO} = \text{HR} \times \text{SV}$.

Cardiac Reserve

The capacity to increase cardiac output above resting levels, calculated as cardiac output during exercise minus resting cardiac output.

Chronotropic Agents

External factors, hormones, or neurotransmitters that change heart rate by altering the firing frequency of SA and AV nodal cells.

Inotropic Agents

Substances that alter myocardial contractility (force of contraction) at a given preload, usually by altering the intracellular concentration of available $\text{Ca}^{2+}$.

Preload

The stretch on the ventricular myocardium immediately prior to contraction, determined by end-diastolic volume (EDV).

Frank-Starling Law of the Heart

The principle stating that an increase in end-diastolic volume stretches the ventricular myocardium, producing more optimal myofilament overlap and greater contractile force, thereby increasing stroke volume.

Afterload

The resistance in arterial trunks (aorta or pulmonary trunk) that must be overcome for the ventricles to eject blood.

Atrial Reflex (Bainbridge Reflex)

An autonomic reflex that protects the heart from overfilling; increased venous return stretches atrial baroreceptors, triggering sympathetic signals to elevate heart rate.

Bulbus Cordis

An expansion of the primitive embryonic heart tube that develops into the trabeculated part of the right ventricle, conus cordis, and truncus arteriosus.