Ch 18: The Heart

Vocabulary terms and definitions covering the anatomy, physiology, electrical conduction, and disorders of the heart based on lecture notes.

Daniel Hale Williams

A black cardiologist who performed the first open heart surgery in 1893.

Mediastinum

The location within the thoracic cavity where the pericardial cavity and heart are situated.

Base

The top portion of the heart.

Apex

The pointed bottom tip of the heart.

Fibrous pericardium

Dense connective tissue that protects the heart, attaches it to surrounding structures, and prevents overfilling.

Parietal layer

The outermost layer of the serous pericardium, deep to the fibrous pericardium.

Visceral layer

Also known as the epicardium, this layer of the serous pericardium attaches directly to the heart muscle.

Pericardial cavity

The space between the parietal and visceral layers containing pericardial fluid.

Myocardium

The thick muscle layer of the heart wall anchored by spiral connective tissue fibers.

Endocardium

The innermost layer of the heart wall made of simple squamous epithelium that reduces friction.

Interatrial septum

The wall that divides the left and right atria.

Interventricular septum

The wall that divides the left and right ventricles.

Atrioventricular (AV) valves

Valves located between the atria and ventricles, including the tricuspid and bicuspid (mitral) valves.

Semilunar valves

Valves located between the ventricles and arteries, specifically the pulmonary and aortic valves.

Tricuspid valve

The right AV valve consisting of three flaps.

Mitral valve

The left AV valve, also called the bicuspid valve, consisting of two flaps.

Chordae tendineae

Cords attached to valve flaps and papillary muscles that anchor valves and prevent them from turning inside out.

Lub

The heart sound caused by the closing of the atrioventricular (AV) valves.

Dup

The heart sound caused by the closing of the semilunar valves.

Stenotic valve

A condition where the valve opening is narrowed or the valves do not open fully.

Pulmonary circulation

The circuit from the heart to the lungs and back to the heart.

Systemic circulation

The circuit from the heart to the rest of the body and back to the heart.

Pulmonary arteries

The only arteries in the body that carry deoxygenated blood, moving it from the heart to the lungs.

Pulmonary veins

The only veins in the body that carry oxygenated blood, moving it from the lungs to the heart.

Coronary sinus

The vessel where coronary veins empty before discharging blood into the right atrium.

Angina pectoris

Painful but brief low blood flow to the myocardium.

Myocardial Infarction (MI)

Commonly known as a heart attack; a blockage of a coronary vessel where cells are replaced by scar tissue.

Intercalated discs

Structures containing desmosomes and gap junctions that allow cardiac muscle to act as a functional syncytium.

Automaticity

The ability of cardiac cells to initiate depolarization without input from nerves.

Absolute refractory period

The period lasting nearly the whole contraction during which another contraction cannot be initiated, making tetanus impossible.

Sinus rhythm

The characteristic rhythm of the heart set by the SA node, typically $75 \times 100$ times per minute.

Sinoatrial (SA) node

The heart's pacemaker located in the wall of the right atrium.

Atrioventricular (AV) node

The part of the electrical system that pauses the depolarization wave for about $0.1$ s to let atria finish contracting.

Purkinje fibers

Also called the subendocardial conducting network, these travel from the apex toward the top of the heart to cause ventricular contraction.

P wave

The EKG wave showing atrial depolarization.

QRS complex

The EKG wave showing ventricular depolarization; it also hides atrial repolarization.

T wave

The EKG wave showing ventricular repolarization.

Systole

Contraction of the heart muscle.

Diastole

Relaxation of the heart muscle.

End Diastolic Volume (EDV)

The maximum amount of blood the ventricles hold right before they contract.

End Systolic Volume (ESV)

The amount of blood remaining in the ventricles after contraction.

Stroke Volume (SV)

The amount of blood pumped out by one ventricle in one heartbeat; calculated as $SV = EDV - ESV$.

Cardiac Output (CO)

The total volume of blood pumped per minute; calculated as $CO = HR \times SV$.

Frank-Starling law of the heart

The principle that more muscle stretch leads to a stronger heart contraction.

Atrial (Bainbridge) reflex

A reflex where stretching of the atrial walls stimulates the SA node and sympathetic system to increase heart rate.

Tachycardia

A heart rate greater than $100$ bpm.

Bradycardia

A heart rate lower than $60$ bpm.

Congestive Heart Failure (CHF)

A progressive weakening of the myocardium where cardiac output drops below tissue needs.