Cardiology and the Cardiovascular System

Introduction to Cardiology

Cardiology is the medical specialty focused on the anatomy, physiology, diseases, and treatments of the cardiovascular system. Understanding medical terminology in this field is essential for accurate communication and patient care.

• Cardi/o-: means heart

• -logy: means study of

Cardiologists use diagnostic tests, medical and surgical procedures, and drugs to treat cardiovascular diseases.

Structures of the Cardiovascular System

The cardiovascular system consists of the heart and blood vessels, forming a continuous pathway that circulates blood throughout the body.

• Heart: Central organ located in the thoracic cavity, behind the sternum and between the lungs.

• Blood Vessels: Include arteries, veins, and capillaries.

Anatomy of the Heart

External Surface and Chambers

The heart is roughly the size of a fist and contracts at least once per second. Its external surface is irregular, with mounds and grooves reflecting internal chambers and containing fat, blood vessels, and nerves.

Membranes and Layers

The heart is surrounded by the pericardium, a two-layered membrane forming the pericardial sac:

• Parietal pericardium: Outer layer

• Epicardium: Inner layer

• Pericardial fluid: Lubricates the space between layers

• Myocardium: Muscular layer responsible for contraction

• Endocardium: Innermost layer lining chambers and valves

Heart Chambers

The heart contains four chambers:

• Atria: Two small upper chambers

• Ventricles: Two large lower chambers

• Septum: Central wall dividing right and left sides

Heart Valves

Four valves control blood flow:

• Tricuspid valve: Between right atrium and right ventricle (three cusps)

• Pulmonary valve: Between right ventricle and pulmonary arteries (three cusps)

• Mitral valve: Between left atrium and left ventricle (two cusps)

• Aortic valve: Between left ventricle and aorta (three cusps)

Chordae tendineae are ropelike strands that help keep the tricuspid and mitral valves closed during ventricular contraction.

Thoracic Cavity and Mediastinum

The thoracic cavity contains the lungs and mediastinum, which houses the heart, great vessels (aorta, vena cavae, pulmonary arteries and veins), esophagus, trachea, and thymus.

Blood Vessels

Types and Functions

Blood vessels are vascular channels for blood circulation. All have a central lumen and are lined with endothelium (intima).

• Arteries: Carry blood away from the heart; most are oxygen-rich and deep beneath the skin.

• Capillaries: Smallest vessels, connect arteries and veins, deliver blood to cells.

• Veins: Carry blood toward the heart; most are oxygen-poor and near the surface.

Arteries

Arteries branch into arterioles and have smooth muscle for vasoconstriction and vasodilation, which regulate blood pressure.

Veins

Veins have valves to ensure one-way blood flow, especially in large veins.

Circulation Pathways

Blood circulates through two main pathways:

• Systemic circulation: Vessels throughout the body except the lungs

• Pulmonary circulation: Vessels to, within, and from the lungs

Blood passes through both pathways in one complete trip.

Physiology of the Heart

Conduction System

The heart's conduction system initiates and transmits electrical impulses:

• Sinoatrial (SA) node: Pacemaker, initiates heartbeat

• Atrioventricular (AV) node: Receives impulse from SA node

• Bundle of His and bundle branches: Transmit impulse through septum

• Purkinje fibers: Cause ventricles to contract

Heart Rate and Rhythm

A normal heartbeat has two phases:

• Systole: Contraction phase

• Diastole: Resting phase

Normal sinus rhythm (NSR) is controlled by the SA node. Heart rate is regulated by the parasympathetic (acetylcholine) and sympathetic (norepinephrine, epinephrine) nervous systems.

Common Cardiovascular Diseases

Heart Diseases

• Angina pectoris: Chest pain due to reduced blood flow to the heart muscle

• Congestive heart failure: Inability of the heart to pump effectively, leading to edema

• Myocardial infarction: Heart attack caused by blocked coronary arteries

Blood Vessel Diseases

• Aneurysm: Abnormal bulging of an artery wall

• Atherosclerosis: Narrowing of arteries due to plaque buildup

• Hypertension: High blood pressure

• Varicose veins: Enlarged, twisted veins

Conduction System Diseases

• Arrhythmias: Abnormal heart rhythms, including bradycardia, tachycardia, fibrillation, and asystole

Laboratory and Diagnostic Procedures

Exercise Stress Tests

Used to assess heart function during physical activity.

Electrocardiography (ECG)

Records electrical activity of the heart using chest leads and produces a 12-lead ECG.

Ultrasonography and Echocardiography

Ultrasound techniques visualize blood flow and heart structure.

Medical Procedures

Blood Pressure Measurement

Manual sphygmomanometer measures systolic and diastolic pressures using an inflatable cuff and stethoscope.

Automatic External Defibrillator (AED)

AEDs are used in emergencies to restore normal heart rhythm.

Pulse Points

Pulse points are locations where arterial pulse can be felt to assess heart rate and blood flow.

Drugs and Surgical Procedures

Cardiovascular Drugs

Digitalis drugs, originally derived from the foxglove plant (Digitalis purpurea), are used to treat heart conditions.

Open Heart Surgery

Involves cutting the sternum to access the heart for various procedures.

Pacemaker Implantation

Pacemakers are implanted to regulate abnormal heart rhythms.

Balloon Angioplasty and Stent Placement

Balloon angioplasty compresses plaque to open arteries; stents provide ongoing support to keep arteries open.

Valve Replacement

Artificial valves are implanted to replace damaged heart valves, ensuring proper blood flow.

Key Medical Terminology and Abbreviations

Understanding abbreviations and terminology is essential for communication in cardiology. Refer to course materials for a comprehensive list.

Summary Table: Types of Blood Vessels

Additional info: Academic context and expanded explanations were added to ensure completeness and clarity for medical terminology students.