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

• Cardiologist: a physician specializing in heart and blood vessel disorders

Structures of the Cardiovascular System

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

• Heart: central organ, pumps blood

• Blood vessels: arteries, veins, capillaries

Anatomy of the Heart

• Location and External Features

The heart is located in the thoracic cavity, behind the sternum and between the lungs. Its external surface is irregular, with mounds and grooves indicating internal chambers and containing fat, blood vessels, and nerves.

Membranes and Layers

The heart is surrounded by a two-layered membrane called the pericardium. The outer layer is the parietal pericardium, and the inner layer is the epicardium. Pericardial fluid between these layers reduces friction. The muscular myocardium lies beneath the epicardium, and the endocardium lines the heart's chambers and valves.

• Pericardium: protective sac

• Epicardium: outer layer

• Myocardium: muscle layer

• Endocardium: inner lining

Heart Chambers

The heart has four chambers: two atria (upper) and two ventricles (lower). The septum divides the heart into right and left sides.

• Atrium: receives blood

• Ventricle: pumps blood out

• Septum: central wall

Heart Valves

Four valves control blood flow:

• Tricuspid valve: right atrium to right ventricle

• Pulmonary valve: right ventricle to pulmonary arteries

• Mitral valve: left atrium to left ventricle

• Aortic valve: left ventricle to aorta

Chordae Tendineae and Heart Sounds

The tricuspid and mitral valves have chordae tendineae, ropelike strands that prevent valve leaflets from inverting during contraction. Heart sounds "lubb-dupp" are produced by valve closure.

• Lubb: tricuspid and mitral valves close

• Dupp: pulmonary and aortic valves close

Thoracic Cavity and Mediastinum

The thoracic cavity contains the lungs and mediastinum. The mediastinum is the central area holding the heart, great vessels, esophagus, trachea, and thymus.

Blood Vessels

Types and Structure

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

• Arteries: carry blood away from the heart

• Veins: carry blood toward the heart

• Capillaries: connect arteries and veins, exchange substances

Arteries

Arteries branch into arterioles and carry oxygen-rich blood. They have smooth muscle for vasoconstriction and vasodilation, regulating blood pressure.

Capillaries

Capillaries are the smallest vessels, allowing single-file passage of blood cells and exchange of gases, nutrients, and waste.

Veins

Veins and venules carry oxygen-poor blood back to the heart. Many veins have valves to ensure one-way flow.

Circulation Pathways

Systemic and Pulmonary Circulation

Blood circulates through two pathways:

• Systemic circulation: vessels throughout the body except lungs

• Pulmonary circulation: vessels to and from the lungs

Blood Flow Sequence

1. Deoxygenated blood from body enters right atrium

2. Passes through tricuspid valve to right ventricle

3. Enters pulmonary circulation via pulmonary valve and arteries

4. In lungs, blood releases CO2, picks up O2

5. Oxygenated blood returns via pulmonary veins to left atrium

6. Passes through mitral valve to left ventricle

7. Exits through aortic valve to aorta and systemic circulation

Physiology of the Heart

Conduction System

The heart's conduction system initiates and transmits electrical impulses, controlling heartbeat.

• Sinoatrial (SA) node: pacemaker, initiates impulse

• Atrioventricular (AV) node: receives impulse

• Bundle of His and bundle branches: transmit impulse

• Purkinje fibers: cause ventricular contraction

Heart Rhythm and Rate

• Systole: contraction phase

• Diastole: relaxation phase

• Normal sinus rhythm (NSR): SA node controls rate

• Ectopic sites: abnormal rhythm

Nervous System Control

• Parasympathetic division: releases acetylcholine, maintains resting rate

• Sympathetic division: releases norepinephrine and epinephrine, increases rate

Common Cardiovascular Diseases

Heart Diseases

• Angina pectoris: chest pain due to reduced blood flow to myocardium

• Congestive heart failure: heart cannot pump effectively, causing edema

• Myocardial infarction: heart attack, tissue death from lack of oxygen

Blood Vessel Diseases

• Aneurysm: abnormal bulging of artery wall

• Atherosclerosis: plaque buildup narrows arteries

• Hypertension: high blood pressure

• Varicose veins: enlarged, twisted veins

Conduction System Diseases

• Arrhythmias: abnormal heart rhythms (bradycardia, tachycardia, fibrillation, asystole)

Laboratory and Diagnostic Procedures

Exercise Stress Tests

• Used to assess heart function under physical stress

Electrocardiography (ECG)

• Records electrical activity of the heart

• Uses chest leads and produces a 12-lead ECG

• ECG tracing shows P wave, QRS complex, T wave

Ultrasonography and Echocardiography

• Ultrasound imaging of arteries and heart

• Doppler ultrasound shows blood flow direction and velocity

• Echocardiography visualizes heart structure and function

Medical Procedures

Blood Pressure Measurement

• Manual sphygmomanometer: inflatable cuff, pressure gauge, stethoscope

• Systolic pressure: force of ventricular contraction

• Diastolic pressure: resting pressure

Automatic External Defibrillator (AED)

• Used to restore normal heart rhythm in emergencies

Pulse Points

• Locations where arterial pulse can be felt

• Used to assess heart rate and blood flow

Drugs and Surgical Procedures

Cardiovascular Drugs

• Digitalis: derived from Digitalis purpurea (foxglove plant), used to treat heart failure

Open Heart Surgery

• Sternum is cut and retracted for access

• Other procedures may use small incisions

Pacemaker Implantation

• Pacemaker placed under skin, wires attached to heart

• Chest x-ray confirms placement

Balloon Angioplasty and Stent Placement

• Balloon angioplasty: catheter with balloon compresses plaque

• Stent: expanded to keep artery open

Valve Replacement

• Artificial valve implanted to restore function

Summary Table: Heart Chambers and Valves

Summary Table: Types of Blood Vessels

Key Equations

• Blood Pressure Formula:

• Cardiac Output Formula:

• ECG Wave Components:

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