The Certified MA Guide - Cardiovascular System

The Certified MA Guide

Cardiovascular System: Overview and Function

1. Introduction to the Cardiovascular System

Definition: The cardiovascular system consists of the heart and blood vessels, working together to circulate blood throughout the body. It is responsible for transporting oxygen, nutrients, hormones, and waste products to and from the cells.
Key Components:
- Heart: The muscular organ that pumps blood.
- Blood Vessels: Arteries, veins, and capillaries that carry blood to and from the body and lungs.
- Blood: Carries oxygen, nutrients, and waste products.

The three major functions of the Cardiovascular System are:

Transportation
- Nutrients to cells
- Oxygen to cells
- Waste from cells
- Carbon Dioxide from cells
Regulation
- Delivery of hormones
- Body Temperature
Protection
- Delivery of the immune system cells

2. The Anatomy of the Heart

Heart Structure: The heart is divided into four chambers—two atria (upper chambers) and two ventricles (lower chambers).
- Right Side of the Heart: Receives deoxygenated blood from the body and pumps it to the lungs for oxygenation (pulmonary circulation).
- Left Side of the Heart: Receives oxygenated blood from the lungs and pumps it to the rest of the body (systemic circulation).
Valves: These regulate blood flow and prevent backflow of blood.
- Tricuspid Valve: Between the right atrium and right ventricle.
- Pulmonary Valve: Between the right ventricle and pulmonary artery.
- Mitral Valve: Between the left atrium and left ventricle.
- Aortic Valve: Between the left ventricle and aorta.
Coronary Circulation: The heart’s own blood supply, which is delivered through the coronary arteries.

3. The Blood Vessels

Arteries: Carry oxygenated blood away from the heart (except the pulmonary artery, which carries deoxygenated blood).
- Structure: Thick-walled to handle high pressure.
- Example: The aorta, the largest artery in the body.
Veins: Carry deoxygenated blood back to the heart (except the pulmonary veins, which carry oxygenated blood).
- Structure: Thinner walls with valves to prevent blood from flowing backward.
- Example: The superior and inferior vena cava, which return deoxygenated blood to the heart.
Capillaries: Tiny, thin-walled vessels where oxygen, nutrients, and waste exchange occurs between the blood and tissues.

4. Circulatory Pathways

Systemic Circulation: Blood flows from the left side of the heart to the body and back to the right side of the heart.
Pulmonary Circulation: Blood flows from the right side of the heart to the lungs for oxygenation and back to the left side of the heart.
Coronary Circulation: Blood supply to the heart muscle itself through the coronary arteries.

As a visual and kinesthetic learner, I have included a graphic to help clarify the flow of blood throughout the body. This illustration demonstrates how deoxygenated blood enters the right side of the heart, is pumped to the lungs where it becomes reoxygenated, and then circulates throughout the body. This cycle continues, ensuring the body receives a constant supply of oxygenated blood.

Additionally, it’s important to note the distinction in terminology used in the pulmonary circulation at the top of this graphic. Typically, arteries carry oxygenated blood and veins carry deoxygenated blood; however, this convention is reversed in the lungs. In the pulmonary circulation, the pulmonary arteries carry deoxygenated blood to the lungs, while the pulmonary veins return oxygenated blood to the heart.

I understand that this graphic may seem overwhelming for those who are just beginning to study the cardiovascular system, so I’ve provided a simpler, revised version. This updated graphic features a divided square that clearly illustrates the circulation of blood through the heart, distinguishing between oxygenated and deoxygenated blood.

Additionally, the graphic on the right shows blood flow through an anatomical heart. This visual will be invaluable as we discuss medical conditions in which blood flow is altered or restricted. A solid understanding of how the heart functions, where blood flows, and the overall circulation process will be crucial when addressing disease states. This knowledge will enable you to pinpoint potential issues, making it easier for you to communicate effectively with patients when explaining the results of their diagnostic tests.

5. How the Heart Pumps Blood

Cardiac Cycle: The sequence of events that occur during one heartbeat. This includes:
- Systole: Contraction phase, where the heart pumps blood out (e.g., ventricles contract to push blood into the arteries).
- Diastole: Relaxation phase, where the heart chambers fill with blood.
Heart Rate: The number of times the heart beats per minute. Typically 60-100 beats per minute at rest in a healthy adult.

6. Cardiac Electrophysiology

The heart is both a mechanical pump and an electrical system. The mechanical function—pumping blood—is driven by electrical signals generated within the heart. These signals cause the heart's chambers to contract in a coordinated manner.

The electrical conduction system of the heart includes specialized cells that generate and propagate electrical impulses. These impulses ensure that the atria contract first, followed by the ventricles, allowing blood to flow efficiently through the heart and into the body.

Key Components of the Cardiac Conduction System

Sinoatrial Node (SA Node)
- Location: Upper wall of the right atrium.
- Function: The SA node is the heart's natural pacemaker, initiating electrical impulses at a regular rate (typically 60-100 beats per minute in a resting adult).
- Importance: Sets the pace for the heart, determining the heart rate.
Atrioventricular Node (AV Node)
- Location: Near the center of the heart, at the junction of the atria and ventricles.
- Function: Receives the electrical impulse from the SA node and delays it slightly before passing it to the ventricles.
- Importance: The delay allows the atria to fully contract and push blood into the ventricles before the ventricles contract.
Bundle of His (AV Bundle)
- Location: Extends from the AV node into the interventricular septum.
- Function: Transmits impulses from the AV node to the bundle branches.
Left and Right Bundle Branches
- Location: Run along the interventricular septum, splitting into two pathways (left and right).
- Function: Carry electrical signals to the ventricles. The left branch serves the left ventricle, while the right branch serves the right ventricle.
Purkinje Fibers
- Location: Network of fibers spread throughout the walls of the ventricles.
- Function: Distribute the electrical signal rapidly to ventricular muscle cells, causing the ventricles to contract.
- Importance: Enables a strong and synchronized ventricular contraction to pump blood effectively.

The Electrical Pathway

The conduction pathway follows a specific sequence:

Electrical impulses originate in the SA node.
The signal spreads through the atria, causing atrial contraction.
The impulse reaches the AV node, where it pauses briefly.
The signal travels down the Bundle of His.
It splits into the left and right bundle branches, which conduct signals to the respective ventricles.
The impulse reaches the Purkinje fibers, stimulating ventricular contraction.

The Heartbeat and the ECG

The cardiac electrical activity generates measurable waves on an electrocardiogram (ECG or EKG):

P Wave: Represents atrial depolarization (electrical activity causing atrial contraction).
QRS Complex: Represents ventricular depolarization (electrical activity causing ventricular contraction).
T Wave: Represents ventricular repolarization (recovery of the electrical system in preparation for the next cycle).

The role of medical assistants often includes preparing patients for EKGs, identifying artifacts, and reporting irregularities such as arrhythmias. (More on this in the clinical skills sections)

7. Blood Pressure

Definition: The force exerted by circulating blood on the walls of blood vessels, particularly arteries.
- Systolic Pressure: The pressure in the arteries when the heart contracts (highest pressure).
- Diastolic Pressure: The pressure in the arteries when the heart is at rest between beats (lowest pressure).
Measuring Blood Pressure: Using a sphygmomanometer (blood pressure cuff) and a stethoscope.
- Example: A reading of 120/80 mmHg is considered normal. (We will cover much more on this in the clinical skills section.)

8. Common Cardiovascular Diseases

Hypertension (High Blood Pressure): A condition where the blood pressure is consistently too high, which can lead to heart disease and stroke.
Atherosclerosis: Hardening and narrowing of the arteries due to plaque buildup, which can lead to heart attacks or strokes.
Myocardial Infarction (Heart Attack): A blockage in one or more of the coronary arteries, leading to damage to the heart muscle.
Congestive Heart Failure (CHF): A condition where the heart is unable to pump enough blood to meet the body’s needs.
Arrhythmia: Irregular heartbeats caused by abnormal electrical impulses in the heart.
Coronary Artery Disease (CAD): Narrowing of the coronary arteries, which can lead to a heart attack or chest pain (angina).
Heart Block: Disruption in electrical signals, often occurring at the AV node or Bundle of His.
Bundle Branch Block: Delay or blockage in the bundle branches, affecting ventricular contraction.

Common Arrhythmias

- Sinus Bradycardia: Slow heart rate, originating from the SA node.
- Sinus Tachycardia: Fast heart rate, originating from the SA node.
- Atrial Fibrillation (A-Fib): Irregular, disorganized electrical activity in the atria.
- Ventricular Tachycardia (V-Tach): Rapid electrical activity in the ventricles, often life-threatening.

9. Medical Assistant’s Role in Cardiovascular Care

You may be asking yourself why in the world you need to know all of these things... The answer is simple; It is your job to know! You aren't alone, your providers will always be there to help teach you and guide you, however, to be a confident and competent medical assistant you should know about the cardiovascular system as it will help you throughout several aspects of your role such as:

Taking Vital Signs:
- Blood pressure: Knowing how to measure and record it correctly. Patients will always ask you if that is a good reading and what the normal range is. Patients with hypertension may ask you why their blood pressure is high, or you may need to educate them on why it is so important that they take their blood pressure medication as it can increase their risk of heart attacks and strokes.
- Pulse: Measuring heart rate and noting rhythm, regularity, and strength. Some patients will have higher or lower than normal resting heart rates. It is known that athletes who are in excellent physical shape may have a lower than normal resting heart rate.
Assisting with Cardiac Procedures:
- Electrocardiogram (ECG/EKG): Understanding what an ECG is, being able to explain to your patient what it does, and being able to know the anatomy well enough to place the leads and capture an image.
Patient Education:
- Explaining blood pressure readings to patients and providing advice on lifestyle changes.
- Explaining certain cardiac labs or studies to patients such as EKG/ECG results, BNP labs, Echocardiograms, or other studies.
- Educating patients on how to prevent cardiovascular disease (healthy diet, exercise, smoking cessation) and the risks associated with not following these directions. Unfortunately, some patients require those consequences to motivate themselves to do better.

Now that we've discussed the cardiovascular system, let's move on to the next lesson, the respiratory system.

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