Lecture Notes on the Cardiovascular System
Introduction to the Cardiovascular System
This lecture is the first in a series of 10 lectures about the cardiovascular system.
Additional resources will be provided, including videos and examples to enhance understanding.
Emphasis on the importance of grasping the anatomy and physiology of the heart, as it forms the foundation for nursing knowledge regarding the heart.
Objectives of the Lecture
Identify major components of the cardiovascular system.
Understand the structure and function of the heart and blood vessels.
Explain key functions of the cardiovascular system.
Identify chambers and valves of the heart and their functions.
Discuss the electrical conduction system responsible for cardiac muscle contractions.
Trace the path of blood through the coronary circulation.
Overview of the Cardiovascular System
The cardiovascular system, also known as the circulatory system, is responsible for:
Transporting blood, nutrients, gases, and waste products throughout the body.
Maintaining perfusion: the delivery of oxygen and nutrients to tissues while removing waste products to sustain life and maintain homeostasis.
Components of the Cardiovascular System
Heart: Muscular pump driving circulation.
Blood Vessels: Network through which blood flows.
Arteries: Carry oxygenated blood away from the heart.
Veins: Return deoxygenated blood to the heart.
Capillaries: Facilitate the exchange of oxygen, nutrients, and waste between blood and tissues.
Blood: Composed of plasma, red blood cells, white blood cells, and platelets.
Size and Location of the Heart
Size is roughly equal to a clenched fist.
Pumps approximately 1,000 gallons of blood daily through a closed circuit of blood vessels.
Beats around 100,000 times per day, circulating blood over a distance of 60,000 miles.
Location: Positioned in the mediastinum between the lungs.
About two-thirds lies left of the midline.
Base lies beneath the second rib; apex lies inferiorly between the fifth and sixth ribs.
Importance of mediastinum and anatomical landmarks for procedures (e.g., EKG leads, cardioversion).
Heart Wall Composition
The heart wall consists of three layers, each with specific structure and function:
Endocardium: Innermost layer; lines heart chambers and is made up of endothelial cells with underlying connective tissue.
Myocardium: Middle layer; thickest, contains cardiac muscle tissue enabling synchronized contraction.
Pericardium: Outer layer; double-layered sac covering the heart, filled with serous fluid to reduce friction during contractions.
Heart Chambers and Their Functions
The heart contains four chambers divided by valves that prevent blood mixing:
Right Atrium:
Receives deoxygenated blood from the body via the superior and inferior vena cavae.
Acts as a holding chamber, pumping blood into the right ventricle.
Right Ventricle:
Receives deoxygenated blood from the right atrium.
Pumps blood to the lungs via the pulmonary artery for oxygenation (pulmonary circulation).
Left Atrium:
Receives oxygenated blood from the lungs through the pulmonary veins.
Moves blood into the left ventricle.
Left Ventricle:
Receives oxygen-rich blood from the left atrium.
Pumps blood out to the body through the aorta (systemic circulation).
The left ventricle is the thickest chamber as it pumps blood under high pressure to all body tissues.
Valves of the Heart
Tricuspid Valve:
Between the right atrium and right ventricle; prevents backflow when ventricle contracts.
Pulmonary Valve:
Between right ventricle and pulmonary artery; allows blood to flow to the lungs, preventing backflow.
Mitral Valve (Bicuspid Valve):
Between left atrium and left ventricle; prevents backflow when left ventricle contracts.
Aortic Valve:
Between left ventricle and aorta; allows oxygenated blood to flow into the aorta, preventing backflow.
Emphasis on the importance of unidirectional flow and valve functions.
The Electrical Conduction System of the Heart
The heart's electrical conduction system controls heart rhythm through impulses that signal contractions.
Key components include:
Nodal Cells and Purkinje Fibers: Cells responsible for automaticity, excitability, and conductivity.
Automaticity: The heart initiates electrical signals on its own without external stimuli.
Excitability: Cells respond to electrical impulses.
Conductivity: Cells transmit impulses from one cell to the next.
Sinoatrial (SA) Node:
Located in the right atrium, acts as the heart's natural pacemaker, generating impulses at 60-100 times per minute.
Atrioventricular (AV) Node:
Delays the impulse to allow for ventricular filling.
Bundle of His: Transmits impulses from the AV node down the interventricular septum.
Bundle Branches: Right and left branches help distribute impulses to both ventricles.
Purkinje Fibers: Located within the ventricular walls, stimulate ventricular contractions.
The Cardiac Cycle
Refers to one complete heartbeat encompassing all electrical and mechanical events.
Phases of the cardiac cycle include:
Diastole:
Relaxation phase, allowing chambers to fill with blood; AV valves are open, semilunar valves are closed.
Atrial Systole:
Contraction of atria pushing blood into ventricles.
Ventricular Systole:
Ventricular contraction, pushing blood into arteries; AV valves close and semilunar valves open.
S1 (lub) and S2 (dub) heart sounds result from the closure of valves during diastole and systole.
Cardiac Output
Definition: Amount of blood the heart pumps in one minute; indicative of the heart's effectiveness in meeting body needs.
Factors:
Stroke Volume (SV): Volume of blood ejected per beat, typically around 70 ml per beat for an average adult.
Heart Rate (HR): Number of heartbeats per minute (normal range 60-100 BPM).
Cardiac Output Formula:
CO = HR imes SV
Example: If HR = 75 and SV = 70, then
CO = 75 imes 70 = 5250 mL/min = 5.25 L/min
Importance of monitoring cardiac output as it affects organ perfusion and can indicate health status.
Blood Vessels
Main types include:
Arteries: Carry blood away from the heart.
Veins: Return blood towards the heart.
Capillaries: Site of nutrient and waste exchange.
Circulatory pathway: Arteries > Arterioles > Capillaries > Venules > Veins.
Types of Circulation
Coronary Circulation:
Supply of blood to the heart muscle itself; pathway from aorta to coronary arteries, then to the heart and back to the right atrium.
Systemic Circulation:
Blood flow from the left side of the heart to the body and back.
Pulmonary Circulation:
Movement of blood from the right side of the heart to the lungs for gas exchange and back to the heart.
Summary and Importance
Understanding the cardiovascular system is vital for nursing as it underpins the body's overall health and the ability to respond to emergent situations.
Knowledge of how components function, including heart chambers, valves, and conduction pathways, is critical for patient care.
Emphasis on the need to grasp the anatomy and physiology of the heart, illustrated through diagrams and videos, aids in developing foundational nursing skills for managing cardiovascular health.
Conclusion
Students are encouraged to revisit the material and utilize additional resources provided. Questions are welcomed during Q&A segments to clarify understanding and ensure a solid foundation in cardiovascular knowledge.