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Course: Medical Surgical Nursing

Topic: Anatomy/Physiology of the Cardiovascular System

The Nurses International Community

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Module Goals

Learners will be able to

Describe the anatomy of the heart.
Discuss the physiology of the cardiovascular (CV) system.
Discuss the age-related CV changes.

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Cardiovascular System

The heart pumps blood through a network of arteries and veins known as the cardiovascular circulatory system.
Blood is pumped through the system to the body’s organs, tissues, and cells.
Blood delivers oxygenated blood and nutrients from the lungs to all cells of the body via arteries and arterioles.
Blood removes carbon dioxide and other waste products made by cells.
Deoxygenated blood is carried through venules and veins back to the lungs for removal from the body (through exhalation).

Betts et al., 2013

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Heart Anatomy

Hollow muscular fist-sized organ.
Primary organ to pump blood
Located between lungs in the middle of the chest, behind and slightly to the left of sternum.
Contains 4 chambers: 2 ventricles and 2 atria.
Powered by electrical impulses: SA node, AV node, Bundle of His, and Purkinje fibers.

Betts et al., 2013

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Position of Heart in Thoracic Cavity

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Heart Anatomy (Continued)

Walls: Have three layers, septum divides heart into left and right chambers.

Endocardium (inner layer)
Myocardium (middle layer)
Epicardium (protective outer layer)

Heart chambers: 4 chambers, septum divides heart into left and right chambers.

Top two chambers are atria
Bottom two chambers are ventricles

Betts et al., 2013

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Heart Anatomy (Continued)

Heart Valves are the “doors” between the heart chambers and the body.

2 atrioventricular valves open between upper and lower chambers.

Tricuspid valve: Between right atrium and right ventricle.
Mitral valve: Between left atrium and left ventricle.

2 semilunar valves open when blood flows out of the ventricles.

Aortic: Located on the aorta, carries blood to the body.
Pulmonary: Located on the pulmonary artery, carries deoxygenated blood to the lungs.

Betts et al., 2013

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Heart Anatomy (Continued)

Blood vessels

Arteries: Carry oxygenated blood from heart to the body’s organs and tissues.
Veins: Carry deoxygenated blood from the tissues to the heart.
Capillaries: Exchange of oxygenated and deoxygenated blood occurs in these vessels.
Coronary arteries: Supply blood directly to the heart.

Betts et al., 2013

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Electrical System of the Heart

Sinoatrial (SA) node: Specialized clump of conducting cells near the superior and posterior walls of the right atrium in close proximity to the orifice of the superior vena cava.

Atrioventricular (AV) node: A second clump of conductive cells located in the inferior portion of the right atrium within the atrioventricular septum.

Betts et al., 2013

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Electrical System of the Heart (Continued)

Bundle of His: Arising from the AV node, proceeds through the interventricular septum.

Purkinje fibers: Conductive fibers that spread the impulse and extend throughout the myocardium from the apex of the heart toward the atrioventricular septum and the base of the heart.

Betts et al., 2013

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Case Study

Which of the following is responsible for sending the deoxygenated blood to the lungs?

Pulmonary artery
Pulmonary veins
Tricuspid valve
Bicuspid valve

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Electrical Conduction System

SA node is the initial impulse site of conduction.
AV node carries electrical impulses from upper chamber to the lower chambers.
Left bundle branch sends electrical impulses to the left ventricle.
Right bundle branch sends them to the right ventricle.

Betts et al., 2013

Cleveland Clinic, 2021

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Electrical Conduction System (Continued)

Bundle of His sends electrical impulses from AV node to Purkinje fibers.

Purkinje fibers run through the apex of heart and cause the ventricles to pump blood out.

Betts et al., 2013

Cleveland Clinic, 2021

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Case Study

Which of the following statements of the electrical conducting system of the heart is correct?

The electrical impulses are generated from the AV node and pass through the SA node, bundle of His, and Purkinje fibers.
The electrical impulses are generated from the SA node and pass through the AV node, bundle of His, and Purkinje fibers.
The electrical impulses are generated from the SA node and pass through the AV node, Purkinje fibers, and bundle of His.
The electrical impulses are generated from the SA node. Purkinje fibers receive the impulses and pass them to the AV node and bundle of His.

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Physiology of the Human Heart

The right atrium receives nonoxygenated blood from superior vena cava and inferior vena cava and pumps it through the tricuspid valve to the right ventricle.

The right ventricle pumps the blood through the pulmonary valve to the lungs where it becomes oxygenated.

Michigan Medicine, 2019

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Physiology of the Human Heart (Continued)

The left atrium receives oxygenated blood from the lungs and pumps it through the mitral valve to the left ventricle.

The left ventricle pumps oxygen-rich blood through the aortic valve to the aorta and the rest of the body.

Betts et al., 2013

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Chambers and Circulation Through the Heart

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Critical Thinking Question

State whether the following statements are true (T) or false (F):

The right atrium receives oxygenated blood from the vena cava
The right ventricle pumps the blood through the pulmonary valve to the lungs
The left ventricle pumps oxygen-rich blood through the aortic valve to the aorta and the rest of the body

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Conduction System: Cardiac Conduction Cells

Sodium (Na ), potassium (K ), and calcium (Ca2 ) ions play a role in the conduction system.
Conductive cells: Contain a series of sodium ion channels.
Conductive cells allow influx of sodium ions and cause the membrane potential to rise slowly- depolarization.
At this point, calcium ion channels open, and Ca2 enters the cell, further depolarizing it.
As the calcium ion channels then close, the K channels open, resulting in repolarization.

Betts et al., 2013

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Sodium (Na ), potassium (K ) and calcium (Ca2 ) ions play critical roles in cardiac conducting cells in the conduction system of the heart
Unlike skeletal muscles and neurons, cardiac conduction cells do not have a stable resting potential
Conductive cells contain a series of Na ion channels that allow an influx of sodium ions that cause the membrane potential to rise slowly and eventually cause spontaneous depolarization. At this point, calcium ion channels open, and Ca2 enters the cell, further depolarizing it.
Calcium ions play two critical roles in the physiology of cardiac muscle. In addition to depolarization, calcium ions also cause myosin to form cross-bridges with the muscle cells that then provide the power stroke of contraction. Medications called calcium channel blockers thus affect both the conduction and contraction roles of calcium in the heart.
The autorhythmicity inherent in cardiac cells keeps the heart beating at a regular pace. However, the heart is regulated by other neural and endocrine controls, and it is sensitive to other factors, including electrolytes.

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Cardiac Conductive Cells (Continued)

When the membrane potential reaches approximately −60 mV, the K channels close, Na channels open, and the prepotential phase begins again.

This phenomenon explains the autorhythmicity properties of cardiac muscle.

Betts et al.,2013

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Cardiac Cycle

Cardiac cycle: The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle.

Systole: The period of contraction that the heart undergoes while it pumps blood into circulation.

Diastole: The period of relaxation that occurs as the chambers fill with blood.

Betts et al., 2013

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Cardiac Cycle (Continued)

At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole).
Blood flows into the right atrium from the superior and inferior venae cavae and into the left atrium from the four pulmonary veins.
Contraction of the atria follows depolarization.
Just prior to atrial contraction, the ventricles contain approximately 130 mL of blood in a resting adult (preload).

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Cardiac Cycle (Continued)

As the atrial muscles contract, pressure rises within the atria and blood is pumped into the ventricles.
Ventricular systole follows the depolarization of the ventricles.
During the ventricular ejection phase, the contraction of the ventricular muscle causes blood to be pumped out of the heart (stroke volume).
Ventricular relaxation, or diastole, follows repolarization of the ventricles.

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Cardiac Output (CO)

Measurement of the amount of blood pumped by each ventricle in one minute.

To calculate CO, multiply stroke volume (SV), the amount of blood pumped by each ventricle, by the heart rate (HR) in beats per minute:

CO = HR × SV

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Age-Dependent Changes to Cardiovascular Tissues

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Cardiovascular Age-Related Changes

Aging is associated with increased risk of health complications and diseases.
Affects heart and arterial system, increases cardiovascular diseases.
Structural changes like fibrosis, hypertrophy, slow propagation of electrical impulses.
Decline in left ventricular diastolic filling rate.
Decrease in left ventricular contractility, ejection fraction, and cardiac output.

North & Sinclair, 2012

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Cardiovascular Age-Related Changes

Ventricular hypertrophy.
Increased arterial thickening, stiffness, dysfunctional endothelium.
Increased systolic pressure.
Major risk for atherosclerosis, hypertension, stroke and atrial fibrillation.
Alteration in cardiac conduction; decreased function of sinoatrial nodal pacemaker cells.
Loss of tissue perfusion results in ischemia.

North & Sinclair, 2012

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Critical Thinking Question

Identify the age-related changes that might occur in the cardiovascular tissue. (Select all that apply).

Decreased heart rate
Increased cardiovascular diseases
Hypertrophy
Slow propagation of electrical impulses
Decline in left ventricular diastolic filling rate
Decrease in left ventricular contractility, ejection fraction, cardiac output

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Cultural Considerations

Religion, culture, beliefs, and ethnic customs can influence how families understand and use health concepts:

Health beliefs: In some cultures, talking about a possible poor health outcome will cause that outcome to occur.
Health customs: In some cultures, family members play a large role in healthcare decision-making.
Ethnic customs: Differing gender roles may determine who makes decisions about accepting and following treatment recommendations.

AHRQ, 2020

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Cultural Considerations (Continued)

Religion, culture, beliefs, and ethnic customs can influence how families understand and use health concepts:

Religious beliefs: Faith and spiritual beliefs may affect health-seeking behavior and willingness to accept treatment.
Dietary customs: Dietary advice may be difficult to follow if it does not fit the foods or cooking methods of the family.
Interpersonal customs: Eye contact or physical touch may be okay in some cultures but inappropriate or offensive in others.

AHRQ, 2020

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References

Agency for Healthcare Research and Quality (AHRQ). (2020). Health literacy universal precautions toolkit (2nd ed.). U.S. Department of Health and Human Services, National Institutes of Health. https://www.ahrq.gov/health-literacy/improve/precautions/tool10.html

Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., & Korol, O. (2013). Anatomy and physiology.. https://openstax.org/books/anatomy-and-physiology/pages/1-introduction

Cleveland Clinic. (2021). Body System and Organ: Heart. https://my.clevelandclinic.org/health/body/21704-heart#:~:text=Your%20heart%20is%20divided%20into,blood%20from%20your%20upper%20body.

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References

Michigan Medicine. (2019). Heart health: Anatomy of a human heart. https://healthblog.uofmhealth.org/heart-health/anatomy-of-a-human-heart

North, B. J., & Sinclair, D. A. (2012, April 13). The intersection between aging and cardiovascular disease. Circulation Research, 110(8), 1097–1108. https://doi.org/10.1161/CIRCRESAHA.111.246876

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