Cardiopulmonary Anatomy and Physiology Illustration

Cardiopulmonary Anatomy and Physiology: What is Cardio A&P?

by | Updated: Apr 22, 2024

Cardiopulmonary anatomy and physiology focuses on two crucial body systems: the cardiovascular and pulmonary systems.

Together, they form the cornerstone of life-sustaining functions in the human body.

The cardiovascular system, with the heart and blood vessels, pumps and distributes blood, supplying oxygen and essential nutrients to cells throughout the body.

Meanwhile, the pulmonary system, consisting mainly of the lungs, facilitates the vital exchange of gases — oxygen intake and carbon dioxide expulsion.

This article will delve into the intricacies of cardiopulmonary anatomy and physiology, providing a detailed yet comprehensive overview of the two systems.

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What is Cardiopulmonary Anatomy and Physiology?

Cardiopulmonary anatomy and physiology is a specialized field of study that focuses on the structure (anatomy) and function (physiology) of the cardiovascular and pulmonary systems, which are the heart, blood vessels, and lungs.

This field is fundamental to understanding how these systems interact and operate to maintain the body’s homeostasis.

The cardiovascular system, comprising the heart and the blood vessels, is responsible for pumping and distributing blood throughout the body.

This is a vital process as blood carries oxygen, nutrients, hormones, and other essential substances to cells in every body part. Furthermore, it removes waste products, including carbon dioxide and metabolic byproducts.

On the other hand, the pulmonary system, primarily made up of the lungs and associated structures, is responsible for gas exchange, a process where oxygen from inhaled air is absorbed into the bloodstream, and carbon dioxide, a waste product of metabolism, is expelled from the body through exhalation.

The study of cardiopulmonary anatomy and physiology is critical in the medical field, including careers that require a thorough understanding of the human body’s functioning.

Respiratory System

The respiratory system is a complex collection of organs and tissues that collectively facilitate the process of respiration, which involves the intake of oxygen and the removal of carbon dioxide from the body.


The primary structures of the respiratory system include the following:

  • Nose
  • Nasal cavity
  • Mouth
  • Pharynx (throat)
  • Larynx (voice box)
  • Trachea (windpipe)
  • Bronchi
  • Alveoli
  • Lungs


Respiration can be broken down into two key phases: inhalation and exhalation.

Inhalation begins when you breathe in air through your nose or mouth, which is then directed through the pharynx and larynx, down the trachea, and into the bronchi and bronchioles in the lungs.

The bronchioles lead to tiny sacs called alveoli, where the oxygen in the air you’ve inhaled diffuses across the thin walls of the alveoli into the surrounding blood vessels.

Once in the bloodstream, the oxygen is carried by red blood cells to cells throughout the body. As the cells use the oxygen for energy production, they produce carbon dioxide as a waste product.

This carbon dioxide is then carried back to the lungs via the bloodstream, where it diffuses into the alveoli and is expelled from the body when you exhale.

Regulation of the respiratory system involves complex neurological and biochemical processes, ensuring that the body’s tissues always receive an adequate supply of oxygen while efficiently removing carbon dioxide.


Diseases and conditions of the respiratory system, such as asthma, pneumonia, and lung cancer, can significantly impact the system’s function, making the study of this system critical for medical professionals.

Its interconnection with the cardiovascular system also underscores the importance of understanding the respiratory system for a comprehensive understanding of overall human physiology.


Ventilation refers to the air movement into and out of the lungs, a process facilitated by the respiratory muscles, mainly the diaphragm and intercostal muscles.

During inhalation, the diaphragm contracts and moves downward while the intercostal muscles contract and lift the rib cage, expanding the thoracic cavity.

This expansion reduces the pressure inside the lungs relative to the atmosphere, allowing air to flow into the lungs.

Conversely, during exhalation, the diaphragm and intercostal muscles relax, causing the thoracic cavity to contract and increase pressure within the lungs, forcing air out.

Pulmonary Function Measurements

Pulmonary function measurements are tests that assess the lung’s ability to move air in and out, exchange gases, and transport oxygen to the tissues.

Some of the most common pulmonary function tests include:

  • Spirometry
  • Lung volume tests
  • Gas diffusion tests

Spirometry measures the amount (volume) and speed (flow) of air during inhalation and exhalation, often assessing parameters like Forced Vital Capacity (FVC), which is the maximum amount of air a person can exhale forcefully after a maximum inhalation.

It also measures the Forced Expiratory Volume (FEV1), which is the amount of air a person can forcefully exhale in one second.

Lung volume tests measure the total capacity of the lungs, the residual volume of air remaining in the lungs after a full exhalation, and other volume-related metrics.

Gas diffusion tests measure how well gases like oxygen move from the lungs into the blood.

Diffusion of Pulmonary Gases

Diffusion of pulmonary gases occurs in the alveoli, the tiny sacs at the end of the bronchioles.

This is where oxygen from inhaled air diffuses across the thin walls of the alveoli into the surrounding capillaries, where it binds to hemoglobin in red blood cells to be transported throughout the body.

Simultaneously, carbon dioxide, a waste product from cellular metabolism carried by the blood, diffuses from the capillaries into the alveoli to be expelled during exhalation.

This process of gas exchange is driven by differences in partial pressures between the alveoli and blood, and it ensures the continuous supply of oxygen and removal of carbon dioxide, which is crucial for cell function and survival.

Cardiovascular System

The cardiovascular system, often referred to as the circulatory system, is a complex network comprised primarily of the heart, blood vessels (arteries, veins, and capillaries), and blood.

Its primary function is transporting oxygen, nutrients, hormones, and other vital substances to cells throughout the body while removing waste products such as carbon dioxide and metabolic byproducts.

The Heart

At the core of this system is the heart, a muscular organ that acts as a pump, propelling the blood through the vast network of vessels. The heart is divided into four chambers: the left and right atria (upper chambers) and the left and right ventricles (lower chambers).

Each heartbeat comprises a cycle of contraction (systole) and relaxation (diastole) phases, allowing blood to be received from the body and lungs and then pumped back out to these areas.

Blood Vessels

The blood vessels form an intricate network that carries blood throughout the body.

Arteries, which typically carry oxygenated blood (except for the pulmonary artery), lead away from the heart and branch out into smaller vessels called arterioles, and then into even smaller vessels called capillaries.

It’s within the capillaries that nutrients, oxygen, and waste products are exchanged with the body’s tissues. From the capillaries, blood flows into small vessels called venules, which merge to form veins, returning deoxygenated blood (except for the pulmonary veins) back to the heart.


The blood itself is a complex fluid composed of red and white blood cells, platelets, and plasma.

  • Red blood cells, carrying the molecule hemoglobin, primarily transport oxygen from the lungs to the body’s tissues and help carry away carbon dioxide.
  • White blood cells are part of the immune system and fight off infections.
  • Platelets aid in clotting, and plasma, the liquid portion of the blood, carries nutrients, hormones, and waste products.

Together, these components of the cardiovascular system work in concert to maintain homeostasis, meeting the metabolic demands of the body’s cells and tissues and playing a vital role in the body’s response to injury and disease.

This makes the cardiovascular system central to the overall functioning of the body.

Oxygen and Carbon Dioxide Transport

Oxygen and carbon dioxide transport in the cardiovascular system is a critical process for maintaining cellular function and overall body homeostasis.

Oxygen, after being inhaled into the lungs and diffusing into the bloodstream via the alveoli, is mostly carried in the blood bound to hemoglobin, a protein found in red blood cells. Each hemoglobin molecule can carry up to four oxygen molecules.

This oxygen-rich blood is then transported from the lungs to the heart, which pumps it out to the rest of the body.

On the other hand, carbon dioxide, a waste product of cellular metabolism, is primarily carried in the bloodstream in the form of bicarbonate ions. It’s also carried to a lesser extent dissolved in plasma and bound to hemoglobin.

This carbon dioxide-rich blood returns to the heart and is then pumped to the lungs, where carbon dioxide diffuses into the alveoli to be exhaled, completing the gas exchange cycle.

Acid–Base Balance and Regulation

The cardiovascular and respiratory systems play a crucial role in maintaining the body’s acid-base balance, which is essential for normal cellular functions. The body maintains a delicate balance of acids and bases in the blood, typically measured using the pH scale.

The normal blood pH range is tightly regulated between 7.35 and 7.45.

The respiratory system regulates acid-base balance by controlling carbon dioxide (CO2) levels through the rate and depth of respiration.

When the blood becomes too acidic (low pH), the respiratory rate increases to expel more CO2, a component of carbonic acid, thus reducing acidity.

Conversely, if the blood is too alkaline (high pH), the respiratory rate decreases to retain more CO2 and increase acidity.

The cardiovascular system contributes to acid-base regulation via the bicarbonate buffering system in the blood. Kidneys also play a significant role in this by regulating the concentration of bicarbonate ions.

Ventilation-Perfusion Relationships

The concept of the ventilation-perfusion relationship, often represented as the ventilation-perfusion ratio (V/Q ratio), is critical in understanding how the respiratory and cardiovascular systems work together to optimize gas exchange.

Ventilation refers to the amount of air reaching the alveoli, while perfusion refers to the amount of blood flow reaching the alveoli through the capillaries.

Ideally, ventilation and perfusion should match, meaning each alveolus should receive an amount of air and blood that allows for optimal gas exchange. However, due to gravity and other factors, there can be mismatches or inequalities in the V/Q ratio in different parts of the lung.

When there’s more ventilation than perfusion, it’s called a high V/Q mismatch, often seen in conditions like pulmonary embolism. Conversely, more perfusion than ventilation, a low V/Q mismatch, can occur in conditions like pneumonia.

The body has mechanisms to adjust blood flow and airflow to correct these mismatches and maintain efficient gas exchange.

Control of Ventilation

The control of ventilation is a complex process that involves various structures in the central nervous system, mainly located in the medulla oblongata and pons in the brainstem.

These areas contain groups of neurons known as the respiratory centers, which send signals to the respiratory muscles, primarily the diaphragm and intercostal muscles, to control the rate and depth of breathing.

The primary driver of ventilation control is the concentration of carbon dioxide in the blood, which affects the pH of the blood and cerebrospinal fluid.

When carbon dioxide levels rise (leading to a decrease in blood pH), the respiratory centers increase the rate and depth of breathing to expel more carbon dioxide and restore the pH balance.

Oxygen levels and other factors can also influence ventilation, but to a lesser extent under normal physiological conditions.

Fetal Development and the Cardiopulmonary System

During fetal development, the cardiopulmonary system undergoes several unique adaptations. The fetus receives oxygen and nutrients from the mother’s blood via the placenta, so the fetal lungs are not involved in oxygenation.

Consequently, fetal circulation includes structures that bypass the lungs, such as the ductus arteriosus (connecting the pulmonary artery and the aorta) and the foramen ovale (a hole in the septum between the right and left atria).

At birth, when the newborn takes its first breath, these structures begin to close as the lungs start to function, marking the transition to an independent cardiopulmonary system.

The closure of the foramen ovale creates a separate circulatory system for the oxygenated (systemic) and deoxygenated (pulmonary) blood, as in adults.

Aging and the Cardiopulmonary System

With aging, various changes occur in the cardiopulmonary system that can affect its function. In the cardiovascular system, aging can lead to a decrease in the elasticity of the blood vessels, leading to conditions like hypertension.

The heart muscle can also undergo changes, leading to reduced maximum cardiac output and slower heart rate recovery after exertion.

In the respiratory system, aging can result in reduced lung function, with decreased elasticity of lung tissues, weaker respiratory muscles, and changes in the control of breathing. These changes may result in lower oxygen levels in the blood and reduced exercise tolerance.

Both systems also become more susceptible to diseases with age, such as heart disease, chronic obstructive pulmonary disease (COPD), and others.

However, healthy lifestyle choices, such as regular exercise, a balanced diet, and smoking cessation, can help maintain cardiopulmonary health as one ages.

Advanced Cardiopulmonary Concepts

Electrophysiology of the Heart

The electrophysiology of the heart involves the generation and propagation of electrical signals that control the heart’s rhythmic contractions. This process begins in the sinoatrial (SA) node, the heart’s natural pacemaker located in the right atrium.

The SA node generates an electrical impulse that travels through the atria, causing them to contract. The electrical signal then reaches the atrioventricular (AV) node, where it’s delayed briefly to allow the ventricles to fill with blood.

From the AV node, the impulse travels down the Bundle of His and into the Purkinje fibers, leading to coordinated contraction of the ventricles. The regular generation and conduction of these signals are vital for maintaining consistent, synchronized heartbeats.

Electrocardiogram (ECG)

An electrocardiogram (ECG or EKG) is a diagnostic tool used to detect and record the electrical activity of the heart. It measures the timing and strength of electrical signals as they pass through each part of the heart.

Clinicians use ECGs to identify abnormal rhythms (arrhythmias), investigate chest pain, and assess the heart’s overall function.

An ECG can show evidence of heart disease, a previous heart attack, or an ongoing heart attack, among other conditions.

Hemodynamic Measurements

Hemodynamic measurements refer to the assessment of blood flow and the forces influencing it.

Some essential parameters include heart rate, blood pressure, cardiac output (the volume of blood the heart pumps per minute), and systemic vascular resistance (the resistance the heart must overcome to pump blood through the circulatory system).

Hemodynamic monitoring can be critical in managing patients with cardiovascular disease, critically ill patients, and during surgeries.

Renal Failure and Cardiopulmonary System

Renal failure, or kidney failure, can significantly impact the cardiopulmonary system. When kidneys fail, they can no longer adequately remove waste products from the blood, leading to a buildup of toxins.

This condition can lead to an increased workload for the heart and changes in blood volume and pressure.

Additionally, renal failure can result in fluid overload, causing pulmonary edema and impairing gas exchange in the lungs. Moreover, chronic kidney disease is a known risk factor for cardiovascular disease.

Sleep Physiology and the Cardiopulmonary System

Sleep has a significant impact on the cardiopulmonary system. During sleep, the body’s metabolic demands decrease, leading to a decrease in heart rate, blood pressure, and respiratory rate.

Sleep disorders, such as obstructive sleep apnea, can disrupt these physiological changes.

Obstructive sleep apnea is characterized by repetitive episodes of upper airway obstruction during sleep, leading to periods of interrupted breathing (apneas).

These episodes can cause fluctuations in blood oxygen levels, increased heart rate, and elevated blood pressure, increasing the risk for heart disease, stroke, and other cardiovascular conditions.

FAQs About Cardiopulmonary Anatomy and Physiology

How Does Exercise Affect the Cardiopulmonary System?

Exercise has significant effects on the cardiopulmonary system. During exercise, the body’s muscles need more oxygen and produce more carbon dioxide as a waste product.

To meet these increased demands, your heart rate and stroke volume (the amount of blood pumped out of the heart with each beat) increase, leading to an increase in cardiac output.

Concurrently, your respiratory rate and depth of breathing increase to facilitate greater oxygen intake and carbon dioxide expulsion.

Regular physical exercise can also have long-term benefits for the cardiopulmonary system, including improved lung function, enhanced heart muscle strength, better blood flow, and reduced risk of cardiovascular disease.

How Does High Altitude Affect the Cardiopulmonary System?

High altitude can significantly affect the cardiopulmonary system due to the decreased availability of oxygen, known as hypobaric hypoxia.

When you ascend to high altitudes, the atmospheric pressure decreases, meaning that less oxygen is available for each breath.

To compensate for the lower oxygen levels, your respiratory rate and depth of breathing increase, a response primarily driven by the carotid bodies, which are oxygen-sensing cells located in the neck.

Additionally, the heart rate and cardiac output increase to deliver more blood (and hence more oxygen) to the body’s tissues. Over time, the body can make additional adaptations to a high altitude, such as producing more red blood cells to carry oxygen.

How Does High-Pressure Environments Affect the Cardiopulmonary System?

High-pressure environments, such as those experienced by scuba divers or workers in certain industrial settings, can significantly affect the cardiopulmonary system.

Under high pressure, the density of breathing gas increases, which can increase the work of breathing and potentially lead to respiratory fatigue.

High pressure can also lead to the increased dissolution of gases like nitrogen in body tissues, which can cause decompression sickness (also known as “the bends”) if the pressure is reduced too quickly.

Furthermore, the high partial pressure of oxygen in these environments can lead to oxygen toxicity, which can result in damage to the lungs and central nervous system.

The body does not naturally adapt to high-pressure environments in the same way it does to high altitudes, and special equipment or procedures are often needed to safely work or explore under high pressure.

What is Respiratory Failure?

Respiratory failure is a serious condition that occurs when your lungs can’t adequately exchange oxygen and carbon dioxide with your blood.

There are two main types: Type 1 (hypoxemic) respiratory failure involves low levels of oxygen in the blood, while Type 2 (hypercapnic) respiratory failure is characterized by high levels of carbon dioxide.

Causes can include lung diseases such as chronic obstructive pulmonary disease (COPD), pneumonia, or acute respiratory distress syndrome (ARDS), as well as conditions that impair the muscles or nerves involved in breathing.

Treatment typically involves addressing the underlying cause and, in many cases, providing supplemental oxygen or mechanical ventilation.

What is the Epiglottic Vallecula?

The epiglottic vallecula, often just referred to as the vallecula, is a small recess located just behind the root of the tongue and in front of the epiglottis.

There are two valleculae, one on either side of the midline of the throat, and they’re separated by a ridge of tissue known as the median glossoepiglottic fold.

The valleculae serve as a kind of reservoir that helps to temporarily hold saliva and prevent aspiration (accidental entry of material into the airway) until swallowing can occur.

What is Dead Space Ventilation?

Dead space ventilation refers to the portion of each breath that does not participate in gas exchange because it remains in the conducting airways or reaches alveoli that are not perfused or poorly perfused with blood.

This “dead space” air doesn’t contribute to the removal of carbon dioxide from the body or the addition of oxygen to the blood.

An increase in dead space can be caused by various lung conditions, such as pulmonary embolism or emphysema, and can lead to inefficient ventilation and gas exchange.

Final Thoughts

Understanding the intricacies of cardiopulmonary anatomy and physiology is fundamental to comprehending the body’s overall function.

The sophisticated interplay between the heart, lungs, blood vessels, and blood is integral to sustaining life, ensuring that oxygen and nutrients reach our cells and metabolic waste is efficiently removed.

It is fascinating how this system adapts to various challenges, from environmental factors such as high altitudes or high-pressure conditions to physical activities and different stages of life.

Yet, it’s also clear how disruptions in this system can lead to significant health issues.

Our ongoing exploration and research into the cardiopulmonary system pave the way for the development of more effective treatments for cardiovascular and respiratory diseases, ultimately contributing to enhancing human health and longevity.

John Landry, BS, RRT

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.


  • Patwa A, Shah A. Anatomy and physiology of respiratory system relevant to anaesthesia. Indian J Anaesth. 2015 Sep
  • Chaudhry R, Miao JH, Rehman A. Physiology, Cardiovascular. [Updated 2022 Oct 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan
  • Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2022 Oct 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-

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