What is the Cardiopulmonary System?

The cardiopulmonary system is responsible for the transportation of gases throughout the body. It comprises the heart, blood, and blood vessels. Each component of the cardiopulmonary system plays an important role in maintaining oxygen and carbon dioxide inside the body.

In multicellular organisms, nutrients and oxygen are provided to the living cells. It is necessary to remove harmful substances for the healthy functioning of the tissues. The cardiopulmonary system is an efficient transport mechanism of gases, hormones, and nutrients to each part of the body.

Heart

The origin of the heart is mesodermal. The chest cavity is located in between the lungs, slightly tilted towards the left lung. The heart is covered and protected by the pericardium. The outer fibrous pericardium forms a tough covering around the heart, whereas the inner pericardium forms a double layer. The pericardial cavity is present between the parietal and visceral layers of the serous pericardium. The pericardial fluid is present in the pericardium. 

Layers of the Heart

Three layers are present in the heart. The external layer is known as the epicardium, the middle layer is known as the myocardium, and the inner layer is the endocardium. 

Chambers of the Heart

Four chambers are present in the heart. The right and left atria are the two superior chambers, and the right and left ventricles are the two inferior chambers. Three veins supply blood to the right atrium; these are the superior vena cava, inferior vena cava, and coronary sinus. The interatrial septum serves as a boundary between the right atrium and the left atrium. Fossa ovalis is present in the inter-atrial septum. A tricuspid valve is present through which blood passes from the right atrium to the right ventricle. From the right atrium, the right ventricles receive the blood. The interventricular septum separates the right ventricle from the right atrium.  

The left atrium receives the oxygenated blood from the lungs with the help of four pulmonary veins. The bicuspid valve from the left atrium helps in the passage of blood into the left ventricle. From the left ventricle, blood is passed through the aortic valve into the ascending aorta. Chordae tendineae are cord-like tendons attached to each atrioventricular valve flap. The papillary muscles are connected with the help of the tricuspid and bicuspid valves.

Heart Valves and Blood Circulation

Two pairs of valves are present in the heart. The atrioventricular valves are also known as AV valves. Their function is to maintain the unidirectional flow of blood between the atria and ventricles. On the right side, the AV valve is known as the tricuspid valve, and on the left side, it is known as the bicuspid valve. The semilunar valves are a pair of valves that ensure that blood flow is one way, that is, out of the ventricles into the arterial system. At the end of the right ventricle, the pulmonary valve is present, and at the exit of the left ventricle, the aortic valve is present. The semilunar valve includes the aortic and pulmonary valve. The name "semilunar" is due to the moon-shaped cusps present in the valves. The pressure builds up within the ventricles on contraction. The semilunar valve opens when the pressure exceeds in the aorta, allowing the blood to release from the ventricles into the pulmonary trunk and aorta. When ventricles relax, the flow of blood occurs towards the heart hence preventing the backflow of blood. The heart consists of two separate pumps: the left side pump represents the systemic circulation, and the right side pump represents the pulmonary circulation.

Blood

Blood comprises blood plasma and formed elements. It is connective tissue. Blood plasma is a liquid extracellular matrix. It is slightly alkaline. The blood volume comprises 5 to 6 liters in an adult male and females 4 to 5 liters.

Cardiopulmonary circulation involves two circulatory routes that carry blood to specific places. In the cardiopulmonary system, the blood vessels are organized, and blood is carried to specific organs in the body. Systemic and pulmonary are two circulatory routes in the cardiopulmonary system.

Systemic circulation:

The systemic circulation comprises arteries and arterioles by which oxygenated blood is carried from the left ventricle to the systemic capillaries, veins, and venules that finally return the deoxygenated blood to the right atrium. Except for the lungs, systemic circulation supplies blood to all organs, and hence it is called peripheral circulation. This system represents the half portion of the cardiopulmonary system.

Aorta is the largest artery in the systemic circuit, with a diameter of 2-3cm. The systemic arteries branch out from the aorta. The superior and inferior vena cava are the largest veins in the body. The coronary circulation and hepatic portal circulation are the subdivisions of the systemic circulation. 

Pulmonary circulation

The function of the pulmonary circulation is to carry deoxygenated blood from the right ventricle to the lungs and finally return the oxygenated blood to the left atrium. After birth, the deoxygenated blood is carried by the pulmonary artery.

The pulmonary arteries divide to form capillaries around the alveoli in the lungs. The union of pulmonary capillaries forms the pulmonary veins that exit the lungs.

To the lungs, deoxygenated blood is carried by the pulmonary arteries, and the pulmonary veins carry oxygenated blood to the heart.

Hepatic Portal Circulation

The system of blood vessels that begins and ends in the capillaries form the portal system. The hepatic portal system starts with the capillary bed of the stomach and intestine and ends in the capillary bed of the liver. It receives blood from two sources, arterial blood from the aorta and venous blood from the gastrointestinal tract. Through the hepatic artery, fresh arterial blood is supplied to the hepatocytes. The blood is directed from parts of the gastrointestinal tract to the liver through the hepatic portal veins. 

Interstitial Fluid and Lymph

The interstitial fluid is formed as a result of the filtration of blood plasma through the blood capillary. When this fluid enters the lymphatic vessels, it is known as lymph. The lymphatic vessels are the vessels that transport lymph throughout the body.

Diseases

Cardiopulmonary diseases affect the heart and lungs.

• Chronic bronchitis: This disease commonly affects smokers. It is characterized by inflamed lungs that exist for a long time.
• Chronic obstructive pulmonary disease (COPD): It includes several chronic conditions that obstruct the airflow to the lungs, causing difficulty in breathing.
• Emphysema: This condition is characterized by damaged alveoli that cause symptoms such as breathlessness. A whistling sound is produced during breathing.
• Congestive heart failure: In this condition, the cardiac muscles fail to pump blood effectively. Various conditions such as a decrease in the diameter of the arteries in the heart or increased blood pressure affect the heart's pumping capacity.

Context and Applications 

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

• Bachelor of Science in Anatomy and Physiology
• Master of Science in Basic Sciences
• Master of Science in Applied Sciences