This anatomy study guide is meant to be an overview of the anatomy and physiology of the Cardiovascular System. For a more in-depth review of this topic click the link at the bottom of this blog post to go the website Nurseslabs.

The cardiovascular system is a vital network that sustains life by delivering oxygen and nutrients to cells while removing waste products. At its core is the heart, a remarkable organ that functions as the system's pump, propelling blood through a vast network of blood vessels. In anatomy study guide we will look at the anatomy of the heart consisting of four chambers—the atria and ventricles—working in coordination with valves to ensure the one-way flow of blood. We will also look at the physiology of the heart which reveals its rhythmic contractions, controlled by electrical impulses, which maintains circulation and regulate blood pressure. Together, the anatomy and physiology of the heart ensure efficient circulation, supporting the body's overall health and function.

THE CARDIOVASCULAR SYSTEM CAN BE BROKEN DOWN INTO THE FOLLOWING TOPICS:

• Functions of the Cardiovascular System
• Anatomy of the Heart
• Physiology of the Heart

Functions of the Heart

The heart is a vital organ responsible for several essential functions that maintain the body’s circulatory system and overall health. These functions include:

• Managing Blood Supply: The heart adjusts its rate and strength of contraction to meet the body's varying metabolic demands. Whether at rest, during exercise, or with shifts in body position, the heart ensures that tissues receive the proper amount of blood needed for oxygen and nutrient delivery

• Producing Blood Pressure: Through its rhythmic contractions, the heart generates the pressure necessary to move blood through the circulatory system. This pressure is crucial for maintaining steady blood flow throughout the body, ensuring that every organ receives the resources it needs.

• Securing One-Way Blood Flow: The heart's valves play a critical role in ensuring blood flows in a single direction, preventing backflow and keeping circulation efficient. This one-way system maintains a streamlined process of pumping blood to and from the heart.

• Transmitting Blood: The heart functions as a dual pump, separating pulmonary circulation (sending blood to the lungs for oxygenation) from systemic circulation (delivering oxygenated blood to the rest of the body). This division ensures that tissues receive oxygen-rich blood while carbon dioxide is transported away for removal.

By efficiently managing these functions, the heart keeps the body supplied with oxygenated blood, supporting life and vitality.

Anatomy of the Heart

The cardiovascular system can be likened to a powerful, muscular pump with one-way valves and a complex network of large and small vessels that carry blood throughout the body. Understanding the heart's anatomy sheds light on its vital role within this system.

Heart Structure and Functions

• Size and Weight: Though small in size, comparable to a person’s fist, and weighing less than a pound, the heart possesses incredible strength and endurance. Its ability to consistently pump blood throughout the body makes it essential to life.

• Mediastinum: The heart is securely housed in the inferior mediastinum, the central region of the thorax, situated between the lungs. This positioning provides both protection and stability as it works to circulate blood.

• Apex and Base: The heart’s pointed apex is angled toward the left hip, resting on the diaphragm at the level of the fifth intercostal space. In contrast, its broad base faces the right shoulder, positioned beneath the second rib, from which the major blood vessels of the body emerge.

• Pericardium: The heart is enveloped by a double-walled sac called the pericardium. This outermost layer serves as a protective shield and secures the heart in place within the chest cavity.

• Fibrous Pericardium: The outer layer of this sac, known as the fibrous pericardium, loosely fits around the heart. It plays a vital role in protecting the heart and anchoring it to surrounding structures like the diaphragm and sternum.
• Serous Pericardium: Beneath the fibrous pericardium is the serous pericardium, a thin, two-layered membrane. Its parietal layer lines the inner surface of the fibrous pericardium, reducing friction as the heart beats.

These anatomical features ensure that the heart functions efficiently, consistently delivering blood to meet the body’s needs.

Layers of the Heart

The heart’s structure is composed of three distinct layers, each playing a crucial role in its function as a powerful, efficient pump. These layers work together to ensure that blood flows smoothly and consistently throughout the body.

• Epicardium: The outermost layer of the heart, known as the epicardium, also called the visceral layer, forms part of the heart wall. It serves as a protective layer, providing a smooth outer surface that helps reduce friction as the heart moves within the chest cavity.

• Myocardium: The myocardium is the thick, muscular middle layer of the heart, composed of bundles of cardiac muscle fibers. These fibers are arranged in a twisted, ring-like fashion, enabling the myocardium to contract forcefully. As the layer responsible for pumping, the myocardium generates the force needed to propel blood throughout the circulatory system.

• Endocardium: The innermost layer of the heart, the endocardium, is a delicate, glistening sheet of endothelium that lines the heart’s chambers. This smooth surface minimizes resistance as blood flows through the heart, ensuring efficient movement between chambers and preventing clot formation.

Together, these three layers work in unison to maintain the heart’s integrity and function, allowing it to fulfill its vital role in circulation.

Chambers of the Heart

The heart is divided into four hollow chambers that work together to circulate blood throughout the body. These chambers consist of two atria and two ventricles, each playing a unique role in the heart’s function.

• Receiving Chambers (The Atria): The two upper chambers, known as atria, serve primarily as receiving chambers. They collect blood returning to the heart from the body and the lungs. While they contribute to the heart’s overall function, their role in pumping is less intense compared to the ventricles.

• Discharging Chambers (The Ventricles): The two lower chambers, called ventricles, are the heart’s primary pumping chambers. These thick-walled, muscular cavities are responsible for propelling blood out of the heart. When the ventricles contract, they forcefully push blood into the arteries, sending it either to the lungs for oxygenation or to the rest of the body for circulation.

• The Septum: The heart is divided longitudinally by a wall of tissue known as the septum. Depending on the location, it is called the interventricular septum when separating the ventricles or the interatrial septum when dividing the atria. This partition ensures that oxygen-rich blood and oxygen-poor blood remain separated, allowing for efficient circulation.

These four chambers work in harmony to ensure that blood flows in the correct direction and is pumped effectively to meet the body’s needs.

Associated Great Vessels

The heart relies on several major blood vessels, known as the great vessels, to facilitate the entire process of cardiac circulation. These vessels are crucial for transporting blood to and from the heart, ensuring oxygenation and the delivery of nutrients throughout the body.

• Superior and Inferior Vena Cava: The heart receives oxygen-poor blood from the body through two large veins: the superior vena cava, which collects blood from the upper body, and the inferior vena cava, which gathers blood from the lower body. This deoxygenated blood is then directed into the heart’s right atrium before being pumped into the pulmonary circulation.

• Pulmonary Arteries: From the right side of the heart, the pulmonary trunk splits into the right and left pulmonary arteries, which transport the oxygen-poor blood to the lungs. Here, the blood undergoes gas exchange—oxygen is absorbed while carbon dioxide is released.

• Pulmonary Veins: After being oxygenated in the lungs, blood returns to the left side of the heart through four pulmonary veins. This oxygen-rich blood is essential for nourishing body tissues, and its journey continues from the heart to the rest of the body.

• Aorta: The aorta, the largest artery in the body, carries oxygenated blood from the left ventricle of the heart into systemic circulation. Branching off from the aorta, smaller arteries deliver oxygen and nutrients to every tissue and organ.

Together, these great vessels play a critical role in maintaining the heart’s circulation, supporting life by ensuring the continuous exchange and delivery of blood.

Heart Valves

The heart contains four valves that play  a vital role in regulating blood flow, ensuring it moves in only one direction through the chambers. These valves act as gates, preventing the back flow of blood and maintaining the efficiency of circulation.

• Atrioventricular (AV) Valves: Located between the atria and ventricles on both sides of the heart, the AV valves prevent blood from flowing back in the atria when the ventricles contract. They serve as essential barriers, ensuring that blood moves forward in to the ventricles during heartbeats.

• Bicuspid (Mitral) Valve: The left AV valve, known as the bicuspid or mitral valve, is composed of two flaps (cusps) made from the endocardium. It prevents back flow of blood from the left ventricle into the left atrium during contraction. 

• Tricuspid Valve: On the right side of the heart, the tricuspid valve, with its three flaps, performs the same function as the mitral valve - preventing the back flow of blood in the right atrium when the right ventricle contracts.

• Semilunar Valves: The second set of heart valves, know as semilunar valves, are positioned at the bases of the large arteries that exit the ventricles. These include the pulmonary semilunar valve which prevents back flow into the right ventricle, and the aortic semilunar valve, which prevents back flow into the left ventricle. These valves ensure blood flows smoothly from the ventricles into the pulmonary artery and aorta without returning to the heart.

Together, these valves ensure the heart pumps efficiently, maintaining proper blood flow and circulation throughout the body.

Cardiac Circulation Vessels

While the heart constantly pumps blood through its chambers, this blood does not directly nourish the heart muscle itself. Instead, the myocardium—the thick muscular layer of the heart—receives its own dedicated supply of oxygen-rich blood through a specialized network of vessels.

• Coronary Arteries: The coronary arteries branch off from the base of the aorta and form a ring around the heart in the coronary sulcus, which sits at the junction between the atria and ventricles. These arteries supply oxygenated blood to the myocardium. During ventricular contraction, the coronary arteries are momentarily compressed, and blood flow to the heart muscle is paused. However, they refill and supply blood when the heart relaxes between beats.

• Cardiac Veins: After the myocardium has been nourished, deoxygenated blood is collected by several cardiac veins. These veins channel the blood into a larger vessel known as the coronary sinus, located on the posterior side of the heart. The coronary sinus then empties the blood back into the right atrium, allowing it to be re-oxygenated in the lungs.

This dedicated system of coronary arteries and veins ensures that the heart muscle itself remains properly nourished, enabling it to function effectively as the body’s central pump.

Blood Vessels

Blood travels through a closed transport system known as the vascular system, which is made up of various blood vessels that carry it to and from the heart. This intricate network ensures the proper circulation of blood, delivering oxygen and nutrients to tissues while removing waste.

• Arteries: With each heartbeat, oxygen-rich blood is forcefully propelled from the heart into large arteries. These vessels carry blood away from the heart, distributing it throughout the body.

• Arterioles: As blood moves away from the heart, it passes through increasingly smaller arteries, eventually reaching the arterioles. These smaller vessels feed blood into the capillary beds within tissues, where the exchange of oxygen, nutrients, and waste products takes place.

• Veins: After blood passes through the capillaries, it is collected by small vessels known as venules. The venules then converge into larger veins, which carry deoxygenated blood back to the heart. Finally, this blood enters the heart through the great veins, ready to be re-oxygenated in the lungs and recirculated.

This continuous movement of blood through arteries, arterioles, veins, and capillaries ensures that every part of the body receives the oxygen and nutrients it needs to function effectively.

Tunics

The walls of blood vessels (except for the microscopic capillaries) are composed of three distinct layers known as tunics. These layers provide structure, regulate blood flow, and protect the vessels as they transport blood throughout the body.

• Tunica Intima: The innermost layer, the tunica intima, lines the interior (lumen) of the vessel. It consists of a thin sheet of endothelium resting on a basement membrane. This smooth layer minimizes friction, allowing blood to flow easily through the vessel without obstruction.

• Tunica Media: The tunica media is the thick, middle layer of the vessel wall, made up primarily of smooth muscle and elastic fibers. This layer is responsible for controlling the diameter of the vessel. By contracting or relaxing, the smooth muscle can cause the vessel to constrict or dilate, which helps regulate blood pressure and blood flow.

• Tunica Extern: The outermost layer, the tunica externa, is composed largely of fibrous connective tissue. Its primary role is to provide structural support and protection for the blood vessel, helping it withstand the pressure of blood flow and preventing damage.

These three tunics work together to maintain the integrity of blood vessels, ensuring that blood is efficiently transported to where it’s needed in the body.

Major Arteries of the Systemic Circulation

The aorta, the largest artery in the body, carries oxygen-rich blood from the heart to the rest of the body. Its branches serve various organs and regions, starting from the heart and continuing through the thorax and into the abdominopelvic cavity. Here's a breakdown of the major branches and the organs they supply: 

1. Ascending Aorta and Coronary Arteries

The aorta begins its journey as the ascending aorta from the left ventricle of the heart. The only branches of this section are the right and left coronary arteries, which are responsible for supplying blood to the heart muscle itself.

2. Arterial Branches of the Aortic Arch

As the aorta curves to the left, forming the aortic arch, it branches off into three major branches:

• Brachiocephalic trunk: This first branch splits into the right common carotid artery, which supplies the right side of the head and neck, and the right subclavian artery, which serves the right arm.

• Left common carotid artery: The second branch divides into the left internal carotid artery, which supplies the brain, and the left external carotid artery, which serves the skin and muscles of the head and neck.

• Left subclavian artery: The third branch gives off the vertebral artery, which also supplies part of the brain. As it travels through the arm, it becomes the axillary artery in the armpit region and the brachial artery in the upper arm.

3. Arterial Branches of the Thoracic Aorta

As the aorta descends through the thoracic cavity, it becomes the thoracic aorta, supplying blood to the thorax:

• Intercostal arteries: Ten pairs of arteries serve the muscles between the ribs and the thoracic wall

4. Arterial Branches of the Abdominal Aorta

The aorta continues into the abdominal cavity as the abdominal aorta, where it branches into several important arteries:

• Celiac trunk: This unpaired branch has three divisions: the left gastric artery supplies the stomach, the splenic artery serves the spleen, and the common hepatic artery supplies the liver.

• Superior mesenteric artery: Another unpaired artery, it supplies most of the small intestine and the first half of the large intestine.

• Renal arteries: These arteries supply the kidneys with blood.

• Gonadal arteries: In females, these are known as ovarian arteries, while in males they are called testicular arteries, serving the respective gonads.

• Lumbar arteries: These arteries serve the muscles of the lower back and trunk.

• Inferior mesenteric artery: This unpaired artery supplies the second half of the large intestine.

• Common iliac arteries: The abdominal aorta terminates in these two arteries, which supply the lower limbs and pelvic region.

This complex network of arteries ensures that oxygenated blood reaches every part of the body, maintaining essential functions and supporting overall health.

Major Veins of the Systemic Circulation

The Major Veins of the Systemic Circulation play a crucial role in returning deoxygenated blood from the body back to the heart. These veins converge on the venae cava, which then empty into the right atrium of the heart.

1. Veins Draining into the Superior Vena Cava

The veins that feed into the superior vena cava are arranged in a distal-to-proximal direction, following the flow of blood toward the heart.

• Radial and ulnar veins: These deep veins drain the forearm, unite to form the brachial vein, which drains the arm and empties into the axillary vein in the shoulder region.

• Cephalic vein: This superficial vein drains the lateral aspect of the arm and empties into the axillary vein.

• Basilic vein: Draining the medial side of the arm, the basilic vein joins with the brachial vein closer to the shoulder.

• Median cubital vein: Located at the elbow, this vein connects the basilic and cephalic veins and is often used for blood draws.

• Subclavian vein: This vein collects blood from the arm through the axillary vein and also from the head and neck via the external jugular vein.

• Vertebral vein: It drains the posterior part of the head.

• Internal jugular vein: It drains blood from the dural sinuses of the brain.

• Brachiocephalic veins: The right and left brachiocephalic veins collect blood from the subclavian, vertebral, and internal jugular veins.

• Azygos vein: This single vein drains the thoracic region and joins the superior vena cava before it reaches the heart.

2. Veins Draining into the Inferior Vena Cava

The inferior vena cava is responsible for returning blood from regions of the body below the diaphragm to the heart. It is much longer than the superior vena cava.

• Tibial veins: The anterior and posterior tibial veins, along with the fibular vein, drain the leg. The posterior tibial vein transitions into the popliteal vein at the knee and the femoral vein in the thigh, eventually becoming the external iliac vein as it enters the pelvis.

• Great saphenous veins: These are the longest veins in the body, running from the foot up the medial side of the leg and emptying into the femoral vein.

• Common iliac vein: Each common iliac vein is formed by the union of the external and internal iliac veins, with the internal iliac draining the pelvis.

• Gonadal veins: The right gonadal vein drains the right ovary in females or the right testicle in males, while the left gonadal vein empties into the left renal vein.

• Renal veins: These veins drain blood from the kidneys.

• Hepatic portal vein: This vein drains blood from the digestive organs and passes it through the liver for processing before it enters the systemic circulation.

• Hepatic veins: These veins collect blood from the liver and empty into the inferior vena cava.

Together, the veins of the systemic circulation efficiently return blood to the heart, completing the cycle of circulation essential for maintaining the body's oxygen and nutrient supply.

Physiology of the Heart

As the heart beats and contracts, it propels blood on a continuous cycle—pumping it into the body and then back to the heart, only to send it out again. This process relies on the heart’s Intrinsic Conduction System, which ensures that the heart maintains a steady rhythm.

Intrinsic Conduction System of the Heart

The heart’s ability to contract regularly and rhythmically is powered by its unique conduction system. This system involves the spontaneous contractions of cardiac muscle cells, which are capable of contracting independently, even when disconnected from the nervous system. While these muscle cells can beat on their own, they maintain different rhythms depending on their location within the heart.

The Role of the Intrinsic Conduction System

• How It Functions: The system directs the heart muscle’s electrical impulses in a coordinated manner. Depolarization of the heart muscles occurs in a single direction, from the atria to the ventricles. This conduction pattern enforces a steady contraction rate of about 75 beats per minute, ensuring that the heart functions as a unified, coordinated organ.

• The SA Node – The Heart’s Pacemaker: At the center of this system is the sinoatrial (SA) node, which has the fastest rate of depolarization in the heart. Because of this, it initiates each heartbeat, earning it the title of the heart’s pacemaker.

• Coordinating Contractions: From the SA node, electrical impulses travel across the atria to the atrioventricular (AV) node, causing the atria to contract and push blood into the ventricles. These impulses then pass through the AV bundle, into the bundle branches, and finally to the Purkinje fibers. This pathway results in a strong, coordinated contraction of the ventricles, starting from the heart’s apex and moving upward toward the atria.

• Blood Ejection: The contraction of the ventricles generates a "wringing" motion that efficiently ejects blood from the heart into the large arteries, ready to be transported throughout the body. Through this intricate conduction system, the heart maintains its continuous and rhythmic flow of blood, keeping the body’s tissues nourished and oxygenated.

The Pathway of the Conduction System

The heart’s electrical conduction system ensures that the heart beats in a coordinated and efficient manner. This system follows a specific pathway that triggers the contraction of the heart's chambers, allowing for effective blood flow. Here's how the conduction system works step by step:

• SA Node: The conduction process begins at the sinoatrial (SA) node, often called the heart's "pacemaker." It initiates the depolarization wave, setting the rhythm for the entire heart.

• Atrial Myocardium: From the SA node, the depolarization wave spreads through the atrial myocardium, causing the atria to begin their contraction, pushing blood into the ventricles.

• Atrioventricular (AV) Node: The wave then reaches the AV node, where it pauses momentarily to allow the ventricles to fill. Once the atria finish contracting, the wave moves on.

• AV Bundle: After the AV node, the signal quickly travels down the atrioventricular (AV) bundle, also known as the bundle of His, which acts as a pathway for the electrical impulse to reach the ventricles.

• Bundle Branches and Purkinje Fibers: The depolarization wave splits into the right and left bundle branches, which carry the signal down the ventricular septum. It finally reaches the Purkinje fibers embedded in the walls of the ventricles, triggering a powerful contraction from the apex upwards, ejecting blood from the heart into the arteries.

This precise conduction pathway ensures that the heart beats in a synchronized manner, maintaining efficient blood circulation throughout the body.

Cardiac Cycle and Heart Sounds

The cardiac cycle describes the sequence of events in a single heartbeat, in which the heart chambers contract and relax to pump blood. In a healthy heart, both atria contract together, followed by the ventricles, maintaining an efficient blood flow through the body. Here’s an overview of the cardiac cycle:

• Systole and Diastole:

• Systole: refers to the contraction phase of the heart, where blood is pumped out of the chambers.
• Diastole: refers to the relaxation phase, when the heart refills with blood.

• Cardiac Cycle Overview: The cardiac cycle consists of both systole and diastole, encompassing one complete heartbeat. With an average of 75 beats per minute, each cycle lasts about 0.8 seconds.

• Mid-to-Late Diastole: The cycle begins when the heart is fully relaxed. During this phase, blood flows passively from the atria into the ventricles. The semilunar valves remain closed while the atrioventricular (AV) valves are open. Near the end of diastole, the atria contract, pushing the remaining blood into the ventricles.

• Ventricular Systole: Following atrial contraction, the ventricles contract. As pressure rises in the ventricles, the AV valves close, and when ventricular pressure exceeds that of the arteries, the semilunar valves open, allowing blood to be ejected. Meanwhile, the atria relax and refill with blood.

• Early Diastole: After ventricular contraction, the ventricles relax, and the semilunar valves close, creating a brief moment when the ventricles are closed off. As pressure drops, the AV valves reopen, and the ventricles refill, completing the cycle.

• Heart Sounds:
  • First Heart Sound ("Lub"): This sound is produced by the closing of the AV valves as the ventricles begin to contract.
  • Second Heart Sound ("Dub"): Occurs when the semilunar valves close at the end of ventricular systole, signaling the end of the contraction phase.

These coordinated contractions and relaxations create the rhythmic heart sounds and ensure continuous blood circulation throughout the body.

Cardiac Output

Cardiac output refers to the amount of blood pumped by each side of the heart in one minute. It is a crucial measure of how well the heart meets the body’s circulatory demands. Cardiac output is calculated as the product of heart rate (the number of beats per minute) and stroke volume (the amount of blood pumped with each beat).

• Stroke Volume: Stroke volume represents the volume of blood ejected by a ventricle with every heartbeat. A higher stroke volume means more blood is being pumped with each contraction, contributing to a greater overall cardiac output.

• Regulation of Stroke Volume: According to Starling’s law of the heart, the key factor in controlling stroke volume is the extent to which cardiac muscle cells are stretched before they contract. The more the muscle fibers are stretched, the stronger the contraction will be. This stretching is typically influenced by the volume and speed of venous return—meaning that the more blood that flows back into the heart, the more forcefully the heart will pump.

• Factors Affecting Heart Rate: While stroke volume impacts cardiac output, heart rate is also subject to regulation. The autonomic nervous system plays a critical role, increasing or decreasing heart rate based on the body’s needs. Other physical factors like age, gender, exercise, and body temperature can also modify the basic heart rate, allowing the heart to adapt to varying levels of physical activity and environmental conditions.

By understanding how stroke volume and heart rate work together, it becomes clear how the heart adjusts its output to meet the body’s changing needs during different activities, from rest to exercise.

Physiology of Circulation

The physiology of circulation refers to how blood moves through the body to deliver oxygen and nutrientsto tissues and remove waste products like carbon dioxide. It involves a complex interaction between the heart, blood vessels, and blood itself, ensuring that the body's cells remain healthy and functional. Key aspects of circulation physiology include:

• Heart Function:The heart is the central pump that drives circulation. It works in two phases:
  • Systole: The contraction phase, where the heart pumps blood into the arteries.
  • Diastole: The relaxation phase, where the heart fills with blood before the next contraction. Blood is pumped into two main circuits.
  • Systemic circulation: Delivers oxygenated blood from the left ventricle to the rest of the body and returns deoxygenated blood to the right atrium.
  • Pulmonary circulation: Carries deoxygenated blood from the right ventricle to the lungs for oxygenation and returns oxygenated blood to the left atrium.

• Blood Pressure: Blood pressure is the force exerted by circulating blood on the walls of the blood vessels. It is essential for driving blood through the circulatory system.
  • Cardiac output: The amount of blood the heart pumps in one minute.
  • Peripheral resistance: The resistance of blood vessels to blood flow, determined by vessel diameter and elasticity.
  • Blood volume:The total amount of blood circulating in the body.

• Blood Vessels: Blood vessels form a network through which blood flows, and they are classified based on function:
  • Arteries: Carry oxygen-rich blood away from the heart (except pulmonary arteries).
  • Veins: Return deoxygenated blood to the heart (except pulmonary veins).
  • Capillaries:Tiny vessels that connect arteries and veins; they are the site of gas, nutrient, and waste exchange between blood and tissues.

• Regulation of Blood Flow: Blood flow is regulated by various factors to meet the metabolic demands of different organs:
  • Autoregulation: Tissues can regulate their own blood flow based on their needs, using mechanisms that adjust blood vessel diameter.
  • Neural control: The autonomic nervous system adjusts heart rate and vessel constriction/dilation to maintain blood pressure and flow.
  • Hormonal control: Hormones such as adrenaline, angiotensin, and antidiuretic hormone (ADH) influence blood vessel tone and fluid balance, affecting circulation.

• Gas and Nutrient Exchange: In the capillaries, oxygen and nutrients diffuse from the blood into tissues, while carbon dioxide and waste products move from the tissues into the blood. This exchange is driven by concentration gradients and blood pressure.
  • Venous Return: Blood returns to the heart through veins, aided by mechanisms such as:
  • Skeletal muscle pump: Muscle contractions help push blood toward the heart.
  • Respiratory pump: Pressure changes in the chest during breathing assist venous return.
  • Valves in veins: Prevent backflow and ensure blood moves in one direction.

• Oxygenation: In pulmonary circulation, deoxygenated blood is pumped from the heart to the lungs, where it picks up oxygen and releases carbon dioxide. The oxygen-rich blood then returns to the heart to be pumped out to the body. 

By maintaining efficient circulation, the body ensures that tissues receive a constant supply of oxygen and nutrients, and that waste products are removed, which is essential for sustaining life and promoting health.

Cardiovascular Vital Signs

Cardiovascular vital signs, which include measurements of arterial pulse, blood pressure, respiratory rate, and body temperature, are essential indicators used in clinical settings to assess overall heart and circulatory health. These signs help medical professionals evaluate how efficiently the heart and blood vessels are functioning to maintain proper blood flow throughout the body.

Arterial Pulse

The arterial pulse is created by the alternating expansion and recoil of an artery as the left ventricle of the heart contracts and relaxes. This creates a pressure wave, or pulse, which travels through the entire arterial system. It’s one of the simplest yet most informative indicators of cardiovascular function.

• Normal Pulse Rate: In a healthy resting person, the pulse rate typically equals the heart rate, with an average of 70 to 76 beats per minute. Variations in this rate can indicate issues such as stress, illness, or cardiovascular disorders.

• Pressure Points: Clinically important pulse points, such as the radial and carotid arteries, can be used not only to measure pulse but also to control blood flow in cases of hemorrhage. These pressure points are strategically located where arteries run close to the skin's surface.

Blood Pressure

Blood pressure refers to the force that circulating blood exerts on the walls of blood vessels. This pressure ensures that blood continues to circulate efficiently even between heartbeats.

• Blood Pressure Gradient: The pressure is highest in the large arteries closest to the heart and gradually decreases as blood moves through the systemic and pulmonary circuits. By the time blood reaches the vena cava, pressure may drop to zero or even become negative.

• Measuring Blood Pressure: Blood pressure is measured in two phases:
  • Systolic pressure: The pressure during ventricular contraction (the peak pressure).
  • Diastolic pressure: The pressure when the ventricles relax (the lowest pressure). This alternating rise and fall in pressure as the heart beats gives insight into the heart’s pumping efficiency and overall circulatory health.

Factors Affecting Blood Pressure

Blood pressure is influenced by several key factors:

• Peripheral Resistance: This refers to the friction the blood encounters as it moves through the vessels. Narrower vessels create more resistance, which raises blood pressure.

• Neural Factors: The autonomic nervous system plays a role in regulating blood pressure. While the parasympathetic system has little effect, the sympathetic division can cause vasoconstriction (narrowing of the blood vessels), increasing blood pressure.

• Renal Factors: The kidneys help regulate blood pressure by adjusting blood volume. When blood pressure rises, the kidneys release more water in the urine, reducing blood volume and pressure.

• Temperature: Cold temperatures cause vasoconstriction, raising blood pressure, while heat causes vasodilation, lowering it.

• Chemicals: Certain chemicals can alter blood pressure:
  • Epinephrine: increases heart rate and blood pressure.
  • Nicotine: causes vasoconstriction, raising blood pressure.
  • Alcohol and histamine: cause vasodilation, which lowers blood pressure.

• Diet: A diet low in salt, saturated fats, and cholesterol is generally recommended to prevent hypertension (high blood pressure), although opinions on the specifics of diet can vary.

Monitoring these cardiovascular vital signs is crucial for maintaining heart health and diagnosing potential issues early on. Proper management of factors like diet, temperature, and chemical exposure can help keep blood pressure and pulse rates within healthy ranges.

Blood Circulation Through the Heart

• Entrance to the Heart:Blood returns to the heart via two large veins—the inferior and superior vena cava. These veins carry oxygen-poor blood from the body and empty it into the right atrium.

• Atrial Contraction: When the right atrium contracts, the blood flows into the right ventricle through the open tricuspid valve. This one-way valve ensures smooth blood flow from the atrium to the ventricle.

• Closure of the Tricuspid Valve: Once the right ventricle is full, the tricuspid valve closes, preventing backflow of blood into the atrium as the ventricle begins to contract. This is crucial to maintain forward movement of the blood.

• Ventricle Contraction and Pulmonary Circulation: As the right ventricle contracts, the blood is pumped through the pulmonic valve into the pulmonary artery, which carries it to the lungs. In the lungs, the blood releases carbon dioxide and picks up fresh oxygen, becoming oxygen-rich.

• Return of Oxygen-Rich Blood: The oxygenated blood then flows back to the heart through the pulmonary veins, which empty into the left atrium.

• Opening of the Mitral Valve: When the left atrium contracts, oxygen-rich blood flows into the left ventricle through the open mitral valve. Like the tricuspid valve, the mitral valve ensures unidirectional blood flow from the atrium to the ventricle.

• Prevention of Backflow: Once the left ventricle is full, the mitral valve closes to prevent backflow of blood into the left atrium during the ventricle’s contraction phase.

Blood Flow to Systemic Circulation

As the left ventricle contracts, blood is ejected through the aortic valve into the aorta. From here, the oxygen-rich blood circulates through the body's systemic arteries to supply organs and tissues with the oxygen they need for survival.

This synchronized system of contractions and valve closures allows for the smooth circulation of blood, ensuring that oxygen-deprived blood gets re-oxygenated in the lungs and oxygen-rich blood is delivered to the entire body.

Capillary Exchange of Gases and Nutrients

• Capillary Network: Capillaries form an intricate, widespread network throughout the body, ensuring that no cell is too far away from a capillary for efficient diffusion. This close proximity allows substances like oxygen, carbon dioxide, nutrients, and waste products to quickly move between the blood and the cells they serve.

• Routes of Exchange: Substances move to and from the blood through several routes across the plasma membranes of endothelial cells, which make up the capillary walls. Depending on the substance's properties, the following pathways are available:

• Lipid-Soluble Substances: These substances, such as oxygen and carbon dioxide, can diffuse directly through the plasma membranes of the capillary endothelial cells, as they are able to pass through lipid barriers.

• Lipid-Insoluble Substances: Substances that are not lipid-soluble, like glucose and certain ions, cannot pass directly through the plasma membranes. Instead, they use vesicles to enter or leave the blood through processes like endocytosis (engulfing substances) and exocytosis (expelling substances).

• Intercellular Clefts: Many capillaries have small gaps between their endothelial cells, called intercellular clefts, which allow for the limited passage of fluids and small solutes. These clefts provide an additional route for substances that are too large to pass directly through the cell membrane.

• Fenestrated Capillaries: In areas where absorption and filtration are critical, such as the kidneys or intestines, capillaries have tiny pores called fenestrations. These fenestrated capillaries permit the free movement of fluids and small solutes, ensuring that substances can be absorbed or filtered efficiently.

This multi-route system ensures that essential nutrients and gases are delivered to tissues, while waste products are efficiently removed, maintaining proper cellular function throughout the body.

Age-Related Physiological Changes in the Cardiovascular System

As the body ages, the heart’s ability to perform at peak efficiency declines. The heart rate in older adults responds more slowly to physical stress or exertion and takes longer to return to a resting state after activity. Additionally, age-related changes in the arteries, such as stiffening or narrowing, can impair blood flow, potentially reducing the effectiveness of the cardiovascular system in delivering oxygen and nutrients to tissues. These changes can increase the risk of cardiovascular issues in the elderly.

Related video on the Cardiovascular System: 

*Source: Mometrix Academy

This study guide provides a brief overview of the cardiovascular system’s anatomy and physiology

For a more in-depth study of the Urinary System go to the following website: Nurseslabs - Cardiovascular System Anatomy and Physiology

Rehab Therapy Supplies offer the following that relates to the Urinary System:

• Anatomical Chart - Human Heart, Laminated
• Anatomical Chart - Human Heart, Paper
• Anatomical Chart - Human Heart, Sticky-Back
• Anatomical Models: Heart Models

*Source: the website nurseslabs.com was used as a source for this blog post.

**If there are any mistakes in this anatomy study guide we would love for you to contact us so we can correct them.