cardiovascular system essay

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Essay: The cardiovascular system

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The cardiovascular system (sometimes called the circulatory system) is practically the most vital part of the human body, without it humanity would’ve been extinct millennia ago. This system consists of the heart, blood vessels, and the veins and arteries that run through the entire human body. Responsible for transporting the nutrients, oxygen, hormones, and the cellular waste products all throughout the body, the cardiovascular system is fueled by the body’s hardest-working organ -the heart. Even at rest, the average human heart easily pumps over five liters of blood throughout the human body every minute. The heart is located just behind and slightly left of the breastbone, where the organs connection to the cardiovascular system keeps the human body alive. It is also the main key organ in the cardiovascular system. The human heart receives commands from the body through the circulatory system, that tells it when to pump more or less blood depending on an individual’s needs. While people are exercising or terrified, the heart pumps even faster to increase the delivery of oxygen due to heightened emotion or activity. There are four chambers that enclose the heart with thick muscular walls. The bottom part of the organ is divided into two chambers called the left and right ventricles, which pump blood out of the heart and throughout the entire body. The interventricular septum is wall that divides the ventricles. The upper part of the heart consists of the other two chambers, called the right and left atria, which receive blood upon entering the heart. The left and right atria are separated from the ventricles by the atrioventricular valves a wall called the interatrial septum divides. These divides are separated by the tricuspid valve, while the mitral valve separates the left atrium and the left ventricle. Another two cardiac valves separate the ventricles and the large blood vessels that carry blood exiting the heart. This is the pulmonic valve, which separates the right ventricle from the pulmonary artery leading up to the lungs, and the aortic valve, which then separates the left ventricle from the aorta which is the body’s largest blood vessel. Arteries transport blood away from the heart. These are known as the thickest blood vessels, with muscular walls that need to contract to keep the blood moving away from the heart and through the body. In the systemic circulation, oxygen-rich blood is pumped from the heart and into the aorta. The huge artery first curves up and back from the left ventricle, then it flows down in front of the spinal column into the abdomen. At the start of the aorta, two coronary arteries branch off and divide into a network of smaller arteries that administer oxygen and nourish the muscles of the heart. Contrary to the aorta, the pulmonary artery transports oxygen-poor blood. The pulmonary artery divides into left and right branches from the right ventricle, en route to the lungs where blood gains oxygen. As arteries get farther from the heart, they begin to branch out into arterioles, which are smaller and less elastic than where they originate. Veins aren’t as muscular as arteries but they do carry blood back to the heart. They contain valves that are used to prevent blood from flowing backwards. Veins are less flexible and thinner than arteries, but they also have the same three layers as arteries do. The two largest veins are the inferior and superior vena cavae. The terms superior and inferior does not mean that one vein is better than the other vein, but that they are located above and below the heart. A network of tiny capillaries is what connects the arteries and veins. Although they are tiny, the capillaries are one of the most important parts of the cardiovascular system because through them, the nutrients and oxygen are delivered to the cells. In addition, the capillaries also remove waste products such as carbon dioxide. Tissues in the cardiovascular system encompass arteries, the heart, pericardium, and veins. These tissues are handled by researchers for investigations in order to find better methods of diagnosing or remedying such disorders as congestive muscular dystrophy, heart failure, coronary artery disease, or cardiomyopathy. The major tissues of the system would be the muscle, nervous, epithelial, and connective tissues. The epithelial tissue is a type of protective tissue that covers the entire human body. It is built from closely packed cells in one or more layers. The Epithelial tissue is found inside the body and is called endothelium. The tissue is usually positioned on top of a thin layer of connective tissue, which is called the “basement membrane.” In the cardiovascular system, epithelial tissue can be located in the structure of the veins, arteries, and capillaries, as it also protects and covers the heart. Epithelial cells are compacted tightly together, with little to none intercellular spaces and only a small amount of intercellular substance. Regardless of the type, epithelial tissue is usually separated from the underlying tissue by a thin sheet of connective tissue; basement membrane. The basement membrane provides structural support for the epithelium and also binds it to neighboring structures. Muscle tissue is made up of muscle cells that are able to contract, whether it is involuntarily or on command. This tissue enables us to move our whole body, or just certain parts when we wish. Muscle tissue also creates involuntary movement inside our bodies in every organ system. The heart is considered the main organ of the circulatory system, and is considered a muscle, therefore is largely made up of muscle tissue. Such contractions may result in the movement of the whole body or a portion of it, which is if the muscles are attached to a movable part of the skeleton. If the muscle is located in the wall of a hollow organ, its contractions may cause the contents of the organ to move. The main function of the nervous tissue is to react to stimuli and send impulses to various organs through the body. This type of tissue is made up a specialized type of cell called neurons. They cells are highly responsive which means that they react quickly to stimuli. The nerve cell fibers embedded in connective tissue makes up the nervous tissue. This tissue is detrimental to the cardiovascular system because it helps the brain to deliver messages to all of the components of the system. Without this tissue, the circulatory system would not function. Connective tissue is sometimes referred to as the “glue” that holds the body together and is the most common and plentiful type of tissue in the entire human body. The connective tissue consists of widely spread cells and its job is to connect, support, or surround other tissues and organs. The connective tissue is what makes up the structure of not only the cardiovascular system, but all of the other organ systems as well. This tissue can be found in the walls of arteries, veins, and capillaries, and, of course, in the makeup of the heart. The cardiovascular system works closely with other systems in our bodies. It supplies oxygen and nutrients to our bodies by working in rhythm with the respiratory system. Simultaneously, the cardiovascular system helps carry waste and carbon dioxide out of the body. Hormones are produced by the endocrine system and are also transported through the blood in the circulatory system. Hormones, as the body’s chemical messengers, transfer information and instructions from one set of cells to another. For example, one of the hormones that are produced by the heart helps control the kidneys’ release of salt from the body. When red blood cells pass by the lungs, the carbon dioxide that they are carrying diffuses into the lungs and in return, some oxygen diffuses into the red blood cells. The red blood cells are then transported all throughout the body through the arteries and give nutrients to organs and tissues by using diffusion. Carbon dioxide from the organs and tissues diffuses into the red blood cells just as oxygen diffuses out of the red blood cells. The cells then carry the carbon dioxide back to the lungs where then diffusion occurs, and the cycle begins yet again. Red blood cells also contain a substance called hemoglobin. Hemoglobin are small molecules found within red blood cells that give the blood its rich red color. Red blood cells are first produced in the bone marrow and then released into the bloodstream once they have matured. The lifespan of the cells is about three or four months, once they have aged or become damaged they are subsequently removed from the bloodstream by the spleen. The most important job of the red blood cells is to transport oxygen and other nutrients to every of the part of the body and get rid of wastes in the body, such as carbon dioxide. Blood doping is a performance enhancing process and is frowned upon in athletic competitions worldwide. It is when an athlete removes some of the blood from their body a few weeks prior to a large competition. During these weeks, their body replenishes the blood that they lost, and then just before the competition, they inject the blood back into their body, giving themselves an irregularly high level of red blood cells in the bloodstream. The more red blood cells mean more oxygen, which in turn gives the athlete a higher endurance, and more stamina. Blood doping is a very dangerous and unsanitary process that will result in immediate disqualification from competition due to the fact that it gives an individual an advantage over the other competitors. The cardiovascular system is instrumental in the body’s ability to maintain homeostatic control of several internal conditions. Blood vessels help maintain a stable body temperature by manipulating the blood flow to the surface of the skin. Blood vessels near the skin’s surface open during times of overheating to allow hot blood to dump its heat into the body’s surroundings. When hypothermia occurs, these blood vessels constrict to keep blood flowing only to vital organs in the body’s core. Blood also helps balance the body’s pH balance due to the presence of bicarbonate ions that act as a buffer solution. Finally, the albumins in blood plasma help balance the osmotic concentration of the body’s cells by maintaining an isotonic environment. Several functions of the cardiovascular system can control blood pressure. Autonomic nerve signals from the brain along with certain hormones affect the rate and strength of heart contractions. Greater contractile force and heart rate will lead to an increase in blood pressure, which can also affect blood pressure. Vasoconstriction decreases the diameter of an artery by contracting the smooth muscle in the arterial wall. The sympathetic division of the autonomic nervous system causes vasoconstriction, which leads to increases in blood pressure and decreases in blood flow in the constricted region. Vasodilation is the expansion of an artery as the smooth muscle in the arterial wall relaxes after the fight-or-flight response wears off or under the effect of certain hormones or chemicals in the blood. The volume of blood in the body also affects blood pressure. A higher volume of blood in the body will raise the blood pressure by increasing the amount of blood pumped by each heartbeat. Thicker and more viscous blood from clotting disorders will also raise blood pressure. Hemostasis, the clotting of blood and formation of scabs, is managed by the platelets of the blood. Platelets normally remain inactive in the blood, that is until they reach damaged tissue or leak out of the blood vessels through a wound. Once they are active, platelets change into a spiny ball shape and become very sticky in order to latch on to damaged tissues. Then they release chemical clotting factors and begin to produce the protein fibrin to act as structure for the blood clot. After which they also begin sticking together to form a platelet plug. The platelet plug will serve as a temporary seal to keep blood in the vessel and keep foreign material out of the vessel until the cells of the blood vessel can repair the damage to the vessel wall. The heart is a four-chambered ‘double pump,’ where each side (left and right) operates as a separate pump. The left and right sides of the heart are divided by a muscular wall of tissue known as the septum of the heart. The right side of the heart receives deoxygenated blood from the systemic veins and pumps it into the lungs for oxygenation. The left side of the heart receives oxygenated blood originating from the lungs and pumps it through the systemic arteries to the tissues of the body. Each heartbeat results in the simultaneous pumping of both sides of the heart, making the heart a very efficient pump. Thus making the cardiovascular system overall the most essential part of the body for a person to live.

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The Circulatory System: Cardiovascular System Essay

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Part of the requirements of living beings is the capability of transporting nutrients, wastes and gases to and from cells. Multicellular organisms have developed the system required for the transport of these products. One of these systems is the circulatory system. This system promotes the transportation of oxygen and food to the cells while removing carbon dioxide and other forms of metabolic waste from those cells (Martini, 84).

The circulatory system is involved in the breakdown of organic molecules during cellular respiration. This breakdown allows the organism to produce the ATP necessary to provide energy toward the body’s requirements. In order to facilitate these transfers organisms must have a system that allows the oxygen to enter the cell and permit carbon dioxide from leaving it (Martini, 816). This has been accomplished through the various forms of the circulatory and cardiovascular systems that are found in the different types of organisms found on our planet (Martini, 816).

In vertebrates the circulatory system includes the cardiovascular system. This system is includes the heart. The heart is the main organ in a closed circulatory system that maintains the blood flow through various vessels of different sizes and wall thickness. The circulatory system also includes lymphatic circulation which is responsible for collecting fluid and returning it to the cardiovascular system.

There are two main ways of circulating fluid and gases throughout the body. One of these is the pulmonary path which takes gases to and from the lungs. The second is the systemic circuit in which blood is transferred throughout the body. The pulmonary veins are responsible for carrying blood from the lungs to the heart. The aorta is the main artery of the systematic circulatory system (Martini, 671). Animals often have a portal system that begins and ends with the capillaries. The gas exchange that is so vital to the proper functioning of a living organism takes place within the capillaries.

The heart is the pump that moves the blood and gases throughout the body. Without a properly functioning heart the transfer of these important nutrients would not occur resulting in the death of the organism. While each organism has its own specializations allowing it to survive in its chosen environment the basic functions of the heart and circulatory systems are similar. The heart is made up of an upper chamber known as the atrium and the lower chamber known as the ventricles. The blood enters the heart through the atriums and when the ventricles contract the blood is forced from the heart through an artery. These contractions allow the blood to circulate through the body providing nutrients to the cells (Martini, 671).

The respiratory system in any organism is made up of similar principles that create the same result even if the mechanisms in the various organisms are different. The principles begin with the movement of a medium that contains oxygen so that it contacts a moist membrane vessel (Martini, 716). Then the oxygen is diffused from that medium into the blood stream. The organism must then be transported to the tissues and cells of the body. The final two components are the diffusion of oxygen from the blood into the cells which is then followed by the removal of carbon dioxide in a reverse path (Martini, 716).

Birds require additional levels of oxygen then other organisms due to the intense levels of energy required for flight. Due to these requirements birds have the most efficient respiratory system of any vertebrate (“Bird Characteristics). Birds have a complex weight-reducing system of air sacs and interconnecting tubes that allow the birds to inhale more oxygen then can be contained in their lungs (“Bird Characteristics). These air sacs are located within all of the available spaces within the body cavity which contributes to the lightness of the bird thus allowing flight.

Birds have a four-chambered heart that separates the oxygen rich blood from the oxygen poor blood. Birds are limited in only having a one-way flow of air into their lungs. As a result of this the lungs of the birds receive oxygen during both inhalation and exhalation.

Due to the constraints of underwater breathing fish have to have an efficient method of extracting oxygen from the water. The gills allow the water to flow over them in one direction while the blood flows through the gill capillaries in the opposite direction. The use of the countercurrent flow maximizes the amount of oxygen that can be obtained from the water. In order to assist in this function the gills are made up of four holobranchs forming the side of the pharynx. Each holobranch has two hemibranchs that project from the gill arch (Moeller, 2008).. The hemibranch have rows of long thin filaments that are called the primary lamella. The primary lamellas have their surface area increased by the secondary lamella. Gas exchange takes place at the level of the secondary lamella (Moeller, 2008). With the exchange of gases, metabolic waste is also removed and some electrolyte exchange occurs. As more oxygen is brought into the body the heart can then transport the oxygen and nutrients throughout the cells of the fish.

In fish the heart only has two chambers in which the single-loop circulatory pattern takes the blood from the heart passing through the ventral aorta and then the afferent branchial arteries to the gills to receive oxygen (Moeller, 2008). Once the blood gains the oxygen it returns through the efferent arteries to the dorsal aorta which then transports the blood throughout the rest of the body. Since the retina has a high demand for oxygen some blood is removed from the dorsal aorta and sent to the pseudobranch increasing the oxygen level before it is sent to the retina (Moeller, 2008).

Most reptiles breathe with their lungs and therefore must be able to move their ribs to breath. They do not have diaphragms like mammals do which increases their chances for a respiratory illness. Their hearts have four chambers that are divided by internal walls referred to as septums. All reptiles except for crocodiles have incomplete septums between the two ventricles allowing oxygenated blood from the lungs to mix with deoxygenated blood from the body. Due to the restrictions that this physiology places on the body this type of heart can not sustain rapid movement due to the increased metabolic demand. This explains why most reptiles lay in wait for their prey conserving their energy until expanding it provides additional sources of energy such as food.

Works Cited

“Bird Characteristics.” Bird Watching-Biss. 2008. Web.

“Biology.” Environmental Protection Agency. 2008. Web.

Martini, Frederic H., et al. Fundamentals of Anatomy and Physiology. 7th ed. Ed. Nicole George. San Francisco, CA: Pearson, 2006.

Moeller, Robert B. “Biology of Fish.” Biology of Fish. 2008. Web.

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Essay on Cardiovascular System

Students are often asked to write an essay on Cardiovascular System in their schools and colleges. And if you’re also looking for the same, we have created 100-word, 250-word, and 500-word essays on the topic.

Let’s take a look…

100 Words Essay on Cardiovascular System

Introduction.

The cardiovascular system, also known as the circulatory system, is a complex network in our body. It consists of the heart, blood, and blood vessels. This system is crucial for maintaining life and health.

Heart’s Role

The heart, a muscular organ, is the main component. It pumps blood throughout the body, supplying oxygen and nutrients to tissues and removing waste products.

Blood and Blood Vessels

Blood carries oxygen, nutrients, hormones, and waste materials. Blood vessels, including arteries, veins, and capillaries, transport blood throughout the body.

The cardiovascular system is vital for survival. It distributes necessary substances, regulates body temperature, and fights diseases.

250 Words Essay on Cardiovascular System

Introduction to the cardiovascular system.

The cardiovascular system, also known as the circulatory system, is a complex network that facilitates the transportation of nutrients, oxygen, and hormones throughout the body. It consists of the heart, blood vessels, and blood, each playing a crucial role in maintaining homeostasis and overall body function.

The Heart: The Powerhouse

The heart, a muscular organ, is the system’s powerhouse. It pumps blood through two primary circuits: the systemic and pulmonary circuits. The systemic circuit distributes oxygen-rich blood to the body’s tissues, while the pulmonary circuit oxygenates the blood by removing carbon dioxide and replenishing oxygen.

Blood Vessels: The Pathways

Blood vessels form an intricate network of pathways that carry blood throughout the body. They are classified into arteries, veins, and capillaries. Arteries transport oxygenated blood from the heart to the body, while veins carry deoxygenated blood back to the heart. Capillaries, the smallest blood vessels, facilitate the exchange of nutrients, oxygen, and waste products between blood and tissues.

Blood: The Vehicle of Transport

Blood, the transport medium, is a complex fluid comprising plasma, red and white blood cells, and platelets. It carries essential nutrients, hormones, and oxygen to cells and removes waste products. It also plays a vital role in immune defense and body temperature regulation.

The cardiovascular system is a marvel of biological engineering, efficiently ensuring the delivery of life-sustaining substances to every cell in the body. Understanding its mechanics and functions provides a foundation for studying health and disease, and for developing treatments for cardiovascular disorders.

500 Words Essay on Cardiovascular System

The heart: the core of the cardiovascular system.

The heart, a four-chambered muscular organ, is the driving force of the cardiovascular system. It consists of two atria and two ventricles. The atria receive blood from various parts of the body, while the ventricles pump it out. The heart’s rhythmic contractions, orchestrated by the sinoatrial node and the atrioventricular node, ensure a steady flow of blood.

Blood Vessels: The Pathways of Circulation

Blood vessels constitute the network that facilitates the transportation of blood. Arteries carry oxygenated blood from the heart to the body’s tissues, except for the pulmonary artery, which carries deoxygenated blood to the lungs for oxygenation. Veins return deoxygenated blood to the heart, except for the pulmonary veins, which carry oxygenated blood from the lungs to the heart. Capillaries, the smallest blood vessels, enable the exchange of oxygen, nutrients, and waste materials between blood and tissues.

Blood: The Vital Fluid

Physiological processes in the cardiovascular system.

The cardiovascular system is involved in several vital physiological processes. It delivers oxygen and nutrients to tissues, removes waste products, transports hormones, maintains body temperature, and participates in immune functions. These processes are achieved through systemic circulation and pulmonary circulation.

In systemic circulation, oxygen-rich blood is pumped from the left ventricle into the aorta, which branches into numerous arteries and arterioles, eventually reaching the capillaries. The oxygen and nutrients are diffused into the cells, and carbon dioxide and other waste products are collected.

The cardiovascular system is integral to the survival and functioning of all other body systems. It ensures the delivery of oxygen and nutrients to cells and the removal of waste products. Understanding the cardiovascular system’s complexities provides insight into how disturbances in its function can lead to diseases such as hypertension, atherosclerosis, and heart failure. Therefore, maintaining cardiovascular health is crucial for overall wellbeing.

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Thompson Rivers University Pressbooks - Human Biology - Introduction to the Cardiovascular System
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Table Of Contents

human cardiovascular system , organ system that conveys blood through vessels to and from all parts of the body, carrying nutrients and oxygen to tissues and removing carbon dioxide and other wastes. It is a closed tubular system in which the blood is propelled by a muscular heart . Two circuits, the pulmonary and the systemic, consist of arterial , capillary , and venous components.

Understanding the human cardiovascular system

The primary function of the heart is to serve as a muscular pump propelling blood into and through vessels to and from all parts of the body. The arteries, which receive this blood at high pressure and velocity and conduct it throughout the body, have thick walls that are composed of elastic fibrous tissue and muscle cells. The arterial tree—the branching system of arteries—terminates in short, narrow, muscular vessels called arterioles , from which blood enters simple endothelial tubes (i.e., tubes formed of endothelial, or lining, cells) known as capillaries. These thin, microscopic capillaries are permeable to vital cellular nutrients and waste products that they receive and distribute. From the capillaries, the blood, now depleted of oxygen and burdened with waste products, moving more slowly and under low pressure , enters small vessels called venules that converge to form veins, ultimately guiding the blood on its way back to the heart.

This article describes the structure and function of the heart and blood vessels, and the technologies that are used to evaluate and monitor the health of these fundamental components of the human cardiovascular system. For a discussion of diseases affecting the heart and blood vessels, see the article cardiovascular disease . For a full treatment of the composition and physiologic function of blood, see blood , and for more information on diseases of the blood, see blood disease . To learn more about the human circulatory system , see systemic circulation and pulmonary circulation , and for more about cardiovascular and circulatory function in other living organisms, see circulation .

Description

The human heart and cardiovascular system explained

The adult human heart is normally slightly larger than a clenched fist, with average dimensions of about 13 × 9 × 6 cm (5 × 3.5 × 2.5 inches) and weight approximately 10.5 ounces (300 grams). It is cone-shaped, with the broad base directed upward and to the right and the apex pointing downward and to the left. It is located in the chest ( thoracic ) cavity behind the breastbone ( sternum ), in front of the windpipe ( trachea ), the esophagus , and the descending aorta , between the lungs , and above the diaphragm (the muscular partition between the chest and abdominal cavities). About two-thirds of the heart lies to the left of the midline.

The heart is suspended in its own membranous sac, the pericardium. The strong outer portion of the sac, or fibrous pericardium, is firmly attached to the diaphragm below, the mediastinal pleura on the side, and the sternum in front. It gradually blends with the coverings of the superior vena cava and the pulmonary (lung) arteries and veins leading to and from the heart. (The space between the lungs, the mediastinum , is bordered by the mediastinal pleura, a continuation of the membrane lining the chest. The superior vena cava is the principal channel for venous blood from the chest, arms, neck, and head.)

Smooth, serous (moisture-exuding) membrane lines the fibrous pericardium, then bends back and covers the heart. The portion of membrane lining the fibrous pericardium is known as the parietal serous layer (parietal pericardium), that covering the heart as the visceral serous layer (visceral pericardium or epicardium ).

The two layers of serous membrane are normally separated by only 10 to 15 ml (0.6 to 0.9 cubic inch) of pericardial fluid, which is secreted by the serous membranes. The slight space created by the separation is called the pericardial cavity . The pericardial fluid lubricates the two membranes with every beat of the heart as their surfaces glide over each other. Fluid is filtered into the pericardial space through both the visceral and parietal pericardia.

The heart is divided by septa, or partitions, into right and left halves, and each half is subdivided into two chambers. The upper chambers, the atria , are separated by a partition known as the interatrial septum; the lower chambers, the ventricles , are separated by the interventricular septum. The atria receive blood from various parts of the body and pass it into the ventricles. The ventricles, in turn, pump blood to the lungs and to the remainder of the body.

The right atrium , or right superior portion of the heart, is a thin-walled chamber receiving blood from all tissues except the lungs. Three veins empty into the right atrium, the superior and inferior venae cavae, bringing blood from the upper and lower portions of the body, respectively, and the coronary sinus, draining blood from the heart itself. Blood flows from the right atrium to the right ventricle. The right ventricle, the right inferior portion of the heart, is the chamber from which the pulmonary artery carries blood to the lungs.

The left atrium, the left superior portion of the heart, is slightly smaller than the right atrium and has a thicker wall. The left atrium receives the four pulmonary veins , which bring oxygenated blood from the lungs. Blood flows from the left atrium into the left ventricle. The left ventricle, the left inferior portion of the heart, has walls three times as thick as those of the right ventricle. Blood is forced from this chamber through the aorta to all parts of the body except the lungs.

Shallow grooves called the interventricular sulci , containing blood vessels, mark the separation between ventricles on the front and back surfaces of the heart. There are two grooves on the external surface of the heart. One, the atrioventricular groove, is along the line where the right atrium and the right ventricle meet; it contains a branch of the right coronary artery (the coronary arteries deliver blood to the heart muscle). The other, the anterior interventricular sulcus, runs along the line between the right and left ventricles and contains a branch of the left coronary artery.

On the posterior side of the heart surface, a groove called the posterior longitudinal sulcus marks the division between the right and left ventricles; it contains another branch of a coronary artery. A fourth groove, between the left atrium and ventricle, holds the coronary sinus, a channel for venous blood.

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The Circulatory System, Essay Example

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The circulatory system consists of the blood, blood vessels and the heart. The system serves a purpose of moving the blood to the places where it can be supplied with enough oxygen as well as where the wastes can be disposed. Therefore circulation ensures that the newly oxygenated blood is brought back to the body tissues. The blood circulation takes place in the organs like the kidneys and the liver, which ensures that the removal of wastes is accomplished. The blood then takes the journey back again for fresh oxygen in the lungs. The process repeats again and again, ad is considered to be healthy for the life of the tissues, cells and the whole organism. The human has a heart that is four chambered to ensure that the oxygenated blood does not meet with the deoxygenated blood. The chambers also ensure that there is continuous and efficient motion of extremely blood that has already been oxygenated to the body organs. This continuous movement is in turn advantageous in the thermal regulation and in the movement of the muscles.

How the Circulatory System Function

The oxygenated blood is carried to the heart by the large veins. The blood which is oxygenated is pumped around the body, by the heart, which in turn nourishes the cells with food and oxygen. Thereafter, the blood is carried by some small tubes known as the blood vessels to the whole part of the body. The blood with carbon dioxide then comes back via some set of tubes. The blood is therefore referred to as a waste product and needs to be excreted. The circulatory system takes back the deoxygenated blood to the lungs where it is taken out through breathing.

How the organ system contributes to physiological homeostasis of the human organism

The circulatory system controls the temperature of the body. The body heat is mostly given out by the heart when the body is at rest. But when the muscles are at work, much heat is generated which more than the heat is given out by the heart. The circulatory system also controls the blood pressure through the kidney, the control of the body Ph as well as the control of the glucose concentration in the body.

The Disease that is Associated with Circulatory System and How It Affects the Human Health

The circulatory system is mostly affected by the cardiovascular disease which affects the heart and the blood vessels. The disease is always linked with unhealthy lifestyle. One of it is the angina which is characterized by the pain in the chest and the discomfort. It comes as a result of insufficient supply of the oxygenated blood to the muscles of the heart.

Collins, R. (2003). The Circulatory System. Oxford: Cornell University.

Kennedy, S. (1992). The Circulatory System and the homeostasis. London: The Hogarth Press.

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Cardiovascular System

Cell Biology
Weather & Climate
B.A., Biology, Emory University
A.S., Nursing, Chattahoochee Technical College

The cardiovascular system is responsible for transporting nutrients and removing gaseous waste from the body. This system is comprised of the heart and the circulatory system . Structures of the cardiovascular system include the heart, blood vessels , and blood . The lymphatic system is also closely associated with the cardiovascular system.

Structures of the Cardiovascular System

The heart is the organ that supplies blood and oxygen to all parts of the body. This amazing muscle produces electrical impulses through a process called cardiac conduction . These impulses cause the heart to contract and then relax, producing what is known as a heart beat. The beating of the heart drives the cardiac cycle which pumps blood to cells and tissues of the body.

Blood Vessels

Blood vessels are intricate networks of hollow tubes that transport blood throughout the entire body. Blood travels from the heart via arteries to smaller arterioles, then to capillaries or sinusoids, to venules, to veins and back to the heart. Through the process of microcirculation, substances such as oxygen, carbon dioxide, nutrients, and wastes are exchanged between the blood and the fluid that surrounds cells.

Blood delivers nutrients to cells and removes wastes that are produced during cellular processes, such as cellular respiration . Blood is composed of red blood cells , white blood cells , platelets , and plasma. Red blood cells contain enormous amounts of a protein called hemoglobin . This iron-containing molecule binds oxygen as oxygen molecules enter blood vessels in the lungs and transports them to various parts of the body. After depositing oxygen to tissue and cells, red blood cells pick up carbon dioxide (CO 2 ) for transportation to the lungs where CO 2 is expelled from the body.

Circulatory System

The circulatory system supplies the body's tissues with oxygen-rich blood and important nutrients. In addition to removing gaseous waste (like CO 2 ), the circulatory system also transports blood to organs (such as the liver and kidneys ) to remove harmful substances. This system aids in cell-to-cell communication and homeostasis by transporting hormones and signal messages between the different cells and organ systems of the body. The circulatory system transports blood along pulmonary and systemic circuits . The pulmonary circuit involves the path of circulation between the heart and the lungs . The systemic circuit involves the path of circulation between the heart and the rest of the body. The aorta distributes oxygen rich blood to the various regions of the body.

Lymphatic System

The lymphatic system is a component of the immune system and works closely with the cardiovascular system. The lymphatic system is a vascular network of tubules and ducts that collect, filter, and return lymph to blood circulation. Lymph is a clear fluid that comes from blood plasma, which exits blood vessels at capillary beds. This fluid becomes the interstitial fluid that bathes tissues and helps to deliver nutrients and oxygen to cells . In addition to returning lymph to circulation, lymphatic structures also filter blood of microorganisms, such as bacteria and viruses . Lymphatic structures also remove cellular debris, cancerous cells , and waste from the blood. Once filtered, the blood is returned to the circulatory system.

Learn About All the Different Organ Systems in the Human Body
How Veins Transport Blood
Blood Composition and Function
Artery Structure, Function, and Disease
Lymphatic Vessels
Anatomy of the Heart: Aorta
The Lungs and Respiration
What Are the Components of the Lymphatic System?
The Cardiac Cycle
Skeletal System and Bone Function
Respiratory System and How We Breathe
Red Blood Cells (Erythrocytes)
10 Fascinating Facts About Your Heart
Facts About Muscle Tissue
Hypothalamus Activity and Hormone Production
Neuroglial Cells

Home — Essay Samples — Nursing & Health — Blood — How the cardiovascular system works

How The Cardiovascular System works

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16.3 Circulatory and Respiratory Systems

Learning objectives.

Describe the passage of air from the outside environment to the lungs
Describe the function of the circulatory system
Describe the cardiac cycle
Explain how blood flows through the body

Animals are complex multicellular organisms that require a mechanism for transporting nutrients throughout their bodies and removing wastes. The human circulatory system has a complex network of blood vessels that reach all parts of the body. This extensive network supplies the cells, tissues, and organs with oxygen and nutrients, and removes carbon dioxide and waste compounds.

The medium for transport of gases and other molecules is the blood, which continually circulates through the system. Pressure differences within the system cause the movement of the blood and are created by the pumping of the heart.

Gas exchange between tissues and the blood is an essential function of the circulatory system. In humans, other mammals, and birds, blood absorbs oxygen and releases carbon dioxide in the lungs. Thus the circulatory and respiratory system, whose function is to obtain oxygen and discharge carbon dioxide, work in tandem.

The Respiratory System

Take a breath in and hold it. Wait several seconds and then let it out. Humans, when they are not exerting themselves, breathe approximately 15 times per minute on average. This equates to about 900 breaths an hour or 21,600 breaths per day. With every inhalation, air fills the lungs, and with every exhalation, it rushes back out. That air is doing more than just inflating and deflating the lungs in the chest cavity. The air contains oxygen that crosses the lung tissue, enters the bloodstream, and travels to organs and tissues. There, oxygen is exchanged for carbon dioxide, which is a cellular waste material. Carbon dioxide exits the cells, enters the bloodstream, travels back to the lungs, and is expired out of the body during exhalation.

Breathing is both a voluntary and an involuntary event. How often a breath is taken and how much air is inhaled or exhaled is regulated by the respiratory center in the brain in response to signals it receives about the carbon dioxide content of the blood. However, it is possible to override this automatic regulation for activities such as speaking, singing and swimming under water.

During inhalation the diaphragm descends creating a negative pressure around the lungs and they begin to inflate, drawing in air from outside the body. The air enters the body through the nasal cavity located just inside the nose ( Figure 16.9 ). As the air passes through the nasal cavity, the air is warmed to body temperature and humidified by moisture from mucous membranes. These processes help equilibrate the air to the body conditions, reducing any damage that cold, dry air can cause. Particulate matter that is floating in the air is removed in the nasal passages by hairs, mucus, and cilia. Air is also chemically sampled by the sense of smell.

From the nasal cavity, air passes through the pharynx (throat) and the larynx (voice box) as it makes its way to the trachea ( Figure 16.9 ). The main function of the trachea is to funnel the inhaled air to the lungs and the exhaled air back out of the body. The human trachea is a cylinder, about 25 to 30 cm (9.8–11.8 in) long, which sits in front of the esophagus and extends from the pharynx into the chest cavity to the lungs. It is made of incomplete rings of cartilage and smooth muscle. The cartilage provides strength and support to the trachea to keep the passage open. The trachea is lined with cells that have cilia and secrete mucus. The mucus catches particles that have been inhaled, and the cilia move the particles toward the pharynx.

The end of the trachea divides into two bronchi that enter the right and left lung. Air enters the lungs through the primary bronchi . The primary bronchus divides, creating smaller and smaller diameter bronchi until the passages are under 1 mm (.03 in) in diameter when they are called bronchioles as they split and spread through the lung. Like the trachea, the bronchus and bronchioles are made of cartilage and smooth muscle. Bronchi are innervated by nerves of both the parasympathetic and sympathetic nervous systems that control muscle contraction (parasympathetic) or relaxation (sympathetic) in the bronchi and bronchioles, depending on the nervous system’s cues. The final bronchioles are the respiratory bronchioles. Alveolar ducts are attached to the end of each respiratory bronchiole. At the end of each duct are alveolar sacs, each containing 20 to 30 alveoli . Gas exchange occurs only in the alveoli. The alveoli are thin-walled and look like tiny bubbles within the sacs. The alveoli are in direct contact with capillaries of the circulatory system. Such intimate contact ensures that oxygen will diffuse from the alveoli into the blood. In addition, carbon dioxide will diffuse from the blood into the alveoli to be exhaled. The anatomical arrangement of capillaries and alveoli emphasizes the structural and functional relationship of the respiratory and circulatory systems. Estimates for the surface area of alveoli in the lungs vary around 100 m 2 . This large area is about the area of half a tennis court. This large surface area, combined with the thin-walled nature of the alveolar cells, allows gases to easily diffuse across the cells.

Visual Connection

Which of the following statements about the human respiratory system is false?

When we breathe in, air travels from the pharynx to the trachea.
The bronchioles branch into bronchi.
Alveolar ducts connect to alveolar sacs.
Gas exchange between the lungs and blood takes place in the alveolus.

Link to Learning

Watch this video for a review of the respiratory system.

The Circulatory System

The circulatory system is a network of vessels—the arteries, veins, and capillaries—and a pump, the heart. In all vertebrate organisms this is a closed-loop system, in which the blood is largely separated from the body’s other extracellular fluid compartment, the interstitial fluid, which is the fluid bathing the cells. Blood circulates inside blood vessels and circulates unidirectionally from the heart around one of two circulatory routes, then returns to the heart again; this is a closed circulatory system . Open circulatory systems are found in invertebrate animals in which the circulatory fluid bathes the internal organs directly even though it may be moved about with a pumping heart.

The heart is a complex muscle that consists of two pumps: one that pumps blood through pulmonary circulation to the lungs, and the other that pumps blood through systemic circulation to the rest of the body’s tissues (and the heart itself).

The heart is asymmetrical, with the left side being larger than the right side, correlating with the different sizes of the pulmonary and systemic circuits ( Figure 16.10 ). In humans, the heart is about the size of a clenched fist; it is divided into four chambers: two atria and two ventricles. There is one atrium and one ventricle on the right side and one atrium and one ventricle on the left side. The right atrium receives deoxygenated blood from the systemic circulation through the major veins: the superior vena cava , which drains blood from the head and from the veins that come from the arms, as well as the inferior vena cava , which drains blood from the veins that come from the lower organs and the legs. This deoxygenated blood then passes to the right ventricle through the tricuspid valve , which prevents the backflow of blood. After it is filled, the right ventricle contracts, pumping the blood to the lungs for reoxygenation. The left atrium receives the oxygen-rich blood from the lungs. This blood passes through the bicuspid valve to the left ventricle where the blood is pumped into the aorta . The aorta is the major artery of the body, taking oxygenated blood to the organs and muscles of the body. This pattern of pumping is referred to as double circulation and is found in all mammals. ( Figure 16.10 ).

Which of the following statements about the circulatory system is false?

Blood in the pulmonary vein is deoxygenated.
Blood in the inferior vena cava is deoxygenated.
Blood in the pulmonary artery is deoxygenated.
Blood in the aorta is oxygenated.

The Cardiac Cycle

The main purpose of the heart is to pump blood through the body; it does so in a repeating sequence called the cardiac cycle. The cardiac cycle is the flow of blood through the heart coordinated by electrochemical signals that cause the heart muscle to contract and relax. In each cardiac cycle, a sequence of contractions pushes out the blood, pumping it through the body; this is followed by a relaxation phase, where the heart fills with blood. These two phases are called the systole (contraction) and diastole (relaxation), respectively ( Figure 16.11 ). The signal for contraction begins at a location on the outside of the right atrium. The electrochemical signal moves from there across the atria causing them to contract. The contraction of the atria forces blood through the valves into the ventricles. Closing of these valves caused by the contraction of the ventricles produces a “lub” sound. The signal has, by this time, passed down the walls of the heart, through a point between the right atrium and right ventricle. The signal then causes the ventricles to contract. The ventricles contract together forcing blood into the aorta and the pulmonary arteries. Closing of the valves to these arteries caused by blood being drawn back toward the heart during ventricular relaxation produces a monosyllabic “dub” sound.

The pumping of the heart is a function of the cardiac muscle cells, or cardiomyocytes, that make up the heart muscle. Cardiomyocytes are distinctive muscle cells that are striated like skeletal muscle but pump rhythmically and involuntarily like smooth muscle; adjacent cells are connected by intercalated disks found only in cardiac muscle. These connections allow the electrical signal to travel directly to neighboring muscle cells.

The electrical impulses in the heart produce electrical currents that flow through the body and can be measured on the skin using electrodes. This information can be observed as an electrocardiogram (ECG) a recording of the electrical impulses of the cardiac muscle.

Visit this site and select the dropdown “Your Heart’s Electrical System” to see the heart’s pacemaker, or electrocardiogram system, in action.

Blood Vessels

The blood from the heart is carried through the body by a complex network of blood vessels ( Figure 16.12 ). Arteries take blood away from the heart. The main artery of the systemic circulation is the aorta; it branches into major arteries that take blood to different limbs and organs. The aorta and arteries near the heart have heavy but elastic walls that respond to and smooth out the pressure differences caused by the beating heart. Arteries farther away from the heart have more muscle tissue in their walls that can constrict to affect flow rates of blood. The major arteries diverge into minor arteries, and then smaller vessels called arterioles, to reach more deeply into the muscles and organs of the body.

Arterioles diverge into capillary beds. Capillary beds contain a large number, 10’s to 100’s of capillaries that branch among the cells of the body. Capillaries are narrow-diameter tubes that can fit single red blood cells and are the sites for the exchange of nutrients, waste, and oxygen with tissues at the cellular level. Fluid also leaks from the blood into the interstitial space from the capillaries. The capillaries converge again into venules that connect to minor veins that finally connect to major veins. Veins are blood vessels that bring blood high in carbon dioxide back to the heart. Veins are not as thick-walled as arteries, since pressure is lower, and they have valves along their length that prevent backflow of blood away from the heart. The major veins drain blood from the same organs and limbs that the major arteries supply.

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Cardiovascular System Anatomy and Physiology

Journey to the heart of our being with the cardiovascular system study guide . Aspiring nurses, chart the pulsating rivers of life as you discover the anatomy and dynamics of the body’s powerful pump and intricate vessel networks.

Functions of the heart, heart structure and functions, layers of the heart, chambers of the heart, associated great vessels, heart valves, cardiac circulation vessels, blood vessels, major arteries of the systemic circulation, major veins of the systemic circulation, intrinsic conduction system of the heart, the pathway of the conduction system, cardiac cycle and heart sounds, cardiac output, physiology of circulation, cardiovascular vital signs, blood circulation through the heart, capillary exchange of gases and nutrients, age-related physiological changes in the cardiovascular system.

The functions of the heart are as follows:

Managing blood supply. Variations in the rate and force of heart contraction match blood flow to the changing metabolic needs of the tissues during rest, exercise, and changes in body position.
Producing blood pressure . Contractions of the heart produce blood pressure , which is needed for blood flow through the blood vessels.
Securing one-way blood flow. The valves of the heart secure a one-way blood flow through the heart and blood vessels.
Transmitting blood. The heart separates the pulmonary and systemic circulations, which ensures the flow of oxygenated blood to tissues.

Anatomy of the Heart

The cardiovascular system can be compared to a muscular pump equipped with one-way valves and a system of large and small plumbing tubes within which the blood travels.

The modest size and weight of the heart give few hints of its incredible strength.

Weight. Approximately the size of a person’s fist, the hollow , cone-shaped heart weighs less than a pound .
Mediastinum. Snugly enclosed within the inferior mediastinum, the medial cavity of the thorax, the heart is flanked on each side by the lungs .
Apex. Its more pointed apex is directed toward the left hip and rests on the diaphragm , approximately at the level of the fifth intercostal space.
Base. Its broad posterosuperior aspect, or base , from which the great vessels of the body emerge, points toward the right shoulder and lies beneath the second rib.
Pericardium. The heart is enclosed in a double-walled sac called the pericardium which is the outermost layer of the heart.
Fibrous pericardium. The loosely fitting superficial part of this sac is referred to as the fibrous pericardium, which helps protect the heart and anchors it to surrounding structures such as the diaphragm and sternum .
Serous pericardium. Deep to the fibrous pericardium is the slippery, two-layer serous pericardium, where its parietal layer lines the interior of the fibrous pericardium.

The heart muscle has three layers and they are as follows:

Epicardium. The epicardium or the visceral and outermost layer is actually a part of the heart wall.
Myocardium. The myocardium consists of thick bundles of cardiac muscle twisted and whirled into ringlike arrangements and it is the layer that actually contracts.
Endocardium. The endocardium is the innermost layer of the heart and is a thin, glistening sheet of endothelium hat lines the heart chambers.

The heart has four hollow chambers, or cavities: two atria and two ventricles.

Receiving chambers. The two superior atria are primarily the receiving chambers, they play a lighter role in the pumping activity of the heart.
Discharging chambers. The two inferior, thick-walled ventricles are the discharging chambers, or actual pumps of the heart wherein when they contract, blood is propelled out of the heart and into circulation.
Septum. The septum that divides the heart longitudinally is referred to as either the interventricular septum or the interatrial septum, depending on which chamber it separates.

The great blood vessels provide a pathway for the entire cardiac circulation to proceed.

Superior and inferior vena cava. The heart receives relatively oxygen-poor blood from the veins of the body through the large superior and inferior vena cava and pumps it through the pulmonary trunk .
Pulmonary arteries. The pulmonary trunk splits into the right and left pulmonary arteries, which carry blood to the lungs, where oxygen is picked up and carbon dioxide is unloaded.
Pulmonary veins. Oxygen -rich blood drains from the lungs and is returned to the left side of the heart through the four pulmonary veins.
Aorta. Blood returned to the left side of the heart is pumped out of the heart into the aorta from which the systemic arteries branch to supply essentially all body tissues.

The heart is equipped with four valves, which allow blood to flow in only one direction through the heart chambers.

Atrioventricular valves. Atrioventricular or AV valves are located between the atrial and ventricular chambers on each side, and they prevent backflow into the atria when the ventricles contract.
Bicuspid valves. The left AV valve- the bicuspid or mitral valve, consists of two flaps, or cusps, of the endocardium.
Tricuspid valve. The right AV valve, the tricuspid valve, has three flaps.
Semilunar valve. The second set of valves, the semilunar valves, guards the bases of the two large arteries leaving the ventricular chambers, thus they are known as the pulmonary and aortic semilunar valves.

Although the heart chambers are bathed with blood almost continuously, the blood contained in the heart does not nourish the myocardium.

Coronary arteries. The coronary arteries branch from the base of the aorta and encircle the heart in the coronary sulcus (atrioventricular groove) at the junction of the atria and ventricles, and these arteries are compressed when the ventricles are contract and fill when the heart is relaxed.
Cardiac veins. The myocardium is drained by several cardiac veins, which empty into an enlarged vessel on the posterior of the heart called the coronary sinus .

Blood circulates inside the blood vessels, which form a closed transport system, the so-called vascular system.

Arteries. As the heart beats, blood is propelled into large arteries leaving the heart.
Arterioles. It then moves into successively smaller and smaller arteries and then into arterioles, which feed the capillary beds in the tissues.
Veins. Capillary beds are drained by venules , which in turn empty into veins that finally empty into the great veins entering the heart.

Except for the microscopic capillaries, the walls of the blood vessels have three coats or tunics.

Tunica intima. The tunica intima, which lines the lumen, or interior, of the vessels, is a thin layer of endothelium resting on a basement membrane and decreases friction as blood flows through the vessel lumen.
Tunica media. The tunica media is the bulky middle coat which mostly consists of smooth muscle and elastic fibers that constrict or dilate, making the blood pressure increase or decrease.
Tunica externa. The tunica externa is the outermost tunic composed largely of fibrous connective tissue, and its function is basically to support and protect the vessels.

The major branches of the aorta and the organs they serve are listed next in the sequence from the heart.

Arterial Branches of the Ascending Aorta

The aorta springs upward from the left ventricle of the heart as the ascending aorta.

Coronary arteries. The only branches of the ascending aorta are the right and left coronary arteries, which serve the heart.

Arterial Branches of the Aortic Arch

The aorta arches to the left as the aortic arch.

Brachiocephalic trunk. The brachiocephalic trunk, the first branch off the aortic arch, splits into the right common carotid artery and right subclavian artery .
Left common carotid artery. The left common carotid artery is the second branch of the aortic arch and it divides, forming the left internal carotid , which serves the brain , and the l eft external carotid , which serves the skin and muscles of the head and neck.
Left subclavian artery. The third branch of the aortic arch, the left subclavian artery , gives off an important branch- the vertebral artery , which serves as part of the brain.
Axillary artery. In the axilla, the subclavian artery becomes the axillary artery.
Brachial artery. the subclavian artery continues into the arm as the brachial artery, which supplies the arm.
Radial and ulnar arteries. At the elbow, the brachial artery splits to form the radial and ulnar arteries, which serve the forearm .

Arterial Branches of the Thoracic Aorta

The aorta plunges downward through the thorax, following the spine as the thoracic aorta.

Intercostal arteries. Ten pairs of intercostal arteries supply the muscles of the thorax wall.

Arterial Branches of the Abdominal Aorta

Finally, the aorta passes through the diaphragm into the abdominopelvic cavity, where it becomes the abdominal aorta.

Celiac trunk. The celiac trunk is the first branch of the abdominal aorta and has three branches: the left gastric artery supplies the stomach ; the splenic artery supplies the spleen , and the common hepatic artery supplies the liver .
Superior mesenteric artery. The unpaired superior mesenteric artery supplies most of the small intestine and the first half of the large intestine or colon .
Renal arteries. The renal arteries serve the kidneys.
Gonadal arteries. The gonadal arteries supply the gonads, and they are called ovarian arteries in females while in males they are testicular arteries .
Lumbar arteries. The lumbar arteries are several pairs of arteries serving the heavy muscles of the abdomen and trunk walls.
Inferior mesenteric artery. The inferior mesenteric artery is a small, unpaired artery supplying the second half of the large intestine.
Common iliac arteries. The common iliac arteries are the final branches of the abdominal aorta.

Major veins converge on the venae cavae, which enter the right atrium of the heart.

Veins Draining into the Superior Vena Cava

Veins draining into the superior vena cava are named in a distal-to-proximal direction; that is, in the same direction the blood flows into the superior vena cava.

Radial and ulnar veins . The radial and ulnar veins are deep veins draining the forearm; they unite to form the deep brachial vein , which drains the arm and empties into the axillary vein in the axillary region.
Cephalic vein. The cephalic vein provides for the superficial drainage of the lateral aspect of the arm and empties into the axillary vein.
Basilic vein. The basilic vein is a superficial vein that drains the medial aspect of the arm and empties into the brachial vein proximally.
Median cubital vein. The basilic and cephalic veins are joined at the anterior aspect of the elbow by the median cubital vein, often chosen as the site for blood removal for the purpose of blood testing.
Subclavian vein. The subclavian vein receives venous blood from the arm through the axillary vein and from the skin and muscles of the head through the external jugular vein .
Vertebral vein. The vertebral vein drains the posterior part of the head.
Internal jugular vein. The internal jugular vein drains the dural sinuses of the brain.
Brachiocephalic veins. The right and left brachiocephalic veins are large veins that receive venous drainage from the subclavian, vertebral, and internal jugular veins on their respective sides.
Azygos vein. The azygos vein is a single vein that drains the thorax and enters the superior vena cava just before it joins the heart.

Veins Draining into the Inferior Vena Cava

The inferior vena cava, which is much longer than the superior vena cava, returns blood to the heart from all body regions below the diaphragm.

Tibial veins. The anterior and posterior tibial veins and the fibular vein drain the leg; the posterior tibial veins become the popliteal vein at the knee and then the femoral vein in the thigh; the femoral vein becomes the external iliac vein as it enters the pelvis.
Great saphenous veins. The great saphenous veins are the longest veins in the body; they begin at the dorsal venous arch in the foot and travel up the medial aspect of the leg to empty into the femoral vein in the thigh.
Common iliac vein. Each common iliac vein is formed by the union of the external iliac vein and the internal iliac vein which drains the pelvis.
Gonadal vein. The right gonadal vein drains the right ovary in females and the right testicles in males; the left gonadal vein empties into the left renal veins superiorly.
Renal veins. The right and left renal veins drain the kidneys.
Hepatic portal vein. The hepatic portal vein is a single vein that drains the digestive tract organs and carries this blood through the liver before it enters the systemic circulation.
Hepatic veins. The hepatic veins drain the liver.

Physiology of the Heart

As the heart beats or contracts, the blood makes continuous round trips- into and out of the heart, through the rest of the body, and then back to the heart- only to be sent out again.

The spontaneous contractions of the cardiac muscle cells occurs in a regular and continuous way, giving rhythm to the heart.

Conduction System of the Heart Anatomy and Physiology

Cardiac muscle cells. Cardiac muscle cells can and do contract spontaneously and independently, even if all nervous connections are severed.
Rhythms. Although cardiac muscles can beat independently, the muscle cells in the different areas of the heart have different rhythms.
Intrinsic conduction system. The intrinsic conduction system, or the nodal system , that is built into the heart tissue sets the basic rhythm.
Composition. The intrinsic conduction system is composed of a special tissue found nowhere else in the body; it is much like a cross between a muscle and nervous tissue.
Function. This system causes heart muscle depolarization in only one direction- from the atria to the ventricles; it enforces a contraction rate of approximately 75 beats per minute on the heart, thus the heart beats as a coordinated unit.
Sinoatrial (SA) node. The SA node has the highest rate of depolarization in the whole system, so it can start the beat and set the pace for the whole heart; thus the term “ pacemaker “.
Atrial contraction. From the SA node, the impulse spread through the atria to the AV node, and then the atria contract.
Ventricular contraction. It then passes through the AV bundle, the bundle branches, and the Purkinje fibers, resulting in a “wringing” contraction of the ventricles that begins at the heart apex and moves toward the atria.
Ejection. This contraction effectively ejects blood superiorly into the large arteries leaving the heart.

The conduction system occurs systematically through:

SA node. The depolarization wave is initiated by the sinoatrial node.
Atrial myocardium. The wave then successively passes through the atrial myocardium.
Atrioventricular node. The depolarization wave then spreads to the AV node, and then the atria contract.
AV bundle. It then passes rapidly through the AV bundle.
Bundle branches and Purkinje fibers. The wave then continues on through the right and left bundle branches, and then to the Purkinje fibers in the ventricular walls, resulting in a contraction that ejects blood, leaving the heart.

In a healthy heart, the atria contract simultaneously, then, as they start to relax, contraction of the ventricles begins.

Systole. Systole means heart contraction .
Diastole. Diastole means heart relaxation .
Cardiac cycle. The term cardiac cycle refers to the events of one complete heartbeat, during which both atria and ventricles contract and then relax.
Length. The average heart beats approximately 75 times per minute, so the length of the cardiac cycle is normally about 0.8 seconds .
Mid-to-late diastole. The cycle starts with the heart in complete relaxation ; the pressure in the heart is low, and blood is flowing passively into and through the atria into the ventricles from the pulmonary and systemic circulations; the semilunar valves are closed, and the AV valves are open; then the atria contract and force the blood remaining in their chambers into the ventricles.
Ventricular systole. Shortly after, the ventricular contraction begins, and the pressure within the ventricles increases rapidly, closing the AV valves; when the intraventricular pressure is higher than the pressure in the large arteries leaving the heart, the semilunar valves are forced open, and blood rushes through them out of the ventricles; the atria are relaxed, and their chambers are again filling with blood.
Early diastole. At the end of systole, the ventricles relax, the semilunar valves snap shut, and for a moment the ventricles are completely closed chambers; the intraventricular pressure drops and the AV valves are forced open; the ventricles again begin refilling rapidly with blood, completing the cycle.
First heart sound. The first heart sound, “lub” , is caused by the closing of the AV valves.
Second heart sound. The second heart sound, “dub” , occurs when the semilunar valves close at the end of systole.

Cardiac output is the amount of blood pumped out by each side of the heart in one minute. It is the product of the heart rate and the stroke volume .

Stroke volume. Stroke volume is the volume of blood pumped out by a ventricle with each heartbeat.
Regulation of stroke volume . According to Starling’s law of the heart , the critical factor controlling stroke volume is how much the cardiac muscle cells are stretched just before they contract; the more they are stretched , the stronger the contraction will be; and anything that increases the volume or speed of venous return also increases stroke volume and force of contraction.
Factors modifying basic heart rate . The most important external influence on heart rate is the activity of the autonomic nervous system , as well as physical factors (age, gender, exercise, and body temperature).

A fairly good indication of the efficiency of a person’s circulatory system can be obtained by taking arterial blood and blood pressure measurements.

Arterial pulse pressure and blood pressure measurements, along with those of respiratory rate and body temperature, are referred to collectively as vital signs in clinical settings.

Arterial pulse. The alternating expansion and recoil of an artery that occurs with each beat of the left ventricle create a pressure wave-a pulse- that travels through the entire arterial system.
Normal pulse rate. Normally, the pulse rate (pressure surges per minute) equals the heart rate, so the pulse averages 70 to 76 beats per minute in a normal resting person.
Pressure points. There are several clinically important arterial pulse points, and these are the same points that are compressed to stop blood flow into distal tissues during hemorrhage , referred to as pressure points.
Blood pressure. Blood pressure is the pressure the blood exerts against the inner walls of the blood vessels, and it is the force that keeps blood circulating continuously even between heartbeats.
Blood pressure gradient. The pressure is highest in the large arteries and continues to drop throughout the systemic and pulmonary pathways, reaching either zero or negative pressure at the venae cavae.
Measuring blood pressure . Because the heart alternately contracts and relaxes, the off-and-on flow of the blood into the arteries causes the blood pressure to rise and fall during each beat, thus, two arterial blood pressure measurements are usually made: systolic pressure (the pressure in the arteries at the peak of ventricular contraction) and diastolic pressure (the pressure when the ventricles are relaxing).
Peripheral resistance. Peripheral resistance is the amount of friction the blood encounters as it flows through the blood vessels.
Neural factors. The parasympathetic division of the autonomic nervous system has little or no effect on blood pressure, but the sympathetic division has the major action of causing vasoconstriction or narrowing of the blood vessels, which increases blood pressure.
Renal factors. The kidneys play a major role in regulating arterial blood pressure by altering blood volume, so when blood pressure increases beyond normal, the kidneys allow more water to leave the body in the urine , then blood volume decreases which in turn decreases blood pressure.
Temperature. In general, cold has a vasoconstricting effect, while heat has a vasodilating effect.
Chemicals. Epinephrine increases both heart rate and blood pressure; nicotine increases blood pressure by causing vasoconstriction; alcohol and histamine cause vasodilation and decreased blood pressure.
Diet. Although medical opinions tend to change and are at odds from time to time, it is generally believed that a diet low in salt , saturated fats , and cholesterol help to prevent hypertension , or high blood pressure.

The right and left sides of the heart work together in achieving a smooth-flowing blood circulation .

Entrance to the heart. Blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart.
Atrial contraction. As the atrium contracts, blood flows from the right atrium to the right ventricle through the open tricuspid valve.
Closure of the tricuspid valve. When the ventricle is full, the tricuspid valve shuts to prevent blood from flowing backward into the atria while the ventricle contracts.
Ventricle contraction. As the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery, and to the lungs where it is oxygenated.
Oxygen -rich blood circulates. The pulmonary vein empties oxygen-rich blood from the lungs into the left atrium of the heart.
Opening of the mitral valve. As the atrium contracts, blood flows from your left atrium into your left ventricle through the open mitral valve.
Prevention of backflow. When the ventricle is full, the mitral valve shuts. This prevents blood from flowing backward into the atrium while the ventricle contracts.
Blood flow to the systemic circulation. As the ventricle contracts, blood leaves the heart through the aortic valve, into the aorta, and to the body.

Substances tend to move to and from the body cells according to their concentration gradients.

Capillary network. Capillaries form an intricate network among the body’s cells such that no substance has to diffuse very far to enter or leave a cell.
Routes. Basically, substances leaving or entering the blood may take one of four routes across the plasma membranes of the single layer of endothelial cells forming the capillary wall.
Lipid-soluble substances. As with all cells, substances can diffuse directly through their plasma membranes if the substances are lipid-soluble.
Lipid-insoluble substances. Certain lipid-insoluble substances may enter or leave the blood and/or pass through the plasma membranes within vesicles, that is, by endocytosis or exocytosis .
Intercellular clefts. Limited passage of fluid and small solutes is allowed by intercellular clefts (gaps or areas of plasma membrane not joined by tight junctions), so most of our capillaries have intercellular clefts.
Fenestrated capillaries. Very free passage of small solutes and fluid is allowed by fenestrated capillaries, and these unique capillaries are found where absorption is a priority or where filtration occurs.

The capacity of the heart for work decreases with age. Older peoples’ rate is slower to respond to stress and slower to return to normal after periods of physical activity . Changes in arteries occur frequently which can negatively affect blood supply.

Health promotion teaching can include risk detection and reduction for cardiovascular diseases, blood pressure and cholesterol level monitoring, ideal weight maintenance, and a low- sodium diet.

Craving more insights? Dive into these related materials to enhance your study journey!

Anatomy and Physiology Nursing Test Banks . This nursing test bank includes questions about Anatomy and Physiology and its related concepts such as: structure and functions of the human body, nursing care management of patients with conditions related to the different body systems.

13 thoughts on “Cardiovascular System Anatomy and Physiology”

very informative!

So great work that could help alot of nurses all over the world, I appreciate it so much.

Nurseslabs have done a very nice work. I wish them good health and strength to continue with the good work.

This excerpt was a magnificent essay of the “Heart Human”.My daughter Arlene Rivera is also an RN and this you wrote about all the heart makes me feel better to know about the knowledge you people possess.Thanks.

In the pathway above, the right subclavian vein is incorrectly labeled as the right pulmonary artery.

For the first time since i leave Nursing school I have now fully understood the cardiovascular system. Keep the good work Matt Vera, you are the best.

Hey Alex, Thank you so much for your kind words! I’m thrilled to hear that our explanations have helped you gain a better understanding of the cardiovascular system. It’s always wonderful to see the impact of educational resources on students and professionals alike.

If there are any more topics or concepts within nursing or healthcare that you’d like to explore or if you have any questions, please don’t hesitate to reach out. Your curiosity and dedication to learning are truly commendable! 🩺🫁📚✨

What is the reference?!

terimakasih atas dedikasinya. super

Enjoy your work, I saw an error in the last image. The right subclavian vein was given the wrong name.

I always found it difficult to find nursing resources since a lot of those that I have seen require payment (and pricey at that). I’m glad I found Nurseslabs. It helps me understand topics that confused me as a student and things I need to refresh since I have been in the profession for a while now.

Easily comprehensible, nice description.

It really helpful

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