Principal Veins About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Principal Veins Veins are blood vessels that carry blood towards the heart, have thin, inelastic walls, and contain numerous valves. Learning Objective Distinguish among the principal veins of the circulatory system Key Points Veins , blood vessels which return blood to the heart , are different in structure and function from the arteries , which carry blood to the circulation. Most veins carry deoxygenated blood from the tissues back to the heart. The exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart, but the umbilical vein deteriorates shortly after birth. The venae cavae are two large veins which drain into the right atrium of the heart, returning the majority of blood from the systemic circulation . Term Register for FREE to remove ads and unlock more features!

Learn more Full Text In the circulatory system, veins are blood vessels that carry blood towards the heart. Veins have thin, inelastic walls, and contain numerous valves in order to prevent backflow of blood. Most veins carry deoxygenated blood from the tissues back to the heart with the exceptions of the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart.

This diagram of the principal veins indicates the sigmoid signus, interior and exterior jugular veins, inferior thyroid vein, pulmonary arteries, heart, inferior vena cava, hepatic veins, renal veins, abdominal vena cava, testicularis vein, common iliac vein, perforating branches, external and internal iliac vein, external pudendal vein, deep femoral vein, great saphenous vein, femoral vein, accessory saphenous veins, superior genicular veins, popliteal vein, inferior genicular veins, small saphenous veins, anterior and posterior tibial veins, deep plantar veins, dorsal venous arch, dorsal digital vein, palmar digital veins, superficial palmar arch, deep palmar arch, ulnar vein, median antebranchial vein, cephalic vein, thoracoepigastric vein, median cubital vein, basilic vein, intercostal vein, brachial veins, axillary vein, internal thoracic vein, and subclavian vein. Veins can be broadly classified based on their depth within the body.

Superficial veins are located close to the surface of the body and have no corresponding arteries, such as the great saphenous vein which runs the length of the leg. The deep veins lie deeper in the body and often run adjacent to corresponding arteries, such as the femoral vein which sits adjacent to the femoral artery in the thigh. Deep veins are often of larger caliber than superficial veins and carry the majority of the blood within the circulatory system. Communicating veins, or perforator veins if they pass through a large muscle mass, directly connect superficial and direct veins. The above veins form part of the systemic circulatory system. The pulmonary veins and venules that run from the lungs to the heart form part of the pulmonary circulatory system and are distinct from other veins in that they carry oxygenated blood. Venae Cavae The venae cavae are the veins with the largest diameter. Both enter the right atrium of the heart with the superior vena cava carrying blood from the arms, head, and thoracic cavity and the inferior vena cava carrying blood from the legs and abdomen. The inferior vena cava runs parallel to the abdominal aorta .

The superior vena cava is formed from the brachiocephalic veins which are in turn formed from the subclavian and internal jugular veins that serve the arm and head respectively. The inferior vena cava is formed from the common iliac veins that serve the legs and abdomen. The renal and hepatic veins from the kidneys and liver respectively also feed into the inferior vena cava. Other Important Veins Other important venous systems include the cardiac veins, which return blood from the heart tissue back to the general circulation. The cardiac veins merge into the coronary sinus , which empties directly into the right atrium. The pulmonary veins are large blood vessels which receive oxygenated blood from the lungs and return it to the left atrium of the heart. There are four pulmonary veins, two from each lung, each of which forms from three to four bronchial veins. In approximately 25% of individuals, the left pulmonary veins may merge into a single vein; the same effect on the right side is only seen in approximately 3% of individuals. The hepatic portal vein carries blood from the gastrointestinal tract to the liver.

The portal vein is often described as a false vein because it conducts blood between capillary networks rather than between a capillary network and the heart. It functions to supply the liver with blood and required metabolites, but also ensures that ingested substances are first processed in the liver before reaching the wider systemic circulation. Great Vessels of the Heart About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Great Vessels of the Heart Great vessels are the major vessels which directly carry blood into or out of the heart. Learning Objective Describe the great vessels that carry blood to and from the heart Key Points Five great vessels enter and leave the heart : the superior and inferior vena cava , the pulmonary artery , the pulmonary vein , and the aorta . The superior vena cava and inferior vena cava are veins that return deoxygenated blood from circulation in the body and empty it into the right atrium .

The pulmonary artery carries deoxygenated blood from the right ventricle into the lungs for oxygenation. The pulmonary veins carry oxygenated blood from the lungs into the left atrium where it is returned to systemic circulation . The aorta is the largest artery in the body. It carries oxygenated blood from the left ventricle of the heart into systemic circulation. The aorta has many subdivisions that branch off into smaller arteries. These subdivisions are the ascending and descending aorta , the aortic arch , and the thoracic and abdominal aorta . Terms Register for FREE to remove ads and unlock more features! Learn more Full Text The human circulatory system is a double system, meaning there are two separate systems of blood flow : pulmonary circulation and systemic circulation. The adult human heart consists of two separated pumps, the right side (right atrium and ventricle,) which pumps deoxygenated blood into the pulmonary circulation, and the left side (left atrium and ventricle), which pumps oxygenated blood into the systemic circulation. Great vessels are the major vessels that carry blood into the heart and away from the heart to and from the pulmonary or systemic circuit. The great vessels collect and distribute blood across the body from numerous smaller vessels.

The Venae Cavae The superior and inferior vena cava are collectively called the venae cavae . The venae cavae, along with the aorta, are the great vessels involved in systemic circulation. These veins return deoxygenated blood from the body into the heart, emptying it into the right atrium. The venae cavae are not separated from the right atrium by valves. The venae cavae and the aorta form the systemic circuit, which circulates blood to the head, extremities and abdomen. Superior Vena Cava The superior vena cava is a large, short vein that carries deoxygenated blood from the upper half of the body to the right atrium. The right and left subclavian veins , jugular veins , and thyroid veins feed into the superior vena cava. The subclavian veins are significant because the thoracic lymphatic duct drains lymph fluid into the subclavian veins, making the superior vena cava a site of lymph fluid recirculation into the plasma . The superior vena cava begins above the heart.

Inferior Vena Cava The inferior vena cava is the largest vein in the body and carries deoxygenated blood from the lower half of the body into the heart. The left and right common iliac veins converge to form the inferior vena cava at its lowest point. The inferior vena cava begins posterior to the abdominal cavity and travels to the heart next to the abdominal aorta. Along the way up the body from the iliac veins, the renal and suprarenal veins ( kidney and adrenal glands), lumbar veins (from the back), and hepatic veins (from the liver) all drain into the inferior vena cava. The Aorta The aorta is the largest of the arteries in systemic circulation. Blood is pumped from the left ventricle through the aortic valve into the aorta. The aorta is a highly elastic artery and is able to dilate and constrict in response to blood pressure and volume. When the left ventricle contracts to force blood through the aortic valve into the aorta, the aorta expands. This expansion provides potential energy to help maintain blood pressure during diastole , when the aorta passively contracts.

Blood pressure is highest in the aorta and diminishes through circulation, reaching its lowest points at the end of venous circulation. The difference in pressure between the aorta and right atrium accounts for blood flow in the circulation, as blood flows from areas of high pressure to areas of low pressure. Components of the Aorta The aortic arch contains peripheral baroreceptors (pressure sensors) and chemoreceptors (chemical sensors) that relay information concerning blood pressure, blood pH , and carbon dioxide levels to the medulla oblongata of the brain . This information is processed by the brain and the autonomic nervous system mediates the homeostatic responses that involve feedback in the lungs and kidneys. The aorta extends around the heart and travels downward, diverging into the iliac arteries. The five components of the aorta are: The ascending aorta lies between the heart and the arch of aorta. It breaks off into the aortic sinuses , some of which form the coronary arteries. The arch of aorta is the peak of the aorta, which breaks off into the left carotid artery , brachiocephalic trunk, and the left subclavian artery.

The descending aorta is the section from the arch of aorta to the point where it divides into the common iliac arteries. It is subdivided into the thoracic and abdominal aorta. The thoracic aorta is the part of the descending aorta above the diaphragm . It branches off into the bronchial, mediastinal, esophageal, and phrenic arteries. The abdominal aorta is the part of the descending aorta below the diaphragm, which divides into the iliac arteries and branches into the renal and suprarenal arteries. This part of the aorta is vulnerable to bursting and hemorrhage (aneurysm) from persistently high blood pressure. The Pulmonary Arteries The pulmonary arteries carry deoxygenated blood from the right ventricle into the alveolar capillaries of the lungs to unload carbon dioxide and take up oxygen. These are the only arteries that carry deoxygenated blood, and are considered arteries because they carry blood away from the heart. The short, wide vessel branches into the left and right pulmonary arteries that deliver deoxygenated blood to the respective lungs. Blood first passes through the pulmonary valve as it is ejected into the pulmonary arteries.

This diagram of the pulmonary arteries labels the right and left pulmonary arteries, right and left pulmonary veins, right and left atria, right and left ventricles, and heart muscle. The Pulmonary Veins The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart. Despite carrying oxygenated blood, this great vessel is still considered a vein because it carries blood towards the heart. Four pulmonary veins enter the left atrium. The right pulmonary veins pass behind the right atrium and superior vena cava while the left pass in front of the descending thoracic aorta. The pulmonary arteries and veins are both considered part of pulmonary circulation. The Human Heart, Health Resource Center, CSULB Health Resource Center HRC Blog The Human Heart The heart is one of the major parts of our body. It is as small as your fist but does a major job in our body. The heart delivers blood throughout our bodies, by arteries, capillaries and veins. It is important for us to understand how it works and how to take care of our heart. The heart is a strong, muscular pump that continuously works around the clock. The heart can be seen as the power needed for life.

Each day the average heart "beats," or expands and contracts, 100,000 times and pumps about 2,000 gallons of blood. In an average lifetime, the human heart beats more than 2.5 billion times. Anatomy of the Heart The heart is divided into four chambers. The upper two are the right and left atria ; the lower two, the right and left ventricles. The heart also has four valves that open and close to allow blood to flow in only one direction when the heart contracts (beats). The four heart valves are: the tricuspid valve, located between the right atrium and right ventricle; the pulmonary or pulmonic valve, between the right ventricle and the pulmonary artery; the mitral valve, between the left atrium and left ventricle; the aortic valve, between the left ventricle and the aorta. Each valve has a set of flaps (also called leaflets or cusps). The right side of the heart receives dark, bluish blood from the superior and inferior vena cava. It pumps this blood to the lungs where waste gas (carbon dioxide) is removed and oxygen is picked up.

The bright red oxygenated blood returns to the left side of the heart which pumps it out through the aorta to be distributed by smaller arteries to all parts of the body. The cardiovascular system, comprising both the heart and the blood vessels, circulates blood throughout the body. It carries essential supplies of food and fuel to every living cell and exchanges them for potentially harmful waste products. The adult circulation consists of thousands of miles of tubing containing about 10 pints (4.7l) of blood. The blood is kept flowing round the body by the pumping action of the heart. Blood is made up of a pale yellow liquid (plasma) containing dissolved nutrients and wastes, plus blood cells, hormones, proteins and other substances. Most numerous of these cells are the disk-shaped red blood cells. Their color comes from the presence of the substance hemoglobin, which combines with oxygen. When red corpuscles charged with oxygen approach body cells, the oxygen is delivered in exchange for the waste product carbon dioxide. Other two-way transportation of materials takes place between the body cells and the plasma, and all unwanted substances are carried away in the blood for excretion by the kidneys, lungs, and liver.

Plasma also contains white blood cells, which help to fight infection, and platelets, which are involved in blood clotting. Blood Flow In its passage through the body, blood is carried in tubes known as arteries and veins. Most arteries transport oxygen-rich (oxygenated) blood, whereas most veins transport carbon dioxide-rich (deoxygenated) blood. The largest artery is the aorta, which stems directly from the heart. The aorta and other large arteries have thick walls lined with muscle. Blood flow is assisted by the contraction of this muscle and the impetus given by the heartbeat. The "push" from the heart can be felt as the pulse wherever large arteries run near the body surface. As they penetrate the tissues, arteries split into narrow branches called arterioles, which in turn divide into capillaries. It is through the very thin capillary walls that the blood gives up its oxygen and nutrients and receives carbon dioxide and wastes. Deoxygenated blood in the capillaries flows into narrow veins (venules), and then into veins. The two largest veins, the venae cavae, return this blood to the heart. Veins have thin walls compared with those of arteries, and blood moves through the veins much more slowly.

Blood flow in the veins is assisted by the action of muscles in surrounding tissues, and backflow is prevented by one-way valves. The walls of arteries and veins comprise the same four tissues, but arteries have more muscle to withstand more blood pressure. Blood flow in veins is aided by nearby muscles; valves prevent backflow. Blood flow in the heart is controlled by valves. The tricuspid valve controls flow from right atrium to right ventricle; the mitral valve controls flow from left atrium to left ventricle. Valves also guard the entrances to the aorta and pulmonary artery in order to prevent backflow of blood after the heart contracts. The deoxygenated blood delivered to the heart along the veins is no use to body cells until it has been recharged with oxygen. To ensure reoxygenation, the circulation has a second "loop." In this part of the system, blood rich in carbon dioxide travels from the heart along the pulmonary artery to the lungs, where carbon dioxide is exchanged for oxygen breathed in. The pulmonary artery is the only artery to carry deoxygenated blood. The newly oxygenated blood is carried back to the heart along the pulmonary vein, the only vein to transport oxygenated blood.

The heart is a muscular organ about the size of a clenched fist. The structure and action of the heart are designed to serve the two loops of the circulation. Inside, the heart is divided vertically by a muscular wall. On each side of this wall is an upper chamber (atrium) and a thicker, lower chamber (ventricle). Blood moves through each side of the heart systematically. Deoxygenated blood is delivered into the right atrium. It then enters the right ventricle, from where it is pumped out into the pulmonary artery and to the lungs. Oxygenated blood returning in the pulmonary veins flows into the left atrium. This blood enters the left ventricle and is then pumped into the aorta for circulation. The flow of blood in each side of the heart is controlled by a series of valves. The pumping action of the heart is achieved by the contraction of the cardiac muscle, of which the heart is largely composed. The rhythm of the heartbeat is regulated by bursts of electrical impulses sent out by a concentration of specialized heart tissue called the pacemaker. Under the influence of the pacemaker, the heart of an adult at rest beats at a rate of 60 to 80 beats a minute.

The pacemaker also helps to ensure the correct sequence of activities during each heartbeat; first the two atria contract, followed rapidly by the ventricles. The powerful contraction of the ventricles pushes blood into the aorta and pulmonary artery. This period of contraction (systole) is followed by a period of relaxation (diastole), during which the heart refills. The complete sequence is accompanied by electrical activity of the muscle, which can be monitored as an electrocardiogram (EKG). An electrocardiogram (EKG) records the waves of nerve impulses of each heartbeat. The P wave starts just before the atria contract; the QRS wave indicates the contraction of the ventricles; and the T wave indicates the recovery period before the next contraction. Aorta Aorta is the largest artery in the body, supplying blood to the organs alongside its course. It starts at the left ventricle of the heart, then arches upward and backward, giving off branch arteries to the heart muscles, head, and arms. The aorta then runs down the back of the chest, in front of the spine and esophagus (gullet), to reach the abdomen.

Just above the pelvis, the aorta divides into the common iliac arteries to the legs Vena cava is one of the two veins (superior vena cava and inferior vena cava) that drain blood from all parts of the body (except the heart) into the right atrium of the heart. The superior vena cava returns blood from the head, neck, and arms to the heart. The inferior vena cava returns blood from the chest, abdomen, and legs to the heart. High Blood Pressure Researchers in recent years have made great strides in the understanding and treatment of high blood pressure (hypertension). High blood pressure is a major risk factor for heart attack, heart failure, stroke, and kidney failure. Heart disease and stroke are the first and third leading causes of death, respectively, in the United States, according to the National Heart, Lung, and Blood Institute. Significant increases in hypertension awareness, treatment and control rates have occurred since the 1960s. Despite those advances, the declines in stroke and heart attack in the U.S. during the last 30 years have leveled off and congestive heart failure and kidney failure are rising.

References and Resources Cardiovascular System - Human Veins, Arteries, Heart Cardiovascular System Home > Cardiovascular System Cardiovascular System The cardiovascular system consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body, the cardiovascular system is powered by the body’s hardest-working organ — the heart, which is only about the size of a closed fist. Even at rest, the average heart easily pumps over 5 liters of blood throughout the body every minute.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image Cardiovascular System Anatomy The Heart The heart is a muscular pumping organ located medial to the lungs along the body’s midline in the thoracic region. The bottom tip of the heart, known as its apex, is turned to the left, so that about 2/3 of the heart is located on the body’s left side with the other 1/3 on right.

The top of the heart, known as the heart’s base, connects to the great blood vessels of the body: the aorta , vena cava, pulmonary trunk, and pulmonary veins. Circulatory Loops There are 2 primary circulatory loops in the human body: the pulmonary circulation loop and the systemic circulation loop. Pulmonary circulation transports deoxygenated blood from the right side of the heart to the lungs , where the blood picks up oxygen and returns to the left side of the heart. The pumping chambers of the heart that support the pulmonary circulation loop are the right atrium and right ventricle. Systemic circulation carries highly oxygenated blood from the left side of the heart to all of the tissues of the body (with the exception of the heart and lungs). Systemic circulation removes wastes from body tissues and returns deoxygenated blood to the right side of the heart. The left atrium and left ventricle of the heart are the pumping chambers for the systemic circulation loop. Blood Vessels Blood vessels are the body’s highways that allow blood to flow quickly and efficiently from the heart to every region of the body and back again. The size of blood vessels corresponds with the amount of blood that passes through the vessel.

All blood vessels contain a hollow area called the lumen through which blood is able to flow. Around the lumen is the wall of the vessel, which may be thin in the case of capillaries or very thick in the case of arteries. All blood vessels are lined with a thin layer of simple squamous epithelium known as the endothelium that keeps blood cells inside of the blood vessels and prevents clots from forming. The endothelium lines the entire circulatory system, all the way to the interior of the heart, where it is called the endocardium. There are three major types of blood vessels: arteries, capillaries and veins. Blood vessels are often named after either the region of the body through which they carry blood or for nearby structures. For example, the brachiocephalic artery carries blood into the brachial (arm) and cephalic (head) regions. One of its branches, the subclavian artery, runs under the clavicle; hence the name subclavian. The subclavian artery runs into the axillary region where it becomes known as the axillary artery. Arteries and Arterioles: Arteries are blood vessels that carry blood away from the heart.

Blood carried by arteries is usually highly oxygenated, having just left the lungs on its way to the body’s tissues. The pulmonary trunk and arteries of the pulmonary circulation loop provide an exception to this rule – these arteries carry deoxygenated blood from the heart to the lungs to be oxygenated. Arteries face high levels of blood pressure as they carry blood being pushed from the heart under great force. To withstand this pressure, the walls of the arteries are thicker, more elastic, and more muscular than those of other vessels. The largest arteries of the body contain a high percentage of elastic tissue that allows them to stretch and accommodate the pressure of the heart. Smaller arteries are more muscular in the structure of their walls. The smooth muscles of the arterial walls of these smaller arteries contract or expand to regulate the flow of blood through their lumen. In this way, the body controls how much blood flows to different parts of the body under varying circumstances. The regulation of blood flow also affects blood pressure, as smaller arteries give blood less area to flow through and therefore increases the pressure of the blood on arterial walls. Arterioles are narrower arteries that branch off from the ends of arteries and carry blood to capillaries.

They face much lower blood pressures than arteries due to their greater number, decreased blood volume, and distance from the direct pressure of the heart. Thus arteriole walls are much thinner than those of arteries. Arterioles, like arteries, are able to use smooth muscle to control their aperture and regulate blood flow and blood pressure. Capillaries: Capillaries are the smallest and thinnest of the blood vessels in the body and also the most common. They can be found running throughout almost every tissue of the body and border the edges of the body’s avascular tissues. Capillaries connect to arterioles on one end and venules on the other. Capillaries carry blood very close to the cells of the tissues of the body in order to exchange gases, nutrients, and waste products. The walls of capillaries consist of only a thin layer of endothelium so that there is the minimum amount of structure possible between the blood and the tissues. The endothelium acts as a filter to keep blood cells inside of the vessels while allowing liquids, dissolved gases, and other chemicals to diffuse along their concentration gradients into or out of tissues.

Precapillary sphincters are bands of smooth muscle found at the arteriole ends of capillaries. These sphincters regulate blood flow into the capillaries. Since there is a limited supply of blood, and not all tissues have the same energy and oxygen requirements, the precapillary sphincters reduce blood flow to inactive tissues and allow free flow into active tissues. Veins and Venules: Veins are the large return vessels of the body and act as the blood return counterparts of arteries. Because the arteries, arterioles, and capillaries absorb most of the force of the heart’s contractions, veins and venules are subjected to very low blood pressures. This lack of pressure allows the walls of veins to be much thinner, less elastic, and less muscular than the walls of arteries. Veins rely on gravity, inertia, and the force of skeletal muscle contractions to help push blood back to the heart. To facilitate the movement of blood, some veins contain many one-way valves that prevent blood from flowing away from the heart. As skeletal muscles in the body contract, they squeeze nearby veins and push blood through valves closer to the heart.

When the muscle relaxes, the valve traps the blood until another contraction pushes the blood closer to the heart. Venules are similar to arterioles as they are small vessels that connect capillaries, but unlike arterioles, venules connect to veins instead of arteries. Venules pick up blood from many capillaries and deposit it into larger veins for transport back to the heart. Coronary Circulation The heart has its own set of blood vessels that provide the myocardium with the oxygen and nutrients necessary to pump blood throughout the body. The left and right coronary arteries branch off from the aorta and provide blood to the left and right sides of the heart. The coronary sinus is a vein on the posterior side of the heart that returns deoxygenated blood from the myocardium to the vena cava. Hepatic Portal Circulation The veins of the stomach and intestines perform a unique function: instead of carrying blood directly back to the heart, they carry blood to the liver through the hepatic portal vein . Blood leaving the digestive organs is rich in nutrients and other chemicals absorbed from food. The liver removes toxins, stores sugars, and processes the products of digestion before they reach the other body tissues.

Blood from the liver then returns to the heart through the inferior vena cava. Blood The average human body contains about 4 to 5 liters of blood. As a liquid connective tissue, it transports many substances through the body and helps to maintain homeostasis of nutrients, wastes, and gases. Blood is made up of red blood cells, white blood cells, platelets, and liquid plasma. Red Blood Cells: Red blood cells, also known as erythrocytes, are by far the most common type of blood cell and make up about 45% of blood volume. Erythrocytes are produced inside of red bone marrow from stem cells at the astonishing rate of about 2 million cells every second. The shape of erythrocytes is biconcave—disks with a concave curve on both sides of the disk so that the center of an erythrocyte is its thinnest part. The unique shape of erythrocytes gives these cells a high surface area to volume ratio and allows them to fold to fit into thin capillaries. Immature erythrocytes have a nucleus that is ejected from the cell when it reaches maturity to provide it with its unique shape and flexibility.

The lack of a nucleus means that red blood cells contain no DNA and are not able to repair themselves once damaged. Erythrocytes transport oxygen in the blood through the red pigment hemoglobin. Hemoglobin contains iron and proteins joined to greatly increase the oxygen carrying capacity of erythrocytes. The high surface area to volume ratio of erythrocytes allows oxygen to be easily transferred into the cell in the lungs and out of the cell in the capillaries of the systemic tissues. White Blood Cells: White blood cells, also known as leukocytes, make up a very small percentage of the total number of cells in the bloodstream, but have important functions in the body’s immune system . There are two major classes of white blood cells: granular leukocytes and agranular leukocytes. Granular Leukocytes: The three types of granular leukocytes are neutrophils, eosinophils, and basophils. Each type of granular leukocyte is classified by the presence of chemical-filled vesicles in their cytoplasm that give them their function. Neutrophils contain digestive enzymes that neutralize bacteria that invade the body.

Eosinophils contain digestive enzymes specialized for digesting viruses that have been bound to by antibodies in the blood. Basophils release histamine to intensify allergic reactions and help protect the body from parasites. Agranular Leukocytes: The two major classes of agranular leukocytes are lymphocytes and monocytes. Lymphocytes include T cells and natural killer cells that fight off viral infections and B cells that produce antibodies against infections by pathogens. Monocytes develop into cells called macrophages that engulf and ingest pathogens and the dead cells from wounds or infections. Platelets : Also known as thrombocytes, platelets are small cell fragments responsible for the clotting of blood and the formation of scabs. Platelets form in the red bone marrow from large megakaryocyte cells that periodically rupture and release thousands of pieces of membrane that become the platelets. Platelets do not contain a nucleus and only survive in the body for up to a week before macrophages capture and digest them. Plasma: Plasma is the non-cellular or liquid portion of the blood that makes up about 55% of the blood’s volume. Plasma is a mixture of water, proteins, and dissolved substances.

Around 90% of plasma is made of water , although the exact percentage varies depending upon the hydration levels of the individual. The proteins within plasma include antibodies and albumins. Antibodies are part of the immune system and bind to antigens on the surface of pathogens that infect the body. Albumins help maintain the body’s osmotic balance by providing an isotonic solution for the cells of the body. Many different substances can be found dissolved in the plasma, including glucose, oxygen, carbon dioxide, electrolytes, nutrients, and cellular waste products. The plasma functions as a transportation medium for these substances as they move throughout the body. Cardiovascular System Physiology Functions of the Cardiovascular System The cardiovascular system has three major functions: transportation of materials, protection from pathogens, and regulation of the body’s homeostasis. Transportation: The cardiovascular system transports blood to almost all of the body’s tissues. The blood delivers essential nutrients and oxygen and removes wastes and carbon dioxide to be processed or removed from the body. Hormones are transported throughout the body via the blood’s liquid plasma. Protection: The cardiovascular system protects the body through its white blood cells. White blood cells clean up cellular debris and fight pathogens that have entered the body.

Platelets and red blood cells form scabs to seal wounds and prevent pathogens from entering the body and liquids from leaking out. Blood also carries antibodies that provide specific immunity to pathogens that the body has previously been exposed to or has been vaccinated against. Regulation: 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 controlling 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. In the case of hypothermia, 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 due to the presence of bicarbonate ions, which act as a buffer solution. Finally, the albumins in blood plasma help to balance the osmotic concentration of the body’s cells by maintaining an isotonic environment. The Circulatory Pump 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 separated 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 to the lungs for oxygenation. The left side of the heart receives oxygenated blood 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. Regulation of Blood Pressure Several functions of the cardiovascular system can control blood pressure. Certain hormones along with autonomic nerve signals from the brain affect the rate and strength of heart contractions. Greater contractile force and heart rate lead to an increase in blood pressure. Blood vessels can also affect blood pressure. Vasoconstriction decreases the diameter of an artery by contracting the smooth muscle in the arterial wall. The sympathetic (fight or flight) 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 raises blood pressure by increasing the amount of blood pumped by each heartbeat. Thicker, more viscous blood from clotting disorders can also raise blood pressure. Hemostasis Hemostasis, or the clotting of blood and formation of scabs, is managed by the platelets of the blood. Platelets normally remain inactive in the blood until they reach damaged tissue or leak out of the blood vessels through a wound. Once active, platelets change into a spiny ball shape and become very sticky in order to latch on to damaged tissues. Platelets next release chemical clotting factors and begin to produce the protein fibrin to act as structure for the blood clot. Platelets 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 foreign material out of the vessel until the cells of the blood vessel can repair the damage to the vessel wall.

Prepared by Tim Taylor, Anatomy and Physiology Instructor The Path of Blood through the Human Body - dummies The Path of Blood through the Human Body The Path of Blood through the Human Body The Path of Blood through the Human Body When a heart contracts and forces blood into the blood vessels, there is a certain path that the blood follows through the body. The blood moves through pulmonary circulation and then continues on through systemic circulation. Pulmonary and systemic are the two circuits in the two-circuit system of higher animals with closed circulatory systems. Humans and other mammals have two-circuit circulatory systems: one circuit is for pulmonary circulation (circulation to the lungs; pulmo = lungs), and the other circuit is for systemic circulation (the rest of the body). As each atrium and ventricle contract, blood is pumped into certain major blood vessels, and from there, continues through the circulatory system. The intertwined circulatory system pathways: Pulmonary circulation and systemic circulation work together. Pulmonary circulation Blood that is lacking oxygen is said to be deoxygenated. This blood has just exchanged oxygen for carbon dioxide across cell membranes, and now contains mostly carbon dioxide.

Deoxygenated blood enters the right atrium through the superior vena cava and the inferior vena cava. Superior means higher, and inferior means lower, so the superior vena cava is at the top of the right atrium, and the inferior vena cava enters the bottom of the right atrium. From the right atrium, the deoxygenated blood drains into the right ventricle through the right atrioventricular (AV) valve, which is so named because it is between the atrium and the ventricle. This valve is also referred to as the tricuspid valve because it has three flaps in its structure. When the ventricles contract, the AV valve closes off the opening between the ventricle and the atrium so that blood does not flow back up into the atrium. As the right ventricle contracts, it forces the deoxygenated blood through the pulmonary semilunar valve and into the pulmonary artery. Semilunar means half-moon and refers to the shape of the valve. Note that this is the only artery in the body that contains deoxygenated blood; all other arteries contain oxygenated blood.

The semilunar valve keeps blood from flowing back into the right ventricle once it is in the pulmonary artery. The pulmonary artery carries the blood that is very low in oxygen to the lungs, where it becomes oxygenated. Systemic circulation Freshly oxygenated blood returns to the heart via the pulmonary veins. Note that these are the only veins in the body that contain oxygenated blood; all other veins contain deoxygenated blood. The pulmonary veins enter the left atrium. When the left atrium relaxes, the oxygenated blood drains into the left ventricle through the left AV valve. This valve is also called the bicuspid valve because it has only two flaps in its structure. Now the heart really squeezes. As the left ventricle contracts, the oxygenated blood is pumped into the main artery of the body — the aorta. To get to the aorta, blood passes through the aortic semilunar valve, which serves to keep blood flowing from the aorta back into the left ventricle. The aorta branches into other arteries, which then branch into smaller arterioles. The arterioles meet up with capillaries, which are the blood vessels where oxygen is exchanged for carbon dioxide.

Capillary exchange Capillaries bridge the smallest of the arteries and the smallest of the veins. Near the arterial end, the capillaries allow materials essential for maintaining the health of cells to diffuse out (water, glucose, oxygen, and amino acids). To maintain the health of cells, it is also necessary for the capillaries to transport wastes and carbon dioxide to places in the body that can dispose of them. The waste products enter near the venous end of the capillary. Water diffuses in and out of capillaries to maintain blood volume, which adjusts to achieve homeostasis. Capillaries are only as thick as one cell, so the contents within the cells of the capillaries can easily pass out of the capillary by diffusing through the capillary membrane. And, because the capillary membrane abuts the membrane of other cells all over the body, the capillary’s contents can easily continue through the abutting cell’s membrane and get inside the adjoining cell. The process of capillary exchange is how oxygen leaves red blood cells in the bloodstream and gets into all the other cells of the body. Capillary exchange also allows nutrients to diffuse out of the bloodstream and into other cells.

At the same time, the other cells expel waste products that then enter the capillaries, and carbon dioxide diffuses out of the body’s cells and into the capillaries. How capillary exchange works. After the capillaries “pick up” the garbage from other cells, the capillaries carry the wastes and carbon dioxide through the deoxygenated blood to the smallest of the veins, which are called venules. The venules branch into bigger vessels called veins. The veins then carry the deoxygenated blood toward the main vein, which is the vena cava. The two branches of the vena cava enter the right atrium, which is where pulmonary circulation begins. Veins and Arteries - Difference and Comparison | Diffen Veins and Arteries There are two types of blood vessels in the circulatory system of the body: arteries that carry oxygenated blood from the heart to various parts of the body and veins that carry blood towards the heart for purification. Comparison chart Arteries versus Veins comparison chart Arteries Arteries carry oxygenated blood (with the exception of the pulmonary artery and umbilical artery).

Veins carry deoxygenated blood (with the exception of pulmonary veins and umbilical vein). Types Superficial veins, deep veins, pulmonary veins and systemic veins Direction of Blood Flow From the heart to various parts of the body. From various parts of the body to the heart. Anatomy Thick, elastic muscle layer that can handle high pressure of the blood flowing through the arteries. Thin, elastic muscle layer with semilunar valves that prevent the blood from flowing in the opposite direction. Disease Arteries are red blood vessels that carry blood away from the heart. resistance vessels Veins are blue blood vessels that carry blood towards the heart. capacitance vessels Thickest layer Aren't present (except for semi-lunar valves) Are present, especially in limbs Contents: Veins and Arteries 5 References Differences in Function The circulatory system is responsible for the delivery of oxygen and nutrients to cells. It also removes carbon dioxide and waste products, maintains of healthy pH levels, and supports the elements, proteins, and cells of the immune system. Two leading causes of death, myocardial infarction and stroke each may directly result from an arterial system that has been slowly and progressively compromised by years of deterioration.

An artery usually carries pure, filtered and clean blood away from the heart, to all the parts of the body with an exception of the pulmonary artery and the umbilical cord. As the arteries move away from the heart, they divide into smaller vessels. These thinner arteries are called arterioles. Veins are needed to carry the deoxygenated blood back to the heart for purification. Anatomy of Arteries vs Veins Anatomy of an artery Arteries that carry blood from the heart to other parts of the body are known as systemic arteries while those that carry deoxygenated blood to the lungs are known as pulmonary arteries. The inner layers of the arteries are generally made of thick muscles which is why the blood moves through it slowly. Pressure is built up and arteries are required to maintain their thickness to withstand the strain they endure. Muscular arteries vary in size from about 1 cm in diameter to about 0.5 mm. Along with the arteries, Arterioles help in transporting the blood to various parts of the body. They are tiny branches of arteries that lead to capillaries and help maintain the pressure and blood flow in the body. Venous valves prevent blood from flowing in the opposite direction.

Connective tissues make up the outermost layer of a vein which is also known as - tunica adventitia or tunica externa. The middle layer is known as tunica media and is made up of smooth muscles. The interior is lined with endothelial cells called tunica intima. The vein also contains venous valves- one way flaps that prevent blood from flowing back and pooling in the lower extremities due to the effects of gravity. To ensure unrestricted flow of blood, a venule (blood vessel) allows deoxygenated blood to return from the capillary beds to the vein. Types of arteries and veins There are two types of arteries in the body: Pulmonary and systemic. The pulmonary artery carries deoxygenated blood from the heart, to the lungs, for purification while the systemic arteries form a network of arteries that carry oxygenated blood from the heart to other parts of the body. Arterioles and capillaries are further extensions of the (main) artery that help transport blood to tinier parts in the body. Veins can be classified as pulmonary veins and systemic veins.

The pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the heart and the Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart. Pulmonary and Systemic veins can either be superficial (can be seen or felt if touched on certain areas on the hands and legs) or embedded deep inside the body. The main arteries in the human circulatory system (click to enlarge) The human veinous system (click to enlarge) Diseases The arteries can get blocked and become incapable of supplying blood to the organs of the body. In such a case, the patient is said to suffer from peripheral vascular disease. Atherosclerosis is another disease where the patient shows an accumulation of cholesterol on the walls of his arteries. This can be fatal in nature. A patient can be affected by venous insufficiency, which is commonly known as varicose veins. Another disease of the vein, that commonly affects man is known as deep vein thrombosis. Here, a clot if formed in one of the 'deep' veins and can result in pulmonary embolism if not treated quickly. Most arterial and vein diseases are diagnosed with an MRA scan .

References Aorta vs Pulmonary Artery - Difference and Comparison | Diffen Aorta vs. Pulmonary Artery Diffen › Science › Biology › Anatomy The aorta and the pulmonary artery are the two most important arteries in the human body. The aorta is the biggest artery and channels oxygenated blood to the rest of the body. The pulmonary artery carries deoxygenated blood to the lungs for purification. Comparison chart Aorta versus Pulmonary Artery comparison chart Aorta The aorta is the artery that carries oxygenated blood to the entire body. The pulmonary artery carries deoxygenated blood to the lungs. Function The function of the aorta is to carry oxygenated blood throughout the body. The function of the pulmonary artery is to deliver blood to the lungs for oxygenation. Location The aorta is located at the top of the heart. The pulmonary artery is located directly beneath the aorta. Type of circulation The aorta is part of the systemic circulation. The pulmonary trunk with left and right arteries are part of the pulmonary circulation. Contents: Aorta vs Pulmonary Artery Structure of the human heart (click to enlarge) Function The aorta supplies oxygenated blood from the heart's pumping chamber to the rest of the body.

Pulmonary artery carries deoxygenated or unaerated blood from the heart to the lungs.Like all arteries, the pulmonary artery carries blood away from the heart. However, the pulmonary artery is the only artery that carries deoxygenated blood from the heart to the lungs. Structure Structure of the aorta (click to enlarge) The aorta is divided into 5 main sections: Aortic root - This is the base of the aorta where it connects to the heart's pumping chamber. It gives rise to two coronary arteries which are responsible for carrying oxygenated blood to the heart muscles. The two coronary arteries end at the beginning of ascending aorta. Ascending aorta - This section of the aorta begins from the aortic root and ascends upwards to the point where the aorta forms an arch. Due to very little support of the surrounding tissue and handling the complete output volume of the cardiac, it is considered one of the most vulnerable parts of the aorta. Aortic arch - This is the curved section of the aorta. Along with brachiocephalic (aka. innominate), left common carotid and left subcalvian arteries it supplies blood to the upper body including the head.

Descending aorta - Beginning from the arch it descends downwards into the body and ends at diaphragm. It supplies oxygenated blood to the spinal cord. Thoracoabdominal aorta - This section begins at the diaphragm and ends at the celiac, superior mesenteric and the visceral vessels. Abdominal aorta – This section begins below the renal arteries and ends at the two iliac arteries. It also contains a small artery named the inferior mesenteric artery. This section supplies blood to the kidneys. Structure of the Pulmonary Artery View of the pulmonary artery The pulmonary artery is divided into 2 main sections: Pulmonary trunk: Also known as pulmonary artery or main pulmonary artery, this section originates at the right ventricle and further branches into left and right pulmonary arteries. Left and Right Pulmonary arteries: Branching from the pulmonary trunk, the left and right pulmonary arteries supply deoxygenated blood to the left and right lung respectively. Disease Aortic and pulmonary diseases are often diagnosed with MRA or MRI scans . Since the aorta is the primary artery which supplies oxygenated blood to the rest of the body, a disease in the aorta can prove fatal.

Some of the aortic diseases include: Aortic Dissection, where the inner layer of the aortic walls tears causing blood to leak into the wall. Aortic Aneurysm, where due to an abnormal bulge in the aortic wall the aorta may rupture causing internal bleeding. The major causes of Aortic Aneurysm known are hypertension, smoking , and family history. Atherosclerosis, where the arteries harden due to high blood pressure, and buildup of fat and cholesterol causing reduced blood supply to the rest of the body. Aortic inflammation, where the aortic wall weakens due to inflammation. Connective tissue disorders, where due to weak aortic walls, a rupture or tear can occur. Usually seen in patients with Marfan Syndrome, Ehler-Danlos syndrome, and other connective tissue disorders, with early detection and proper treatment, patients can continue to enjoy a normal life. [1] Pulmonary heart diseases can be acute or chronic in nature. Pulmonary embolisms, the acute form, is when there is a sudden obstruction to the blood flow causing disruptions to the blood supply to the lungs.

Pulmonary hypertension (PAH) is considered chronic when high blood pressure causes poor circulation of blood and an increase in arterial pressure which can be damaging to the heart, lungs and as well as liver. Factors that can cause PAH vary from the inflammation of the arteries to the tighteing of the aortic wall, etc. [2] Did You Know? American Heart Association Reports the following findings based on 2005-2006 data analysis: In the United States, someone has a heart attack every 40 seconds. Nearly 2400 Americans die of Cardio vascular disease each day—an average of 1 death every 37 seconds. Each year, about 795 000 people experience a new or recurrent stroke in America. Approximately 65% of men and 70% of women had been screened for high cholesterol in the previous 5 years.

From 1971–1974 to 2003–2006, Overweight (body mass index–for–age values at or above the 95th percentile) percentage in, Infants and Toddlers (between the ages of 6 and 23 months), increased from 7.2% to 11.5%. Children (6 to11 years of age) increased from 4.0% to 17.0%. Adolescents (12 to 19 years of age) increased from 6.1% to 17.6%. Over 12% of preschool children 2 to 5 years of age are overweight in 2003–2006. Video explaining the differences Heart and Cardiovascular System of the Upper Torso Home > Cardiovascular System > Heart and Cardiovascular System of the Upper Torso Heart and Cardiovascular System of the Upper Torso The cardiovascular system of the upper torso includes the heart and most of the major blood vessels of the circulatory system.

These vital structures are critical to the process of pumping deoxygenated blood to the lungs for gas exchange as well as pumping oxygenated blood to the body’s tissues to support their metabolic functions. The heart is the body’s circulatory pump that is responsible for the movement of blood throughout the entire body. The heart acts as a double pump by pushing both deoxygenated blood to the lungs and oxygenated blood to the body’s tissues with each heartbeat.... Move up/down/left/right: Click compass arrows Rotate image: Click and drag in any direction, anywhere in the frame Identify objects: Click on them in the image 2D Interactive 3D Rotate & Zoom Change Anatomical System Change View Angle Full Heart and Cardiovascular System of the Upper Torso Description [Continued from above] . . . The heart is mostly made of cardiac muscle tissue, which requires its own constant supply of oxygenated blood. The left and right coronary arteries provide this blood supply to feed the heart’s own energy demands. Small blockages in the coronary arteries lead to chest pain called angina pectoris; complete blockages of the coronary arteries lead to myocardial infarctions, better known as heart attacks.

The pulmonary arteries and pulmonary veins provide vital but short distance blood flow between the heart and the lungs. Exiting the heart from the right ventricle, deoxygenated blood flows into the large pulmonary trunk before splitting at the left and right pulmonary arteries. The pulmonary arteries carry blood to smaller arterioles and on to the vast capillary beds of the lungs where carbon dioxide is released and oxygen is obtained from the air in the alveoli of the lungs. These capillaries converge into larger venules, which further converge to form the left and right pulmonary veins. Each pulmonary vein carries blood from a lung back to the heart where it reenters through the left atrium. Oxygenated blood exits the left ventricle of the heart and enters the aorta, the largest artery in the human body. The ascending aorta extends superiorly from the heart before making a 180-degree turn to the left in a portion called the arch of the aorta. From there it passes posterior to the heart as the thoracic aorta on its way toward the abdomen. The aorta branches as it passes through the thorax, branching off into several major arteries as well as many minor ones.

The left and right coronary arteries branch off from the ascending aorta, supplying the heart with its vital blood supply. The arch of the aorta branches off into three major arteries – the brachiocephalic trunk, left common carotid artery, and left subclavian artery. These arteries collectively supply the head and arms with oxygenated blood. The thoracic aorta continues to branch into many tiny arteries that supply blood to the organs, muscles, and skin of the thorax before entering the abdomen as the abdominal aorta. Blood from the abdominal aorta supplies oxygen and nutrients to the vital organs of the abdomen through arteries such as the celiac trunk and common hepatic arteries. Functioning at the end of the circulatory cycle, the veins of the upper torso carry deoxygenated blood from the tissues of the body back to the heart to be pumped through the body again. Blood returning to the heart from the lower torso and legs enters the upper torso in a large vein called the inferior vena cava. The inferior vena cava picks up deoxygenated blood from the hepatic and phrenic veins before entering the right atrium of the heart.

Blood returning from the head enters the torso through the left and right jugular veins while blood returning from the arms enters through the left and right subclavian veins. The jugular and subclavian veins on each side merge to form the left and right brachiocephalic trunks, which go on to merge into the superior vena cava. Several smaller veins carrying blood from the organs, muscles, and skin of the upper torso also merge into the superior vena cava. The superior vena cava carries all of the blood from the arms and head into the right atrium of the heart. Prepared by Tim Taylor, Anatomy and Physiology Instructor Blood Vessels | The Franklin Institute The Franklin Institute Blood Vessels Blood vessels may be tiny but they cover a lot of ground. The smallest blood vessels measure only five micrometers. To give you some perspective, a strand of human hair measures about 17 micrometers. But if you took all the blood vessels out of an average child and laid them out in one line, the line would stretch over 60,000 miles. An adult’s would be closer to 100,000 miles long.

There are three kinds of blood vessels: arteries, veins, and capillaries. Each of these plays a very specific role in the circulation process. Arteries carry oxygenated blood away from the heart. They’re tough on the outside but they contain a smooth interior layer of epithelial cells that allows blood to flow easily. Arteries also contain a strong, muscular middle layer that helps pump blood through the body. Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart. Veins carry the blood back to the heart. They’re similar to arteries but not as strong or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.

Question: What are the only arteries in the adult human body to carry deoxygenated blood?
Answer: Pulmonary