LESSON 6 CARDIOVASCULAR AND LYMPHATIC SYSTEMS

INTRODUCTION In order to perform the many functions of the body, the body must have a very efficient way of providing energy to each of the cells of the body. The cells of each tissue and organ receive energy from the food substances that reach them after being taken into the body. Food contains potential energy that can be converted into kinetic energy whenever it is needed. This conversion of potential energy into the kinetic energy inside the cells occurs when food, water, and oxygen combine inside the cells during the chemical processes of metabolism. The organs of the body need small amounts of other nutrients like vitamins for metabolism to occur quickly. Each cell of each organ is dependent on a constant supply of food, water, oxygen, and other nutrients in order to provide sufficient energy to work correctly.

How the body assures that adequate supplies of oxygen, water, and food will be delivered to its cells is a function of the cardiovascular system. The cardiovascular system consists of about 12 pints of a fluid called blood, many miles of vessels to deliver the blood and then return to the heart, and a double phase pump called the heart, to transport food, water, and oxygen to all organs and cells of the body. About ½ cup of blood is moved through the blood vessels with each contraction of the heart. Blood vessels in the lungs take-up the oxygen that has been breathed in from the air, and blood vessels in the intestines absorb food and water from the digestive tract. Blood vessels carry waste materials such as carbon dioxide and nitrogen from the cell and transport these substances to the lungs and kidneys, where they can be expelled from the body.

BLOOD VESSELS AND THE CIRCULATION OF BLOOD

Blood Vessels

There are three major kinds of blood vessels in the body. These are arteries, veins, and capillaries. Arteries are the large blood vessels that lead blood away from the heart. Their walls are strong and are made of connective tissue, elastic fibers, and an innermost layer of epithelial cells called endothelium. Arteries are strong to withstand the high pressure required to carry blood away from the heart to every single cell of the body. The elastic walls of the arteries allow them to expand as the heart muscle forces blood throughout the body. Smaller branches of arteries are called arterioles. Arterioles are thinner than arteries and carry the blood to the smallest of blood vessels, called the capillaries.

Capillaries have walls that are only one cell thick. These delicate, microscopic vessels carry oxygenated blood from the arteries and arterioles to the body cells. Their walls are thick enough to allow passage of oxygen and other nutrients out of the bloodstream and

into the lymph fluid surrounding the cells and then into the cell. Once inside the cells, the nutrients are burned in the presence of oxygen and water to release the needed energy for functioning of the cell. As discussed above, this process is called metabolism. At the same time, waste products such as carbon dioxide, nitrogen and water, pass out of the cells and into the one cell thick capillaries. The blood then flows back from the cell to the heart by small veins called venules, and then into larger vessels called veins.

Veins have thinner walls than arteries. They carry deoxygenated blood toward the heart from the cells. Veins have much lower blood pressure than arteries, about 15 mm/hg at their beginning to about 5 mm/hg at the vena cava. In order to keep blood moving back toward the heart, veins have many valves that prevent the backward flow of blood and keep the blood moving toward the heart. Muscular action greatly helps the movement of blood in veins toward the heart.

Circulation of Blood

Arteries, arterioles, veins, venules, and capillaries, together with the heart, form a circulatory system for the flow of blood. Deoxygenated blood flows into the heart cavity through two large vessels called the vena cava, coming from the body’s capillaries to the heart. The blood becomes deoxygenated in the tissue capillaries where oxygen leaves the blood and enters the cells.

Deoxygenated blood enters the right side of the heart and travels through that side and exits into the pulmonary artery. This vessel then divides in two-- one branch leading to the left lung, the other branch to the right lung. The arteries continue dividing and subdividing in the lungs, forming smaller blood vessels called arterioles and finally reaching the tiny capillaries of the lungs. The pulmonary artery is unusual in that it is the only artery in the body that carries deoxygenated blood.

While passing through the lung’s capillaries, blood absorbs the oxygen that entered the body during respiration. The newly oxygenated blood returns to the heart through pulmonary veins. The pulmonary veins are unusual in that they are the only veins in the body that carry oxygenated blood. The circulation of blood through the vessels from the heart to the lungs and then back to the heart again is known as the pulmonary circulation.

Oxygenated blood enters the left side of the heart from the two pulmonary veins. The muscles in the left side of the heart pump the blood out of the heart through the largest single vessel in the body, the aorta. The aorta moves upward (ascending aorta), then arches over dorsally (aortic arch), and finally downward just anterior to the vertebral column (the descending aorta). The aorta divides into numerous branches called arteries that carry the oxygenated blood to all parts of the body.

The relatively large arterial vessels branch to form smaller arterioles. The arterioles, still containing oxygenated blood, branch into smaller capillaries, which are near to the body cells. Oxygen leaves the blood and passes through the thin capillary walls to the lymph fluid and then enters the body cells. There, food is broken down in the presence of oxygen and water to release energy in the form of Adenosine triphosphate (ATP). This chemical process is accomplished in the mitochondria of the cells and is most often called the Kreb cycle or citric acid cycle.

One product of this process is carbon dioxide (CO2). CO2 is produced in the cell but a large amount is harmful to the cell if it remains. It must thus be expelled from the cells and into the capillaries at the same time that oxygen is entering the cell. As the blood makes its way back toward the heart in the venules and veins, it is full of waste gas CO2. In nature, plants are dependent on CO2, so it is not wasted. The circuit is completed when deoxygenated blood re-enters the heart from the vena cava. This circulation of blood from the body organs to the heart and back again is called systemic circulation.

Anatomy of the Heart

The heart weighs about one pound, and it is roughly the size of a doubled-up fist. It lies just behind the breastbone in the mediastinum area of the thoracic cavity. The heart consists of four chambers: two upper chambers called atria and two lower chambers called ventricles. It is actually a double phase pump bound into the heart muscle. The primary phase is the movement of blood from the heart to the lungs. This pump is called the sinoatrial node. The secondary phase is the movement of blood from the heart to the cells of the body. This pump is called the atrioventricular node.

Blood must pass through each chamber in a definite pattern. The primary phase station, sinoatrial node, is located high in the wall on the right side of the heart. When it is activated, the two top chambers (atrial) of the heart contract and send deoxygenated blood to the lungs where the blood picks up oxygen and releases carbon dioxide. The newly oxygenated blood returns to the left side of the heart. The secondary pump station, atrioventricular nodes, then activates and sends a contraction wave through the lower heart chambers that forces the oxygenated blood out of the aorta to the body. At the cellular level, the blood loses its oxygen and then returns via the veins and venules to the right side of heart, where the process is repeated over and over again as the primary and secondary stations continue to activate and contract in a normal rhythmatic process. In this process, deoxygenated blood is sent out to the lungs and oxygenated blood is sent to every single cell of the body over and over again.

Deoxygenated blood enters the heart through the two largest veins in the body, the vena cava. The superior vena cava drains blood from the superior portion of the body, and the inferior vena cava carries blood from the inferior parts of the body.

The vena cava brings deoxygenated blood into the right atrium, the upper right chamber of the heart. The right um contracts to force blood through the tricuspid valve into the right ventricle, which is the lower right chamber of the heart. The tricuspid valve allows for a one-way passage of the blood, so that the blood flows in only one direction. As the right ventricle contracts, it pumps deoxygenated blood out through the pulmonary valve into the pulmonary artery. The tricuspid valve stays closed preventing blood from moving back into the right atrium. The pulmonary artery then branches to carry deoxygenated blood to each lung.

The blood that enters the lung's capillary bed from the pulmonary artery will soon lose a large quantity of carbon dioxide into the lung tissue. Carbon dioxide is then expelled from the lungs during exhalation. Oxygen enters the capillaries of the lungs and is brought back to the heart by the pulmonary vein. There are several pulmonary veins that transport oxygen-rich blood back to the left side of the heart from the lungs. The newly oxygenated blood enters the left atrium of the heart from the pulmonary veins. The walls of the left atrium contract to force blood through the bicuspid valve into the left ventricle.

The left ventricle is much more muscular than the other chambers of the heart. It must pump blood with such force that the blood travels to the smallest of arteries in all parts of the body. As the blood leaves the left ventricle it is passed through the aortic valve and into the aorta, which will finally branch to carry blood to all parts of the body. There is, at this time, a great back washing of blood from the aorta. This forced back washing of blood is responsible for sending the richest oxygenated blood into the coronary arteries. The aortic valve prevents the back washed blood from returning to the left ventricle.The four chambers of the heart are separated by partitions called septa (singular: septum). The interatrial septum separates the two upper chambers (atria). The interventricular septum is a muscular wall that comes between the two lower chambers (ventricles).

The heart wall is composed of three layers. The endocardium is a smooth layer of endothelial cells that lines the inside of the heart and the heart valves. The pericardium is a fibrous and membranous sac that surrounds the heart. It has two layers, the visceral pericardium, which is attached to the heart, and the parietal (parietal means wall) pericardium, which lies next to the outer fibrous layer. The pericardial cavity (between the visceral and the parietal pericardium) usually contains 15 ml. of fluid. This fluid is responsible for the lubrication of the pericardium while the heart beats.

Physiology of the Heart: Heartbeat and Heart Sounds

The double pump system has a contraction and relaxation phase. The contraction phase is called systole. Systole occurs as the walls of the right and left ventricles contract to push blood out of the heart into the pulmonary artery and the aorta. Both the tricuspid and the mitral valves are closed during systole, thus preventing the back flow of blood

back into the atria. During systole, blood is forced from the heart into the aorta and pulmonary artery, then into the arteries, arterioles, capillaries, venules and veins.

The relaxation phase is called diastole. Diastole occurs when the ventricle walls relax after contraction and blood flows into the heart from the vena cava and the pulmonary veins. The tricuspid and bicuspid valves are open during diastole when blood enters the right and left atria. Some of the blood will flow naturally into the ventricles. The pulmonary and aortic valves are closed during diastole. This cardiac cycle occurs about 72 times per minute. The heart pumps about ½ cup of blood with each contraction. This means that about 6 quarts of blood are pumped by the heart in one minute, 80 gallons per hour, and more than 2000 gallons per 24 hour days.

The beat of the heart as felt through the walls of the arteries on the skin’s surface is called the pulse. The pulse is a wave of blood that travels within the arteries as the heart contracts in systole. The pulse is best felt at the wrist on the radius side or at the neck’s carotid artery just to the side of the larynx or the Adam's Apple.

The heart valves produce low audible sounds such as “lub, dub” that can be heard when listening to a normal heart through a stethoscope. The “lub” is the closure of the tricuspid and mitral valves at the beginning of systole and the “dub” is the closure of the aortic and pulmonary valves at the end of systole. The”lub” sound is called the first heart sound and the “dub” is the second heart sound because the normal cycle of the heartbeat starts with the beginning of systole. Abnormal heart sounds are known as heart murmurs. Murmurs have a “lub, dub, swish” sound or sometimes a “lub, swish, dub” sound. They are usually detected when getting a physical from a medical doctor.

Conduction System of the Heart

Although the heart does contain nerves that can affect its rate, they are not primarily responsible for its beat. It is known that the heart starts beating 12 days after fertilization in the embryo before the heart is supplied with nerves, and it will continue to beat even when the nerve supply is cut.Primary responsibility for initiating the heartbeat is a small area of specialized muscle- nerve tissue high in the posterior portion of the right atrium. This is where an electrical impulse originates. This region of the right atrium is called the sinoatrial node (SA node). The SA node is also called the pacemaker of the heart. The flow of electrical current generated by the pacemaker causes the walls of the atria to contract and force blood into the ventricles. The SA node is responsible for the primary pumping functions of the heart muscle.

Almost like ripples in a lake when a stone is thrown, the wave of electricity passes from the pacemaker to another region of the myocardium. This region is at the posterior portion of the interatrial septum and is called the atrioventricular node (AV node). The

AV node immediately sends the electrical wave to some specialized set of muscle-nerve fibers called the bundle of His (pronounced hiss). Within the interventricular septum, the bundle of His divides into right and left branches, which carry the impulse to the right and left ventricles, causes both to contract. Systole then occurs and the blood is pumped away from the heart.

The AV node is responsible for the secondary pumping functions of the heart muscle. Following these two pumping actions, a rest period will normally follow that lasts for about 0.6 seconds. After this rest period the pacemaker node begins the pumping process through the heart once again. The whole process from activation of the SA node to the rest period is normally about 0.8 seconds while in the resting stage. Of course the heart rate goes up according to the amount of activity placed on the body and heart.

The record of these electrical changes in the heart muscle as the heart contracts is called an electrocardiogram (EKG or ECG), from the Greek word root kardiu. The normal EKG shows five waves that represent the electrical changes as an electrical wave spreads across the heart. The waves are labeled P, QRS, and T. The F wave represents electrical activity of the SA node impulse formation and the change in the electrical activity in the wall of the atria, called atrial depolarization. The QRS wave is ventricular depolarization as electricity passes through the bundle of His and the ventricular wall. This is by far the largest wave because the right and left ventricles contain heavier muscular walls. The T wave represents ventricular depolarization as the ventricular wall relaxes and recovers from contraction. The EKG is used to diagnose a heart attack, which causes abnormal deflections.

Normal heart contraction is called sinus rhythm. Abnormal sinus rhythm is called arrhythmia. Sympathetic nerve activity speeds up the heart rate during conditions of stress or exercise. Parasympathetic nerve activity slows the heart rate when the need for faster pumping and more oxygen to the tissue is no longer needed.

Blood Pressure

Blood pressure is the force exerted on the walls of the arteries. This pressure is measured with a device called a sphygmomanometer. The sphygmomanometer consists of a hollow rubber sac covered with a cloth cuff that is wrapped around the upper arm just above the elbow and over the brachial artery. The rubber bag is inflated with air by means of a rubber bulb. As the bag is pumped up, the pressure within the sac increases and is measured on a pressure recording device attached to the cuff.

The air pressure in the bag compresses the arteries in the upper arm. When there is sufficient air in the bag to stop the flow of blood in the brachial artery of the arm, the person taking the blood pressure listens with a stethoscope as the pressure drops. At the point when the person listening with the stethoscope hears the first sounds of the pulse

beat, the reading on the device attached to the cuff shows the higher systolic blood pressure. As air continues to escape, the sounds become progressively louder. Finally, when a change in sound from loud to soft occurs, the observer makes note of the pressure on the recording device. This is called the diastolic blood pressure.

Blood pressure is expressed as a fraction: for example, 120mm/60 Hg. in which 120 represents the systolic pressure and 60, the diastolic pressure. Students of college age will have a lower diastolic pressure, usually around 60 mm/Hg, while older people will have a higher diastolic pressure, usually around 80 mm/Hg. The same is true for the systolic pressure, 120 mm/Hg for college age persons and 130 mm/Hg for people in their 40's.

Hypertension or high blood pressure usually occurs when the Systolic is greater than 140 and the Diastolic is greater than 90. There are several medications available to lower the blood pressure in hypertensive patients. Some of these medications work by affecting the nephron to release more water, called diuretics, and others work by changing the blood vessel resistance, called beta blockers.

INFORMATION ON BLOOD

Introduction

The major function of blood is to maintain a state of homeostasis for the other living cells of the body. Blood is the system responsible to transport foods, gases, and wastes throughout the body. Food that is digested in the stomach and intestine moves into the bloodstream through the cells of the intestine and is carried by the blood to all parts of the body’s cells. Oxygen enters the body through the alveoli of the lungs and is transported by the blood to cells throughout the body. Cells and travel through the blood to the lungs where carbon dioxide is expelled and to the kidneys release gaseous waste, such as carbon dioxide, and solid wastes, such as urea, uric acid, and creatin, where nitrogen wastes and electrolytes are excreted in the urine.

The blood from their secretion sites in the glands, such as the adrenal or pituitary glands, to sites where they act to regulate growth, reproduction, and energy regulation, transports chemical messengers called hormones.

Blood contains proteins and white blood cells that help fight infections and thrombocytes that help the blood to clot when one suffers an injury.

Composition and Formation of Blood

Blood is composed of cells and chemical compounds suspended in a clear, white-colored liquid called plasma. The cells include red blood cells, white blood cells, and

thrombocytes, which constitute of about 45 percent of the total blood volume. The remaining 55 percent of blood is plasma, a solution of water, proteins, sugars, electrolytes, hormones, and vitamins.

Cells

Most blood cells are formed in the bone marrow. Both the red blood cells that carry oxygen and the white blood cells that fight infection arise from the same immature cells called stem cells or hematocytoblasts. Under the influence of proteins found in the bloodstream and bone marrow, the primitive hematocytoblasts change their size and shape and assume a different form. This process causes the cells to change in size from large immature cells to small immature cells where the cell nucleus either shrinks or disappears.

Erythrocytes

As a red blood cell matures from the primitive hematocytoblast to the functioning erythrocyte, its nucleus is removed and the cell takes on a disk shape. This shape allows the large surface area on the erythrocyte to absorb and release gases such as oxygen and carbon dioxide. Red blood cells contain the protein hemoglobin, which consists of an iron-containing pigment called heme and a protein part called globin. Hemoglobin on the erythrocyte enables the cell to attach oxygen to its surface. The combination of oxygen and hemoglobin, called oxyhemoglobin, produces the bright red color of oxygenated blood.

Erythrocyte production begins in the bone marrow and is stimulated by a hormone called erythropoietin. Erythropoietin is manufactured and secreted by the kidney. Erythrocytes live in the circulating bloodstream for about 120 days. The worn out red blood cells are destroyed by specialized cells called macrophages. Macrophages are manufactured in the spleen, liver, and bone marrow. Macrophages break the hemoglobin down into the heme and protein portions. The heme releases iron and decomposes into a dark green pigment called bilirubin. The iron in hemoglobin is used to form new red cells or may be stored in the spleen, liver, or bone marrow. Bilirubin is excreted with the bile from the liver. The bile enters the small intestine where it can be excreted with the stools. It makes a dark brown color stool. Millions of red blood cells are being destroyed daily, but because they are being replaced constantly, the number of circulating red blood cells remains constant at about 4-6 million per cubic/mm.

Leukocytes

White blood cells, 7000-9000 cells per cubic/mm, are less numerous than erythrocytes but there are five different types of mature leukocytes. These are the following:

1. Polymorphonuclear leukocytes, also known as granulocytes, are the most numerous leukocytes, about 60 percent.

1. Basophils contain dark-staining cytoplasmic granules that stain with a basic pH dye. The granules contain heparin, an anti-clotting substance, and a histamine, a chemical that is released in allergic responses.

3. Eosinophils contain granules that stain with a red acidic pH dye called eosin. These granulocytes increase in numbers in allergic responses and are thought to engulf substances that trigger the allergies.

4. Neutrophils contain granules that are neutral; that is, they do not stain intensely with either dye.

5. Neutrophils are phagocytes that accumulate at sites of infection where they ingest and destroy bacteria.

Granulocytes and their precursor cells are considered part of the myeioid type of cells. Their growth and proliferation in the bone marrow are stimulated by specific proteins called colony-stimulating factors (CSFs). Granulocyte-CSF, Granulocyte macrophage CSF, interleukin-1, and interleukin-3 have been produced commercially and are administered to promote tumor fighting medicines, chemotherapy, in cancer patients.

All granulocytes are polymorphonuclear, which means they have multiple or many nuclei. The term polymorphonuclear leukocyte is used most often to describe the neutrophil, which is the most numerous of the granulocytes.

Agranulocytes are mononuclear leukocytes that do not have the dark-staining granules in their cytoplasm. These are the lymphocytes and monocytes. Lymphocytes arise in lymph nodes and circulate both in the bloodstream and the lymphatic system.

Lymphocytes play a very important role in the immune response to protect the body against invading pathogens or other antigens. They are able to directly attack antigen matter as well as make antibodies which neutralize and destroy antigens, such as bacteria and viruses. Monocytes are phagocytic cells that fight pathogens. They move from the bloodstream into tissues and dispose of dead and dying cells and other damaged tissue. Once they move into the tissues they are called macrophages. The process of removing these types of cells and tissue is called phagocytosis.

Platelets

Thrombocytes are formed in the red bone marrow from very large multi-nucleated cells known as megakaryocytes. Small sections of the megakaryocyte break off from the cell to form platelets. The main function of platelets is to help in blood clotting.

When arteries become damaged by atherosclerosis and arteriosclerosis, platelets can form and attach to the inside of arteries leading to a blockage. Aspirin and some other chemicals reduce this process of platelet coagulation and therefore, are used to help prevent heart attacks caused by blood clotting.

Plasma

Plasma is the liquid portion of the blood. It consists of water, proteins, sugar, wastes, salts, hormones, and other substances. The four major plasma proteins are albumin, globulin, fibrinogen, and prothrombin; the last two are clotting proteins.

Albumin maintains the proper amounts of water in the blood. It cannot pass easily through capillary walls so must remain in the blood. Albumin carries other smaller molecules on its surface. It attracts water from the tissues back into the bloodstream, which has the affect of opposing the normal characteristic of water to leave the blood and leak out into tissue spaces. The leaking of fluid into the tissue spaces is called edema or tissue swelling. When albumin escapes from the capillaries as a result of injury to the tissues, such as in third degree burns, water cannot be held in the blood and the blood volume drops. Volemic shock will result if the loss of water is too much.

The globulin portion of plasma contains antibodies, which are a part of the body’s immune system. These destroy foreign substances called antigens. There are three different types of globulins in plasma. They are called alpha, beta, and gamma, and are separated by the electrophoresis process. Placing the plasma in a special solution and then passing an electric current through it do this process. The different protein molecules in the plasma separate out and migrate at different times to the source of the electricity where they are collected.

Immunoglobulins are a specific type of chemical structure of gamma globulin. They are capable of acting as antibodies. Examples of immunoglobulin antibodies are IgG, which are found in high concentration in the plasma, and IgA, which are found in breast milk, saliva, tears, and respiratory mucus. There are other immunoglobulins, but they are not described here. These are IgM, IgD, and IgE.

Plasmapheresis (-apheresis means to remove) is the process of separating plasma from the formed elements in the blood. This separation is mechanical, not electrical, as is

electrophoresis. In plasmapheresis, the entire blood sample is spun in a centrifuge machine, and the lighter particles like plasma, being lighter, settle on the top of the sample.

Blood Groups

Transfusions are used to replace “whole blood” cells and plasma during surgery, or during other extreme medical states. If a patient is anemic and needs only red blood cells, a transfusion of packed red cells, which is whole blood with most of the plasma removed, is given. Transfusion cannot be made between any two people at random because of blood incompatibilities. Human blood falls into four main groups called A, B, AB, and O, and are harmful when transfusing blood from a donor of one blood group into a recipient who has blood of another blood group.

Each of the blood groups has a specific combination of factors, antigens and antibodies that are inherited from their parents. The antigen and antibody factors of the four main blood types are:

1. Type A, containing A antigen and anti-B antibody2. Type B, containing B antigen and anti-A antibody3. Type AB, containing A and B antigens and no anti-A and anti-B antibodies4. Type O, containing no A or B antigens and both anti-A and anti-B antibodies

The problem in transfusing blood from a type A donor into a type B recipient is that A antigens will react adversely with the anti-A antibodies in the recipient’s type B bloodstream. The adverse reaction is called agglutination, or clumping of the recipient’s blood. The agglutination is often fatal to the recipient because it clogs the flow of blood. Similar problems can occur in other transfusions if the donor’s antigens are incompatible with the recipient’s antibodies.

People with type O blood are known as universal donors because their blood contains neither A nor B antigens. The anti-A and anti-B antibodies in O blood do not have an effect in the recipient because the antibodies are diluted in the recipient’s bloodstream. Those with type AB blood are known as universal recipients because their blood contains neither anti-A nor anti-B antibodies, so that neither the A nor the B group antigens will cause agglutination in their blood.

Besides A and B antigens, there are many other antigens situated on the surface of red blood cells. One of these is called the Rh factor, named because it was first found in the blood of the rhesus monkey. The term Rh-positive refers to a person who is born with the Rh antigen on his or her red blood cells. An Rh-negative person does not have the Rh antigen. There are no anti-Rh antibodies normally present in the blood of an Rh-positive or an Rh-negative person. When Rh-positive blood is transfused into an Rh-negative

person, the recipient will start to develop antibodies that would agglutinate any Rh-positive blood if another transfusion were to occur later. The similar reactions occur during pregnancy if the fetus of an Rh-negative woman happens to be Rh-positive. A medicine known as RhoGAM is given to prevent this after the mother has delivered the baby.

Blood Clotting

Blood clotting is a complicated process involving many different substances and chained-chemical reactions. The final result is the formation of a fibrin clot from the plasma protein fibrinogen. This usually takes about 5 to 15 minutes. Platelets are the most important factor in the beginning of this process following an injury to tissues. The platelets clump at the site of injury releasing a protein called thromboplastin, which, in combination with calcium and the release of other clotting factors, promotes the formation of a fibrin clot. Hemophilia is where the person is missing one of these specific protein clotting factors.

After the fibrin forms the clot and the blood cells become trapped in the injury, the clot will retract into a tight ball leaving behind a clear fluid called serum. Clots normally do not form in blood vessels unless the vessel is damaged. Anticoagulant substances in the bloodstream inhibit blood clotting so thrombi and emboli do not form. Heparin, produced by tissue cells, especially liver cells, is one of the main anticoagulants. Other drugs may be given to patients with thromboembolic diseases to prevent the formation of clots. This is common in patients who have had previous heart attacks associated with the formation of blood clots.

THE LYMPHATIC SYSTEM

Introduction

Lymph is a clear, watery fluid that surrounds body cells and flows through the body in a system of lymph vessels. Over fifty percent of the body’s mass is made up of fluids under normal conditions. The fluids of the body are responsible for the transportation of many different chemicals and structures to the cells and the removal of wastes. The most important body fluid is blood. Blood is composed of a liquid portion called plasma and several different solid parts. Hematology is the study of blood and its forming tissues. The blood forming tissues are the bone marrow and lymphoid tissues, which are composed of lymph nodes, spleen, and tonsils.

Lymph is very different than blood, but it is a part of the body’s vascular system. Lymph fluid does not contain erythrocytes or platelets but does contain two types of white blood cells, lymphocytes and monocytes. The liquid part of lymph-like blood plasma contains water, salts, sugar, and wastes of metabolism such as urea and creatinine, but it differs in

that it contains less protein. Lymph actually originates from the blood as fluid filters out of small blood vessels into the interstitial spaces between cells. The fluid that surrounds the cells of the body is then called interstitial fluid. Interstitial fluid passes continuously into vessels called lymph capillaries, which are located throughout the interstitial tissue spaces. The fluid inside the lymph capillaries is called lymph. It passes through larger lymphatic vessels and finally reaches the large lymph vessels of the upper chest and neck, where it finally enters the large blood vessels of the neck and the upper chest.

There are several functions of the lymphatic system. One function is to act as a drainage system to transport needed proteins and fluid that have leaked out of the blood capillaries into the interstitial fluid and then back to the bloodstream by way of the veins. The lymphatic vessels in the intestines absorb lipids (fats) from the small intestine and transport them to the bloodstream. This is done so as not to overload the arteries with large fat molecules, which may lead to the clogging of the arteries or its small branches.

Another function of the lymphatic system is related to the immune system. White blood cells originating in lymph nodes and organs such as the spleen and thymus gland, protect the body by producing antibodies and by eliminating pathogens either by phagocytosis or one of the other methods used to protect the body against invading antigens.

Anatomy

Lymph capillaries begin at the interstitial spaces around cells throughout the body. They are thin-walled tubes and carry lymph from the tissue’s interstitial spaces to larger lymph vessels. Lymph vessels have thicker walls than those of lymph capillaries. They contain valves so that lymph flows only in one direction, toward the chest and neck. Collections of stationary lymph tissue called lymph nodes are located along the path of the lymph vessels. A fibrous connective tissue capsule surrounds the lymph tissue.

The function of lymph nodes is to produce lymph cells and filter lymph and trap substances from inflammatory and cancerous lesions. Special cells, called macrophages, are located in the lymph node, as well as in the spleen, liver, lungs, brain, and spinal cord. Lymph nodes engulf and destroy foreign substances. When bacteria are present in lymph nodes they become swollen and tender. Lymph nodes fight disease with lymphocytes that produce antibodies. These are located in the cervical, axillary (armpit), mediastinal and inguinal (groin) regions of the body. The tonsils are lymph tissue in the throat, and the adenoids are enlarged lymph tissue in the part of the throat near the nasal passages.

Lymph vessels all lead toward the chest and empty into two large ducts in the upper chest. These are called the right lymphatic duct and the thoracic duct. The thoracic duct drains the lower body and left chest. The right lymphatic duct drains the right chest. Both of these ducts drain the lymph into the large veins of the neck.

Spleen and Thymus Gland

The spleen and the thymus gland are organs composed of lymph tissue. The spleen is located in the left upper quadrant of the abdomen, adjacent to the stomach. Although the spleen is not essential to life, it has several important functions:

Destruction of old erythrocytes by macrophages. Because of hemolytic activity in the spleen, bilirubin is formed there and added to the bloodstream.

Filtration of microorganisms and other foreign material from the blood.

Activation of lymphocytes as it filters out antigens from the blood.

Activated lymphocytes produce antibodies and engulf the antigens.

Storage of blood, especially platelets.

The spleen is an organ that is easily and frequently injured. A sharp blow or injury to the upper abdomen, most common in the impact of a car’s steering wheel against the abdomen, may cause rupture of the spleen. Massive hemorrhage usually occurs when the spleen is ruptured. Immediate surgical removal is generally required. After a splenectomy, the liver, bone marrow, and lymph nodes will take over the functions of the spleen.

The thymus gland is a lymphatic organ located in the upper chest’s mediastinum, which is located between the lungs. In the fetus and during childhood, it is large but it becomes smaller in adults. The thymus gland plays an important role in the body’s ability to protect itself from disease, especially in the fetus and the early years of life. It is known that a thymectomy, performed in an animal during the first weeks of life, impairs its ability to make antibodies and to produce immune cells that fight against foreign antigens such as bacteria and viruses.

IMMUNE SYSTEM

The immune system is the body’s special defense response against foreign organisms. This system includes the lymph nodes, spleen, and thymus gland and their products.

Immunity is the capacity to resist all types of organisms and toxins. Natural immunity is one’s own ability to fight off disease. When bacteria enter the body, natural immunity protects the body against infection by ingesting the bacteria. They may release proteins that attract other immune cells and cause local heat and inflammation. Macrophages will then move in to clear away the dead cells and debris as the inflammation subsides.

Besides having natural immunity, a person may acquire immunity through active or passive means. Acquired immunity is important for protection against invading organisms that the body does not have a natural immunity against. The body develops powerful specific immunity or antibodies against invading agents such as pathogenic bacteria, viruses, toxins, and even foreign tissues from other organisms. Acquired active immunity occurs in two ways; first, by having the disease, or second, by receiving a vaccine containing a dead or weakened pathogen or its toxins, which stimulate the production of antibodies. Once the antibodies are formed, they stay active for the rest of the person’s life.

Sometimes, like in the exposure to the AIDS virus, it is necessary to provide an immediate protection against getting the disease. This is called acquired passive immunity. In these cases, injections of gamma globin, containing antibodies, give protection against disease or lessen its severity. In some patients, they may receive immune serum containing antibodies produced in another animal, such as antitoxins for a poisonous snakebite or tetanus and diphtheria injections.

Acquired active immunity has two major disease fighters-- B cell lymphocytes (humoral immunity), and T cell lymphocytes (cell-mediated immunity). Humoral immunity originates from bone marrow stem cells and migrates to lymph nodes and other lymphoid tissue. When a B cell meets up with a specific type of antigen, it transforms into an antibody-producing cell called a plasma cell. The antibodies that are made by plasma cells are immunoglobulins such as IgM, IgG, IgD, IgE, and IgA. Immunoglobulins travel to the site of the infection to react with and neutralize the invading antigens.

Cell-mediated immunity originates in the stem cells of the bone marrow and are processed in the thymus gland where they are acted upon by thymic hormones. Then they migrate to lymph nodes and lymphoid organs. When antigens encounter a T cell, the T cell multiplies quickly and engulfs and digests the antigen, bacterium, virus, cancer cell, fungus or other foreign matter with a DNA molecule in their structure. T cells react to foreign tissues such as skin graphs and transplanted organs.

Some T cells are killer cells (or cytotoxic) whereas other T cells produce chemicals, interferons and interleukins that destroy cells or bacteria. One type of T cell, called helper cells, stimulates antibody production. T cells are attacked by the human immunodeficiency virus in AIDS. Another type of T cell, suppressor cells, regulates the amount of antibody produced by inhibiting the activity of the B cell lymphocytes.

LESSON 6 GRAPHICS

TERMS FOR LESSON 6: CARDIOVASCULAR AND LYMPH SYSTEMS

Terms to Know

hearttricuspid valvebicuspid valvesemilunar valvespericardiumepicardiumparietalmyocardiumendocardiumarteriesarteriolesaortaveinsvenulesvena cavacapillariespre-capillary sphincterpost-capillary sphincterplasmaerythrocytesleukocytesplateletslymphlymph nodesspleenthymus gland

Word Roots to Know - Cardiovascular/Lymphaticangi/oaort/o

arteri/oatri/ocardi/ocoron/olymph/ophleb/osplen/othym/ovalv/ovalvul/oventricul/oather/oech/oelectr/oisch/osphygm/osteth/otherm/othromb/oaer/ochlor/ochrom/ocoagul/ocyte/oerythr/ofibrin/ohem/ohemat/oglobin/ohydr/ois/okary/oleuk/o

lys/omacr/omegal/o

Prefixes to Know - Cardiovascular/Lymphaticbrady-tachy-mal-megal-anti-poly-hyper-hypo-trans-

Suffixes to Know - Cardiovascular/Lymphatic-ac-centesis-crit-gram-graph-meter-poiesis-sclerosis-odynia-cyte-emia-lysin-lysis-lytic-oid-ous-penia

-scope-y

Diagnostic Terms to Know: Cardiovascular/Lymphaticangiocarditisangiomaangiostenosisaortic stenosisarteriorrhexisarteriosclerosisarteriolosclerosisatherosclerosisatrioventricular defectbradycardiacardiodyniacardiomegalycardiovalvulitiscoronary ischemiacoronary thrombosisendocarditismyocarditispericarditistachycardiahematocytopeniahematomalymphadenitissplenomegalythymomaanemiaaneurysmangina pectorisarrhythmiacardiac arrest

coarctation of the aortacongenital heart diseasecongestive heart failurecoronary occlusionembolusembolifibrillationhemophiliahemorrhoidHodgkin’s diseasehypertensionleukemiamyocardial infarctionthromboangiitis obliteransvaricose veins

Surgical Terms to Know: Cardiovascular/Lymphaticangioplastyangiorrhaphyendarterectomypericardiostomyphlebotomysplenectomysplenopexythymectomyaneurysmectomycardiac pacemakercoronary artery bypasshemorrhoidectomyvein ligation

Diagnostic Procedural Terms to Know: Cardiovascular/Lymphaticangiographyaortogramarteriogramechocardiogramelectrocardiographyphonocardiogramsphygmocardiographstethoscopevenogramerythrocyte counthematocritleukocyte countlymphadenographylymphangiogramlymphangiographycardiac catheterizationcardiac scanDoppler flow studiessphygmomanometertreadmill stress testhemoglobinprothrombin time

Additional Terms to Know: Cardiovascular/Lymphaticcardiaccardiologistcardiologyhematologisthematologyhematopoiesishemolysishemostasis

hypothermiamalignant hypothermiaauscultationblood pressurecardiopulmonary resuscitationdefibrillationdiastolehypotensionlumenoccludepercussionperipheral vascularsystolevasoconstrictorvasodilatorvenipunctureanticoagulantdyscrasiahemorrhagemanometerplasmaserum

PRACTICE EXERCISES FOR LESSON 6CARDIOVASCULAR & LYMPHATIC SYSTEMS

DEFINE:cardi/oatri/oplasm/oangi/ocoron/oaort/ovalv/o

splen/othym/ophleb/oventricul/oarteri/ovalvul/olymph/oech/osteth/othromb/oisch/otherm/osphygm/oather/oelectr/o

DEFINE PREFIXES AND SUFFIXES:brady-tachy--crit-graphy-penia-sclerosis-odynia-poriesis-poiesis-poietin-poietic-ac-centesis

DEFINE:endocarditisbradycardiacardiomegalyarteriosclerosiscardiovalvulitisangiocarditisarteriorrhexistachycardiaangiostenosisatrioventricular defectcoronary ischemiapericarditisaortic stenosiscoronary thrombosisatherosclerosismyocarditisangiomahematocytopeniaerythrocytopeniahematocytopoiesiserythrocytopoiesis

DEFINE:pericardiostomythymectomyangioplastysplenopexyangiorrhaphyendarterectomyphlebotomysplenectomyphlebectomy

electrocardiogramsphygmocardiographvenogramangiographyechocardiogramstethoscopeaortogramelectrocardiogram (EKG, EGG)phonocardiogramarteriogramelectrocardiographyerythrocyte countlymphangiogramhematocritlymphadenographyleukocyte countlymphangiographyhypothermiahematopoiesishematologyhemostasisdefibrillationvenipuncturevasodilator

ASSIGNMENT FOR LESSON 6Medical Terminology, HS 280

Cardiovascular and Lymphatic Systems

MATCHING:1 aorta a white blood cell---- 2 artery b between left atrium and left ventricle---- 3 arterioles c last valve in heart flow---- 4 atria d inner lining of heart---- 5 bicuspid valve e move blood toward body---- 6 blood f smallest blood vessels---- 7 capillaries g red blood cell---- 8 endocardium h main and largest vessel of body---- 9 tricuspid valve i connect arteries and capillaries---- 10 erythrocyte j carries blood to heart muscle---- 11 aortic valve k composed of plasma and cells---- 12 leukocyte l upper chamber of the heart---- 13 lymph m second node---- 14 coronary artery n colorless tissue fluid---- 15 AV node o pacemaker---- 16 SA node p 1st valve of heart blood flow

MATCHING:---- 17 angi/o a atrium---- 18 atri/o b vein---- 19 cardi/o c spleen---- 20 phleb/o d thymus gland---- 21 splen/o e vessel---- 22 thym/o f ventricle---- 23 ventricul/o g heart---- 24 ather/o h electrical---- 25 ech/o i yellow, fatty plague---- 26 electr/o j sound---- 27 isch/o k deficiency, blockage---- 28 sphygm/o l clot---- 29 steth/o m pulse---- 30 therm/o n chest---- 31 thromb/o o heat---- 32 odynia p abnormal reduction---- 33 penia q formation---- 34 poiesis r hardening---- 35 sclerosis s pain

Assignment for Lesson 6, Cardiovascular/Lymph, pg. 2

DEFINE:

36 angiostenosis

37 pericarditis

38 hematoma

39 lymphoma

40 anemia

41 arrhythmia

42 congestive heart failure

43 hemorrhoid

44 leukemia

45 angioplasty

46 phlebectomy

47 aneurysmectomy

48 coronary artery bypass

49 EKG or EGG

50 hematocrit

51 diasytolic

52 sytolic

53 hematopoietin

54 hematopoiesis

55 erythropoietin

56 erythropoiesis