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If no activated Tcells are present cheap kamagra gold 100mg otc, re-activation within the local lymph nodes must first take place cheap kamagra gold 100 mg on line, and hence migration into the dermis will require more time discount 100mg kamagra gold with mastercard. By this time the small amount of introduced diagnostic peptide, or protein, will have been digested or will have decayed and thus will no longer be present at the injection site in the quantity required for induction of a local reaction. A positive delayed hypersensitivity reaction is, therefore, an indicator of the pre- sence of activated T cells. The absence of a reaction indicates either that the host had never been in contact with the antigen, or that the host no longer pos- sesses activated Tcells. In the case of tuberculosis, a negative skin test can indicate that; no more antigen or granuloma tissue is present, or that the systemic immune response is massive and the pathogen is spread throughout the body. In the latter case, the amount of diagnostic protein used is normally insufficient for the attrac- tion of responsive T cells to the site of injection, and as a consequence no measur- able reaction becomes evident (so that the Mantoux test may be negative in Land- ouzy sepsis or miliary tuberculosis). Control of cytopathic viruses requires so- luble factors (antibodies, cytokines), whilst control of noncytopathic viruses Kayser, Medical Microbiology © 2005 Thieme All rights reserved. Usage subject to terms and conditions of license 100 2 Basic Principles of Immunology and tumors is more likely to be mediated via perforins and cytolysis. How- ever, cytotoxic immune responses can also cause disease, especially during noncytopathic infections. Development of an evolutionary balance between infectious agents and immune responses is an ongoing process, as reflected by the numerous mechanisms employed by pathogens and tumors to evade 2 immune-mediated defenses. Natural humoral mechanisms (antibodies, comple- ment, and cytokines) and cellular mechanisms (phagocytes, natural killer cells, T cells) are deployed by the immune system in different relative amounts, during different phases of infection, and in varying combinations. Gross simplifications are not very helpful in the immunological field, but a small number of tenable rules can be defined based on certain model in- fections. Such models are mainly based on experiments carried out in mice, or on clinical experience with immunodeficient patients (Fig. General Rules Applying to Infection Defenses & Non-specific defenses are very important (e. Antibodies are also likely to make a major contribution to the host-parasite balance occur- ring during chronic parasitic infections. Usage subject to terms and conditions of license Immune Defenses against Infection and Tumor Immunity 101 General Schemes of Infectious Diseases 2 Fig. Infection by cytopathic pathogens can only be controlled if pathogenic proliferation is slow and the pathogen remains localized; otherwise the outcome is usually fatal. In the case of noncytopathic pathogens, the cytotoxic T-cell response is the critical parameter. The T-cell response can be halted by pathogens which proliferate rapidly and spread widely due to the deletion of responding Tcells. For pathogens which exhibit moderate rates of proliferation and spread, the T-cell response may cause extensive immunopathological damage, and thus reduce the proportion of surviving hosts, some of which will controll virus, some not. A weakened immune defense system may not progress beyond an unfavorable virus-host balance, even when confronted with a static or slowly replicating patho- gen which represents an initially favorable balance. Although de- tails of the process are still sketchy, IgE-dependent basophil and eosinophil defense mechanisms have been described for model schistosomal infections. Usage subject to terms and conditions of license 102 2 Basic Principles of Immunology & Avoidance strategies. Infectious agents have developed a variety of stra- tegies by which they can sometimes succeed in circumventing or escaping immune responses, often by inhibiting cytokine action. Short-lived IgM responses can control bacteria in the blood effectively, but are usually insufficient in the controlof toxins. In such cases, immunoglobulinsof the IgGclass are more efficient, as a result of their longer half-life and greater facility for diffusing into tissues. Avoidance Mechanisms of Pathogens (with examples) Influence on the complement system. Some pathogens prevent complement fac- tors from binding to their surfaces: & Prevention of C4b binding; herpes virus, smallpox virus. Viruses can avoid confrontation with the immune defenses by restricting their location to peripheral cells and or- gans located outside of lymphoid tissues: & Papilloma viruses; infect keratinocytes. Infection agents can avoid immune defenses by mutating or reducing their expression of T- or B-cell epitopes. Usage subject to terms and conditions of license Immune Defenses against Infection and Tumor Immunity 103 Continued: Avoidance Mechanisms of Pathogens (with examples) Influence on lymphocytes and immunosuppression. Immune Protection and Immunopathology Whether the consequences of an immune response are protective or harmful depends on the balance between infectious spread and the strength of the ensuing immune response. As for most biological systems, the immune de- fense system is optimized to succeed in 50–90% of cases, not for 100% of cases. For example, immune destruction of virus-infested host cells during the eclipse phase of a virus infection represents a potent means of preventing virus replication (Fig. If a noncytopathic virus is not brought under im- mediate control, the primary illness is not severe—however, the delayed cy- totoxic response may then lead to the destruction of very large numbers of infected host cells and thus exacerbate disease (Tables 2. Since an infection with noncytopathic viruses is not in itself life-threatening to the Kayser, Medical Microbiology © 2005 Thieme All rights reserved. Usage subject to terms and conditions of license 104 2 Basic Principles of Immunology Table 2. Auto- “Healthy” or unknown infections, immunity occult carrier viruses, bacteria, (although infec- and endogenous tious agent is retroviruses unknown) Clinical None Chronic Variable disease symptoms disease symptoms, some- times delayed or asymptomatic Kayser, Medical Microbiology © 2005 Thieme All rights reserved. Usage subject to terms and conditions of license Immune Defenses against Infection and Tumor Immunity 105 Table 2. A similar situation is also observed for the cellular immune response against facultative intracellular tuberculosis and leprosy bacilli which themselves have relatively low levels of pathogenicity (Table 2. A healthy immune system will normally bring such infectious agents under control efficiently, and the immunological cell and tissue damage (which oc- curs in parallel with the elimination of the pathogen) will be minimal, en- suring that there is little by wayof pathological or clinical consequence. How- ever, should the immune system allow these agents to spread further, the result will be a chronic immunopathological response and resultant tissue destruction—as seen during hepatitis B as chronic or acute aggressive hepatitis and in leprosy as the tuberculoid form. Should a rapidly spreading infection result in exhaustion of the T cell response, or should an insufficient level of immunity be generated, the infected host will become a carrier. This carrier state, which only occurs during infections characterized by an absent or low- level of cytopathology, is convincingly demonstrated in hepatitis B carriers and sufferers of lepromatous leprosy. Because the im- muneresponse also acts toinhibit virus proliferation, the process of cellulardestruc- tion is generally a gradual process. Paradoxically, the process of immunological cell destruction would helpthevirus survivefor longer periodsin the host and hence facilitate its transmission. From the point of view of the virus this would be an as- tounding, and highly advantageous, strategy—butone with tragic consequences for the host following, in most cases, a lengthy illness. Influence of Prophylactic Immunization on the Immune Defenses Vaccines provide protection from diseases, but in most cases cannot entirely prevent re-infection. Vaccination normally results in a limited infection by an attenuated pathogen, orinduces immunity through the useofkilled patho- gens or toxoids. The former type of vaccine produces a very mild infection or illness capable of inducing an immune response and which subsequently protects the host against re-infection. The successful eradication of smallpox in the seventies so far represents the greatest success story in the history of vaccination. The fact is that vaccinations never offer absolute security, but instead improve the chances of survival by a factor of 100 to 10 000. A special situation applies to infections with noncytopathic agents in which disease results from the immune response itself (see above). Under certain circum- stances, and in a small number of vaccinated persons, the vaccination pro- cedure may therefore shift the balance between immune defense and infec- tion towards an unfavorable outcome, such that the vaccination will actually strengthen the disease. Rare examples of this phenomenon may include the Kayser, Medical Microbiology © 2005 Thieme All rights reserved. Generally, it should be kept in mind that most of the successful immunization programs developed to datehavemediated protectionvia antibodies. This par- 2 ticularly applies to the classic protective vaccines listed inTable 1. This ex- plains why successful vaccines all protect via neutralizing antibodies, because this pathway has been selected by co-evolution. As mentioned earlier, with regard to immunological memory, memory T cells appear to be essential to host immune protection, particularly in those situations when antigen per- sistence is controlled efficiently by means of infection-immunity (e. Tumor Immunity Our knowledge concerning the immune control of tumors is still modest. However this is apparently not sufficient for induction of an efficient immune defense. There is also the problem of tumor diagnosis; the presence of tumors is sometimes confirmed using a functional or immunological basis, yet the tumor cannot be located because conventional examinations are often unable to discover them until they reach a size of about 109 cells (i.

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A series of four sections and associated exercises outline how you can become aware of your breath and use it to control your stress buy kamagra gold 100 mg low cost. Each section and its accompanying exercises purchase kamagra gold 100mg with mastercard, builds on the section before discount kamagra gold 100mg, so please be patient and do each section’s exercises before moving on. Step 1: Awareness In this first step, all that’s really involved is bringing your awareness to your breath. Having an awareness of your breath and an acceptance of how it is without trying to change it is a perfect example of mindfulness in action. When you stop breathing in between your exhalation and inhalation that’s okay too. Now that you have some idea of what you’ll be observing as you notice your own breathing patterns, set your timer for two H minutes, close your eyes, be aware of your breath and come back to the book when you’re done. The next interesting aspect of breathing that you’ll notice is what happens to the nature, rhythm, and ease of the breath as you continue to observe it. You will find that, as you bring the practice of mindfulness to your breath, it does change, just because it knows you’re watching it. Simply bringing your attention to your breath will usually change the nature and rhythm of your breathing without you having to do anything else. If you have a calmer breathing pattern, you’ll have a more relaxed mind, which is less likely to overreact to whatever is going on around you. Bringing your awareness to your breathing can also give you a clue as to what sort of mental or physical state you may be in. Breath-awareness also has the added advantage of putting you in touch with the present moment. This can give you a break from all the worrying that your mind likes to do about your memories of the past and your fantasies of the future. You’re less likely to get caught up in all the endless thinking and worrying if your attention is exclusively on your breathing. You’ll find that it can sometimes be difficult for you to completely surrender to the movement of the breath without trying to control it. You can experience this sense of surrender if you take a deep breath in and then emphasize breathing out until there is no more breath left. Then you would rest in the prolonged pause between the exhalation and inhalation until your body automatically wanted to start breathing again. You’re still simply observing your experience of the automatic movements of breathing. Any moment, any second, that you do pay attention to your breath, you’re taking a huge step toward dealing with stress. The most important point is to remember to be aware of your breath as often as you can. Mindfulness and the Breath • 59 The following are helpful exercises that you can do over the next week to develop your breath-awareness. For approximately ten minutes in the morning and/or ten minutes in the evening, sit in a chair, relax and observe your breath with your eyes closed. Initially count your breaths, as counting can help you to remain focused on your breathing. This way you won’t become distracted as you focus on how much time you have been practicing, and it can help prolong your practice should you become restless or bored before your scheduled time is up. Throughout the day, use normal daily activities or times to remind you to bring your awareness to your breath. For example, pay attention to your breathing before each meal, whenever you hang up the phone, before you go for a walk, when you’re stopped at a red light, whenever you get on the bus or train, during television commercials, or even after a visit to the washroom. It’s all up to you to think of what events in your day you can use to remind yourself to spend a few moments focusing on your breathing. You can put Post-it notes in different locations around your house, or place of work, that perhaps simply say “breathe,” as a reminder to yourself to do a little breath watching. Another helpful trick is to set the alarm on your watch or cell phone for every two to three hours to remind you to bring your attention to your breath. Try to follow your breathing for a minimum of five breaths when you see one of your reminders. Step 2: Breathe Calmly In the last section, you observed that, as your breathing became smoother, deeper and more even, you felt more relaxed. When you get upset, your breathing becomes irregular and shallow and you may even hold your breath. However, you can consciously control your breathing so as to duplicate the type of breathing that will bring about a state of calmness. Instead of just observing your breathing, you’re going to try to gently change it and make it calmer. Consciously deepening your breathing will make use of your entire lung area, keep your chest muscles active, reduce stale, trapped air in the lungs and allow you to inhale more fresh air. You’re going to be practicing breath exercises that will start to re-train your body to breathe healthier. You may need to keep your mouth closed in order to re-route your breath through your nose. They are also a wonderful point to mentally focus on, as you follow the movement of your breath in and out of your body. If you’re bent over, it will be more difficult to have an even, deep, full breath. A bent body position can crowd your lungs, so try to make sure your back is relatively straight but still relaxed. Now that you have a better idea of how to consciously breathe calmly, set your timer for two minutes, close your eyes, and H give it a try. As your breathing became calmer did you notice that you were mentally, emotionally and physically beginning to relax? The following are exercises that you can do to further develop the practice of breathing in a calm and smooth manner: 1. For approximately ten minutes in the morning and/or ten minutes in the evening, sit in a chair, relax and consciously breathe in a calm manner with your eyes closed. Initially count your breaths, as counting can help you to remain focused on your breathing. Throughout the day, use normal daily activities or times to remind you to consciously breathe calmly. For example, pay attention to your breathing before each meal, whenever you hang up the phone, before you go for a walk, when you’re stopped at a red light, whenever you get on the bus or train, during television commercials, or even after a visit to the washroom. It’s all up to you to think of what events in your day you can use to remind yourself to spend a few moments focusing on your breathing. You can put Post-it notes in different locations around your house, or place of work, that perhaps simply say “breathe,” as a reminder to yourself to do conscious, calm breathing. Another helpful trick is to set the alarm on your watch or cell phone for every two to three hours to remind you to breathe calmly. Try to follow your breathing for a minimum of five breaths when you see one of your reminders. Step 3: Breathing from Your Diaphragm Welcome to step three of the breathing exercises. The diaphragm is a muscle that separates the chest from the belly or abdominal area. With diaphragmatic breathing, or what’s commonly known as belly breathing, your abdomen expands, rather than the chest, with each in-breath. Air flows deeply into the lower part of the lungs, which are actually better at taking up oxygen than the upper lungs. When you are anxious or stressed, tension forms in the chest, neck and belly and you predominantly breathe from your chest. Your breathing becomes shallow, and at times you may even hold your breath without knowing it. If you can consciously learn to use the diaphragm, or belly, to breathe more deeply, you will automatically be breathing in larger amounts of fresh air. Wear loose-fitting Mindfulness and the Breath • 63 clothes for this exercise, as tight clothes around the waist will limit your belly’s movement.

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The typical aortic stenosis murmur is heard loudest over the second intercostal space to the right of the sternum and may radiate to the neck buy generic kamagra gold 100mg on-line. It usually is a crescendo/ decrescendo murmur that may range from mid- to holosystolic kamagra gold 100 mg online. An aortic insufficiency murmur usually is loudest in the fourth intercostal space to the left of the sternum proven kamagra gold 100 mg, and is a diastolic decrescendo murmur that can be heard best with the patient leaning forward, and may be associated with a widened pulse pressure. Mitral stenosis is heard loudest at the apex of the heart, which usually is not displaced, since left ventricular enlargement is unusual. A mitral insufficiency murmur is holosystolic, blowing, loudest at the apex, and may radiate to the axilla. Chest X-Ray Frequently, the history and physical give an accurate picture by which the diagnosis can be made. The chest x-ray can be helpful for con- firming signs of cardiomegaly, chamber enlargement, pulmonary congestion, etc. An associated aortic dilatation of an ascending aortic aneurysm associated with aortic insufficiency may be present. Conduction defects, especially in the presence of active endocarditis, should be sought. Other changes are suggestive of associated coronary artery disease that also must be addressed. Echocardiogram The easiest and currently most accurate noninvasive test used in evaluating valvular heart disease is the echocardiogram, more specif- ically the transesophageal echocardiogram. These studies permit a simple screening for the presence and severity of a valvular lesion. At the same time, the presence of chamber enlargement or dysfunction can be determined. A simple method thus exists to permit the ongoing eval- uation of patients not yet deemed candidates for surgery. The presence or absence of calcification that might increase the complexity of surgery can be identified, and information can be provided on the suitability of a patient for mitral valve repair. If these studies indicate the need, cardiac catheterization usually is recommended. If surgery is not needed at the time of initial evaluation, echocardiogram provides a simple method for ongoing evaluation. Cardiac Catheterization Both left and right heart catheterizations are performed on most patients being evaluated for valve surgery. Right heart catheteriza- tion usually employs a Swan-Ganz catheter inserted via a large vein into the right heart. Measurements of right-sided chamber pressures, the pulmonary artery pressure, and the pulmonary capillary wedge pressure (which reflects the left atrial pressure) are made. In a left heart catheterization, a catheter is passed from the femoral or brachial artery back though the aorta to the heart. It is used to measure pressures in the aortic root and left ven- tricular chamber. The gradient across the mitral valve is the differ- ence between simultaneous measurements of pulmonary capillary wedge pressure (the equivalent of left atrial pressure) and left ventric- 274 A. The valve areas then can be calcu- lated using the Gorlin formula that relates the area of the valve to the pressure gradient across the valve and the cardiac output. Coro- nary angiography is performed to look for any associated coronary disease that could be repaired simultaneously during surgery. In some younger patients and in some emergency situations, the information provided by the echocardiogram may be sufficient and heart catheter- ization may not be required. Therapeutic Intervention Indication for Surgery Decisions regarding the management of patients with valvular heart disease are based on the recognized progression of the various lesions and the risk versus benefit of surgical intervention. Until the ideal replacement valve is developed, the inherent risks associated with prosthetic valves (limited durability, need for anticoagulation, propensity for infection, sound) must be considered along with the risk of the operation itself. One pathologic situation (the deformed valve) is being substituted with another (the prosthetic valve when needed), although with a different array of potential problems. Associated coro- nary artery disease, especially in the presence of mitral regurgitation, significantly increases operative mortality. Thus, the decision is one of the benefits of preventing further deterioration in ventricular function, death, or other complications related to the valve disease versus the risk of surgery, the patient’s likelihood to regain or main- tain an acceptable lifestyle, and the risks inherent in the new valve substituted. Patients with new-onset symptoms are treated medically to relieve symptoms of congestive heart failure or angina. Congestive heart failure is treated with diuretics, digoxin, and afterload reduction when it can be tolerated. Great care must be taken in patients with aortic stenosis to avoid overdiureseis or too much preload reduction (with nitroglycerine and diuretics), which can result in inadequate filling of the left ventricle and subsequent syncope or low output. Heart rate must be controlled with beta-blockers digoxin or calcium channel blockers to permit adequate chamber filling, espe- cially when stenotic lesions are present. Anticoagulants are needed for patients in atrial fibrillation to prevent systemic embolization. There is some evidence that the use of the calcium channel blocker Procardia in asymptomatic patients with aortic insufficiency may delay their need for surgery. Once diagnostic studies have been completed, recommendations for chronic medical therapy or surgery are made. Heart Murmurs: Acquired Heart Disease 275 must be made on an individual basis and must involve an informed consent from the patient and family. Medical therapy is used for those patients when it is believed the surgical risk is too high or their long-term benefit is not sufficient for surgery. Others who are not yet ready for surgery receive medical therapy but are followed closely until indications for surgery become manifest. As noted, the surgical management of valvular heart disease is dependent on the risk-benefit ratio for the patient. Unfortunately, this is not always so clear when the risk of the operation is high and the benefit to an individual patient not clear. However, generalized indi- cations for surgery have evolved based on short- and long-term outcome studies. Detailed diagnostic and therapeutic guidelines are well summarized in “Consensus Statement on Management of Patients with Valvular Heart Disease,” developed by a combined task force of the American Heart Association and the American College of Cardiology. Any patient with symptomatic aortic stenosis should undergo valve replacement unless there are significant contraindica- tions or the patient’s life expectancy is otherwise severely limited. Even those patients with significant organ dysfunction secondary to the low output state may be considered. In the past, it also was believed those asymptomatic patients with aortic stenosis and a valve area of less than 1cm2 or a gradient >60mmHg also should undergo valve replacement. More recently, with the ability to follow patients closely with echocar- diography, surgery may be delayed until symptoms develop without increased risk to the patient as long as surgery occurs rapidly fol- lowing the onset of symptoms. Studies have shown that a patient with aortic insufficiency and a normal ven- tricle can undergo replacement with little surgical risk. On the other hand, once the ventricle begins to fail, the risk increases dramatically. Even in the absence of symptoms, increased operative mortality occurs in the presence of indicators of deteriorating ventricular function. At the present time, valve replacement is the recommended treat- ment for surgical correction of aortic valvular diseases. There are a few patients with aortic insufficiency in whom valvuloplasty has been successful, although replacement remains the standard. Spotnitz Mitral Stenosis and Mitral Insufficiency Mitral valve disease is different from aortic valvular disease in that reconstructive surgery often can be done instead of replacement of the valve. The operative mortality has been less with a repair when the long-term risks of a prosthetic valve are avoided. Mitral stenosis was the first valve problem approached surgically and was performed suc- cessfully in the late 1940s several years before the first successful use of the heart lung machine (by Gibbon3 in 1953). In any case, either direct commissurotomy and reconstruction, if needed, of the subvalvular apparatus are performed, or valve replacement is done. Because of the success of mitral valvuloplasty for mitral stenosis and the detailed diagnostic images of the valves now obtainable by echocardiography, certain patients with mitral stenosis are treated using percutaneous methods in the catheterization laboratory using balloon dilators (larger balloons but similar technique to angioplasty) with good success.

Patient was a heavy smoker and states that he quit smoking for a short while but now smokes 3-4 cigarettes a day generic kamagra gold 100mg with mastercard. When compared with a portable chest film taken 22 months earlier cheap 100 mg kamagra gold free shipping, the current study most likely indicates interstitial vascular congestion buy 100mg kamagra gold overnight delivery. Use a medical dictionary such as Taber’s Cyclopedic Medical Dictionary, the appendices of this book, or other resources to define each term. Then review the pronunciations for each term and practice by reading the medical record aloud. We do believe he would benefit from further diuresis, which was implemented by Dr. Should there continue to be concerns about his volume status or lack of response to Lasix therapy, then he might benefit from right heart catheterization. We plan no change in his pulmonary medication at this time and will see him in return visit in 4 months. Other than the respiratory system, what other body systems are identified in the history of present illness? Vascular System • Describe the functional relationship between the Arteries cardiovascular system and other body systems. Capillaries • Identify, pronounce, spell, and build words related Veins Heart to the cardiovascular system. Conduction System of the Heart • Describe pathological conditions, diagnostic and Blood Pressure therapeutic procedures, and other terms related Fetal Circulation to the cardiovascular system. Connecting Body Systems–Cardiovascular System • Explain pharmacology related to the treatment Medical Word Elements of cardiovascular disorders. Pathology • Demonstrate your knowledge of this chapter by Arteriosclerosis Coronary Artery Disease completing the learning and medical record Endocarditis activities. The heart is a hollow, lary, and (3) vein—carry blood throughout the muscular organ lying in the mediastinum, the body. The pumping action of the heart propels blood containing oxygen, nutrients, and other vital prod- Arteries ucts from the heart to body cells through a vast Arteries carry blood from the heart to all cells of network of blood vessels called arteries. Because blood is propelled thorough the branch into smaller vessels until they become arteries by the pumping action of the heart, the microscopic vessels called capillaries. It is at the walls of the arteries must be strong and flexible capillary level that exchange of products occurs enough to withstand the surge of blood that results between body cells and blood. When this transporta- (5) tunica media is the middle layer composed of tion system fails, life at the cellular level is not smooth muscle. Pronunciation Help Long Sound a—rate ¯ e—rebirth¯ ¯ı—isle o—over¯ u—unite¯ Short Sound a—alone˘ e—ever˘ ˘ı—it o—not˘ u—cut˘ Anatomy and Physiology 187 (7) Lumen (7) Lumen Endothelium Endothelium (10) Valve (6) Tunica Heart intima (6) Tunica intima Elastic layer (5) Tunica media (5) Tunica Vena cava media (4) Tunica Aorta (4) Tunica externa externa (3) Vein (1) Artery (9) Venule Precapillary sphincter Endothelial cell Smooth muscle (8) Arteriole (2) Capillary Figure 8-1. When it contracts, it causes vasocon- called (8) arterioles and, finally, to the smallest striction, resulting in decreased blood flow. The (6) tunica intima is the Capillaries thin, inner lining of the lumen of the vessel, com- Capillaries are microscopic vessels that join the posed of endothelial cells that provide a smooth arterial system with the venous system. Because capillary walls are composed of associated with the pumping action of the heart, a only a single layer of endothelial cells, they are very cut or severed artery may lead to profuse bleeding. This thinness enables the exchange of water, Arterial blood (except for that found in the pul- respiratory gases, macromolecules, metabolites, monary artery) contains a high concentration of and wastes between the blood and adjacent oxygen (oxygenated) and appears bright red in cells. The right lary system is partially regulated by the contraction ventricle pumps blood to the lungs (pulmonary of smooth muscle precapillary sphincters that lead circulation) for oxygenation, and the left ventricle into the capillary bed. When tissues require more pumps oxygenated blood to the entire body blood, these sphincters open; when less blood is (systemic circulation). Once the exchange of prod- Deoxygenated blood from the body returns to ucts is complete, blood enters the venous system the right atrium by way of two large veins: the for its return cycle to the heart. From the right atrium, blood passes from smaller vessels called (9) venules that devel- through the (7) tricuspid valve, consisting of three op from the union of capillaries. When the heart con- sive network of capillaries absorbs the propelling tracts, blood leaves the right ventricle by way of pressure exerted by the heart, veins use other meth- the (8) left pulmonary artery and (9) right pul- ods to return blood to the heart, including: monary artery and travels to the lungs. During con- traction of the ventricle, the tricuspid valve closes to • skeletal muscle contraction prevent a backflow of blood to the right atrium. The • gravity (10) pulmonic valve (or pulmonary semilunar valve) • respiratory activity prevents regurgitation of blood into the right ven- • valves. In the lungs, the The (10) valves are small structures within veins pulmonary artery branches into millions of capillar- that prevent the backflow of blood. Here, carbon found mainly in the extremities and are especially dioxide in the blood is exchanged for oxygen that important for returning blood from the legs to the has been drawn into the lungs during inhalation. These vessels contain smooth muscle that propels blood toward carry oxygenated blood back to the heart. From there, blood Blood carried in veins (except for the blood in the passes through the (13) mitral (bicuspid) valve, pulmonary veins) contains a low concentration of consisting of two leaflets to the left ventricle. Upon oxygen (deoxygenated) with a corresponding high contraction of the ventricles, the oxygenated blood concentration of carbon dioxide. Deoxygenated leaves the left ventricle through the largest artery of blood takes on a characteristic purple color. The aorta contains the continuously circulates from the heart to the lungs (15) aortic semilunar valve (aortic valve) that per- so that carbon dioxide can be exchanged for oxygen. The aorta branches into many smaller arteries that carry blood to all parts of Heart the body. Some arteries derive their names from the The heart is a muscular pump that propels blood organs or areas of the body they vascularize. It example, the splenic artery vascularizes the spleen is found in a sac called the pericardium. Instead, an arterial system and is continuous with the endothelium of composed of the coronary arteries branches from the arteries and veins the aorta and provides the heart with its own blood • myocardium, the muscular layer of the heart supply. The artery vascularizing the right side of • epicardium, the outermost layer of the heart. If blood flow upper portion of the right atrium and possesses its in the coronary arteries is diminished, damage to own intrinsic rhythm. When severe damage by external nerves, it has the ability to initiate and occurs, part of the heart muscle may die. Cardiac rate may be altered by impulses known as conduction tissue has the sole function of from the autonomic nervous system. For example, the heart highly specialized cells that possess characteristics beats more quickly during physical exertion and of nervous and cardiac tissue: more slowly during rest. These Several factors influence blood pressure: fibers extend up the ventricle walls. The Purkinje • resistance of blood flow in blood vessels fibers transmit the impulse to the right and left • pumping action of the heart ventricles, causing them to contract. Blood is now • viscosity, or thickness, of blood forced from the heart through the pulmonary • elasticity of arteries artery and aorta. The Impulse transmission through the conduction process of gas exchange, the procurement of nutri- system generates weak electrical currents that can ents, and the elimination of metabolic wastes occur be detected on the surface of the body. This remarkable structure delivers ment called an electrocardiograph records these nutrients and oxygen from the mother to the fetus electrical impulses, using a needle, or stylus, that and removes waste products from the fetus and records the activity on graph paper. The pla- deflection of the electrocardiograph produces centa develops during pregnancy and is expelled waves or peaks designated by the letters P, Q, R, S, after the delivery of the infant. From the left atrium, blood heartbeat: the contraction phase (systole) when enters the (11) left ventricle and finally exits the the blood is forced out of the heart, and the heart through the aorta, where it travels to the relaxation phase (diastole) when the ventricles head and upper extremities. Systole produces the max- nonfunctional, most of the blood in the pulmonary imum force; diastole, the weakest. These meas- arteries is shunted through a connecting vessel urements are recorded as two figures separated called the (12) ductus arteriosus to the aorta. Systolic pressure is given first, Immediately after birth, the ductus arteriosus followed by diastolic pressure. As circulation increases in blood pressure of 120/80 mm Hg means a sys- the neonate, the increase of blood flow to the right tolic pressure of 120 with a diastolic pressure of atrium forces the foramen ovale to close. Connecting Body Systems-Cardiovascular System The main function of the cardiovascular system is to provide a network of vessels though which blood is pumped by the heart to all body cells. Specific functional relationships between the cardio- vascular system and other body systems are discussed below. Blood, lymph, and immune Endocrine • Cardiovascular system transports the • Cardiovascular system delivers oxygen and products of the immune system.

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