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The circulatory system is an organ system of the human body comprising the heart and blood vessels. Its major function is to transport nutrients and respiratory gasses to and from the cells. The lymphatic system is also considered part of the circulatory system. The various parts of the circulatory system are hereby considered.
The heart is a muscular organ responsible for pumping blood throughout the body through blood vessels. It consists of four chambers, the right and left atria, and the right and left ventricles. A septum runs between the right and left chambers of the heart. The atria are separated from the ventricles by the mitral and the tricuspid valves. Valves assist the pumping action of the heart by preventing the backflow of blood (Ganong, 2005).
There are three primary types of blood vessels namely arteries, veins, and capillaries. Arteries mostly carry oxygenated blood from the heart to peripheral sites at high pressure. They are characterized by a thick muscular wall and narrow lumen. Veins, also known as capacitance vessels, carry mostly deoxygenated blood from the periphery to the heart. They have a wide lumen, a thin wall, and valves. Blood in veins is under low pressure and flow. Therefore, the valves prevent backflow in the veins.
The capillaries connect the arteries and veins and are responsible for delivering blood to the remote parts of the body. They have a wall one-cell thick that allows the exchange of gasses, nutrients, and waste with the interstitial fluid. Lymphatics, which include lymph vessels and lymph nodes, play a central role in circulation. They collect plasma proteins and fluid that has escaped from capillary circulation and return them back into the venous circulation (Ganong, 2005).
This paper will discuss two major diseases of the circulatory system: hypertension and congestive heart failure (CHF).
Hypertension is defined as arterial blood pressure above 140 mmHg (systolic) or 90 mmHg (diastolic). There are two types of hypertension: essential or primary hypertension and non-essential or secondary hypertension. The more common primary hypertension has a complex etiology, and genetic and environmental factors may be implicated. On the other hand, secondary hypertension is mainly caused by underlying vascular, endocrine, and renal defects.
Under normal circumstances, blood pressure in a healthy adult is 120/80 mmHg.
Several physiologic factors such as exercise and anxiety lead to blood pressure elevation, but a return to normal pressure is achieved afterward. However, in hypertension, the blood pressure remains elevated albeit in the absence of symptoms. Most patients will not know they are hypertensive until it is detected in a routine screening.
Several features underlie the development of hypertension. An elevated heart rate, which causes increased cardiac output, may lead to hypertension. Hormones such as adrenaline and electrolyte imbalances are a common cause of an elevated heart rate. An increase in peripheral vascular resistance as seen in elderly persons is observed in hypertension. This may be due to increased calcification and loss of elasticity of blood vessels that naturally occur in aging. Lipidaemia, which is a condition characterized by elevated blood lipids, may cause the deposition of plaques in arteries reducing their elasticity and, consequently, promoting the development of hypertension. Sodium and water retention, which occurs as a result of renal dysfunction, may lead to excess fluid in the circulatory system resulting in hypertension.
Diagnosis of hypertension is often made using a simple sphygmomanometer that measures arterial blood pressure. Additional measures are a detailed history and electrocardiography, which are used to characterize the likely cause and complications of the disease (Katakam, Brukamp, & Townsend, 2008).
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Treatment of Hypertension
The approach to treatment has multiple facets namely diet, lifestyle, and pharmacologic treatment. Dietary control involves eating a balanced diet with sufficient vegetables and fruits. Whole foods are advised as over-processed foods. Patients are encouraged to avoid fatty foods and high-sugar beverages since these are associated with further worsening of hypertension. Dietary control is very important and is even indicated in pre-hypertension (120-139/80-89 mmHg) as part of a non-pharmacological therapy that is effective without the use of drugs. Salt restriction is also indicated for hypertensive patients. A daily intake of fewer than 6 grams of sodium chloride is advised (Chobanian, Bakris, & Black, 2003).
Regular exercise has been shown to result in better blood pressure control. Patients are advised to undertake a minimum of 30 minutes of strenuous exercise at least three times a week. Obese and overweight patients are encouraged to lose weight since this approach will improve blood pressure levels. Restricted use of alcohol is recommended. No more than 30 ml of ethanol should be consumed per day for men or 15 ml of ethanol for women and lightweight individuals.
Pharmacologic therapy for hypertension involves the use of the following agents: Angiotensin receptor blockers (ARBs), angiotensin-converting enzyme inhibitors (ACEIs), beta-blockers, calcium channel blockers, and diuretics. Clinicians mostly use a combination of two classes of antihypertensive agents depending on patient characteristics and individual responses to the drugs although more than two agents may be used concurrently in patients with difficult cases (James, Oparil, & Carter, 2014). Due consideration is made to the various adverse effects of the different drugs and their cost.
Clinical Manifestations of Hypertension
As mentioned above, most hypertensive are asymptomatic until the disease reaches advanced stages. Patients with untreated hypertension may, however, experience frequent headaches, blurred vision, and dizziness among other non-specific symptoms. End-organ damage may occur due to prolonged high blood pressure. Patients may suffer from stroke as a result of cerebral vessel rupture due to high pressure. Other patients may suffer acute renal failure due to altered renal hemodynamics. Other complications of hypertension include congestive heart failure and aortic dissection.
Hypertension is neither an autoimmune disorder nor a genetic defect. However, primary hypertension shows strong hereditary patterns. If a parent suffered from primary hypertension, then the offspring is likely to develop the condition. Hypertension is also a non-communicable disease, which means it cannot be transmitted from one individual to another.
Congestive Heart Failure (CHF)
Congestive Heart Failure or simply heart failure refers to a disorder characterized by the inability of the heart to sustain sufficient cardiac output to support body metabolism. The heart is the primary organ whose function is impaired. Two distinct defects are identified in heart failure. Systolic failure refers to the inability of the heart to contract optimally to deliver blood to the periphery. Diastolic failure arises from the inability of the heart to fill optimally due to reduced myocardial flexibility. Both defects result in a reduced stroke volume and may occur individually or concurrently.
There are many complex factors that may lead to heart failure, but most factors lead to damage to cardiac myocytes. Myocardial infarction and chronic hypertension are some important causes of CHF. Heart failure may be categorized as the more common left heart failure and the rare right heart failure (cor-pulmonale). Cor-pulmonale occurs in association with pulmonary hypertension or pulmonary stenosis.
Several adaptations occur to counter the falling cardiac output, but these adaptations are responsible for the further worsening of heart failure. Baroreceptor and chemoreceptor systems respond to the low cardiac output by triggering increased sympathetic outflow and, hence, cause high heart rate resulting in increased cardiac workload. This translates to poor contractility and inadequate time for ventricular filling resulting in lower cardiac output. On the other hand, reduced renal perfusion stimulates the renin-angiotensin-aldosterone system resulting in increased sodium and fluid retention. This results in higher arterial blood pressure and elevated afterload that impairs cardiac function (Lam, Lyass, & Kraigher-Krainer, 2011).
Diagnosis and treatment of Congestive Heart Failure
Diagnosis of heart failure is mainly clinically based on observation of major symptoms. Electrocardiography can be done to characterize the CHF and identify the cause (Hunt, Abraham, & Chin, 2009).
Treatment of heart failure depends on a combination of lifestyle modifications and pharmacologic therapy. Patients are advised to include more vegetables and fruits in their daily diet. Salt intake is tightly controlled to reduce fluid overload that is seen in CHF. Drug therapy involves the following agents: diuretics, beta-blockers, digoxin, ACEIs, ARBs, and vasodilators among other agents (Lainščak, Cleland, Lenzen, Follath, & Komajda, 2007). Diuretics are for reducing fluid overload manifested as edema; furosemide is commonly used. Beta-blockers are used to modify neuroendocrine responses to CHF while vasodilators reduce both preload and afterload.
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The symptoms of CHF include dyspnea, orthopnea, peripheral edema, cough, exercise intolerance, and pulmonary edema. If untreated, CHF is fatal. CHF is not an autoimmune disorder or genetic defect but rather a functional syndrome. It is also a non-communicable disease, hence, cannot be transmitted.
- Chobanian, A. V., Bakris, G. L., & Black, H. R. (2003). Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of high blood pressure. Hypertension, 1206-1252.
- Ganong, W. F. (2005). Review of medical physiology. San Francisco, CA: McGraw-Hill Companies. Print.
- Hunt, S. A., Abraham, W. T., & Chin, M. H. (2009). 2009 focused update incorporated into the ACC/AHA 2005 guidelines for the diagnosis and management of heart failure in adults. Journal of the American College of Cardiology.
- James, P. A., Oparil, S., & Carter, B. L. (2014). 2014 Evidence-based guideline for the management of high blood pressure in adults. The JAMA Network, 507-520.
- Katakam, R., Brukamp, K., & Townsend, R. R. (2008). What is the proper workup for a patient with hypertension? Cleveland Clinic Journal of Medicine, 663-672.
- Lainščak, M., Cleland, J. G., Lenzen, M. J., Follath, F., & Komajda, M. (2007). International variations in the treatment and co-morbidity of left ventricular systolic dysfunction: data from the EuroHeart Failure Survey. Europen Journal of Heart Failure, 292-299.
- Lam, C. S., Lyass, A., & Kraigher-Krainer, E. (2011). Cardiac dysfunction and noncardiac dysfunction as precursors of heart failure with reduced and preserved ejection fraction in the community. Circulation, 24-30.