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PATHOPHISIOLOGY II – SUMMER 2016 TEST 1 CHAPTER 31- Structure and Function of the Cardiovascular and Lymphatic System A. Circulatory System a. Right Heart Function i. Pumps blood through lungs ... (pulmonary circulation) ii. Delivers blood to the lungs for oxygenation iii. Low pressure system iv. Failures common in IV drug users and back up into lungs b. Left Heart Function i. Pumps oxygenated blood through the systemic circulation ii. Delivers metabolic waste products to the lungs, kidneys and liver iii. High Pressure system iv. Failures back up into the periphery B. The Heart a. Structures that Direct Circulation Through the Heart i. Function 1. Structural Support: includes heart wall and fibrous skeleton which encloses and supports the heart and divides it into four chambers, the valves that direct flow, and the great vessels that conduct blood to and from the heart 2. Maintenance of heart cells: the vessels of coronary circulation- the arteries and veins that serve the metabolic needs of all the heart cells 3. Stimulation and control of heart action: the nerves and specialized muscle cells that direct rhythmic contraction and relaxation, propelling blood throughout circulation ii. Heart wall has 3 layers: 1. Pericardium- outermost, double walled membranous sac that encloses the heart. A surface layer of mesothelium over a thin layer of connective tissue. The visceral layer (epicardium) is the inner layer that folds back on itself and becomes continuous with the parietal pericardium, allowing the large vessels to enter and leave the heart without breaching the pericardial layers. There is a pericardial cavity that separates the layer of the pericardium with 10-30mL of fluid secreted by mesothelium cells to lubricate and minimize friction a. Prevents displacement of the heart during gravitational acceleration or deceleration b. A physical barrier that protects the heart against infection and inflammation from the lungs and pleural space. c. Contains pain receptors and mechanoreceptors that can elicit reflex changes in blood pressure and heart rate 2. Myocardium- the thickest layer of the heart composed of cardiac muscle and is anchored to the fibrous skeleton. Thickness varies from chamber to chamber. Biggest concern for injury to this layer 3. Endocardium- the internal lining of the myocardium composed of connective tissue and a layer of squamous cells. The endocardial lining of the heart is continuous with the endothelium that lines all the arteries,veins and capillaries of the body, creating a continuous, closed circulatory system iii. Chambers- atria are smaller than the ventricles; thickness depends on amount of pressure or resistance it must overcome to eject blood. 1. Right atrium- 2mm thick, low pressure 2. Left atrium- 3-5mm thick, low pressure 3. Right Ventricle- 3-5mm thick; shaped like a crescent enabling it to efficiently eject large volumes of blood through a very small valve into the low-pressure pulmonary system 4. Left Ventricle- 13-15mm thick, high pressure; large bullet shaped, to eject blood through a relatively large valve opening into the highpressure systemic circulation iv. Valves- ensure one-way blood flow. The flaps/cusps are attached to the papillary muscles by the chordae tendinae. The papillary muscles are extensions of the myocardium that pull the cusps together and downward at the onset of ventricular contraction. 1. Atrioventricular valves- allow blood flow from higher pressure atria to relaxed ventricles. AS pressure increases, the valves shut to prevent backflow. Much larger than SL a. Tricuspid valve- 3 cusps and largest diameter b. Bicuspid (mitral) valve- 2 cusps; The anterior cusp of the mitral valve is continuous with the supporting tissues of the aortic semilunar valve cusps and the left coronary valve cusps. 2. Semilunar valves- open when intraventricular pressure exceeds aortic and pulmonary pressures; close when pressure falls a. Pulmonic valve- 3 cup-shaped cusps that arise from the fibrous skeleton. Thinner cups than the aortic valve b. Aortic valve- 3 cup-shaped cusps that arise from the fibrous skeleton v. Great Vessels 1. Superior an inferior Vena Cava- enter the right atrium 2. Pulmonary Artery- right and left pulmonary arteries 3. Four Pulmonary Veins- 2 from the right lung and 2 from the left lung that carry oxygenated blood to the left atrium 4. Aorta- branches: brachiocephalic, left common carotid, left subclavian vi. Blood Flow 1. Diastole- relaxation and blood fills the ventricles. Blood from the veins of the systemic circulation enters the right atrium from the SVC/IVC. Venous blood from the coronary circulation enters the right atrium through the coronary sinus. The right atrium fills and distends, pushing open the tricuspid valve filling the ventricle. A split second earlier, the four pulmonary veins carry blood to the left atrium. As the left atrium fills, it pushes the cusps of the mitral valve open and fills the left ventricle. Left atrial contraction “atrial kick” provides significant increase of blood to the left ventricle. 2. Systole- contraction and blood is propelled out into the circulation; ventricular contraction 3. Cardiac Cycle Phasesa. Phase 1- Atrial systole (ventricular diastole) begins with opening of the mitral and tricuspid valves and ventricular filling from the atria occurs. The ventricles fill rapidly in early diastole and again in late diastole with the atria contract [Show More]

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