Anatomy and Physiology of the Heart. Essay

The heart is located in the left side of the mediastinum; it consists of three muscle layers the Endocardium, myocardium, and epicardium. The epicardium is the outermost layer of the heart. The myocardium is the idle layer of and actual contracting muscle of the heart. The endocardium is the innermost layer and lines the inner chambers and heart valves. Pericardial sac: The pericardial sac encases and protects the heart from trauma and infection.

The pericardial sac has two layers which are the parietal pericardium which is the tough, fibrous outer membrane that attaches anteriorly to the lower half of the sternum, posteriorly to the thoracic vertebrae, and inferiorly to the diaphragm. The visceral pericardium is the thin inner layer that closely adheres to the heart. The pericardial space is between the parietal and visceral layers it holds 5 to 20 ml of pericardial fluid lubricates the pericardial surfaces and cushions the heart. Chambers: There are four heart chambers two upper atria (right and left) and two lower ventricles (right and left).

The right atrium receives deoxygenated blood from the body via the superior and inferior vena cava. The right ventricle receives blood from the right atrium and pumps it to the lungs via the pulmonary artery. The left atrium receives oxygenated blood from the lungs via four pulmonary veins. The left ventricle is the largest and most muscular chamber. It receives oxygenated blood from the lungs via the left atrium and pumps blood into the systemic circulation via the aorta. Valves: There are four valves in the heart two atrioventricular (AV) valves – the tricuspid and the mitral – that lie between the atria and ventricles.

The tricuspid is located on the right side of the heart. The bicuspid or mitral valve is located on the left side of the heart. The AV valves close at the beginning of the ventricular contraction and prevent blood from flowing back into the atria from the ventricles. These valves open when the ventricle relaxes. Two semilunar valves – the pulmonic and the aortic – The pulmonic semilunar valve lies between the right ventricle and the pulmonary artery. The aortic semilunar valve lies between the left ventricle and the aorta.

The semilunar valves prevent the blood from flowing back into the ventricles during relaxation. They open during ventricular contraction and close when the ventricles begin to relax. Heart Sounds The first heart sound is the (S1), referred to as lubb, which occurs when the ventricles contract during systole and when the mitral and tricuspid valves close; The second heart sound (S2), called dupp, occurs during ventricular relaxation or diastole and is caused by the closing of the aortic and pulmonic valves Describe the flow of blood through the heart and coronary vessels Coronary Blood Flow.

Left coronary artery and the right coronary artery – Left coronary artery branches into the left anterior descending and circumflex arteries; Right coronary artery branches to supply the sinoatrial (SA) and the atrioventricular (AV) nodes, the RA and RV, and the inferior part of the LV Venous system parallels the arterial system: the great cardiac vein follows the left anterior descending artery and the small cardiac vein follows right coronary artery. Veins meet to form the coronary sinus (largest coronary vein), which returns deoxygenated blood from the myocardium to the right atrium Name the elements of the heart’s conduction system.

Conduction SA node, called the pacemaker, initiates the impulse; the impulse is carried throughout the atria to the AV node, located on the floor of the RA; Impulse is delayed in the AV node, then transmitted to the ventricles through the bundle of His; The bundle is made up of Purkinje cells and is located where the atrial and ventricular septa meet Bundle of His divides into left and right bundle branches the Left branch divides into anterior and posterior branches: known as fascicles (small bundle or tight cluster);

Terminal ends of right and left branches: known as the Purkinje ? bers; when impulse reaches Purkinje ? bers, ventricles contract State the order in which normal impulses are conducted through the heart Cardiac innervation Heart innervated by sympathetic and parasympathetic ? bers of the autonomic nervous system. The Sympathetic ? bers are distributed throughout the heart; Sympathetic stimulation results in increased heart rate, increased speed of conduction through the AV node, and more forceful contractions. Parasympathetic ?

bers (part of the vagus nerve) found primarily in the SA and AV nodes and the atrial tissue; Parasympathetic stimulation results in slowing of heart rate, slowing of conduction through the AV node, and decreased strength of contraction Cardiac Function includes the Cardiac cycle – Contraction and relaxation of the heart make up one heartbeat Cardiac output is the Amount of blood (in liters) ejected per minute; Factors that affect stroke volume: preload, contractility, and afterload; myocardial oxygen consumption – Myocardial tissue routinely needs 70% to 75% of the oxygen delivered to it by the coronary arteries Age-Related Changes:

Heart – Increased density of connective tissue and decreased elasticity; Number of pacemaker cells in the SA node decreases, as does the number of nerve ? bers in the ventricles Blood vessels – Changes in connective tissue and elastic fibers in arteries cause them to become stiffer Veins stretch and dilate, leading to venous stasis and sometimes impaired venous return Nursing Assessment of Cardiac Function.

Chief Complaint and History of Present Illness any Symptoms related to cardiac disorders include fatigue, edema, palpitations, dyspnea and pain; Note when symptoms occur, what aggravates them, and what relieves them Medical History – Hypertension, kidney disease, pulmonary disease, stroke, rheumatic fever, streptococcal sore throat, and scarlet fever document any previous cardiac disorders and hospitalizations. List recent and current medications and note allergies in appropriate records.

Family History – Assess whether immediate relatives have had hypertension, coronary artery disease (CAD), other cardiac disorders, or diabetes mellitus. Review of Systems – Systematically assess whether the patient has experienced the following: weight gain, fatigue, dyspnea (shortness of breath), cough, orthopnea (difficulty breathing in a supine position), paroxysmal nocturnal dyspnea (sudden dyspnea during sleep), palpitations, chest pain, syncope (fainting), concentrated urine, or leg edema. Functional Assessment – Determine how this illness has affected the patient’s ability to carry out usual activities.

Record any Activity and rest patterns and usual diet; Ask about sources of stress and coping strategies; Physical Examination – Vital signs: Blood pressure, pulses, and respirations, Skin, Heart sounds – Heart murmurs and extremities Diagnostic Tests and Procedures: Electrocardiogram (ECG), Ambulatory ECG (Holter monitor), Implantable loop monitor/recorder (ILR), Echocardiogram (heart sonogram), Transesophageal echocardiogram (TEE), Magnetic resonance imaging (MRI);

Multiple-gated acquisition scan, Stress test (exercise tolerance test), Perfusion imaging Thallium imaging, Ultrafast computed tomography, Cardiac catheterization and Electrophysiology study (EPS) Laboratory Tests: Arterial blood gases; Pulse oximetry; Cardiac enzymes; Creatine phosphokinase; Cardiac protein markers; Complete blood count; Lipid profile; B-type natriuretic peptide (BNP); and C-reactive protein (CRP) Drug Therapy: Cardiac glycosides, Antianginals, Antidysrhythmics, Angiotensin-converting enzyme (ACE) inhibitors (ACEIs), Diuretics, Anticoagulants, Heparin, Low-molecular-weight heparin (LMWH)’.

Warfarin’ Antiplatelet agents Fibrinolytic agents (also called thrombolytics), Lipid-lowering agents and Analgesics Diet Therapy: Low-fat, high-fiber diet – a well-balanced diet Emphasis on fruits, vegetables, grains, and proteins low in fat (fish, legumes, poultry, and lean meats); Cholesterol intake should be limited to 200 mg/day; foods with trans fatty acids, limited to 8.

Sodium – diet containing sodium 2 g/day most often prescribed; Potassium Patients taking potassium-wasting diuretics need adequate potassium in the diet; An Exercise program may help achieve optimal weight. Other Therapeutic Measures include oxygen therapy, Pacemakers: Temporary and Permanent; cardioversion;

Cardiac Surgery – Common surgical procedures: Pacemaker insertion, Repair or replace valves or septa or remove tumors and coronary artery bypass surgery Preoperative nursing care for a pt that has had Cardiac Surgery – Interventions: Fear and Anxiety Postoperative nursing care Interventions – Ineffective Breathing Pattern; Pain, Ineffective Thermoregulation; Decreased Cardiac Output; Risk for Infection and Anxiety.

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