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The Heart FUN FACTS • Center of the circulatory system • Beats over 100,000x/day • Pumps 1835 gallons/day • Study of the heart and accompanying diseases –cardiology • Heart lies within the mediastinum –Center of chest • 2/3 lies to the left of the mediastinum Pericardium • Prevents overdistension of the heart • Anchors heart within mediastinum Three layers to the heart 1. Epicardium: outer layer 2. Myocardium: middle layer made up of cardiac muscle 3. Endocardium: inner lining of the heart, covers valves and the tendons that hold valves open What is??? • Epicarditis • Myocarditis • Endocarditis Four Chambers • 2 atria (singular is atrium): holding chambers of heart • 2 ventricles: pump blood out of heart to body Blood Vessels • Superior vena cava: brings oxygen-poor blood to heart from upper portions of body. • Inferior vena cava: brings oxygen-poor blood to heart from lower portions of body • Right and left pulmonary arteries: brings oxygen-poor blood from heart to lungs • Right and left pulmonary veins: brings oxygenated blood from lungs back to heart Question??? • How are pulmonary arteries and pulmonary veins different from all other arteries and veins in your body? Valves • Atrioventricular (AV) valves or cuspid valves: between atria and ventricles – Tricuspid: on right side of heart – Bicuspid: on left side of heart • Semilunar valves: between ventricles and arteries leaving heart – Pulmonary semilunar valve – Aortic semilunar valve Circulatory Problems • Ischemia: reduced oxygen. Weakens but does not kill heart cells • Angina pectoralis: chest pain due to ischemia – Causes: • Stress • Over exertion • Artherosclerosis • Fever • anemia Myocardial Infarction • Heart attack • Infarction: death of tissue due to interrupted heart flow Conduction System • Your heart is innervated by the autonomic nervous system, but only to regulate speed of contractions • Heart has an internal conduction system – Sinoatrial Node (SA node): special heart tissue that causes heart to contract A Cut To The Heart SA node • Called the “pacemaker” • Self excitation about 75 times/minute • Located in the right atrial wall just below superior vena cava opening • Initiates excitation…spreads to both atria. – Causes them to contract After spreading to atria • AV node and bundle of His distribute impulse to ventricles via Purkinje fibers Blood Vessels The 3 major types of vessels Arteries – carry blood away from the heart Veins – carry blood toward the heart Capillaries – contact tissue cells (Serving cellular needs) Capillaries · Very narrow (10 µm diameter, the red blood cells that travel through capillaries are 6 µm in diameter). Blood Functions • Transports – – – – – Dissolved gasses Nutrients Waste products to lungs and kidneys Enzymes Hormones from endocrine organs Functions • Regulates • pH • Electrolyte concentration of body fluids • Body temperature • Restricts fluid loss • Defends pathogens and toxins Components • Blood is the body’s only fluid tissue • It is composed of liquid plasma and formed elements • Plasma (55%) – 90% water – minerals, sugars, lipids, hormones, proteins (fibrinogen, and albumen) • Formed elements (45%) include: – Erythrocytes, or red blood cells (RBCs) – Leukocytes, or white blood cells (WBCs) – Platelets Physical Characteristics and Volume • Blood is a sticky, opaque fluid with a metallic taste • Color varies from scarlet (oxygen-rich) to dark red (oxygen-poor) • The pH of blood is 7.35–7.45 • Blood accounts for approximately 8% of body weight • Average volume of blood is 5–6 L for males, and 4–5 L for females Blood maintains: • Appropriate body temperature by absorbing and distributing heat • Normal pH in body tissues using buffer systems • Adequate fluid volume in the circulatory system Protection • Blood prevents blood loss by: – Activating plasma proteins and platelets – Initiating clot formation when a vessel is broken • Blood prevents infection by: – Synthesizing and utilizing antibodies – Activating complement proteins – Activating WBCs to defend the body against foreign invaders Erythrocytes (RBC’s) Erythrocytes • Biconcave discs & anucleate allow for a huge surface area to volume ratio • Hematocrit – percentage of RBCs out of the total blood volume. (Ave) 46 adult men & 42 adult women. • There are roughly 5 million RBCs in each microliter of blood; they transport oxygen and carbon dioxide, and have large surfaceto volume ratios. • Red blood cells account for slightly less than half the blood volume. Erythrocytes • Erythrocytes are unable to perform normal maintenance operations and usually degenerate after about 120 days in the circulation. • Each red blood cell contains molecules of hemoglobin (Hgb), which can reversibly bind oxygen. Leucocytes (White Blood Cells) • Nuclei • No hemoglobin • Functions: – leucocytes are phagocytic - What does that mean? – effective against bacteria, viruses, fungi, transplanted cells and cancer cells