The Cardiovascular System PDF

The Cardiovascular System  Objectives Identify the major components of the cardiovascular system. Examine the composition and functions of blood. Discuss hemostasis. Discuss tissue perfusion. Describe the structure and function of the heart. Exp...

The Cardiovascular System  Objectives Identify the major components of the cardiovascular system. Examine the composition and functions of blood. Discuss hemostasis. Discuss tissue perfusion. Describe the structure and function of the heart. Explain pulmonary and systemic circulations. Identify types of blood vessels. Compare and contrast arteries, veins, and capillaries. Discuss the cardiac conduction system. Outline the major events of the cardiac cycle. Describe the electrical events of a normal electrocardiogram (ECG).  The cardiovascular system consists of: 1. Blood. 2. Heart. 3. Blood vessels. The Heart pumps blood through blood vessels. Blood carries oxygen and nutrients to cells and carbon dioxide and wastes away from cells.  Characteristics of Blood Blood is viscous (5 times greater than water). Blood temperature is slightly higher than normal body (38 °C). pH of blood averages about 7.4. Oxygenated blood is bright red, while deoxygenated blood is darker red. Oxygenated Deoxygenated blood blood Functions of Blood Transportation: gases, nutrients, hormones, etc. Maintenance of Homeostasis: e.g. temperature regulation. Defense: fighting pathogens.  Blood Composition Blood is composed of : a cellular portion and a fluid portion. Centrifuge Hematocrit: the percentage of red blood cells in a blood sample. Cellular Components of Blood White blood cells Platelets + Red blood cells (RBCs) + White blood cells (WBCs) + Platelets Red blood cells 8  Red Blood Cells RBC + Biconcave discs that lack nuclei and contain (erythrocyte) hemoglobin, which transports oxygen. + RBC formation occurs in adult red bone Biconcave marrow of certain bones. shape + RBCs live about 120 days, after which macrophages, located mainly within the bone marrow, liver, and spleen destroy them. Transportation Red Blood Cells  White Blood Cells + WBCs (leukocytes) play a major role in the body’s defenses against disease. 1 + They protect the body against invading microorganisms and body cells with mutated DNA, and they clean up debris. 2 Defense 3  Five White Blood Cells Types and Their Functions There are two different kinds of white blood cells and each looks different from one another under the microscope. These include granulocytes and agranulocytes. Granulocytes have visible granules or grains inside the cells that have different cell functions. Types of granulocytes include basophils, neutrophils, and eosinophils. Agranulocytes are free of visible grains under the microscope and include lymphocytes and monocytes. Together, they coordinate with one another to fight off things like cancer, cellular damage, and infectious diseases Five White Blood Cells Types  Platelets + Fragments of the cytoplasm of a cell called a megakaryocyte (a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. +They help stop blood loss from damaged blood vessels by forming a platelet plug (blood clotting). + Platelets are key players in the process of hemostasis.  Hemostasis Hemostasis has 3 steps: 1. Vascular spasm: constriction of the damaged blood vessel to minimize blood loss. 2. Formation of a platelet plug: platelets clump up together and form a plug around the site of injury 3. Blood clotting: a blood clot is formed to seal the damaged blood vessel. Failure of any of these steps will result in hemorrhage (excessive bleeding).  Hemostasis Platelets Platelet plug Blood clot +ve feedback Maintenance of Homeostasis ABO BLOOD SYSTEM ABO Blood Types The Rh System Blood types are either “positive” or “negative,” depending on the absence or presence of a protein called the Rh factor. This is called the Rh system. Being RhD positive is more common than being RhD negative. Positive (+): Red blood cells have the RhD antigen. Negative (-): Red blood cells don’t have the RhD antigen.  What are the different blood types? There are eight blood types included in the ABO and Rh blood group systems The most common blood type in the United States is O positive (O+). The least common blood type in the U.S. is AB negative (AB-). The majority of people, about 85%, are Rh-positive. Blood transfusions and organ transplants depend on donors and recipients having compatible blood types. Which blood types are compatible?  Tissue Perfusion The main function of the heart and blood vessels is to maintain adequate perfusion. Maintaining adequate perfusion requires: 1. Continuous pumping of the heart. 2. Healthy blood vessels. Tissue perfusion refers to the process of delivering blood to the capillary beds in tissues, ensuring that oxygen and nutrients are provided to cells while waste products are removed.  Tissue Perfusion The heart generates blood pressure, which is required to force blood through the blood vessels. Blood vessels form a network that allows blood to flow from the heart to all the living cells of the body and then back to the heart. If the heart fails to pump enough volumes of blood, or the vessels become blocked, adequate amount of blood may not reach the body’s cells and tissues will be deprived of needed oxygen and nutrients, waste products accumulate, and cell death may occur.  The Heart The heart is a muscular organ about the size of a fist. Located between the lungs in the middle of the chest. 39 million beat that pumps 10,000,000 liters of blood per year!  The Heart Three anatomical features are essential for the normal function of the heart: 1. Two sides 2. Great vessels 3.Valves (Mitral valve) (Tricuspid valve)  The Heart 1. Two sides: each side has a receiving chamber (atrium) and a pumping chamber (ventricle). 2. Great vessels: great vessels are large arteries and veins that are directly attached to the heart. 3. Valves: heart valves prevent backflow to ensure one-way blood flow. Atria receive blood. Ventricles pump blood.  The Heart Diastole: the time during which cardiac muscle relaxes. Systole: the time during which the muscle contracts.  Heart Sound Listening to sounds within the body is called auscultation; it is usually done with a stethoscope. In a healthy heart, there are only two heart sounds. https://www.youtube.com/watch?v=dDg7GDpR1RE5 Heart Sound  Layers of the Heart Endocardium: innermost layer (epithelial and connective tissue). Myocardium: middle layer composed of cardiac muscle tissue. Epicardium: outermost layer Endocardium (epithelial and connective tissue). Myocardium Epicardium The left and right ventricles pump the same amount of blood per contraction Muscle of left ventricle is thicker and better developed than the right ventricle. Muscle of right ventricle is less thick than that of the left ventricle. The left ventricle must generate The right ventricle does not need a great amount of pressure to to generate as much pressure, overcome the high resistance since the pulmonary circulation is needed to pump blood into the shorter and provides less long systemic circulation. resistance.  Cardiovascular System Circulations The heart is actually two pumps in one: The right side of the heart pumps blood to the lungs and back to the left side of the heart through vessels of the pulmonary circulation. The left side of the heart pumps blood to all other tissues of the body and back to the right side of the heart through vessels of the systemic circulation.  Cardiovascular System Circulations Pulmonary circulation (steps 1, 2 and back to step 3). Systemic circulation (steps 3, 4 and back to step 1).  Blood Vessels Blood vessels are the pipes that transport blood throughout the body. Arteries: transport blood away from the heart. Veins: transport blood toward the heart. Capillaries: sites of exchange of gases.  Arteries vs. Veins Both arteries and veins have a tunica intima, tunica media, and tunica externa.  Arteries vs. Veins Tunica intima: innermost layer (epithelial and connective tissue). Provides a smooth surface for blood movement through the lumen of the blood vessel. Tunica media: Middle layer. Circularly arranged layers of smooth muscle cells that are supported by elastic fibers. Tunica adventitia: outermost layer of the blood vessel wall. composed of connective tissue that contains elastic and collagen fibers.  Arteries vs. Veins Contraction of smooth muscle in the tunica media results in vasoconstriction or narrowing of the blood vessel lumen. Relaxation of the smooth muscle causes vasodilation or widening of the blood vessel lumen. Arteries vs. Veins  Capillaries contain only the tunica Capillaries intima composed of an endothelium and its underlying basement membrane. Having this thin barrier allows for rapid gas and nutrient exchange between the blood in capillaries and the tissues. Endothelium Basement membrane Capillary Capillary bed Gas Exchange in Capillary Beds  Atherosclerosis Atherosclerosis is the buildup of fats, cholesterol and other substances in artery walls. This buildup, called plaque, narrows arteries and blocks blood flow. The plaque can also burst, leading to a blood clot.  Cardiac Conduction System ▪ The human heart is continuously working pump that doesn’t stop throughout life. ▪ The pump needs electricity to work! ▪ The heart is able to create its own electrical impulses. ▪ The cardiac conduction system is a network of specialized cardiac muscle cells that works to ensure that cardiac chambers contract in a coordinated manner, which makes the heart an effective pump.  Cardiac Conduction System https://www.youtube.com/watch?v=RYZ4daFwMa8 Cardiac Conduction System 1. Sinoatrial node (SA node): Node of specialized cardiac muscle cells (pacemaker cells). 1 The natural pacemaker of the heart (usually 60 to 100 beats per minute for 2 adults at rest). Located in the wall of the right atrium. It starts each heartbeat. 2. Atrioventricular node (AV node): Located at the junction of the atria and ventricles. Cardiac Conduction System 3. Atrioventricular bundle (Bundle of His): A bundle of fibers that extends from the AV node into the interventricular septum (which divides the heart into right and left sides). The AV bundle transmits cardiac impulses. 4. Left and right bundle branches: the AV 5 bundle splits into the right and left bundle branches. These bundles carry cardiac 3 impulses to both sides of the heart. 4 5. Purkinje fibers: At the ends of the AV 4 bundle branches are the Purkinje fibers, which deliver the impulse to the myocardial cells, causing the ventricles to contract.  The Cardiac Cycle 1. The electrical impulse starts at the SA node. The right and left atria contract together, pumping blood into the right and left ventricles, respectively. 2. The impulse passes to the AV node, which sends it to the AV bundle (bundle of His). In the meantime, the right and left atria relax. 3. The impulse passes into the right and left bundle branches and ultimately into the Purkinje fibers, causing the right ventricle to contract and to pump its deoxygenated blood into the pulmonary arteries and the lungs. And, the left ventricle contracts, pumping oxygenated blood into the aorta. 4. The ventricles relax while the atria begin contracting, and the cycle starts all over again. Electrocardiogram When impulses pass through the heart, electrical currents are generated that spread throughout the body. These impulses can be detected on the body surface and recorded digitally to produce an image called an electrocardiogram (ECG or EKG).  Electrocardiogram P wave: records the electrical activity of atrial depolarization or atrial contraction. QRS complex: records the electrical activity of ventricular depolarization as the impulse spreads through the right and left ventricles and their resultant contraction. T wave: records the electrical activity of ventricular repolarization or the relaxation of the ventricles But where is atrial repolarization? Electrocardiogram  Electrocardiogram Normal Sinus Rhythm: the normal rhythm of the heart. Bradycardia: a slow resting heart or pulse rate under 60 beats/min. Tachycardia: a rapid resting heart or pulse rate over 100 beats/min. Asystole: when the heart’s electrical system fails entirely, which causes the heart to stop pumping.  Fibrillation Fibrillation is uncontrolled heartbeat which prevents it from being able to pump effectively. Atrial fibrillation (A-Fib): a serious condition, but as long as the ventricles continue to pump blood is not dangerous. Ventricular fibrillation (V-Fib): a medical emergency that requires life support, because the ventricles are not effectively pumping blood.  Defibrillators The most common treatment for fibrillation is defibrillation, which uses special paddles to apply a charge to the heart from an external electrical source in an attempt to establish a normal sinus rhythm. The shock actually stops the heart from beating so that the natural pacemaker of the heart can hopefully reset. 48