The Cardiovascular System Chapter 11 1

Components 1. There are two components to the system: the heart and the blood vessels. 2. The heart pumps the blood so it flows to tissue capillaries and lung capillaries. 3. There are (3) types of blood vessels: arteries, veins, and capillaries. 4. The blood vessels transport blood and its components. 2

Importance The cardiovascular system connects the body’s cells with its organs of exchange 1. Lungs- oxygen enters, carbon dioxide exits blood 2. Small intestine- nutrient molecules enter the blood 3. Kidneys- metabolic wastes exit the blood 3

Anatomy of the Heart 1. Hollow, cone- shaped, muscular organ the size of a fist 2. Base (widest part), apex (pointed tip) 3. On a slant- base directed toward right shoulder, apex points to left hip 4

Functions of the Heart 1. Keeps oxygen-poor blood separate from oxygen-rich blood 2. Keeps blood flowing in one direction— blood flows away from and then back to heart 3. Creates blood pressure, which moves blood through the circuits 4. Regulates the blood supply based on the current needs of the body 5

The Wall and Coverings of the Heart 1. Epicardium (visceral pericardium)- serous membrane that lines outer surface of the heart 2. Myocardium- thickest part of heart wall, made up of cardiac muscle. When cardiac muscle contracts  heart beats 3. Endocardium- inside lining of heart wall, composed of simple squamous epithelium, smooth nature prevents blood from clotting 6

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Chambers of the Heart 1. Four hollow chambers a) Two superior atria (sing. Atrium) b) Two inferior ventricles 2. Atria have thin walls- send blood into adjacent ventricles 3. Ventricles have thicker walls- pump blood into blood vessels that travel to parts of the body a) Left ventricle thicker wall- pumps blood to all other parts of body b) Right ventricle- pumps blood to lungs (nearby) 8

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Right Atrium 1. Receives oxygen-poor blood from three veins a) Superior vena cava b) Coronary sinus c) Inferior vena cava 2. Atrioventricular valve (AV) or tricuspid valve- three cusps/ flaps, venous blood passes from right atrium into right ventricle 10

Right Ventricle 1. Tricuspid valve connected to fibrous cords called the chordae tendineae (“heart strings”) 2. Blood from right ventricle passes through a semilunar valve into the pulmonary trunk 3. This pulmonary semilunar valve prevents blood from flowing back into the right ventricle. 4. The pulmonary trunk divides into left and right pulmonary arteries 11

Left Atrium 1. Receives oxygen-rich blood from four pulmonary veins 2. Bicuspid (mitral) valve- passes blood from left atrium into left ventricle 12

Left Ventricle 1. Forms the apex of the heart 2. Contains thicker and stronger chordae tendineae than the right ventricle 3. Blood passes from left ventricle into the aortic semilunar valve (also larger and thicker) and then into the aorta 4. Some blood goes into the coronary arteries which nourish the heart itself 5. The aorta is the largest blood vessel in the body. 13

Operation of Heart Valves 1. AV valves normally open 2. When ventricles contract, pressure of blood forces cusps of AV valve to meet and close 3. Papillary muscles contract and causes the chordae tendineae to tighten and pull on valve (prevents blood from going into atrium) 4. Semilunar valve is usually closed, the contraction of ventricle opens it 5. Valves can leak, close improperly, and/or cause backflow 14

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Superior View showing closed valves. 16

17 Physiology of the Heart a.k.a. The Pumping System

18 Nodal Tissue 1. Referred to as the “nodes” 2. Has both muscular and nervous characteristics 3. Located in (2) regions of heart : a) SA (sinoatrial node)- upper posterior wall of right atrium; called the “pacemaker” b) AV (atrioventricular node)- base of right atrium

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20 Conduction System of the Heart 1. Stimulus originates in sinoatrial node and travels across walls of the atria, causing them to contract 2. Stimulus arrives at the atrioventricular node and travels along the AV bundle 3. Stimulus descends to the apex of the heart through the bundle branches 4. After the stimulus reaches the Purkinje fibers, the ventricles contract

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22 Electrocardiogram (ECG) Graph that records electrical activity of myocardium during cardiac cycle

23 ECG Waves 1.P wave: depolarization of atria; atria about to contract 2.QRS wave: depolarization of ventricles; ventricles about to contract Shows greater voltage than P wave because ventricles are more muscular 3.T wave: repolarization of ventricles; ventricles about to relax

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25 Arrhythmias- Irregular or Abnormal Heartbeats 1. Bradycardia- fewer than 60 beats/minute 2. Tachycardia- more than 100 beats/minute 3. Fibrillation- heart beats rapidly but contractions uncontrolled

26 Cardiac Cycle 1. Cardiac cycle- all the events that occur during one heartbeat 2. There are three stages: atrial systole, ventricular systole, and atrial & ventricular diastole 3. Phase 1- Atrial Systole (0.15 sec) a) Atria contracted and ventricles relaxed b) Blood enters two ventricles, AV vavles open, semilunar valves closed

27 3. Phase 2- Ventricular Systole (0.30 sec) a) Both ventricles contracted, atria relaxed b) Rising blood pressure forces blood to enter pulmonary trunk and aorta through semilunar valves c) Semilunar valves open, AV valves closed

28 4. Phase 3 (0.40 sec)- Atrial and Ventricular Diastole a) Both atria and both ventricles relaxed b) Pressure in heart chambers low c) Blood returning to heart flows in passively d) Both AV valves open, semilunar valves closed

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30 Heart Sounds 1. “LUB-DUP” “LUB-DUP a) “lub”- ventricles contract and AV valves close b) “dup”- relaxation of ventricles allows semilunar valves to close 2. Heart murmurs- clicking or swishing sounds after “lub”, due to leaky valves Heart murmurs-

31 Cardiac Output (CO) 1. Volume of blood pumped out of ventricle in one minute 2. Dependent on : a) heart rate (HR)- beats per minute b) stroke volume (SV)- amt of blood pumped by ventricle each time it contracts 3. Average Human CO is 5.25 L per minute (~total volume of blood in human body)