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The Cardiovascular System Chapter 12 Human Anatomy & Physiology I. Overview of the Cardiovascular System The circulatory system can be thought of as the transport system of the body. A closed system consisting of the heart, blood vessels, and blood – The heart pumps blood – Blood vessels allow blood to circulate to all parts of the body Function: Deliver oxygen & nutrient-rich blood to body cells and remove carbon dioxide and waste A. Overview of the Heart The heart is located in the thoracic cavity between the lungs slightly to the left A hollow, cone-shaped muscle about the size of a fist Made up of cardiac muscle II. Anatomy of the Heart 1. Coverings: Pericardium – a double serous membrane – Visceral pericardium (epicardium) Next to heart – Parietal pericardium Outside layer Serous fluid fills the space between the layers of pericardium 2. Heart Walls: Three layers a] Epicardium – Outside layer – This layer is the visceral pericardium b] Myocardium – Middle and thickest layer – Mostly cardiac muscle c] Endocardium – Inner layer – Made up of simple squamous epithelium 3. Chambers The heart has 4 chambers – Left & right atria – receive blood – Left & right ventricles pump blood out Chambers are separated by a septum 4. Heart Valves Valves are flaps of connective tissue between the atria and ventricles Moves the blood through the heart in one direction Valves open as blood is pumped through Held in place by chordae tendineae (“heart strings”) Valves are closed to prevent backflow Four valves a. Atrioventricular valves – between atria and ventricles, open valves – left atrium bicuspid valve left ventricle – right atria tricuspid valve right ventricle b. Semilunar valves - between ventricle and artery, closed valves – right ventricle pulmonary semilunar valve pulmonary artery – left ventricle aortic valve aorta 5. Major Vessels Aorta – Blood leaves left ventricle towards body Pulmonary arteries – Oxygen-poor blood leaves right ventricle towards lung Vena cava – Superior and inferior – Blood from the body enters the right atrium Pulmonary veins (4) – Oxygen-rich blood from lungs enters left atrium IV. Anatomy of Blood Vessels Blood Vessels are tubes which transport blood A. Function: – Transport blood – Carry out the exchange of gases and waste – Regulate blood pressure – Direct blood flow B. Types of Blood Vessels 1. Arteries Blood vessels which carry oxygen-rich blood away from the heart to the body. The aorta is the largest artery in our body Thick walls 2. Capillaries Microscopic blood vessels which connect arteries and veins together Where exchange of oxygen, carbon dioxide, nutrients, and waste occur One cell layer thick 3. Veins Blood vessels which carry oxygen-poor blood from the body back to the heart. Thin walls Requires muscles to push blood back to the heart C. Diseases 1. Arteriosclerosis – The hardening of the arteries due to the formation of scar tissue – Leads to hypertension, heart attack, & stroke 2. Varicose veins – Valves in the veins become weak leading to abnormal dilations in the superficial veins 3. Phlebitis – Inflammation of a vein – Very serious because it can lead to thromboembolism and death IV. Circulation of Blood in the Body Circulation is the transportation of blood A. The goal is to 1. Send oxygen-poor blood to the the lungs to pick up oxygen and then 2. To pump oxygen-rich blood from the heart to the body cells B. Three circulation pathways 1. Pulmonary circulation 2. Systemic circulation 3. From heart to lungs From heart to body Coronary circulation From heart to heart muscle C. Pulmonary Circulation 1. Flow of blood from the heart to the lungs DEOXYGENATED BLOOD must have carbon dioxide removed, so it is sent to the lungs – Body cells > 1 – Veins > 6 – Vena cava (1)> 3 4 4 – R Atrium (2)> – Tricuspid valve > 5 2 – R Ventricle > – Pulmonary Semilunar valve> – Pulmonary ARTERY (3) > – Lungs 1 D. Systemic Circulation 1. Flow of blood from the heart to the body OXYGENATED BLOOD coming back from the lungs is pumped to the body cells – Lungs > – Pulmonary VEINS (4)> – L Atrium > – Bicuspid (mitral) valve > – L Ventricle (5) > – Aortic Valve > – Aorta (6)> – Arteries > – Body cells 1 6 3 4 2 1 4 5 Happy Days: Pump your blood http://www.youtube.com/watch?v=upctP Ua6RhA C. Coronary Circulation 1. Flow of blood to the heart tissues The heart has its own nourishing circulatory system – Coronary arteries – from aorta to myocardium (heart muscle) – Cardiac veins – from the myocardium to the ventricle 2. Coronary disorders a. Atherosclerosis – blockage of the arterial walls due to the build up of cholesterol that can lead to a heart attack b. Thromboembolism – blood clot that breaks away from its origin and is carried to a new location Can lead to a heart attack if embolus blocks a coronary artery Comparison of Arteries 3. Prevention & Treatment a. Aspirin – reduces stickiness of platelets, therefore prevents clots b. Surgery – i. Balloon Angioplasty – tube is guided through the blood vessel to the blockage where is inflated to open up the vessel or break the clot – ii. Coronary Bypass Operation – a blood vessel from another part of the body is sutured from the aorta to the coronary artery, past the blocked area – Allows blood to flow to cardiac muscle Videos Balloon Angioplasty – http://www.youtube.com/watch?v=F_gVBK6Y kPA Coronary Bypass – http://www.youtube.com/watch?v=8nbscVKK Sm8 V. Blood The only fluid tissue in the human body Taste, odor, 5x thicker than water Color range – Oxygen-rich blood is scarlet red – Oxygen-poor blood is dull red pH must remain between 7.35–7.45 5-6 Liters or about 6 quarts/body A. Composition 1. Blood Plasma Makes up 55% of blood Composed of 90% of water Contains nutrients, salts (metal ions), respiratory gases, hormones, proteins, waste products 2. Erythrocytes – Red Blood Cells The main function is to carry oxygen Biconcave disks Anucleate (no nucleus) Outnumber white blood cells 1000:1 Each erythrocyte has 250 million hemoglobin molecules – Iron-containing protein – Binds strongly to oxygen 3. Leukocytes – White Blood Cells Crucial in the body’s defense against disease 4. Platelets Small fragments produced from ruptured cells (megakaryocytes) Needed for the clotting process B. Blood Disorders 1. Anemia – caused by low iron or hemoglobin – Symptoms: fatigue, dizziness, headaches, short of breath 2. Sickle cell Anemia – recessive genetic disorder – Symptoms: fatigue, bone pain, ulcers, delayed growth, short of breath 3. Hemophilia – recessive sex-linked bleeding disorder – Blood lacks clotting factors – Minor injuries can cause uncontrolled bleeding VI. Physiology of the Heart A. Conduction System of the Heart Initiates, stimulates, and coordinates the contraction of the atria and ventricles – Makes the heart an effective pump 2 types of Nodal tissue controls the heartbeat – SA (sinoatrial) Node – found in right atrium Initiates the heartbeat every 0.85 seconds Serves as the pacemaker – AV (atrioventricular) Node – bottom of right atrium The SA node sends out an impulse causing the atria to contract. The impulse reaches the AV node and travels along the AV bundle. The impulses travels throughout the ventricles to the Purkinje fibers. Ventricles contract. B. Cardiac Cycle & Heart Sounds Cardiac cycle includes all the events that occur in one heartbeat – Heart beats ~70x/minute L & R atria contract simultaneously Atria relaxes then L & R ventricles contract simultaneously Systole – contraction Diastole - relaxation 1. Atrial systole – 0.15 sec – Atria is systole (contracted) pumping blood into ventricles (diastole-relaxed) 2. Ventricle Systole - 0.30 sec – Ventricle fills with blood and contracts pumping blood to the aorta and pulmonary arteries 3. Atrial & Ventricle Diastole – 0.40 sec – Both atria & ventricles are diastole (relaxed) as blood from the body fills the atria Bicuspid Valve What is that sound? - Lup: closing of the bicuspid and tricuspid valve - Dup: closing of aortic and pulmonary valve C. Measuring the Cardiac Cycle Electrocardiograms (EKG or ECG) are used to measure the electrical rhythm of the heart’s contraction PQRST Waveform D. Disorders Damage to AV node = muscles cells in the ventricles do not beat together results in a slower heart beat – Slower heart beat can lead to fibrillation Fibrillation = lack of blood flow to the heart Arrhythmia = irregular heart beat Tachycardia = more than 100 beats/min Bradychardia = less than 60 beats/min Pacemaker Used to maintain a consistent heart rate when the body’s natural pacemaker (SA node) is not properly functioning C. Vital Signs 1. Pulse The stretching and recoiling of the arterial wall as blood surges through Monitored at “pressure points” where pulse is easily palpated 2. Blood Pressure A device called a sphygmomanometer measures the pressure in large arteries – Systolic: pressure at the peak of ventricular contraction – Diastolic: pressure when ventricles relax Pressure in blood vessels decreases as the distance away from the heart increases http://blood-pressure.emedtv.com/high-blood-pressure-video/what-is-bloodpressure-video.html Measuring blood pressure Variations in blood pressure – Normal 140–110 mm Hg systolic 80–75 mm Hg diastolic – Hypotension (Low BP) Low systolic (below 110 mm HG) Often associated with illness – Hypertension (High BP) High systolic (above 140 mm HG) Can be dangerous if it is chronic Warning sign for stroke and heart attack risk Hypertension Effects of High Blood Pressure http://www.youtube.com/watch?v=pPxnI h_WTb8&feature=related http://blood-pressure.emedtv.com/highblood-pressure-video/what-is-bloodpressure-video.html