Ch. 18-The Cardiovascular System "The Heart"

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Misc. Facts

1) Heart pumps over 1 million gallons per year (5 liters per min). 2) Over 60,000 miles of blood vessels

Heart location

Heart is located in the mediastinum (Area from the sternum to the vertebral column and between the lungs)

Heart Orientation

1) Apex- pointed end of the heart located between the 5th and 6th ribs on the left side 2) Base- directed posteriorly, superiorly and to the right


1) Heart is enclosed in a double-walled sac called the pericardium (like a Wal-Mart bag). 2) Two layers: Fibrous (visceral) pericardium (Attached to diaphragm and fused to major blood vessels, Protects and anchors the heart and prevents over stretching), Serous (parietal) pericardium (Thin delicate membrane, Contains 2 layers). 3) Parietal layer of serous pericardium lines internal surface of fibrous pericardium. 4) Visceral layer of serous pericardium is the covering of the heart (In between is pericardial cavity with pericardial fluid which allows the heart to work in an almost friction free environment)


1) Inflammation of the pericardium which roughens the membranes. 2) Hear rubs against pericardial sac making creaking noise (heard with stethoscope)

Heart has 3 layers

Epicardium- covers hear muscle (visceral layer of serous pericardium). 2) Myocardium- heart muscle (cardiac muscle layer is the bulk of the heart). 3) Endocardium- lining of the heart (delicate, slick lining of the heart which lines the chambers and covers the valves)

Four Chambered Heart

1) 2 upper atria- superior to the ventricles (Atria are sacs theat receive blood, Right atria receives deoxynigated blood from the body, Left atria receives blood from the lungs). 2) 2 lower ventricles- does the pumping of the blood (Right ventricle supplies blood to the lungs and there is little flow resistance, Left ventricle wall is the thickest to supply systemic circulation)

Myocardial Thickness and Function

1) Thickness of myocardium varies according to the function of the chamber. 2) Atria are thin walled, deliver blood to adjacent ventricles. 3) Ventricle walls are much thicker and stronger (Right ventricle supplies blood to the lungs with little flow resistance, Left ventricle wall is thickest to supply systemic circulation)

Heart valves

1) The heart valves keep blood going forward. 2) 4 valves (Pulmonary semi-lunar valves- blood passes through here on its way to the lungs, Aortic semi-lunar valves- blood passes through here on it's way to the body, Right atrioventricular valve or tricuspid- blood passes through here on it's way to right ventricle, Left AV valve or Bicuspid or mitral valve- blood passes through here on it's way to left ventricle)

Atrioventricular valves open

When these valves open, blood flows from atria into ventricles when ventricular pressure is lower than atrial pressure

Atrioventricular valves close

1) AV valves close preventing back flow of blood into atria. 2) occurs when ventricles contract

Semilunar valves

1) SL valves open with ventricular contraction (Allow blood to flow into pulmonary trunk and aorta). 2) SL valves close with ventricular relaxation (Prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the SL valves)

Blood circulation: trace the path of blood through the heart (essay)

1) heart is a double pump. 2) Deoxygenated blood comes into the right atria from two main veins (Superior vena cava collects blood from head and arms, Inferior vena cava collects from rest of the body). 3) Right atria contracts and dumps into the right ventricle through the right atrioventricular/tricuspid valve. 4) Right ventricle contracts and pumps blood through pulmonary artery to the lungs through the pulmonary semilunar valve. 5) Blood picks up oxygen at lungs and enters left atria through the pulmonary veins. 6) from left atria it goes through left atrioventricular/bicuspid valve into left ventricle. 7) Left ventricle contracts and sends blood through the aortic semilunar valve into the aorta.

Ausculation (Heart Sounds)

1) Stethoscope 2) Sounds of heartbeat are caused by the closing of heart valves (First heart sound/lub is created with the closing of the atrioventricular valves: Ventricular pressure is higher than atrial pressure, called systol, blood pressure in arteries is the highest at this point due to contraction of ventricles, Second heart sound/dub is created with the closing of semilunar valves: called diastol, blood pressure is lower or constant due to relaxation of ventricles)

Blood Pressures

1) Normal blood pressure is 120mmHg Systolic over 80mmHg Diastolic (Systolic is the highest pressure that results from left ventricular contraction pushing blood, Diastolic is normal pressure when ventricle is relaxed) 2) The volume of blood ejected from each ventricle is 70ml


1) Abnormal heart sounds are called Heart Murmurs 2) Usually caused by valve damage (Damage can be congenital or at birth but often follow inflammation such as rheumatic fever and syphilis, Sounds like a swish or rushing sound occur when blood flows backwards, Occurs when turbulence makes vibrations that make sound or when a mitral stenosis is present)

Heart Problems

1) Persistent heart rate changes usually signals cardiovascular disease 2) Tachycardia is a condition where the heart beats too rapidly, usually 100 beats per minute (High body temp, stress, heart disease) 3) Bradycardia is a slowness of heart beats, usually under 60 beats per minute (Low body temp, drugs, or parasympathetic activity) 4) Fibrillation is when the heart beats too raped and uncoordinated 5) First degree heart block is when the atrial impulse takes longer than usual to reach ventricles

Coronary Circulation

1) Coronary circulation is blood supply to the heart (Heart is a very active muscle and needs lots of O2) 2) When the heart relaxes high pressure of blood in aorta pushes blood into coronary vessels

Coronary Arteries

1) Branches off aorta above aortic semilunar valve (Both carry blood to the myocardial arteries) 2) Left coronary artery (Supplies left atrium and left ventricle, Anterior interventricular artery supplies both ventricles) 3) Right coronary artery (Supplies right ventricle, Posterior interventricular artery supplies both ventricles)

Coronary Veins

1) Collects wastes from cardiac muscle 2) Drains into a large sinus on posterior surface of heart called the coronary sinus 3) Coronary sinus empties into right atrium

Conduction System of the Heart

1) Autorhythmic Cells (Cells fire spontaneously, act as pacemaker and form conduction system for the heart) 2) Sinoatrial or SA mode (Cluster of cells in wall of right atria, Begins heart activity that spreads to both atria, Excitation spreads to AV node) 3) Atrioventricular or AV mode (In atrial septum, transmits signal to bundle of His) 4) AV bundle of His (The connection between atria and ventricles (found in interventricular septum, Divides into bundle branches & purkinje fibers, large diameter fibers conduct signals quickly)

Rhythm of Conduction System

1) Timing is such that the atrium both contract at once and then the ventricles both contract

Cardiac Cycle

1) One complete heartbeat 2) At 75 beats/min, once cycle requires 0.8 sec. (Systol/ contraction and diastol/relaxation of both atria, plus the systol and diastol of both ventricles) 3) End diastolic volume (EDV) (Volume in resting ventricle at end of diastole, about 130ml) 4) End systolic volume (ESV) (Volume in contracting ventricle at end of systole, about 60ml) 5) Stroke volume (SV) (The volume ejected per beat from each ventricle, about 70ml, SV=EDV-ESV)

Cardiac Output

Amount of blood pushed into aorta or pulmonary trunk by ventricle: 1) At 70ml stroke volume & 75 beat/min---5 and 1/4 liters/min 2) Entire blood supply passes through circulatory system every minute

Regulation of Heartrate

1) Nervous control from the cardiovascular center in the medulla (Sympathetic impulses such as fright or anxiety increase heart rate and force of contraction, Parasympathetic impulses decrease heart rate, Baroreceptors or pressure receptors detect change in blood pressure and send info to the cardiovascular center, Located in the arch of the aorta and carotid arteries) 2) Heart rate is also affected by hormones (Epinephrine, norepinephrine, thyroid hormones, Ions:Na+, K+, Ca2+, Age, gender, physical fitness, and temperature)

Electrocardiogram EKG or ECG

1) EKG- action potentials of all active cells can be detected and recorded 2) P wave- Atrial depolarization 3) P to Q interval- Conduction time from atrial to ventricular excitation 4) T wave- ventricular repolarization

Risk factors in heart disease

1) Risk factors in heart disease: High blood cholesterol level (High blood pressure, Cigarette smoking, Obesity & lack of regular exercise) 2) Other factors include: Diabetes mellitus, genetic predisposition, male gender, high blood levels of fibrinogen, left ventricular hypertrophy

Plasma Lipids and Heart Disease

1) Risk factor for developing heart disease is high blood cholesterol level (Promotes growth of fatty plaques, Most lipids are transported as lipoproteins such as low-density lipoproteins, high-density lipoproteins, very low-density lipoproteins, HDLs remove excess cholesterol from circulation, LDLs are associated with the formation of fatty placques, VLDLs contribute to increased fatty plaque formation) 2) There are two sources of cholesterol in the body (In foods we ingest & formed by liver)

Exercise and the heart

1) Sustained exercise increases oxygen demand in muscles 2) Benefits of aerobic exercise (any activity that works large body muscles for at least 20 minutes, preferebly 3-5 times per week) are: (Increased cardiac output, Increased HDL and decreased triglycerides, Improved lung function, Decreased blood pressure, Weight control)

Developmental Anatomy of the Heart

1) The heart develops from mesoderm before the end of the third week of gestation 2) The tubes develop into the four-chambered heart and great vessels of the heart

Coronary Artery Disease

1) Heart muscle receiving insufficiant blood supply (Narrowing of vessels- atherosclerosis, artery spasm or clot, Atherosclerosis- smooth muscle & fatty deposits in walls of arteries) 2) Treatment: Drugs, bypass graft, angioplasty, stent

Clinical Problems

1) MI= myocardial infarction (Death of area of heart muscle from lack of O2, Replaced with scar tissue, Results depend on size & location of damage) 2) Blood clot (use clot dissolving drugs streptokinase or t-PA & heparin, Balloon angioplasty) 3) Angina pectoris- heart pain caused by lack of blood delivery to heart (Causes ischemia or lack of O2 in cardiac muscle)

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