Cardiovascular System The Heart

Heart Facts The cardiovascular system is composed of the heart and a closed system of vessels through which blood is circulated. Hollow muscular organ Tipped slightly so that a part of it sticks out and taps against the left side of the chest (apex), which is what makes it seem as though it is located there. During an average lifetime, the human heart will beat more than 2.5 billion times. Beats over 100,000 times/day and 35 million times/year to pump blood around the body's 60,000 miles of blood vessels. 5 pints of blood pump throughout your entire body with one single heartbeat.

External Structure of the Heart Layers Edocardium (inner layer) Epicardium (outer layer) Myocardium (middle layer) Pericardium - the protective membrane surrounding the heart Coronary arteries – supply blood to the outside of the heart

External Structure

Internal Structure Septum Atria and ventricles atria contract while the ventricles relax ventricles contract while the atria relax. Atrioventricular (AV) Valves Bicuspid (Mitral) Valve – between left atria and ventricle Tricuspid Valve – between right atria and ventricle Semilunar (SL) Valves Pulmonary SL Valve – between right ventricle and pulmonary artery Aortic SL Valve – between left ventricle and aorta Ventricular Septum - right and left ventricles are divided by a thick muscular wall babies born with "hole in the heart“ Why problematic? Septum

connect papillary muscles to AV valves “heartstrings”

The Cardiac Cycle The events associated with one heartbeat. A single cardiac cycle lasts 0.8 seconds Described as the contraction and relaxation of the four heart chambers. During relaxation, chambers fill with blood (diastole). During contraction, chambers expel blood (systole). Heart Sounds The first heart sound (lubb) occurs during ventricular contraction when the tricuspid and bicuspid valves (AV valves) close. The second heart sound (dubb) occurs during ventricular relaxation when the pulmonary and aortic valves (SL valves) close.

The walls of the left ventricle are thicker as it has to pump blood to all the tissues, compared to the right ventricle which only pumps blood as far as the lungs. Septum

Blood Pressure Blood moves through circulatory system from areas of high pressure to low pressure. (Contraction of the heart produces the pressure.) Blood Pressure is a measurement of the force that blood exerts against the inner walls of arteries. 120/80 is normal = systole/diastole systolic pressure - The maximum pressure during ventricular contraction; systolic pressure is the peak arterial pressure. diastolic pressure - The lowest pressure of blood in the arteries during ventricular relaxation (diastole); the arterial pressure drops.

Blood Pressure vs. Distance From Left Ventricle

Conduction System Heart muscle cells contract without stimulation from the nervous system in a continuous, rhythmic pattern. Contraction is initiated by the sinoatrial (SA) node (pacemaker). SA node is located in the right atrium Cells of the SA node can reach threshold on their own SA node initiates one action potential after another (~70-80 times/min) Pathway of electrical impulse Sinoatrial (SA) node Atrioventricular (AV) node Atrioventricular bundle (bundle of His) Bundle branches Purkinje fibers There is a momentary delay as the ventricles fill before they contract

Electrocardiograms (ECG / EKG) A recording of the electrical changes that occur within the myocardium as the heart contracts. R vent cont L vent cont R atr cont

Electrocardiograms (ECG / EKG) Atria repolarized Ventricle depolarized Heart relaxed Ventricular walls repolarize AV node and walls depolarize Atrial walls completely depolarized Atria repolarizes Ventricle depolarizes

Cardiomyopathies Heart Valves Stenosed Valves – valves that are narrower than normal, slowing blood flow from heart chamber Rheumatic Heart Disease – delayed inflammatory response to streptococcal infection that occurs most often in children; valves become inflammed Mitral Valve Prolapse (MVP) – affects bicuspid or mitral valve; flaps of valve extend back into the left atrium causing the valve to leak; asymptomatic or pain and fatigue Aortic Regurgitation – blood ejects into aorta and regurgitates back into left ventricle due to leaky aortic SL valve; ventricle becomes too full and can cause MI

Cardiomyopathies Myocardium Coronary Artery Disease (CAD) – One of leading causes of death in US; reduced blood flow to myocardial tissue; occlusion causes cells deprived of oxygen and eventually die Heart Attack Myocardial Infarction (MI) myocardial = heart muscle tissue infarction = tissue death due to oxygen starvation A blood clot completely blocks a coronary artery (or one of its branches), cutting off oxygen supply to that part of the heart. This results in cardiac tissue death. Atherosclerosis – hardening of the arteries due to fatty build up Angina pectoris – myocardium deprived of oxygen causing severe chest pain; warning that coronary arteries can not supply heart with necessary oxygen Coronary Bypass Surgery – treatment for coronary artery blood flow constriction; veins are harvested from other areas of body and used to bypass blockages Congestive Heart Failure (CHF) – “left-side heart failure”; inability of left ventricle to pump blood effectively; could result from MI caused by CAD

Cardiomyopathies Arteries Arteriosclerosis – hardening of the arteries causing blockage and weakening of the arterial walls; calcium deposits form; painful and life threatening Ischemia – decreased blood supply to tissue; gradual cell death Necrosis – tissue death Gangrene – necrosis that has progressed to having decomposing bacteria Angioplasty – procedure to mechanically open the affected area of an artery like in atherosclerosis patients; catheter inserts balloon to inflate and push out plaque; stents can be inserted to keep artery open Aneurysm – arterial wall damage due to arteriosclerosis or other factors; section of artery abnormally widened because of weak arterial wall; causes clot formation that travels (thrombus) that can cause an embolism (blockage) in the heart; tendency to burst resulting in death Cerebrovascular Accident (CVA) aka Stroke – results from brain tissue ischemia caused by an embolism or ruptured aneurism; effects range from hardly noticeable to crippling effects

Balloon Angioplasty

Cardiomyopathies Veins Varicose Veins – enlarged veins where blood tends to pool rather than continuing to the heart; occur in superficial veins Hemorrhoids – varicose veins in the anal canal due to excessive straining Phlebitis – vein inflammation Thrombophlebitis – acute phlebitis caused by a thrombus; pain and discolored tissue Pulmonary Embolism – embolus lodged in lung; death quickly

Heart Attack In this illustration, a clot is shown in the location of #1. Area #2 shows the portion of the damaged heart that is affected by the clot. Heart Attack Animation

Heart Transplant

The surgeon will begin by exposing the chest cavity through a cut in the ribcage. The surgeon will then open the pericardium (a membrane that covers the entire heart) in order to remove your diseased heart. The back part of your own left atrium will be left in place, but the rest of the heart will be removed.

Your new heart will be carefully trimmed and sewn to fit the remaining parts of your old heart. This transplant method is called an "Orthotopic procedure". This is the most common method used to transplant hearts. You will be given medications both before and during the operation to prevent you from rejecting the new heart.

Live heart to be transplanted into patient