The Heart

Overview of the Heart double pump about the size of a fist - cone shaped weight less than 1 lb.

located mid-thoracic cavity between the lungs lies at an angle under the sternum angles to the left

covered with double walled membrane - pericardium outer layer is tough inner is a serous potential space between pericardial cavity with serous fluid to reduce friction

3 Layers of Heart Wall pericardium – myocardium – endocardium – outer cardiac muscle bulk of the heart contracts endocardium – lines chambers

Heart Chambers

Heart Chambers 4 chambers as in all birds and mammals 2 1 3 4

R and L Atria Left Atrium Right Atrium receive blood small and thin walled Left Atrium Right Atrium

R and L Ventricles RV pumps blood to the lungs LV pumps blood to the body large and thick walled because has hardest job to do

septum divides the heart into R and L sides

Great Vessels

Great Vessels RA superior vena cava inferior vena cava blood from superior body to heart inferior vena cava blood from below heart RA

pulmonary veins 4 total from lungs LA

pulmonary trunk to lungs RV

aorta largest artery to all organs LV

Heart Valves

Atrioventricular Valves = AV valves between atrium and ventricle right is tricuspid left is the bicuspid or mitral

papillary muscles attached to chordae tendineae contraction pulls valves open when V begins to contract, blood is forced against valve and it shuts

Semilunar Valves Aortic Semilunar Valve between ventricle and aorta Pulmonary Semilunar Valve between ventricle and pulmonary trunk

Semilunar Valves force of blood pushes them open attempted backflow after contraction closes them

Left Atrium Right Atrium Left Ventricle Right Ventricle

Superior Vena Cava Inferior Vena Cava

Pulmonary Trunk L Pulmonary Artery R Pulmonary Artery

Left Pulmonary Veins Right Pulmonary Veins

Aorta Aorta

Aorta Pulmonary Trunk Superior Vena Cava L Pulmonary Artery R Pulmonary Artery Left Pulmonary Veins Right Pulmonary Veins Inferior Vena Cava Aorta

Pulmonary Semilunar Valve Aortic Semilunar Valve Tricuspid Valve Bicuspid Valve

Septum Chordae Tendineae Apex

Circulation

Pulmonary Circulation right side of heart from body to heart to lungs for oxygen

Pulmonary Circulation From body ↓ Superior and inferior vena cava Right atrium Tricuspid valve Right ventricle Pulmonary Semilunar valve Pulmonary trunk R and L pulmonary arteries Capillary beds of lungs (gas exchange) Pulmonary veins

System Circulation left side of heart supplies body with oxygenated blood

Aortic Semilunar valve Superior and Inferior Vena Cava Systemic Circulation From lungs ↓ Pulmonary Veins Left atrium Bicuspid valve Left ventricle Aortic Semilunar valve Aorta Arteries Capillary beds of body (gas exchange) Superior and Inferior Vena Cava

Coronary Arteries

Coronary Arteries supply the heart muscle with oxygen rich blood

Atherosclerosis these are clogged with plaque contract in spasms called angina or get clots stuck in them one cause of heart attack

cardiac muscles that die are not replaced dead cells = infarct myocardial infarction or MI is proper term for a heart attack

coronary bypass surgery is most common surgery in USA

Conduction System

Conduction System coordinated activity depends on gap junctions and “in house” conduction system

Steps: sinoatrial node in RA near superior vena cava acts as “pace maker” by initiating each wave of nerve activity wave moves to atrioventricular node in septum between atria

to the AV bundle (bundle of His) in upper ventricular region of septum to the Pyrkinje fibers which branch down septum to ventricles

5. contraction starts a bottom (apex) of ventricles to push blood up and out arteries

Fibrillation uncoordinated contractions A fibs - rapid flutters and weakness

V fibs - fatal unless heart is defibrillated shocked back into normal

Electrocardiogram ECG measures electrical events of the heart

Heart Excitation Related to ECG

Electrocardiography

Cardiac Cycle

Cardiac Cycle all the events associated with the flow of blood through the heart in 1 beat Diastole - period of cardiac ventricle filling Systole - period of cardiac ventricle pumping (contracts)

Heartsounds LUB-dup closing of valves LUB - AV valves closing, longer and louder dup - Semilunar valves closing, shorter and sharper

Murmurs abnormal sounds are called murmurs and are usually caused by leaky of narrowed valves