The Heart

The Heart

Location of the heart• About the size of a

clenched fist• Rests on the

diaphragm, located in the mediastinum

• Major blood vessels enter and exit the heart at the base

• Projects to the left of midline

Structure of the pericardium and heart wall

• Pericardium holds heart in position while allowing movement

• Serous pericardium is a double layer– Parietal layer is fused

to fibrous pericardium– Visceral layer is fused

to epicardium– Pericardial fluid lies

between

Layers of the heart wall

• Epicardium- lubrication

• Myocardium- bulk of cardiac muscle

• Endocardium- continuous with endothelium of blood vessels; covers valves

Chambers of the heart

Chambers of the heart are bounded by sulci

Right and left ventricleAtria andventricles

Fibrous skeleton of the heart is formed from dense connective tissue

• Fibrous rings• Right and left fibrous

trigone• Conus tendon• Functions

– Limits stretching of valves

– Controls movement of electrical impulses through heart

Heart valves• Atrioventricular

– Tricuspid– Bicuspid (mitral)

• Semilunar– Pulmonary– Aortic– Control ejection of

blood into arteries• Prevent backflow of

blood

The heart is a double pump

Coronary circulation

• Coronary arteries branch from ascending aorta

• Anastomoses connect arteries and provide alternate pathways

Coronary circulation

• Coronary veins drain into coronary simus

Cardiac conduction system

• SA node• AV node• Av bundle• Bundle branches• Purkinje fibers

Activity may be measured by ECG

Cardiac cycle• Relaxation- all

chambers in diastole• Atrial systole forces

blood into ventricles• Ventricular systole

forces blood into arteries

• Heart sounds associated with valve activity (auscultation)

The heart appears very early in development

Congenital heart defects

Coronary artery disease

Heart problems can be congenital, degenerative or both

• Conduction problems– Arrhythmias– Blocks– Fibrillations

• Congestive heart failure– Cumulative damage– Right side-peripheral edema– Left side- pumonary edema