HEART

• Located at the left side of mediastinum

A. LAYERS

• Epicardium - covers the outer surface of the heart

• Myocardium - middle layers; contracting muscle

• Endocardium - innermost layer; lines inner chamber and heart valves

B. PERICARDIUM - encases and protects the heart from trauma and infection

• Parietal Pericardium - Tough fibrous membrane that attach to the sternum, thoracic vertebrae and   diaphragm

• Visceral Pericardium - Thin membrane that attach to the heart

• Pericardial Space - In between: holds 5-20 ml 0f fluid which lubricates the pericardial surfaces

C. HEART CHAMBERS

• Right Atrium - receives deoxygenated blood from the body via SVC and IVC

• Right Ventricle - receives blood from the RA and pumps it to the lungs via Pulmonary Artery

• Left Atrium - Receives oxygenated blood from the lungs via the 4 pulmonary veins

• Left Ventricle - largest and most muscular chamber and receives oxygenated blood from the LA and pumps  blood into the systemic circulation via aorta

D. HEART VALVES

• Atrio-Ventricular Valves - lies between the atria and the ventricles Closed at the beginning of ventricular contraction and prevents blood from flowing back to the atria, Opens when ventricles relax

• Semilunar Valves - Opens when ventricles contact and prevent blood from flowing back into ventricles, Closed when ventricles relax

• Bicuspid or Mitral Valve - located at the left side of the heart

• Tricuspid Valve - located at right side of the heart

• Pulmonic Valve - Between RV and Pulmonary Artery

• Aortic Semilunar Valve - Between LV and Aorta

E. ELECTRICAL CONDUCTIVITY OF THE HEART

1. Sinoatrial Node (SA node) - Pacemaker of the Heart; initiates each heart beat

   • Located at junction of SVC and RA

   • Generates electrical impulse at 60-100 times/ min

2. Atrioventricular Node (AV node) - Located at the lower aspect of the atrial septum

   • Receives electrical impulse from the SA node

3. Bundle of HIS (AV Bundle) - Fuses with AV node to form another pacemaker site

   • Branches into the left and right Bundle Branch and terminates into Purkinjie Fibers

   • If SA node fails it can initiate and sustain HR of 40-60bpm

4. Purkinjie Fibers - Spread waves of depolarization through ventricles

F. CORONARY ARTERIES - Supply the myocardium with blood

G. HEART SOUNDS

• S11st heart sound - heard when AV valve closed

• S2 2nd heart sound - heard when semilunar valve closed

• S3 3rd heart sound - CHF

• S4 4rth heart sound - HTN