THE HEART

THE HEART

1. Pericardium

   • double layered serous membrane
     • between layers is is pericardium fluid so they don't rub together
     • outer parietal and inner visceral layers
   • protects the heart, holds it in position, prevents overfilling, 'friction free' environment

2. Function

   • pump blood around body
     • Pulmonary Circuit
       • right side of heart
         • to lungs and back (gas exchange)
     • Systemic Cirulation
       • left side
         • rest of body

3. Structure

   • two sides separated by Interventricular Septum
   • right side walls are thinner as it only has to pump to lungs
   • Heart Wall has 3 layers
     • Outer Epicardium
       • supports blood vessels and nerves
     • Middle Myocardium
       • made of cardiac muscle
     • Inner Endocardium
       • squamous epithelium
         • smooth for easy blood flow
   • Four Chambers
     • Two atria
       • filling chambers
     • Two ventricles
       • pumps
         • very thick
   • Four Valves
     • two atrioventricular
       • between atria and ventricles
       • bicuspid
         • prevents backflow from left vent to left atr
       • tricuspid
         • stops backflow from right V to right A
     • two semilunar
       • between ventricles and main arteries
     • valves are anchored by chordae tendinae and papillary muscles

4. Heart Valves Opening and Closing

   • The AV valves are open when the pressure in the atria is greater than in the ventricles
     • AV valves open when blood has just come into heart
   • AV valves close when pressure in the ventricles is greater
     • when ventricles are full
   • When the ventricle contracts, the pressure increases (AV closes) and semilunar opens
   • when the ventricle relaxes, pressure decreases (AV opens) and semilunar closes
     • preventing backflow into ventricles