• TOUGH
• OPAQUE
• FIBROUS MEMBRANE
• SURROUNDS HEART

• Parietal pericardium lines the pericardial sac
• Visceral pericardium covers the outer surface of the heart
• Secretes pericardial fluid (watery, lubricating)

• Small space between parietal and visceral pericardium
• Contains pericardial fluid

• Same as the visceral pericardium
• Thin, outermost layer of the heart wall

• Middle, thickest layer 
• Composed of cardiac muscle

• Thin, innermost layer
• Lines the chambers of the heart
• Continous with the endothelium of the great vessels

• deep groove on the surface of the heart 
• separates the atria from the ventricles

INTERVENTRICULAR SULCI

(POSTERIOR AND ANTERIOR)

• shallower groove, separates the two ventricles
• Contains vessels of coronary circulation and lots of adipose tissue

• Thin muscular partition separating the 2 atria internally

• Thick muscular partition separating the 2 ventricles internally

• Thin walled (thin myocardium)
• Received blood returning to the heart
• Contract weakly to pump blood into the ventricleS

• Thick walled (much thicker myocardium)
• Receives blood from the atria
• Contract strongly to pump blood out of the heart

• Contracts quickly to pump blood through the triscupid valve into the right ventricle.
• Receives blood returning to the heart from the systemic circuit via the:

-Superior & Inferior Vena Cava

 -Coronary Sinus

• Blood from the head, neck, thorax,and upper extremities

• Blood from the abdomen and lower extremities

• Blood from the coronary circulation

• Receives blood returning to the heart from the pulmonary circuit via the pulmonary veins
• Contract weakly to pump blood through the bicuspid valve into the left ventricle (LV)

• Receives blood from the RA
• Contracts strongly to pump blood through the pulmonary semilunar valve into the pulmonary trunk
•  Pump for the pulmonary circulation

• Receives blood from the LA
• Contracts strongly to pump blood through the aortic semilunar valve into the ascending aorta
• Pump for the systemic circuit

RV VS LV

LV:

• Rounder shape
• Thickest myocardium, 
• Strongest contraction
• Develops the greatest pressure

• The triscuspid valve between the RA and RV
• The biscupid (mitral) between the LA and LV

•  Atrial pressure exceeds ventricular pressure and the AV valves open to allow blood to flow into the ventricles

• Ventricular pressure exceeds atrial pressure and the AV valves close to prevent backflow of blood into the atria

• Located between the ventricles and the arteries leading out of the ventricles
• The aortic valve between the LV and the aorta
• The pulmonary valve between the RV and the pulmonary trunk

• Ventricular pressure exceeds arterial pressure and valves open to allow blood to exit the ventricles and flow into the arteries

• Arterial pressure exceeds ventricular pressure and the valves close to prevent backflow of blood into the ventricles

• Valve is too narrow when opened

VALVE DISORDER

• Valve doesn't close properly
• EX:MITRAL VALVE PROLAPSE-ONE OR BOTH CUSPS EXTEND BACK INTO THE LA DURING LV SYSTOLE

• Part of the systemic circulation
• Supplies blood to the myocardium
• Begins with the right and left coronary arteries, which originate at the base of the ascending aorta
• Ends with the great cardiac vein and coronary sinus (a type of vein), which empties into the RA

• Partial or complete blockage of coronary circulation due to accumulation of atherosclerotic plaque 
• Leads to coronary ischemia (inadequate blood flow to the myocardium)
• Leads to hypoxia (inadequate O2)
• Leads to angina pectoris (chest pain)

-Pain may be absent at rest but appear during exertion (reason for stress electrocardiogram)

• Complete blockage of some part of coronary circulation
• Usually due to thrombus forming at site of plaque, which obstructs blood flow
• Cardiac muscle cells die from lack of O2 (eventually replaced by scar tissue)
• Effect on the heart depends on location and area

• Striated:  like skeletal muscle
• Involuntary:  unlike skeletal muscle
• Cell shape:  branched or forked
• Intercalated discs
• Autorhythmicity
• Depends upon aerobic cellular respiration, of fatty acids and glucose (also lactic acid during exercise)

• Gap junctions which allow muscle action potentials to spread directly from cell to cell

• A network of specialized cardiac muscle cells that initiates and distributes electrical impulses to the myocardium

• The natural pacemaker of the heart 
• Located in the posterior wall of the RA
• Determines the heart rate

• conduct signal through atrial walls to AV node
• Meanwhile the signal spreads from cell to cell in the atria so atria can contract

• Located in the floor of the RA
• Signal slows, allowing atria to contract before the ventricles start contraction

• Located in the interventricular septum
• Distributes the signal to the bundle branches

• One for each ventricle
• Also located in the interventricular septum
• Branch into multiple Purkinje fibers

• Carry the signal throughout the ventricular myocardium including the papillary muscles

• AV node fails to transmit the signal from the SA node
• The atria will be paced normally by the SA node
• The ventricles will be paced by the AV bundle or bundle branches independent of the SA node and at a much slower rate than the atria

• Non-invasive method for assessing heart function
• Electrical signals from the heart are recorded by electrodes on the body surface

• Atrial Depolarization

• Ventricular Depolarization

• Ventricular Repolarization

• From the start of atrial depolarization to the start of ventricular depolarization
• Abnormally long of this indicates problem at AV node

• Time required for ventricles to complete one cycle of depolarization and repolarization
• Measured from end of P-R to end of T wave
• Lengthened of this interval could reflect myocardial ischemia

• Any irregularity in the normal rhythm of the heart
• With a complete AV block, since the atria and ventricles would be paced independently, QRS waves could occur anytime with respect to P waves

• Loss of coordination in ventricles (ventricles quiver)
• Pumping of blood ceases
• Rapidly fatal

• Completes ventricular filling by pushing blood through the open AV valves into the ventricles (the ventricles were already 70% filled)
• The EDV is the volume of blood in either ventricles at the end of here
• The ventricles are as filled as they are going to be at the end of here

VENTRICULAR SYSTOLE

(PHASE 1)

• Isovolumetric contraction

• Rising ventricular pressure closes the AV valves, but is not yet enough to open the semilunar valves
• All heart valves are closed 
• Volume of ventricles does not change
• Blood has not yet been ejected from the ventricles

VENTRICULAR EJECTION

(PHASE 2 OF V.S)

• Increasing ventricular pressure opens the semilunar valves
• Blood is ejected into the pulmonary trunk and aorta
• The volume of blood ejected is called the stroke volume (SV)
• Late in systole ventricular pressure decreases rapidly to less than arterial pressure
• Semilunar valves close ending phase

VENTRICULAR DIASTOLE

(EARLY)

• Isovolumetric relaxation 

• Ventricles are relaxed
• Ventricular pressure has not fallen enough to allow opening of the AV valves
• All valves are closed

VENTRICULAR DIASTOLE

(LATER)

• Ventricular decreases to less than atrial pressure, allowing AV valves to open
• Blood pours through the relaxed atria and the open AV valves into the ventricles
• Most ventricular filling (70%) occurs here