Trace the pathway of blood (     )through the body using the following terms: – Aorta – Right atrium – Left atrium – Right ventricle – Left ventricle – Lungs – Vena Cava – Venules – Arterioles – Capillaries – Body tissues – Pulmonary artery – Pulmonary vein

The Heart

Functions of the Heart Generating blood pressure Routing blood – Heart separates pulmonary and systemic circulations Ensuring one-way blood flow – Heart valves ensure one-way flow Regulating blood supply – Changes in contraction rate and force match blood delivery to changing metabolic needs

Size, Shape, Location of Heart Size of a closed fist Shape – Apex: Blunt rounded point of cone – Base: Flat part at opposite of end of cone Located in thoracic cavity in mediastinum

External Anatomy Four chambers – 2 atria – 2 ventricles Major veins – Superior& Inferior vena cava – Pulmonary veins Major arteries – Aorta – Pulmonary trunk

External Anatomy

External anatomy: anterior

External anatomy: posterior

Pericardium

Heart Wall Three layers of tissue – Epicardium: (aka visceral pericardium) This serous membrane of smooth outer surface of heart – Myocardium: Middle layer composed of cardiac muscle cell and responsibility for heart contracting – Endocardium: Smooth inner surface of heart chambers

Myocardium Cardiac muscle Fibrous skeleton of the heart – Consists of four dense connective tissue rings – Prevents overstretching of the valves – Serves as a point of insertion for cardiac muscle and as an electrical insulator.

Cardiac Muscle Elongated, branching cells containing 1-2 centrally located nuclei Contains actin and myosin myofilaments Intercalated disks: Specialized cell-cell contact with Desmosomes and gap junctions Electrically, cardiac muscle behaves as single unit

Histology of cardiac muscle tissue

The chambers of the heart

Systemic & Pulmonary Circulation

Heart Valves Atrioventricular (AV) – Tricuspid – Bicuspid or mitral Semilunar – Aortic – Pulmonary Prevent blood from flowing back

The AV valves

The semilunar valves

Location of Heart Valves

Blood Flow Through Heart

Intrinsic Conduction System Sinoatrial node/pacemaker – Crescent shaped node in right atrium – Enforces a contraction rate of 75 beats/min Atrioventricular node – Junction of atria and ventricles Atrioventricular bundle/bundle of His – In interventricular septum Purkinje fibers – Spread within the muscle of the ventricle walls

The conduction system

The excitation of the heart and ECG Systole  contraction Diastole  Relaxation Events of the Cardiac Cycle

Normal Cardiac Cycle

20-25 Cardiac Cycle

Heart sounds Lup-dup, pause, lupdup, pause First heart sound or “lubb” – Closing of AV valves at beginning of ventricular systole Second heart sound or “dupp” – Closing of SL valves at beginning of ventricular diastole, lasts longer Third heart sound (occasional) – Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

Heart Mnemonics ValvesTRIPS BIAS TRIcuspid Pulmonary Semilunar BIcuspid Aortic Semilunar ValvesTRIPS, MI ASs (uses MItral instead of BIcuspid) TRIcuspid Pulmonary Semilunar MItral Aortic Semilunar Valves-Atriums"LAB RATs" Left Atrium: Bicuspid Right Atrium: Tricuspid Heart valves: closure sequence Many Things Are Possible": Mitral, Tricuspid, Aortic, Pulmonary Electrical SignalThe patient's family are all having Heart attacks, you must SAVe HIS KIN!" SA node ---> AV node ---> HIS (bundle of) --> PurKINje fibers Aorta BranchesKnow your ABC'S: Aortic arch gives rise to: Brachiocephalic trunk left Common Carotid left Subclavian

Electrocardiogram P wave  depolarization of the atria QRS complex  depolarization of the ventricle T wave  repolarization of ventricles

The cardiac cycle: Ventricular filling

The cardiac cycle: Ventricular systole

The cardiac cycle: Isovolumetric relaxation

Resources Heart Sounds & Cardiac Arrhythmias Live Cardiac Exam Video Anatomy Links Cardiac Cycle Cardiac Cycle Graphics Interactive Physiology Review