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 contractionDiastole RelaxationEvents 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 MnemonicsValves TRIPS BIAS  TRIcuspid

PulmonarySemilunarBIcuspidAortic Semilunar

Valves TRIPS, MI ASs(uses MItral instead of

BIcuspid)

TRIcuspidPulmonarySemilunarMItralAortic Semilunar

Valves-Atriums "LAB RATs" Left Atrium: BicuspidRight Atrium: Tricuspid

Heart valves: closure sequence

Many Things Are Possible":

Mitral, Tricuspid, Aortic, Pulmonary

Electrical Signal The patient's family are all having Heart attacks, you must SAVe HIS KIN!"

SA node --->AV node --->HIS (bundle of) -->PurKINje fibers

Aorta Branches Know your ABC'S: Aortic arch gives rise to:Brachiocephalic trunkleft Common Carotidleft 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