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The Cardiovascular System: The Heart

• Heart pumps over 1 million gallons per year

• Over 60,000 miles of blood vessels

Functions

• Transport oxygen & carbon dioxide to and from tissues

• Transports nutrients, waste products, and hormones

• Regulates body temperature• Plays a role in the immune response

Important Facts

• A healthy adult heart pumps about 5 liters of blood out per minute.

• During vigorous exercise, the amount of blood pumped out of the heart per minute drastically increases.

• If the heart stops contracting, blood flow throughout the body stops.

• If the heart stops functioning for a few minutes life will end.

Circulation

• Heart is two pumps in one!!!• Pulmonary —right side of heart

forcing blood to flow to the lungs and back to the left side of the heart

• Systemic —left side of heart forces blood to flow to all other tissues in the body and back to the right side of the heart

Circulation

Size, Form, and Location of Heart

• Shaped like a blunt cone

• About the size of a closed fist

• In thoracic cavity between the lungs

• Apex —blunt, rounded point; most inferior part of heart

• Base —larger, flat portion; directed superiorly and slightly posteriorly

Anatomy of the Heart

• Pericardium —double layered, closed sac that surrounds the heart– Pericardial cavity —

space around the heart

• Filled with a thin layer of pericardial fluid—helps reduce friction as the heart moves within the pericardial sac

Layers of Heart Wall

• Epicardium– visceral layer of

serous pericardium

• Myocardium – cardiac muscle

layer is the bulk of the heart

• Endocardium– chamber lining &

valves

Concept Check

• About how big is your heart? What is the inferior portion called? The superior?

• How many miles of blood vessels does your body contain?

• What are the two types of circulation the heart does?

• What are the functions of the circulatory system?

• What are the three layers of the heart?• What surrounds the heart in the body?

Myocardial Thickness and Function

• Thickness of myocardium varies according to the function of the chamber

• Atria are thin walled, deliver blood to adjacent ventricles

• Ventricle walls are much thicker and stronger– right ventricle supplies blood to the lungs (little flow resistance)– left ventricle wall is the thickest to supply systemic circulation

Thickness of Cardiac Walls

Myocardium of left ventricle is much thicker than the right.

External Anatomy of Heart

• Superior/Inferior Vena Cava —carry blood from body to right atrium

• Pulmonary veins —carry blood from lungs to left atrium

• Pulmonary arteries —carry blood from heart to the lungs

• Aorta —carry blood from the heart to the rest of the body

Heart Chambers

• Atria—2 upper chambers– Receives blood from veins– Contraction of atria forces blood into

ventricles • Ventricle—2 lower chambers

– Pump blood out of the heart into arteries– Left is thicker than rightSeptum—separates heart into right and

left sections

Right atrium

Right ventricle

Left atrium

Left ventricle

Septum

SuperiorVena Cava

Aorta

Heart Valves

• Atrioventricular valves—located between atria and ventricles– Prevent blood from

backflow into atrium

• Tricuspid valve—between right atrium & right ventricle

• Bicuspid (mitral) valve—between left atrium & left ventricle

tricuspid

bicuspid

Heart Valves

• Aortic semilunar valve—blood flow from left ventricle to aorta– Prevents backflow

• Pulmonary semilunar valve—blood flow from right ventricle to pulmonary trunk– Prevents backflow

Path of Blood Through Heart

• Enters through Superior/Inferior Vena Cava—Right atrium—tricuspid valve—Right ventricle—pulmonary semilunar valve—pulmonary arteries—lungs—Left atria—bicuspid valve—left ventricle—aortic semilunar valve—aorta

• SA node– cluster of cells in wall of Rt. Atria– begins heart activity that spreads to both atria– excitation spreads to AV node

• AV node– in atrial septum, transmits signal to bundle of

His

• AV bundle of His – the connection between atria and ventricles– divides into bundle branches & purkinje fibers,

large diameter fibers that conduct signals quickly

Conduction System of Heart

Electrocardiogram---ECG or EKG

• EKG– Action potentials of all

active cells can be detected and recorded

• P wave– atrial depolarization

• P to Q interval– conduction time from

atrial to ventricular excitation

• QRS complex – ventricular depolarization

• T wave– ventricular repolarization

Conduction of the Heart

• Fibrillation—heart acting as a lot of pacemakers causing the heart to contract rapidly – Reduces the output of the heart by only a few

milliliters of blood per minute when it occurs in the ventricles—these needs to stop quickly before death sets in

• Defibrillation—a strong electrical shock is applied to the chest region– Trying to cause heart to go back into normal

fibrillation

Auscultation

• Stethoscope• Sounds of heartbeat are from

turbulence in blood flow caused by valve closure– first heart sound (lubb) is created with the

closing of the atrioventricular valves– second heart sound (dupp) is created with

the closing of semilunar valves

Blood Pressure

• Systole—contraction of the ventricles– Atria are relaxed allowing blood to collect– Immediately atrioventricular valves closes– Once pressure builds beyond pressure in aorta

and pulmonary trunk, blood is forced into pulmonary trunk and aorta

• Diastole—relaxation of the ventricles– Atria contract allowing blood to flow into

ventricles– Ventricular pressure decreases– Semilunar valves close

Exercise and the Heart

• Sustained exercise increases oxygen demand in muscles.

• Benefits of aerobic exercise (any activity that works large body muscles for at least 20 minutes, preferably 3-5 times per week) are;– increased cardiac output– increased HDL and decreased triglycerides– improved lung function– decreased blood pressure– weight control.

Congestive Heart Failure • Causes of CHF

– coronary artery disease, hypertension, MI, valve disorders, congenital defects

• Left side heart failure– less effective pump so more blood remains in

ventricle– heart is overstretched & even more blood remains– blood backs up into lungs as pulmonary edema– suffocation & lack of oxygen to the tissues

• Right side failure – fluid builds up in tissues as peripheral edema

Risk Factors for Heart Disease

• Risk factors in heart disease: – high blood cholesterol level– high blood pressure– cigarette smoking– obesity & lack of regular exercise.

• Other factors include:– diabetes mellitus– genetic predisposition– male gender– high blood levels of fibrinogen– left ventricular hypertrophy

Coronary Artery Disease • Heart muscle receiving

insufficient blood supply– narrowing of

vessels---atherosclerosis, artery spasm or clot

– atherosclerosis--smooth muscle & fatty deposits in walls of arteries

• Treatment– drugs, bypass graft,

angioplasty, stent

Clinical Problems• MI = myocardial infarction

– death of area of heart muscle from lack of O2

– replaced with scar tissue– results depend on size & location of damage

• Blood clot– use clot dissolving drugs streptokinase or t-

PA & heparin– balloon angioplasty

• Angina pectoris----heart pain from ischemia of cardiac muscle

By-pass Graft

Stent in an Artery

• Maintains patency of blood vessel

Cardiac Cycle

• Repetitive pumping process that begins with the onset of cardiac muscle contraction and ends with the beginning of the next contraction

• Pressure changes—Blood moves from areas of high pressure to low pressure

• Blood Pressure– Systole– Diastole

Abnormal Heart Sounds

• Called murmurs• Result of faulty valves—valve doesn’t

close tightly allowing blood to enter• Makes a swishing sound immediately

after closure of the valve– Example: incompetent bicuspid valve

makes a swishing sound after first heart sound

Regulation of Heart Function

• Cardiac output— volume of blood pumped by either ventricle of the heart each minute– Cardiac output= stroke volume x heart

rate• Stroke volume— the volume of blood

pumped per ventricle each time the heart contracts

• Heart rate— the number of times the heart contracts each minute