THE HEART

HEART LOCATION & ANATOMY

right lungleft lung

pericardium

apex of heart

diaphragmMEDIASTINUM

PERICARDIAL LAYERS

FIBROUS PERICARDIUM

SEROUS PERICARDIUM (parietal layer)

pericardial cavity

SEROUS PERICARDIUM visceral layer (epicardium)

myocardium

endocardium

heart chamber

HEART MUSCLE

cardiac muscle bundles

v Three Layers Endocardium Myocardium Epicardium

HEART CHAMBERS

ANTERIOR

INTERIOR

Right atrium

Right ventricle Left ventricle

Left atrium

Interventricular septum

HEART CHAMBERS: ATRIA

pectinate muscles

fossa ovalis

tricuspid valve

(L) pulmonary veins

bicuspid valve

HEART CHAMBERS: VENTRICLES

papillary muscles

pulmonary semilunar valve

chordae tendineae

trabeculae carneae

aortic semilunar valve

aorta

PULMONARY AND SYSTEMIC CIRCULATION

CIRCULATION THROUGH THE HEARTVena cavae (R) ATRIUM (R) VENTRICLE

Pulmonary trunk

Pulmonary arteries

LUNGS Pulmonary veins (L) ATRIUM

(L) VENTRICLEAorta

CORONARY CIRCULATION

(L) coronary artery

(R) coronary artery

marginal artery

posterior interventricular artery anterior interventricular artery

circumflex artery

CORONARY CIRCULATION

great cardiac vein

anterior cardiac veins

small cardiac vein

middle cardiac vein

coronary sinus

CORONARY CIRCULATION SUMMARYAorta

(R)Coronary artery (L)Coronary artery

Posteriorinterventricular

artery

Marginalartery

Circumflexartery

Anteriorinterventricular

artery

Ventricularwalls

Walls of (R) atrium& (R) ventricle

Walls of (L) atrium& (L) ventricle Ventricular

walls

Cardiac veins

Coronary sinus

(R)atrium

CARDIAC HISTOLOGYv Cardiac Muscle Cells

Striated

1 to 2 nuclei Numerous, large

mitochondria

Intercalated discs

CARDIAC CONDUCTION SYSTEM

v Nodal System Autorhythmic Cells

1% of cardiac cells Initiate and conduct and impulse Unstable resting membrane potential Continuously depolarize Trigger contractions of heart muscle

CARDIAC CONDUCTION SYSTEMv Nodal System

Sinoatrial (SA) Node Mass of autorhythmic cells Near SVC entrance Depolarizes 70 to 80 times

a minute (100 if no neural control)

Depolarization spreads through atria

Atria contract

CARDIAC CONDUCTION SYSTEMv Nodal System

Atrioventricular (AV) Node Autorhythmic cells Above tricuspid valve in

interatrial septum Passes impulse on to AV

bundle (Bundle of His)

Bundle of His (AV Bundle) Conducts impulse to

right and left bundle branches

CARDIAC CONDUCTION SYSTEMv Nodal System

Bundle Branches Right and left branches Branch into purkinje

fibers Purkinje Fibers

Enter myocardium of ventricle walls and papillary muscles

Carry impulse to ventricles

Ventricular contraction

CARDIAC CONDUCTION SYSTEM SUMMARY

Sinoatrial Node

AV Node

AV Bundle

Bundle Branches

Purkinje Fibers

EXTRINSIC INNERVATIONv Autonomic Nervous System

Can slow or accelerate heart Cannot initiate a contraction Cardiac centers in medulla Stimulation by sympathetic

neurons Increase heart rate Increase force of contraction

Inhibition by parasympathetic neurons

Via Vagus nerve Decrease heart rate Decrease force of contraction

CARDIAC CYCLE

v Interval from end of one contraction to the following contraction

v 0.8 sec.v Consists of Two Phases:

Systole phase Diastole phase

CARDIAC CYCLEv Systole Phase

Contraction phase Blood ejected Atrial Systole (0.1 sec.)

Following passive filling with blood

AV valves open, semilunar valves closed

Ventricles fill with blood

RA

LA

RV

LV

semilunar valves (closed)

tricuspid (open)

bicuspid (open)

CARDIAC CYCLEv Systole Phase (cont.)

Ventricular Systole (0.3 sec.)

AV and semilunar valves closed until pressure opens semilunar valves

Blood pushed into pulmonary trunk

120 mm Hg pressure Atria in diastole

RA

LA

RV

LV

tricuspid (closed)

bicuspid (closed)

semilunar valves (open)

CARDIAC CYCLE

v Diastole Phase Relaxation phase Ventricular Diastole

Follows ventricular systole

AV valves reopen and filling begins

80 mm Hg pressureRA

LA

RV

LV

semilunar valves (closed)

tricuspid (open)

bicuspid (open)

ELECTRICAL EVENTS: ECG

P wave:atrial depolarization

QRS complex:ventricular depolarization

QRS complex

T wave:ventricular repolarization

ECG READINGSNormal

SA Node Dysfunctionno P waves

2nd Degree Heart Block(more P waves)

Ventricular Fibrillation

HEART SOUNDSv Lub-dub

AV valves closing for ventricular systole Semilunar valves closing

v Pause Quiescent period (0.4 sec.) Ventricles and atria in diastole simultaneously

CARDIAC OUTPUT

v Amount of blood pumped out by each ventricle in 1 minute

v Sympathetic stimulation needed if CO more than 14 liters/min. is needed

v Starling’s Law The greater the volume of blood returned to the

heart by the veins, the greater the volume of blood the heart will pump

HEART RATE REGULATION: Nervous System

v Cardiac Inhibitory Center Medulla Parasympathetic Vagus nerve Continually slows heart to

maintain average of 70 beats/min. v Cardiac Accelerator Center

Medulla Sympathetic Increases heart rate and force

of contraction when needed

OTHER REGULATORS v Hormonal Regulation

Accelerators Epinephrine, norepinephrine Thyroxine, T3

v Body Temperature Increase temp. = increase heart rate Decrease temp.= decrease heart rate

v Baroreceptors Carotid sinus and aortic arch

Stretch impulses to inhibitory center vagus nerve decreased heart rate

v Bainbridge (Atrial) Baroreceptors Measure intraatrial pressure

Stimulate accelerator center Increased heart rate and force of contraction

DISORDERSv Tachycardia

Abnormally high heart rate (over 100)v Bradycardia

Abnormally low heart rate (under 60)v Myocardial Infarction

Death of myocardium Replaced with scar tissue

v Arrhythmia Uncoordinated pattern of heart contractions

v Fibrillation Rapid and out of phase contractions

v Angina Pectoris Pain caused by deficiency in blood delivery to the myocardium

DISORDERSv Pericarditis

Inflammation of the pericardium Can result in cardiac tamponade

v Congestive Heart Failure Inadequate pumping of the heart Blood back-up in lungs or body Excessive fluid in tissues

v Atherosclerosis Formation of fatty plaque on artery walls Decrease in vessel elasticity and possible blockage

v Ischemic Heart Disease Inadequate blood supply to cardiac muscle Temporary or chronic

v Heart Murmur Defective valve allowing back flow of blood Hissing sound from turbulence

BLOOD VESSELS: ARTERIESv Arteries

Carry blood away from heart high in oxygen Branch into arterioles Three groups:

Elastic Arteries Largest Elastic fibers in tunica media Expand and recoil (pulse) Examples:

Aorta, pulmonary trunk, common iliac arteries

BLOOD VESSELS: ARTERIES Three groups (cont.)

Muscular arteries Medium size

Carry blood from elastic arteries to arterioles

Active in vasoconstriction

Examples: Femoral, brachial, axillary arteries

Arterioles

Smallest arteries

Carry blood to capillaries

Regulate blood flow to capillaries

BLOOD VESSELS: VEINSv Carry blood from body back to heartv Low in oxygen

v Venules empty into veins

v May contain valvesValve

(closed)

Valve (open)

OTHER VESSELSv Capillaries

Smallest vessels Connect arterioles to venules Exchange of nutrients, gases with tissue cells

v Sinusoids Vessels in place of capillaries In liver, spleen, bone marrow

v Anastomoses Connections between vessels such as arteries and veins

without a capillary bed in between

STRUCTURE OF BLOOD VESSELSv Arteries and Veins

Three tunics Tunica interna

(intima) Tunica media Tunica externa

(adventitia)

ARTERY VEIN

tunica externa

tunica media

tunica interna Vasa vasorum

STRUCTURE OF BLOOD VESSELSv Capillaries

Thin walls Pre-capillary sphincters

CAPILLARY

ARTERIOLE

smooth muscle cell

endothelium

CAPILLARY STRUCTUREPre-capillary sphincters

TERMINAL ARTERIOLE

POSTCAPILLARY VENULE

CAPILLARIES

BLOOD PRESSUREv Pressure exerted on vessel wallsv mm Hg pressure in systemic arteriesv Measured with sphygmomanometer

Pressure in cuff compresses artery until no pulse heard Systolic pressure: taken at first pulse as pressure in cuff released

(ave. 120) = pressure while heart ventricles contracting Diastolic pressure: taken when cuff released to point where sound

no longer audible (ave. 80) = pressure when ventricles not contracting

Pulse pressure = systolic - diastolic (measure of stress exerted on small arteries)

INFLUENCES ON B.P.v Blood Pressure varies directly with the following:

Cardiac Output Stroke volume X heart rate Normal is 5.5 liters/min.

Peripheral Resistance Opposition to blood flow

with blood viscosity with length of vessel with in vessel diameter (has the greatest influence on

B.P.)

INFLUENCES ON B.P.v Blood Pressure varies directly with the following:

Blood Volume Mainly regulated by kidneys in blood volume = in B.P. in blood vol. = decrease in B.P.

REGULATION OF B.P.v By nervous system, kidneys and chemical controlsv Nervous Regulation:

Sympathetic nerve fibers Vasoconstriction of blood vessels

diameter, resistance B.P.

Vasomotor center in medulla Controls cardiac output Controls degree of vessel constriction

REGULATION OF B.P.v Nervous Regulation (cont.)

Baroreceptors Pressure sensitive mechanoreceptors In aortic arch, carotid sinuses, large elastic arteries of head

and thorax Stretching impulses to vasomotor center Vasomotor center inhibited dilation of vessels, decreased

heart rate and output decreased B.P. Chemoreceptors

Monitor O2, CO2 levels and pH of blood In carotid and aortic bodies Send impulses to vasomotor center if O2 or pH drop or CO2

rises Vasoconstriction B.P.

CHEMICAL REGULATION OF B.P.v Epinephrine and Norepinephrine

Vasoconstriction cardiac output

v ANF (Atrial Natriuretic Factor) Release of more sodium and water in urine blood volume B.P.

v ADH (Antidiuretic Hormone) Stimulates kidneys to reabsorb water blood volume B.P.

v Renin Released from kidneys in response to low B.P. Stimulates angiotensin/aldosterone system Kidneys reabsorb sodium and water blood volume and B.P.

RENIN / ANGIOTENSIN / ALDOSTERONE SYSTEM

CHEMICAL REGULATION OF B.P.

v Other Chemical Controls: Endothelin

Nitric oxide

Inflammatory chemicals (histamine)

Alcohol (inhibits ADH release and depresses the vasomotor center)

RENAL REGULATION OF B.P.v Kidneys may alter B.P. directly

Increased B.P. more blood filtered by kidneys More urine produced and released blood volume B.P.

v Kidneys may alter B.P. indirectly Renin/angiotensin system activated with B.P. Vasoconstriction, water reabsorption due to aldosterone

release blood volume B.P.

DISORDERS

v Hypotension Low B.P. (systolic below 100 mm Hg)

Aging, poor nutrition, anemia, hypothyroidism, Addision’s disease, low blood protein levels or circulatory shock

DISORDERSv Hypertension

Sustained B.P. of 140/90 or higher “Silent killer” Higher risk with:

Age Diet Obesity Stress Smoking Genetics

DISORDERSv Circulatory Shock

Not enough blood to fill the vessels and circulate normally Hypovolemic shock

Large loss of blood volume Diarrhea, vomiting, hemorrhage, burns

Vasoconstriction, weak pulse, sharp drop in B.P.

DISORDERSv Circulatory Shock (cont.)

Not enough blood to fill the vessels and circulate normally Vascular shock

Extreme vasodilation Poor circulation, rapidly dropping B.P. Normal blood volume Problems with vasomotor center, nervous regulation

or bacterial infections Cardiogenic shock

Heart cannot pump adequate blood supply Usually from myocardial damage

HEAD AND NECK ARTERIES

ABDOMINAL AORTA

CELIAC TRUNK