Chapter 11The

Cardiovascular System

The Cardiovascular SystemThe Cardiovascular System Closed system of the heart and blood vessels

Heart pumps blood

Blood vessels allow blood to circulate to all parts of the body

Blood is the transport vehicle Carries oxygen, nutrients, cell wastes, &

hormones, to and from the cells to maintain homeostasis

Function of the cardiovascular system To deliver oxygen and nutrients and to remove

carbon dioxide and other waste products

The HeartThe Heart

Location Mediastinum

Middle cavity of the thorax, between the lungs

Pointed apex directed toward left hip

The great vessels of the heart emerge from the base which points toward the right shoulder and lies beneath the second rib

About the size of your fist Less than 1 lb.

The HeartThe Heart

The Heart: CoveringsThe Heart: Coverings

Pericardium – a double serous membrane Visceral pericardium

Hugs the external surface of the heart & is part of the heart wall

Parietal pericardium Outside layer

Serous fluid fills the space between the layers of pericardium

The Heart: Heart WallThe Heart: Heart Wall Three layers

Epicardium Outside layer This layer is the visceral pericardium Connective tissue layer

Myocardium Middle layer Mostly cardiac muscle – Allows contraction

Endocardium Inner layer Endothelium

External Heart AnatomyExternal Heart Anatomy

The Heart: ChambersThe Heart: Chambers Right & left sides act as separate pumps Four chambers

Atria Receiving chambers

Right atrium Left atrium

Ventricles Discharging chambers

Right ventricle Left ventricle

Blood CirculationBlood Circulation

The Heart: Associated Great VesselsThe Heart: Associated Great Vessels

Aorta Leaves left ventricle

Pulmonary arteries Leave right ventricle

Vena cava Enters right atrium

Pulmonary veins (four) Enter left atrium

The Heart: ValvesThe Heart: Valves Allows blood to flow in only one direction Four valves

Atrioventricular valves – between atria and ventricles Bicuspid (mitral) valve (left) Tricuspid valve (right)

Semilunar valves between ventricle and artery Pulmonary semilunar valve Aortic semilunar valve

The Heart: ValvesThe Heart: Valves

Valves open as blood is pumped through

Held in place by chordae tendineae (“heart strings”)

Close to prevent backflow

Aortic Valve Replacement Surgery

Operation of Heart ValvesOperation of Heart Valves

Coronary CirculationCoronary Circulation Blood in the heart chambers does not nourish

the myocardium

The heart has its own nourishing circulatory system

Right and left coronary arteries & their major branches

Are compressed when the ventricles are contracting and fill when the heart is relaxed

Cardiac veins

Drain the myocardium

Blood empties into the right atrium via the coronary sinus

Angina & Myocardial Infarctionwebsite

Bypass SurgeryWebsiteCoronary Bypass Surgery

Balloon Angioplasty Coronary Angioplasty & Stenting

Heart View

The Heart: Conduction SystemThe Heart: Conduction System Autonomic Nervous system

Nerves = brakes & accelerators to decrease or increase heart rate Accelerators = Sympathetic Nervous system

Brakes = Parasympathetic Nervous system

Intrinsic conduction system- Nodal system

Heart muscle cells contract, without nerve impulses, in a regular, continuous fashion

Built into the heart tissue & sets its basic rhythm

Causes heart muscle depolarization in only 1 direction (From the atria to the ventricles)

Enforces a contraction rate of 75 beats/minute

Heart beats as a coordinated unit

Intrinsic Conduction SystemIntrinsic Conduction System

Special type of tissue Sets the pace Sinoatrial (SA) node

Located within the right atrium Pacemaker Starts each heartbeat

Atrioventricular (AV) node Located at the junction of the right & left atria and

ventricles Atrioventricular bundle (Bundle of His) Bundle branches (right and left) Purkinje fibers

Spread within the muscle of the ventricle walls

Heart ContractionsHeart Contractions

• Three formations– P wave:

– Small & signals the depolarization of the atria immediately before they contract

– QRS complex:– Complicated shape– Depolarization of the ventricles

– T wave:– Repolarization of the ventricles

Electrocardiograms (EKG/ECG)

Electrocardiograms (EKG/ECG)

Abnormal EKG

Pathology of the HeartAbnormal ECG:

Heart Block:Damage to AV node Ventricles are partially or totally released

from the control of the SA node Result = slower heart beatOther conditions can damage the SA node resulting in a

slower heart rateSurgically installation of an artificial pacemaker

Fibrillation Results from a lack of blood flow to the heart (ischemia)Rapid uncoordinated heartbeat that makes the heart useless as a

pump Major cause of death from heart attacks in adultsTachycardia (If prolonged, can lead to fibrillation)

+100 beats/minBradycardia

Less than 60 beats/min

The Heart: Cardiac CycleThe Heart: Cardiac Cycle Cardiac cycle

Events of 1 complete heartbeat

Both atria & ventricles contract and then relax

Atria contract simultaneously and then relax ventricles then contract simultaneously and then relax

Systole

Contraction of the ventricles

Diastole

Relaxation of the ventricles

Filling of Heart Chambers – Filling of Heart Chambers – the Cardiac Cyclethe Cardiac Cycle

The Heart: Cardiac OutputThe Heart: Cardiac Output

Cardiac output (CO)

Amount of blood pumped out by each side of the heart (each ventricle) in one minute

CO = (heart rate [HR]) x (stroke volume [SV])

Varies with the demands of the body

Stroke volume (SV)

Volume of blood pumped out by a ventricle with each heartbeat

The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate

Stroke volume usually remains relatively constant

Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction

Changing heart rate is the most common way to change cardiac output

Regulation of Heart RateRegulation of Heart Rate

Increased heart rate Sympathetic nervous system stimulation

Activated in times of “Fight or Flight” Hormones

Epinephrine Thyroxine

Exercise Fever

Increases the metabolic rate of heart cells

The Heart: Regulation of Heart The Heart: Regulation of Heart RateRate

Decreased heart rate

Parasympathetic nervous system stimulation

Congestive heart failure

Heart is worn out and pumps weakly

Digoxin

Works to provide a slow, steady, but stronger beat

Cardiac Output RegulationCardiac Output Regulation

Congestive Heart Failure (CHF)Decline in pumping efficiency of the heart

Leading to inadequate circulationProgressive condition

Causes: Coronary atherosclerosis, high blood pressure and a history of multiple myocardial infarctions

Left side failsPulmonary congestion suffocation

Right side failsPeripheral congestion and edema

Blood Vessels: Blood Vessels: The Vascular SystemThe Vascular System

Taking blood from the heart to the tissues and back Arteries

Arterioles

Capillaries

Venules

Veins

Blood Vessels: AnatomyBlood Vessels: Anatomy Three layers (tunics)

Tunic intima Lines the lumen or interior of the vessels Endothelium slick surface, decreases friction as

blood flows through

Tunic media Middle coat Smooth muscle

Controlled by sympathetic nervous system Changes the diameter of the vessels

Constriction blood pressure increases Dilation blood pressure decreases

Tunic externa Mostly fibrous connective tissue Outermost tunic

The Vascular SystemThe Vascular System

Differences Between Blood Vessel Differences Between Blood Vessel TypesTypes

Walls of arteries are the thickest

Lumens of veins are larger than arteries

Skeletal muscle “milks” blood in veins toward the heart

Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

Movement of Blood Through Movement of Blood Through VesselsVessels

Most arterial blood is pumped by the heart

Veins use the milking action of skeletal muscles to help move blood

Varicose Veinswebsite

Capillary BedsCapillary Beds

Capillary beds consist of two types of vessels

Vascular shunt – directly connects an arteriole to a venule

Capillary BedsCapillary Beds

True capillaries – exchange vessels

Oxygen and nutrients cross to cells

Carbon dioxide and metabolic waste products cross into blood

Diffusion at Capillary BedsDiffusion at Capillary Beds

Vital SignsArterial pulseBlood pressureRespiratory RateBody Temperature

PulsePulse

Pulse – pressure wave of blood

Monitored at “pressure points” where pulse is easily palpated

Blood PressureBlood Pressure

Measurements by health professionals are made on the pressure in large arteries

Systolic – pressure at the peak of ventricular contraction

Diastolic – pressure when ventricles relax

Pressure in blood vessels decreases as the distance away from the heart increases

Blood Pressure Changes

Measuring Arterial Blood PressureMeasuring Arterial Blood Pressure

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

Neural factors Autonomic nervous system adjustments

(sympathetic division)

Renal factors

Regulation by altering blood volume

Renin – hormonal control

Blood Pressure: Effects of FactorsBlood Pressure: Effects of Factors

Temperature

Heat has a vasodilation effect

Cold has a vasoconstricting effect

Chemicals

Various substances can cause increases or decreases

Diet

Variations in Blood PressureVariations in Blood Pressure Human normal range is variable

Normal 140–110 mm Hg systolic 80–75 mm Hg diastolic

Hypotension Low systolic (below 110 mm Hg) Often associated with illness

Hypertension High systolic (above 140 mm Hg) High diastolic (above 90) Can be dangerous if it is chronic

Varicose Veinswebsite

Blood Distribution