The Circulatory System

Interesting Facts

• The heart beat is strong enough to squirt blood 30 feet

• The longer a boy’s ring finger is, the less likely they are to have a heart attack (according to one study)

• The human heart beats ~35 million times per year

• The heart pumps ~1,000,000 barrels of blood in a lifetime

• Most heart attacks occur between 8-9 a.m.

Interesting Facts• The blue whale has the largest heart – it weighs ~

one ton• The hummingbird has a heart that beats 1000

times per minute• Your entire volume of blood goes through your

entire body once every minute• Humans have ~60,000 miles of blood vessels in

their bodies (more than twice the circumference of the earth!)

• Your heart beats 100,000 times and pumps ~2000 gallons of blood every day

• Pig and baboon hearts have been transplanted into humans

Cardiovascular System

• Heart, vessels, blood• Function: transport

gases, nutrients, wastes, hormones

The Heart

• Size of a fist; less than a pound

• In thorax; flanked by lungs; rests on diaphram

• Top: base

• Bottom: apex

Pericardium• Double-layered sac

covering the heart• Outer layer

anchors heart in chest

• Inner layer (epicardium) attached to heart wall

• Lubricating fluid in pericardial space (between layers) reduces friction

Pericarditis

Decrease in fluid causes

layers to cling & rub

against each other

resulting in pain &

decreased efficiency of

heart

Pericardial Tamponade

• Bleeding into pericardial space after chest trauma

• Excess blood restricts expansion of heart during pumping

• Causes shock or death if not corrected

Heart Wall

3 layers:

• Epicardium: outer wall joined with pericardium

• Myocardium: the actual cardiac muscle that contracts

• Endocardium: lines heart chambers & vessels

Heart Chambers

Four chambers:

• 2 atria: top of heart – receive blood from veins

• 2 ventricles: bottom of heart – pump blood through arteries

Heart Chambers

• Septum: divides left from right heart

• Valves: keep blood flowing in one direction

• Four valves: – 2 AV valves, – 2 semilunar valves

Heart sounds (Lupp-dupp) from valves closing

Atrioventricular Valves

AV valves: between atria and ventricles• Bicuspid (mitral) valve: on the left• Tricuspid valve: on the right

• When valves are open blood drains from atria into ventricle

• When ventricle contract, valve flaps are forced shut, blocking blood from reentering atria

Semilunar Valves

• Located in arteries leaving

ventricles

• Pulmonic valve: at base of

pulmonary artery

• Aortic valve: at base of aorta

• When ventricles contract, valves are forced open & let blood flow

• When ventricle relaxes, backflow of blood fills flaps of valve & forces them to shut

Blood VesselsBlood Vessels• Arteries: carry blood away from the heart

• Veins: carry blood to the heart

• Capillaries: connect arteries to veins & exchange gases with tissues

Arteries

• Carry blood at high pressure

• Very thick, stretchy walls that expand in size

• Most carry oxygenated blood (red)

• Damaged arteries spurt in time to heart beat

Arteries

• Aorta: largest vessel (diameter of a garden hose) –receives blood from left ventricle

• Arteriole: smaller vessels connecting arteries to capillaries

Veins• Carry blood at low pressure

• Have valves to prevent backflow of blood against gravity

• Most carry de-oxygenated blood (purple)

• Damaged veins ooze blood

Veins• Vena Cava: dump all

blood from the body into the right atria– superior vena cava:

receives blood from upper body

– inferior vena cava: receives blood from lower body

• Venules: smaller vessels connecting veins to capillaries

Capillaries

• Connect arteries and veins• Walls are one cell thick• Allow exchange of gases through thin walls

– Drop off oxygen delivered from heart by arteries

– Pick up CO2 and send it to the heart thru veins

How Blood Travels thru Vesselsheart artery arteriole capillary venule vein heart

• Narrowing of vessel lumen due to plaque/fat formation on inside of walls

• Causes: diet high in fat, cholesterol, salt; inactive lifestyle; smoking

• Risks: high BP, enlarged heart, embolus blocking circulation; stroke

Atherosclerosis

Coronary Artery

Disease

• When Atherosclerosis affects the arteries that supply the heart muscle

• Symptoms: short of breath after simple exertion, angina (chest pain)

• Risk: MI, cardiac arrest, death

How is CAD treated?

• Medication

• Angioplasty (balloon surgery) – balloon is inserted and inflated in blocked vessel to compress fatty mass against the artery wall

How is CAD Treated?• Stent – wire mesh inserted into the artery to expand its

lumen• Coronary Artery Bypass – arteries are removed from

leg and grafted into the heart to restore circulation

Vessel Disorders

Varicose Veins:

twisted, dilated veins resulting from pooling of

blood due to long periods of

standing, obesity, or inactivity

Vessel Disorders

Thrombophlebitis:

inflammation of a vessel due to clot formation & poor circulation. Clot can become an embolus if freed.

Aneurysm

• Weaking in the wall of a vessel, causing it to balloon outwards.

• Rupture of the site causes– Stroke (if in the brain)– Death (in a large artery – aorta).

Cardiac Circulation

• Coronary arteries exit the aorta & supply oxygen/blood to heart muscle (myocardium)

• Coronary veins pick up & return deoxygenated blood from myocardium

Defects in Coronary

Circulation

• Angina Pectoris: impaired circulation to myocardium causes oxygen deprivation & pain

• Myocardial infarction: “heart attack” – blockage of circulation to section of myocardium causes the muscle to infarct (die)

Pulmonary Circulation• Right ventricle pumps deoxygenated blood

through pulmonary artery to the lungs

• The blood picks up O2 from the lungs and dumps CO2 into the lungs

• Oxygenated blood is returned to the left atrium thru the pulmonary vein

Systemic Circulation

• Oxygenated blood is pumped from left ventricle thru aorta to the body

• Blood dumps oxygen into tissues and picks up CO2

• Deoxygenated blood travels from body to vena cava to the right atrium

The Circulation

Play the Game

Number the parts 1 – 17 (just write the correct order on a piece of paper). Pass your

paper to a classmate when you finish. We will grade them as a class.

Congestive Heart Failure• Heart is ‘worn out’ from hypertension,

multiple MI, atherosclerosis, or age

• Heart pumps too weakly to meet tissue needs

• If one side is weaker than the other, blood will back up in system

Congestive Heart Failure• Left ventricle is failing:

– Pulmonary congestion– Pulmonary edema

(blood in lungs) causes suffocation

• Right ventricle is failing:– Peripheral congestion– Edema in distal body

parts (ankles, feet)

Pulmonary Edema

Pulmonary edema (A); normal lung

(B)

Peripheral Edema

Swelling of feet and ankles due to CHF

Conduction System of the Heart

Heart is under two types of control:

• Autonomic Nervous system– Sympathetic: speeds up contractions– Parasympathetic: the “brakes” that slows

down contractions

• Intrinsic Conduction System– Also called “nodal system”– Heart determines its own rate of contractions

Intrinsic Conduction System

• Nodes are heart tissue that

stimulate heart muscle to

depolarize (contract)

• Depolarization moves from base to apex

• Different areas of the heart have different nodes, each with a different rate

• Node rate gets slower as it moves downwards

• Faster nodes will override slower nodes

Nodes (you need to know these)

                          

                             

3 Stages:• SA node fires, atria

contract (depolarize)• Impulse travels to AV

node, then travels thru bundle of His, bundle branches, & Purkinje fibers – ventricles contract (depolarize)

• Contraction of ventricles has ‘wringing’ action, pushing blood upward and out through large arteries

• Heart muscle repolarizes

Parts of the Conduction

System

SA node:

• “The Heart’s Pacemaker”

• In atria

• Normally sets the pace of 60 – 70

• SA can increase rate when stimulated by drugs, fever, or sympathetic NS (exercise, stress, emotion)

AV Node:• Between atria & ventricles• Special tissues transmit signal from SA to AV

node• Intrinsic rate: 40 - 60

Parts of the Conduction System

Bundle of His: • Transmits impulse

to ventricles • Rate: 30 – 40

beats/minBundle Branches:• Within ventricular

muscles• Rate: 20 – 30

beats/minPurkinje fibers:• Terminal end of

branches

What if Damage Occurs?

• If SA node is damaged or its signal is blocked, the AV node takes over setting the pace (40-60/min)

• If AV node is next damaged, the bundles set the rate (20 – 40/min)

What is a Pacemaker?

If heart is unable to generate

impulse, or pace is too slow,

mechanical pacemaker is

surgically implanted to

provide artificial impulses

Electrocardiogram (ECG/EKG)

• Electrical impulses in heart are measured with ECG

• Electrical activity is translated into waves

Electrocardiogram (ECG/EKG)• P Wave: atria depolarize

• QRS complex: ventricles depolarize

• T wave: repolarization

Abnormalities in ECG

• Heart Monitor hooked up with pads on chest

• Abnormalities in ECG used to diagnose heart damage

• Diagnostic signs: changes in shape of wave, distance between waves, lack of waves…

Irregular Heart Rhythms

• Tachycardia: heart is beating too fast

• Bradycardia: heart is beating too slow

• Heart Block: no connection between atria & ventricles – ventricles beat at their own rate

• Ventricular Fibrillation: heart is ‘shivering’ – no contractions or pulse (cardiac arrest)

• Asystole: dead heart – no electrical activity

Comparing Rates• Normal Sinus Rhythm

• Sinus Bradycardia

• Sinus Tachycardia

• Elevated ST segment (sign of a MI)

• Ventricular Tachycardia

• Heart Block

• PVC (premature ventricular fibrillation)

• Ventricular Fibrillation

• Asystole

Cardiac Cycle

Cardiac Cycle: The events within one heartbeat. Three main stages:

• Mid-to-late diastole: SL valves are closed, AV open; atria contract; blood is forced into ventricles

• Ventricular systole: ventricular pressure forces AV closed; SL forced open; blood rushes out of ventricles; atria relax & refill

• Early diastole: SL shut; AV open; ventricles relax and refill passively

Heart Sounds

• Cardiac cycle heard with a stethoscope

• Two sounds: “lub dup” (pause) “lub dup” (pause) …..– Lub = closing of AV valves (ventricular systole)– Dup = Closing of semilunar valves (between

ventricular systole & diastole)

• Murmurs: abnormal heart sounds that usually indicate valve problems

Valve Disorders

• Leaky Valves: caused by incompetent or deformed valves that force the heart to re-pump blood because of backflow

Stenosis Valves are stiff and do not open completely.

Heart has to pump harder

Murmur: stenosis

Mitral Valve Prolapse• The most common valve disorder

(5-10% of people)

• Mitral valve opens (prolapses) into atrium when shutting & allows blood backflow

Cardiac Output

• Cardiac Output: the amount of blood pumped by each side of the heart per minute

• Cardiac output = heart rate X stroke volume

• Stroke volume = the amount of blood pumped with each contraction

What is the cardiac output if….

HR = 75 bpm; SV = 70 ml/beat?

This is the normal cardiac output for a resting adult.

How is the output affected with exercise?

Do you think it increases or decreases?

What affects Stroke Volume?(you don’t have to write this down)

Increase in Stroke volume:

• Increased venous blood return– exercise (muscles force blood into heart)– Slow hr (more time to fill ventricles)

Decrease in stroke volume

• Decreased venous return– Hemorrhage (less blood volume)– Tachycardia (not enough time to fill)

What affects Heart Rate?(you don’t have to write this either)

Increase:• Decline in SV (heart

compensates by hr)• Babies and kids• Females• During exercise• Sympathetic NS

Decrease:• Parasympathetic NS• Getting older• Males• Being fit (heart is

more efficient)• Cold temperatures

Taken to assess overall health status

• Arterial pulse

• Blood Pressure

• Respiratory Rate

• Temperature

Arterial Pulse• Alternating expansion and recoil of arteries with each heart beat

• Measured in beats per minute

• Normal resting pulse: 60 – 100 bpm

• Taken at pulse points: place where pulse is easily palpated (felt)

Pulse Points Can also be

used as pressure

points to stop bleeding

Blood Pressure

• Pressure of the blood against artery walls• Measured as systolic/diastolic (ex. 120/80)

– Systolic: pressure at peak of contraction– Diastolic: pressure during ventricular relaxation

• Can be taken by:– Auscultation (listening for pulse)– Palpation (feeling for pulse)

• Normal: 100 + age / 60-90

What Determines the

BP?

• Cardiac Output (blood pumped per min)

• Peripheral Resistance – friction inside vessel that hampers flow of blood– Usually results from narrowing of arteries

What affects BPIncreases BP:• Atherosclerosis• Thick blood• Drugs/nicotine• Obesity

Decreases BP:• Shock/blood loss• MI• Drugs• Physical fitness

Problems with BP• Hypotension (low BP):

– Systolic < 90mm/Hg– Cause: MI; warning sign of shock; athletes

• Hypertension (high BP)– Systolic >140; Diastolic >90– Heart is forced to work hard for extended time– Vessels damaged due to higher pressure– Causes: obesity, diet, exercise, smoking, genes– Risks: heart attack, stroke