The Heart and Cardiovascular System

What you will learn…

■ The location of the heart ■ 3 layers and covering of the heart ■ Explain the function of the heart as 2 separate

pumps ■ Identify the 4 chambers of the heart ■ Explain the functions of the 4 heart valves ■ What makes the 2 heart sounds? ■ Describe how blood flows through the heart

■ List the vessels that supply blood to the heart ■ Identify the major components of the heart’s

conduction system ■ Describe the events of the cardiac cycle ■ Name 5 factors that affect heart rate ■ List 2 ways in which stroke volume may be

altered ■ Describe the pulmonary and systemic

circulations ■ Describe the structure and function of arteries,

capillaries, and veins

■ List the major arteries and veins ■ Factors that determine blood pressure

I. Structure of the Heart

1. Hollow, muscular organ, made up of cardiac muscle

2. Function: to pump and force blood through the blood vessels of the body, providing every cell in the body with vital nutrients and oxygen

■ The heart pumps an average of 72 times each minute for your entire lifetime

■ If you live to be 75, your heart will beat in excess of 3 billion times!

3. The adult heart is about the size of a closed fist

4. It sits in the chest between the 2 lungs

5. 2/3 of the heart is located to the left of the midline of the sternum

■ The lower, more pointed end of the heart is called the APEX

■ PERICARDIUM: membrane that surrounds heart

■ The PERICARDIUM attaches the heart to surrounding structures, such as the diaphragm

II. Layers and Coverings of the Heart1. The heart is made up of 3 layers of

tissue ■ ENDOCARDIUM ■ MYOCARDIUM ■ EPICARDIUM

2. Endocardium■ Thin, innermost layer ■ Composed of simple

squamous epithelium ■ The smooth, shiny

surface allows blood to flow over it easily

■ Also forms the inner lining of blood vessels

3. Myocardium■ Thick middle layer ■ Composed of

cardiac muscle ■ Allows the heart to

contract, forcing blood through the blood vessels

4. Epicardium■ The thin outermost layer

5. Pericardium■ Between the epicardium

and the pericardium is a space called the PERICARDIAL SPACE, or PERICARDIAL CAVITY

■ The pericardium is a serous membrane, secreting a thin, slippery fluid into the pericardial space

5. Pericardium

■ The pericardial fluid lubricates the surfaces of the membranes and allows them to slide past one another

III. Circulation

1. The myocardium enables the heart to pump blood (made of cardiac muscle)

2. The heart is like a DOUBLE PUMP – or 2 pumps that beat as one

3. The right heart receives unoxygenated blood from the SUPERIOR and INFERIOR VENA CAVAE – large veins that collect blood from all parts of the body

4. The right heart is always colored blue because it symbolizes unoxygenated blood

■ It pumps blood to the lungs, where the blood is oxygenated

■ PULMONARY CIRCULATION right side of the heart to and through the lungs and back to the left side of the heart

■ Function of pulmonary circulation is to load the blood with O2 and unload CO2

■ This happens by DIFFUSION

5. The left side of the heart receives the oxygenated blood from the lungs and pumps it to all the organs of the body

■ The left side of the heart is colored red because it symbolizes oxygenated blood

■ SYSTEMIC CIRCULATION left side of the heart to all the organs of the body and back to the right heart

IV. The Heart’s Chambers and Large Vessels

1. The heart has 4 chambers: 2 atria and 2 ventricles

■ ATRIA (singular ATRIUM) receive the blood – the upper chambers

■ VENTRICLES pump the blood out of the heart – the lower chambers

Heart Chambers

2. Right Atrium

■ A thin-walled cavity ■ Receives unoxygenated

blood (blue) from: ■ SUPERIOR VENA CAVA

– collects blood from the head, upper body region

■ INFERIOR VENA CAVA – receives blood from the lower part of the body

3. Right Ventricle■ Receives unoxygenated

blood from the right atrium

■ Pumps it to the lungs through the pulmonary artery

■ The pulmonary artery divides into right and left branches to carry the blood to both right and left lungs

4. Left Atrium

■ Thin-walled cavity that receives oxygenated (red) blood from the lungs through 4 pulmonary veins

5. Left Ventricle■ Receives oxygenated

blood from the left atrium

■ Primary function: to pump blood into the systematic circulation

■ Blood leaves through the AORTA – the largest artery of the body

■ Notice the thickness of the myocardial layer of the ventricles

■ This thick muscle is needed to generate enough force to pump blood out of the heart

■ Notice that the LEFT ventricular myocardium is thicker than the RIGHT

■ This is due to the greater amount of force required to pump blood into the systematic circulation

6. Heart Valves■ The purpose of the heart valves is

to keep the blood flowing in a FORWARD DIRECTION

■ The 4 heart valves lie at the entrance and exit of the VENTRICLES

7. Atrioventricular Valves■ Entrance valves ■ Located between atria and

ventricles on both sides of the heart

■ Have CUSPS or flaps ■ When the ventricles are

relaxed, the cusps hang loosely

■ In this position the valves are open and permit the flow of blood from the atria into the ventricles

■ When the ventricles contract, the heart muscle compresses and squeezes the blood in the ventricles

■ The blood pushes the cusps upward toward the atria into a closed position

■ The closed AV valves prevent the backward flow of blood from the ventricles to the atria

■ The cusps are attached to the ventricular wall by tough fibrous bands of tissue called CHORDAE TENDINEAE

■ As blood pushes the cusps into a closed position, the chordae tendineae are stretched to their full length

■ They hold onto the cusps and prevent them from “blowing” through into the atria

■ The right AV valve is called the TRICUSPID VALVE – it has 3 cusps

■ The left AV valve is called the BISCUSPID VALVE – it has 2 cusps

■ The left AV valve is also called the MITRAL VALVE

8. Semilunar Valves■ 2 SEMILUNAR VALVES are exit valves

■ PULMONIC VALVE (PULMONARY VALVE, RIGHT SEMILUNAR VALVE) – located between the right ventricle and the pulmonary artery

■ When the right ventricle relaxes, the valve is closed

■ When the right ventricle contracts, blood forces the pulmonic valve open

■ Blood flows through the open valve into the pulmonary artery to the lungs

■ When the ventricle relaxes the pulmonic valve snaps close

■ The AORTIC VALVE or the LEFT SEMILUNAR VALVE is located between the left ventricle and the aorta

■ It works in the same way – when the left ventricle contracts, blood is forced into the aorta

■ It snaps close when the ventricle relaxes

■How do the semilunar valves close?

■ They close when the pressure in the ventricles becomes less than that in the vessels – it pulls the valves close

9. Heart Sounds■ The “heart beat” we hear is made by the

vibrations caused by the closure of the valves

■ We hear “lubb-dubb”

■ The first sound, “lubb”, is due to the closure of the AV valves

■ The second heart sound, “dubb”, is due to the closure of the semilunar valves

■ When the valves become faulty, the heart sounds change

■ Abnormal heart sounds are called MURMURS

What happens when your heart valve becomes leaky?

■ The valve allows blood to leak back into the chamber from which it has just been pumped

■ The blood is allowed to flow in the wrong direction

■ This increases the workload of the heart and causes other serious problems

■The blood flow pathway

10. Blood supply to the Heart■ Although blood constantly flows through

the heart, this blood does NOT nourish the myocardium

■ The blood supply that nourishes and oxygenates the myocardium is provided by the CORONARY ARTERIES

■ The CORONARY VEINS collect the blood that nourishes the myocardium

■ The blood then travels to the CORONARY SINUS where it empties into the right atrium

■ The myocardium depends on a constant supply of oxygenated blood

■ If this blood supply is interrupted even for a short period of time, the myocardium can be damaged

■ If a blood clot (thrombosis) occludes (blocks) a coronary artery, myocardial cell death occurs

■ This event is a MYOCARDIAL INFARCTION (MI), or a HEART ATTACK

V. Cardiac Conduction System1. The heart’s conduction

system initiates an ELECTRICAL SIGNAL and then moves that signal along a pathway through the heart

2. Why is this electrical signal so important?

3. The electrical signal stimulates the heart muscle to contract

4. No electrical signal means no myocardial contraction

5. The CARDIAC CONDUCTION SYSTEM not only provides the STIMULUS for muscle contraction but also COORDINATES the pumping activity of the atria and ventricles

6. Both atria must contract AT THE SAME TIME, followed by the simultaneous contraction of both ventricles

7. The conduction system is located within the wall of the heart and in the SEPTUM (separates the right and left hearts)

8. It consists of the following structures: - sinoatrial node - atrial conducting fiber - atrioventricular node - His-Purkinje system

9. Sinoatrial Node (SA Node)■ Located in the upper

posterior wall of the right atrium

■ An electrical signal originates in the SA node

■ This signal is called the CARDIAC IMPULSE

■ The SA node fires a cardiac impulse 60 – 100 times/minute (ave 72)

■ It sets the rate at which the heart beats, or contracts

■ The SA node is called the PACEMAKER of the heart

■ The cardiac impulse spreads from the SA node through both atria along the ATRIAL CONDUCTING FIBERS

10. Atrial Conducting Fibers

11. Atrioventricular Node (AV Node)

■ Located in the floor of the right atrium

■ The cardiac impulse spreads from the SA node across the atrial fibers to the AV node

■ The impulse SLOWS as it moves through the AV node into the BUNDLE OF HIS, specialized conduction tissue in the septum

■ The slowing of the cardiac impulse is important

■ It delays ventricular activation, thereby allowing the relaxed ventricle time to fill with blood following atrial contraction

12. His-Purkinje System■ The BUNDLE OF HIS

divides into 2 branches, the right and left bundle branches

■ These bundle branches send out numerous long fibers called PURKINJE FIBERS

■ Purkinje fibers are distributed throughout the myocardium

■ They are fast-conducting fibers

■ They conduct the cardiac impulse VERY RAPIDLY throughout the ventricles, ensuring a coordinated contraction of both ventricles

13. Electrocardiogram (ECG or EKG)■ The cardiac impulse is an

ELECTRICAL SIGNAL

■ It can be measured by placing electrodes on the surface of the chest and attaching electrodes to a recording device

■ The record of these signals is called the ELECTROCARDIOGRAM

VI. Cardiac Cycle1. The CARDIAC CYCLE is the

sequence of events that occurs during ONE HEARTBEAT

2. It is the coordinated CONTRACTION and RELAXATION of the chambers of the heart

3. Contraction of the heart muscle (myocardium) is called SYSTOLE

■ SYSTOLE squeezes blood out of a chamber

4. Relaxation of the myocardium is called DIASTOLE

■ Blood fills a chamber during DIASTOLE

5. The cardiac cycle has 3 stages – Atrial systole, ventricle diastole – Ventricle systole, atrial diastole – Atrial and ventricle diastole

6. Atrial systole, ventricle diastole

■ The atria contract (systole) and pump blood into the ventricles

■ AV valves are open ■ Ventricles are relaxed

7. Ventricular systole, atrial diastole■ At end of atrial systole,

the ventricles contract

■ Blood is forced against the AV valves, they snap shut

■ The semilunar valves are pushed open, allowing blood to flow into the pulmonary artery and aorta

8. Atrial and Ventricular Diastole■ For a brief period both

the atria and ventricles are in diastole (relaxation)

■ AV valves are open ■ A period of blood

filling

9. Cardiac output■ CARDIAC OUTPUT is the amount of blood

pumped by each ventricle in 1 minute

■ Normal cardiac output is about 5 liters/minute (5000 mL)

■ Since total blood volume is about 5 liters, the entire blood volume passes through the heart every minute

10. 2 factors determine cardiac output: heart rate and stroke volume

cardiac output = heart rate × stroke volume

11. HEART RATE is the number of heartbeats/minute

12. The heart rate is commonly measured as the PULSE

13. Factors affecting heart rates■ Gender – woman have faster heart rates ■ Age – younger = faster rate ■ Exercise – exercising increases heart rate ■ Fitness – more fit, lower heart rate ■ Hormones – several affect rate ■ Pathology – some diseases affect rate ■ Medications – can affect rate up or down

14. STROKE VOLUME – the amount of blood pumped/beat

■ An average resting stroke volume is 60 – 80 mL per beat (2 ounces)

■ Only about 65% of the blood in the ventricles is pumped out at a time – 35% is left behind

VII. Blood Vessels1. Classified as: - ARTERIES

- CAPILLARIES

- VEINS

2. ARTERIES carry blood AWAY from the heart

■ Large arteries repeatedly branch into smaller and smaller arteries

■ The smallest arteries are called ARTERIOLES

■ All these vessels carry oxygenated blood and are colored red (except the pulmonary artery)

■ Arterioles flow into CAPILLARIES, the smallest and most numerous of all blood vessels

■ There is a capillary close to every cell in the body!

■ This provides every cell with a continuous supply of oxygen and nutrients

3. Blood flows from capillaries into VENULES, the smallest veins

■ The venules converge to form larger VEINS

■ The large veins empty into the right atrium of the heart

■ Veins carry blood to the heart

■ They carry unoxygenated blood and are colored blue (except the pulmonary veins)

4. Structure of blood vessels■ Notice how thick the

walls of arteries are ■ They are thick, tough,

and elastic because they must withstand the high pressure of the blood pumped from the ventricles

■ Notice capillaries are just a thin layer of squamous epithelium for easy diffusion to occur

5. Major Arteries■ AORTA – orginates in

the heart’s left ventricle ■ Extends upward

(ASCENDING AORTA) then curves in an arch-like fashion

■ It descends (DESCENDING AORTA) behind the heart in front of the vertebral column

■Major arteries of the body

6. Major Veins■ If you look at the back of your hand, you can

see several veins but no arteries, Why?

■ Arteries are usually located in deep and well-protected areas

■ SUPERFICIAL VEINS are close to the surface

■ Other veins are located more deeply and usually run parallel to the arteries, called DEEP VEINS

■ With few exceptions, the names of the deep veins are identical to the names of the companion arteries

■ Example: the femoral artery in the thigh is accompanied by the femoral vein

■ Veins converge from all over the body to deliver blood to the heart

■ The VENA CAVA is the largest vein in the body

■ It is divided into the SUPERIOR VENA CAVA and the INFERIOR VENA CAVA

7. Blood Pressure■ What causes the blood to move through the

circulatory system?

■ Blood is pushed through the arterial blood vessels primarily because of the pressure produced by the contraction of the ventricles of the heart

■ BLOOD PRESSURE is the force exerted by blood against the walls of the blood vessels

■ The maintenance of normal blood pressure is extremely important

■ If blood pressure becomes too low, blood flow to vital organs decreases

■ If blood pressure becomes elevated, the blood vessels may burst, or rupture

■ A ruptured blood vessel in the brain, for example, is a major cause of STROKE

■ A long-term, or chronic, elevation of blood pressure is called HYPERTENSION

■ Hypertension puts added strain on the heart, damages blood vessels in the kidneys, and damages the retina, causing loss of vision

8. Measurement of Blood Pressure■ 120/80 mmHg…..what does it mean??

■ When the ventricles contract, a volume of blood is ejected, or pushed, out of the ventricle into the artery, increasing pressure

■ The pressure in the arteries at the peak of ventricular contraction (systole) is called the SYSTOLIC PRESSURE – it is the top number, 120 mmHg

■ The DIASTOLIC PRESSURE is the pressure in the large arteries when the ventricles of the heart are relaxing (diastole)

■ The diastolic reading is the bottom number, 80 mmHg

9. New Guidelines for Normal Blood Pressure

■ Normal blood pressure: 119/79 or less

■ Prehypertension: 120/80 – 139/89

■ Hypertension: 140/90 and greater

10. Taking a Blood Pressure■ Measurement of blood

pressure provides valuable information regarding a person’s general health

■ Most commonly measured over the brachial artery

■ Measured in millimeters of mercury - mmHg

■ The instrument used to take blood pressure is called the SPHYGMOMANOMETER

■ The sounds heard through the stethoscope are called KOROTKOFF SOUNDS

■ Korotkoff sounds are caused by the flow of blood through the brachial artery

11. Taking blood pressure measurement

12. What is Pulse??■ When blood is pumped into the arteries they

slightly expand ■ When the heart rests the arteries slightly

recoil ■ This expansion and recoil causes a pressure

wave which travels through all arteries ■ This wave is called the PULSE ■ The pulse is also called the HEARTBEAT

Sites where pulses are easily felt

General Risk Factors ■ The following risk factors can increase a

person’s risk for cardiovascular disease: - genetics - hypertension - smoking - stress level - diet - other diseases like - weight diabetes - activity level - age - drug/alcohol use