Circulatory SystemCirculatory System

Do NowDo Now

Why is it important for your heart to Why is it important for your heart to continue beating even when you’re continue beating even when you’re sleeping?sleeping?

What does your body need? What does your body need? What are some wastes?What are some wastes?

Circulation and RespirationCirculation and Respiration

Each breath brings Each breath brings oxygenoxygen rich air into rich air into your bodyyour body

Your cells need that oxygenYour cells need that oxygen Your heart delivers oxygen Your heart delivers oxygen to your cellsto your cells

Working together, your circulatory and Working together, your circulatory and respiratory systems respiratory systems supply cells supply cells throughout the body with the nutrients throughout the body with the nutrients and oxygenand oxygen that they need to stay alive! that they need to stay alive!

Multicellular NeedsMulticellular Needs

UnicellularUnicellular organisms organisms don’tdon’t need a need a circulatory system, because the cell is in circulatory system, because the cell is in direct contact with the environment and direct contact with the environment and oxygen, nutrients and wastes can easily oxygen, nutrients and wastes can easily diffuse across the cell membrane by diffuse across the cell membrane by diffusiondiffusion. .

MulticellularMulticellular organisms need a circulatory organisms need a circulatory system to system to transporttransport substances made in substances made in one part of the body to sites where they one part of the body to sites where they are needed in another part of the body.are needed in another part of the body.

FunctionFunction

The circulatory system The circulatory system transportstransports substances including oxygen, substances including oxygen, nutrients and wastes to and from nutrients and wastes to and from cells responding to changing cells responding to changing demands by demands by diffusiondiffusion (from high to (from high to low concentration along low concentration along concentration gradient).concentration gradient).

StructureStructure Humans have a Humans have a closedclosed circulatory system. circulatory system.

– Blood is pumped through a system of vesselsBlood is pumped through a system of vessels(In an open system, blood flows in vessels and (In an open system, blood flows in vessels and

sinuses/gills)sinuses/gills) Sometimes the circulatory system is also Sometimes the circulatory system is also

called the “cardiovascular system” because:called the “cardiovascular system” because:– Cardio = Cardio = heartheart– Vascular = Vascular = vesselsvessels

The human circulatory system consists of: The human circulatory system consists of: – The heartThe heart– A series of blood vesselsA series of blood vessels– Blood that flows through themBlood that flows through them

The HeartThe Heart Located near the center of your chestLocated near the center of your chest A hollow organ about the size of your fist A hollow organ about the size of your fist

composed of composed of cardiac musclecardiac muscle.. Enclosed in a protective sac of tissue called the Enclosed in a protective sac of tissue called the

pericardiumpericardium Inside there are two thin layers of epithelial and Inside there are two thin layers of epithelial and

connective tissueconnective tissue Contractions of the Contractions of the myocardiummyocardium, a thick cardiac , a thick cardiac

muscle, pump blood through the circulatory muscle, pump blood through the circulatory systemsystem

The heart contracts about 72 times a minuteThe heart contracts about 72 times a minute Each contraction pumps about 70 mL of bloodEach contraction pumps about 70 mL of blood

HeartHeart SeptumSeptum, or wall, , or wall,

separates the right separates the right side form the left side side form the left side preventing mixing of preventing mixing of oxygen-rich blood and oxygen-rich blood and oxygen-poor bloodoxygen-poor blood

Flaps of connective Flaps of connective tissue called tissue called valvesvalves divide each side into 2 divide each side into 2 chambers: totaling chambers: totaling 4 4 chamberschambers– Upper chambers Upper chambers

receivereceive blood = blood = atriumatrium– Lower chambers pump Lower chambers pump

blood blood outout of heart = of heart = ventricleventricle

Types of CirculationTypes of Circulation

PulmonaryPulmonary circulation = from circulation = from rightright side of the heart to side of the heart to lungslungs where where carbon dioxide leaves the blood and carbon dioxide leaves the blood and oxygen is absorbedoxygen is absorbed

SystemicSystemic circulation = from circulation = from leftleft side side of the heart to of the heart to organsorgans– CoronaryCoronary circulation = through circulation = through heartheart

tissuetissue

Pulmonary CirculationPulmonary Circulation

The right side of the heart pumps blood The right side of the heart pumps blood from the heart to the lungs from the heart to the lungs

In the lungs, In the lungs, carbon dioxide leaves carbon dioxide leaves the the blood while blood while oxygen is absorbedoxygen is absorbed..

The oxygen-rich blood goes into the left The oxygen-rich blood goes into the left side of the heartside of the heart

Systemic CirculationSystemic Circulation The oxygen-rich blood from The oxygen-rich blood from

the left side of the heart is the left side of the heart is pumped to the rest of the pumped to the rest of the bodybody

Oxygen-poor blood returns Oxygen-poor blood returns to the right side of the heartto the right side of the heart

This blood is oxygen-poor This blood is oxygen-poor because the cells absorbed because the cells absorbed the oxygen and released the oxygen and released carbon dioxide into the carbon dioxide into the bloodblood

The oxygen-poor blood is The oxygen-poor blood is ready for another trip to the ready for another trip to the lungs to get oxygen againlungs to get oxygen again

Section 37-1

Figure 37-2 The Circulatory System

Capillaries of head and arms

Capillaries of abdominal organs and legs

Inferior vena cava

Pulmonary veinCapillaries of

right lung

Superior vena cava

Aorta Pulmonary artery

Capillaries of left lung

Coronary CirculationCoronary Circulation

Remember: the Remember: the heart is an organ heart is an organ and needs and needs nutrients, oxygen nutrients, oxygen and creates and creates wastes.wastes.

Blood flows to the Blood flows to the tissues of the heart tissues of the heart too!too!

Blood Flow through the Blood Flow through the heartheart

Blood leaves the heart in arteries, and blood returns to heart in veins. Blood leaves the heart in arteries, and blood returns to heart in veins.

Oxygenated blood returns from the lungs through the pulmonary veins to Oxygenated blood returns from the lungs through the pulmonary veins to the left atrium.the left atrium.

Oxygenated blood is pumped from the left atrium through the mitral valve Oxygenated blood is pumped from the left atrium through the mitral valve to the left ventricle.to the left ventricle.

Oxygenated blood leaves the left ventricle through the aortic valve to the Oxygenated blood leaves the left ventricle through the aortic valve to the aorta, which is the largest artery of your body.aorta, which is the largest artery of your body.

The aorta branches into various arteries pumping blood through your body.The aorta branches into various arteries pumping blood through your body. Deoxygenated blood returns from the top of your body through the Deoxygenated blood returns from the top of your body through the

superior vena cava and from the bottom of your body through the inferior superior vena cava and from the bottom of your body through the inferior vena cava to the right atrium. vena cava to the right atrium.

Deoxygenated blood is pumped from the right atrium through the tricuspid Deoxygenated blood is pumped from the right atrium through the tricuspid valve to the right ventricle.valve to the right ventricle.

Deoxygenated blood leaves the right ventricle through the pulmonary Deoxygenated blood leaves the right ventricle through the pulmonary valve to the pulmonary arteries.valve to the pulmonary arteries.

The pulmonary arteries pump blood to the lungs to absorb oxygen and The pulmonary arteries pump blood to the lungs to absorb oxygen and release carbon dioxide.release carbon dioxide.

Heart circulation animation: http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw_pumping.html

The Path of BloodThe Path of Blood

ValvesValves Blood enters into the atria of the heart, separated from the Blood enters into the atria of the heart, separated from the

ventricles by valves, ventricles by valves, preventing back-flow of bloodpreventing back-flow of blood keeping keeping the blood flowing in the blood flowing in one directionone direction

When the atria contract, the valves open and blood flows When the atria contract, the valves open and blood flows into the ventricles into the ventricles

When the ventricles contract, the valves close preventing When the ventricles contract, the valves close preventing blood from flowing back into the atria and blood flows out blood from flowing back into the atria and blood flows out of the heartof the heart

At the exits of the ventricles, there are valves that prevent At the exits of the ventricles, there are valves that prevent blood from flowing back into the heartblood from flowing back into the heart

The “lub-dup” sound of your heart is caused by the closing The “lub-dup” sound of your heart is caused by the closing of the heart’s valves. The “lub” is when the ventricles of the heart’s valves. The “lub” is when the ventricles contract and blood being forced against the artioventricular contract and blood being forced against the artioventricular or A-V (tricuspid or mitral) valves. The “dup” is the blood or A-V (tricuspid or mitral) valves. The “dup” is the blood being forced against the semilunar (aortic or pulmonary) being forced against the semilunar (aortic or pulmonary) valves.valves.

Section 37-1

Figure 37-3 The Structures of the Heart

Right Ventricle

Right Atrium

Left Atrium

Inferior Vena CavaVein that brings oxygen-poor blood from the lower part of the body to the right atrium

Tricuspid ValvePrevents blood from flowing back into the right atrium after it has entered the right ventricle

Pulmonary ValvePrevents blood from flowing back into the right ventricle after it has entered the pulmonary artery

Pulmonary VeinsBring oxygen-rich blood from each of the lungs to the left atrium

Superior Vena CavaLarge vein that brings oxygen-poor blood from the upper part of the body to the right atrium

AortaBrings oxygen-rich blood from the left ventricle to the rest of the body

Pulmonary ArteriesBring oxygen-poor blood to the lungs

Aortic ValvePrevents blood from flowing back into the left ventricle after it has entered the aorta

Mitral ValvePrevents blood from flowing back into the left atrium after it has entered the left ventricle

Left Ventricle

Septum

HeartbeatHeartbeat There are two muscle contractions in the heart: There are two muscle contractions in the heart:

– The atriaThe atria– The ventriclesThe ventricles

Each contraction begins in a small group of cardiac Each contraction begins in a small group of cardiac muscle cells in the right atrium that stimulate the rest of muscle cells in the right atrium that stimulate the rest of the muscle cells = the muscle cells = sinoatrial node (SA node)sinoatrial node (SA node)

Since the sinoatrial node sets the pace for the heart it is Since the sinoatrial node sets the pace for the heart it is also called “also called “the pacemaker”the pacemaker”

The impulse spreads from the pacemaker The impulse spreads from the pacemaker through fibers through fibers in the atria to the in the atria to the atrioventricular node (AV node) atrioventricular node (AV node) and and through fibers through fibers in the ventriclesin the ventricles

When the atria contract, blood flows into the ventriclesWhen the atria contract, blood flows into the ventricles When the ventricle contract, blood flows out of the heartWhen the ventricle contract, blood flows out of the heart

Sinoatrial (SA) node

Atrioventricular (AV) node

Conducting fibers

Contraction of Atria Contraction of Ventricles

Section 37-1

The Sinoatrial Node

Changing HeartbeatChanging Heartbeat

Your heart can beat faster or slower, Your heart can beat faster or slower, depending on your body’s need for oxygen-depending on your body’s need for oxygen-rich bloodrich blood

When you When you exerciseexercise, your heart rate can , your heart rate can increaseincrease to 200 beats per minute to 200 beats per minute

The The autonomicautonomic nervous system influences nervous system influences heart rateheart rate– Neurotransmitters released by neurons in the Neurotransmitters released by neurons in the

sympathetic nervous system can increase heart sympathetic nervous system can increase heart rate, and those released by the parasympathetic rate, and those released by the parasympathetic nervous system can decrease heart ratenervous system can decrease heart rate

Blood vesselsBlood vessels

Blood circulates in one direction and Blood circulates in one direction and it is moved by the pumping of the it is moved by the pumping of the heartheart

As blood flows through the As blood flows through the circulatory system, it moves through circulatory system, it moves through three types of blood vessels:three types of blood vessels:– ArteriesArteries– CapillariesCapillaries– VeinsVeins

ArteriesArteries LargeLarge vessels that carry blood vessels that carry blood

awayaway from the heart to tissues from the heart to tissues of the bodyof the body

Except for the pulmonary Except for the pulmonary arteries, all arteries carry arteries, all arteries carry oxygen-rich bloodoxygen-rich blood..

Arteries have Arteries have thick walls thick walls of of elastic connective tissue, elastic connective tissue, contractible smooth muscle, and contractible smooth muscle, and epithelial cells that help them epithelial cells that help them withstand the powerful pressure withstand the powerful pressure produced when the heart produced when the heart contracts and pushes blood into contracts and pushes blood into the arteries.the arteries.

CapillariesCapillaries

The The smallestsmallest of the of the blood vessels blood vessels connecting arteries connecting arteries and veinsand veins

Walls are Walls are one cell thick one cell thick allowing for easier allowing for easier diffusiondiffusion of nutrients of nutrients and oxygen from and oxygen from capillaries to body cells capillaries to body cells and wastes and carbon and wastes and carbon dioxide from body cells dioxide from body cells to capillaries to capillaries

VeinsVeins ReturnReturn blood to the heart blood to the heart Veins have walls of connective Veins have walls of connective

tissue and smooth muscletissue and smooth muscle Large veins contain Large veins contain valvesvalves that that

keep blood flowing towards the keep blood flowing towards the heartheart

Many veins are located Many veins are located near near skeletal musclesskeletal muscles, so when the , so when the muscles contract, they help force muscles contract, they help force blood through the veins, even blood through the veins, even against gravityagainst gravity

Exercise helps prevent Exercise helps prevent accumulation of blood in limbs accumulation of blood in limbs and stretching veins out of shapeand stretching veins out of shape

Section 37-1

Figure 37-5 The Three Types of Blood Vessels

Capillary

Connective tissue

Connective tissue

Smooth muscle

Smooth muscle

Endothelium

Endothelium

Valve

Venule

Endothelium

Arteriole

VeinArtery

Blood PressureBlood Pressure The heart produces pressure when it contracts.The heart produces pressure when it contracts. The The force of blood on the arteriesforce of blood on the arteries’ walls = blood ’ walls = blood

pressurepressure Blood pressure decreases when the heart relaxes, Blood pressure decreases when the heart relaxes,

but there must always be some pressure to keep but there must always be some pressure to keep the blood flowingthe blood flowing

Doctors measure blood pressure with a Doctors measure blood pressure with a sphygmomanometer recording two numberssphygmomanometer recording two numbers– Systolic pressure = force felt in arteries when ventricles Systolic pressure = force felt in arteries when ventricles

contractcontract– Diastolic pressure = force of blood felt in arteries when Diastolic pressure = force of blood felt in arteries when

ventricles ventricles relaxrelax Average adult’s blood pressure = Average adult’s blood pressure = 120/80120/80

Regulating Blood PressureRegulating Blood Pressure With the nervous system:With the nervous system:

– Sensory neurons at several places in the body detect Sensory neurons at several places in the body detect blood pressure and send impulses to brain stem blood pressure and send impulses to brain stem (medulla oblongata)(medulla oblongata)

– When too high, the autonomic nervous system releases When too high, the autonomic nervous system releases neurotransmitters that cause the smooth muscles neurotransmitters that cause the smooth muscles around blood vessels to relax, lowering blood pressure. around blood vessels to relax, lowering blood pressure.

– When too low, neurotransmitters are released that cause When too low, neurotransmitters are released that cause the smooth muscles to contract, elevating blood the smooth muscles to contract, elevating blood pressure.pressure.

With the endocrine/excretory system: With the endocrine/excretory system: – Hormones produced by the heart and other organs Hormones produced by the heart and other organs

cause kidneys to remove more water from the blood cause kidneys to remove more water from the blood when blood pressure is too high, reducing blood volume when blood pressure is too high, reducing blood volume and lowering blood pressureand lowering blood pressure

DisordersDisorders Disorders of the circulatory Disorders of the circulatory

system are very common:system are very common:– High Blood PressureHigh Blood Pressure– Heart AttackHeart Attack– StrokeStroke

Most stem from Most stem from atherosclerosisatherosclerosis = fatty = fatty deposits (deposits (plaqueplaque) builds up on ) builds up on walls of arteries, walls of arteries, obstructingobstructing blood flow, increasing blood blood flow, increasing blood pressure and risk of blood clotspressure and risk of blood clots

High Blood PressureHigh Blood Pressure

Also known as Also known as HypertensionHypertension Forces heart to work harder, which may Forces heart to work harder, which may

weaken or damage the heart muscle and weaken or damage the heart muscle and vesselsvessels

More likely to develop heart disease and More likely to develop heart disease and increased risk of increased risk of heart attack and strokeheart attack and stroke

Heart AttackHeart Attack

A medical emergencyA medical emergency Coronary arteries Coronary arteries (supplying heart blood) (supplying heart blood)

bring oxygen and nutrients to the heart bring oxygen and nutrients to the heart muscle itselfmuscle itself

BlockageBlockage of coronary artery may damage of coronary artery may damage or kill part of heart muscle (myocardium) or kill part of heart muscle (myocardium) due to due to lack of oxygen lack of oxygen = heart attack= heart attack– Symptoms include: chest pain/pressure, Symptoms include: chest pain/pressure,

feeling of heartburn/indigestion, sudden feeling of heartburn/indigestion, sudden dizziness, or brief loss of consciousnessdizziness, or brief loss of consciousness

StrokeStroke Blood clots Blood clots may break free from vessels and get may break free from vessels and get

stuck in a blood vesselstuck in a blood vessel leading to a part of the leading to a part of the brainbrain = stroke = stroke

Brain cells relying on that vessel may begin to die Brain cells relying on that vessel may begin to die from from lack of oxygenlack of oxygen and brain function in that and brain function in that region may be lostregion may be lost

Strokes can also occur when a weakened artery Strokes can also occur when a weakened artery in the brain burst, flooding the area with bloodin the brain burst, flooding the area with blood

PreventionPrevention Cardiovascular diseases are Cardiovascular diseases are

easy to prevent:easy to prevent:– ExerciseExercise – increases – increases

respiratory system’s respiratory system’s efficiencyefficiency

– Weight control Weight control – reduces – reduces body fat and stressbody fat and stress

– Sensible diet – Sensible diet – low in low in saturated fat saturated fat reduces risk reduces risk of heart diseaseof heart disease

– Not smoking – reduces Not smoking – reduces risk of heart diseaserisk of heart disease