CIRCULATIONCIRCULATION

CHAPTER 22CHAPTER 22

Circulatory SystemsCirculatory Systems

Blood flows through blood vesselsBlood flows through blood vessels Heart generates force to keep Heart generates force to keep

blood movingblood moving Closed system Closed system

– Blood is confined to vessels and heartBlood is confined to vessels and heart Open systemOpen system

– Blood mingles with fluid in tissuesBlood mingles with fluid in tissues

Velocity of Flow VariesVelocity of Flow Varies

Volume of blood flow through vessels Volume of blood flow through vessels always has to equal heart’s output always has to equal heart’s output

Flow velocity is highest in large-Flow velocity is highest in large-diameter transport vesselsdiameter transport vessels

Flow velocity is slowest in capillary Flow velocity is slowest in capillary beds; blood spreads out into many beds; blood spreads out into many vessels with greater vessels with greater totaltotal cross- cross-sectional areasectional area

Flow AnalogyFlow Analogy

river in river out

lake

1 2 3 1 2 3

1 2 3

Vertebrate SystemsVertebrate Systems

FishFish– Two-chambered heart pumps blood through Two-chambered heart pumps blood through

one circuitone circuit AmphibiansAmphibians

– Heart pumps blood through two partially Heart pumps blood through two partially separate circuitsseparate circuits

Birds and mammalsBirds and mammals– Four-chambered heart pumps blood through Four-chambered heart pumps blood through

two entirely separate circuitstwo entirely separate circuits

Functions of BloodFunctions of Blood

Transports oxygen and nutrients to Transports oxygen and nutrients to cellscells

Carries carbon dioxide and wastes Carries carbon dioxide and wastes away from cellsaway from cells

Helps stabilize internal pHHelps stabilize internal pH Carries infection-fighting cellsCarries infection-fighting cells Helps equalize temperature Helps equalize temperature

Blood Cell DevelopmentBlood Cell Development

Stem cells in bone marrow are Stem cells in bone marrow are unspecialized cells that retain the unspecialized cells that retain the capacity to divide capacity to divide

Some daughter cells of stem cells Some daughter cells of stem cells differentiate to form blood cells differentiate to form blood cells

Body must continually replace Body must continually replace blood cellsblood cells

Erythrocytes (Red Cells)Erythrocytes (Red Cells)

Most numerous cells in the Most numerous cells in the bloodblood

Transport oxygen and carbon Transport oxygen and carbon dioxidedioxide

Colored red by oxygen-binding Colored red by oxygen-binding pigment (hemoglobin)pigment (hemoglobin)

Have no nucleus when matureHave no nucleus when mature

Leukocytes (White Cells)Leukocytes (White Cells)

Function in housekeeping and defenseFunction in housekeeping and defense Cell typesCell types

BasophilsBasophils Dendritic cellsDendritic cells

EosinophilsEosinophils B lymphocytesB lymphocytes

NeutrophilsNeutrophils T lymphocytesT lymphocytes

Macrophages Macrophages NK cellsNK cells

Mast cellsMast cells

PlateletsPlatelets

Membrane-bound cell fragmentsMembrane-bound cell fragments Derived from megakaryocytes, which Derived from megakaryocytes, which

arise from stem cellsarise from stem cells Release substances that initiate Release substances that initiate

blood clottingblood clotting

The HeartThe Heart The The heartheart is a cone-shaped, muscular is a cone-shaped, muscular

organ located between the lungs behind organ located between the lungs behind the sternum.the sternum.

The heart muscle forms the The heart muscle forms the myocardiummyocardium, with tightly interconnected , with tightly interconnected cells of cells of cardiac musclecardiac muscle tissue. tissue.

The The pericardiumpericardium is the outer is the outer membranous sac with lubricating fluid.membranous sac with lubricating fluid.

The heart has four chambers: two upper, The heart has four chambers: two upper, thin-walled thin-walled atriaatria, and two lower, thick-walled , and two lower, thick-walled ventriclesventricles..

The The septumseptum is a wall dividing the right and is a wall dividing the right and left sides. left sides.

Atrioventricular valvesAtrioventricular valves occur between the occur between the atria and ventricles – the atria and ventricles – the tricuspidtricuspid valvevalve on on the right and the the right and the bicuspid valvebicuspid valve on the left; on the left; both valves are reinforced by both valves are reinforced by chordae chordae tendinaetendinae attached to muscular projections attached to muscular projections within the ventricles.within the ventricles.

Semilunar valvesSemilunar valves occur between the occur between the ventricles and the attached arteriesventricles and the attached arteries

External heart anatomyExternal heart anatomy

Coronary artery circulationCoronary artery circulation

Passage of Blood Through the Passage of Blood Through the HeartHeart

Blood follows this sequence through the Blood follows this sequence through the heart: superior and inferior vena cava heart: superior and inferior vena cava →→ right atrium right atrium → tricuspid valve →→ tricuspid valve → right right ventricle ventricle → pulmonary semilunar valve → pulmonary semilunar valve →→ pulmonary trunk and arteries to the pulmonary trunk and arteries to the lungs lungs →→ pulmonary veins leaving the pulmonary veins leaving the lungs lungs →→ left atrium left atrium → bicuspid valve →→ bicuspid valve → left ventricle left ventricle → aortic semilunar valve →→ aortic semilunar valve → aorta aorta → to the body→ to the body. .

Internal view of the heartInternal view of the heart

Path of blood through the heartPath of blood through the heart

The HeartbeatThe Heartbeat Each heartbeat is called a Each heartbeat is called a cardiac cyclecardiac cycle.. When the heart beats, the two atria When the heart beats, the two atria

contract together, then the two contract together, then the two ventricles contract; then the whole ventricles contract; then the whole heart relaxes.heart relaxes.

SystoleSystole is the contraction of heart is the contraction of heart chambers; chambers; diastolediastole is their relaxation. is their relaxation.

The The heart soundsheart sounds, lub-dup, are due to , lub-dup, are due to the closing of the atrioventricular the closing of the atrioventricular valves, followed by the closing of the valves, followed by the closing of the semilunar valves.semilunar valves.

Conduction system of the heartConduction system of the heart

Conduction and ContractionConduction and Contraction

SA node in right SA node in right atrium is pacemakeratrium is pacemaker

Electrical signals Electrical signals cause contraction of cause contraction of atriaatria

Signal flows to AV Signal flows to AV node and down node and down septum to ventriclesseptum to ventricles

SA node

The ElectrocardiogramThe Electrocardiogram

An An electrocardiogramelectrocardiogram ( (ECGECG) is a ) is a recording of the electrical changes recording of the electrical changes that occur in the myocardium that occur in the myocardium during a cardiac cycle. during a cardiac cycle.

Atrial depolarizationAtrial depolarization creates the creates the P P wavewave, , ventricle depolarizationventricle depolarization creates the creates the QRS waveQRS wave, and , and repolarizationrepolarization of the ventricles of the ventricles produces the produces the T waveT wave..

ElectrocardiogramElectrocardiogram

The Vascular PathwaysThe Vascular Pathways

The cardiovascular system includes The cardiovascular system includes two circuits:two circuits:

1)1) Pulmonary circuitPulmonary circuit which circulates which circulates blood through the lungs, andblood through the lungs, and

2)2) Systemic circuitSystemic circuit which circulates which circulates blood to the rest of the body.blood to the rest of the body.

3)3) Both circuits are vital to Both circuits are vital to homeostasis.homeostasis.

Pulmonary CircuitPulmonary Circuit

This loop This loop

oxygenates oxygenates

bloodblood

right pulmonary artery left pulmonary artery

capillarybed ofrightlung

pulmonarytrunk

capillary bedof left lung

(to systemic circuit)

pulmonary veins

lungs

(fromsystemiccircuit)

heart

Systemic Systemic CircuitCircuit

Longer loop Longer loop

carries blood to carries blood to

and from body and from body

tissuestissues

capillary beds of headand upper extremities

(to pulmonarycircuit)

aorta

(frompulmonarycircuit)

heart

capillary beds of otherorgans in thoracic cavity

capillary bed of liver

capillary beds of intestines

capillary beds of other abdominalorgans and lower extremities

Cardiovascular system Cardiovascular system diagramdiagram

The The cardiovascular systemcardiovascular system has three has three types of blood vessels:types of blood vessels:

ArteriesArteries (and (and arteriolesarterioles) – carry blood ) – carry blood away from the heartaway from the heart

CapillariesCapillaries – where nutrient and gas – where nutrient and gas exchange occurexchange occur

VeinsVeins (and (and venulesvenules) – carry blood ) – carry blood toward the heart.toward the heart.

The Blood VesselsThe Blood Vessels

Blood vesselsBlood vessels

The ArteriesThe Arteries

ArteriesArteries and arterioles take blood and arterioles take blood away from the heart. away from the heart.

The largest artery is the The largest artery is the aortaaorta. . The middle layer of an artery wall The middle layer of an artery wall

consists of consists of smooth musclesmooth muscle that can that can constrict to regulate blood flow and constrict to regulate blood flow and blood pressure. blood pressure.

ArteriolesArterioles can constrict or dilate, can constrict or dilate, changing blood pressure.changing blood pressure.

Blood FlowBlood Flow

The beating of the heart is necessary The beating of the heart is necessary to homeostasis because it creates to homeostasis because it creates pressure that propels blood in pressure that propels blood in arteries and the arterioles.arteries and the arterioles.

Arterioles lead to the capillaries Arterioles lead to the capillaries where nutrient and gas exchange where nutrient and gas exchange with tissue fluid takes place.with tissue fluid takes place.

Blood Flow in ArteriesBlood Flow in Arteries Blood pressureBlood pressure due to the pumping of due to the pumping of

the heart accounts for the flow of the heart accounts for the flow of blood in the arteries. blood in the arteries.

Systolic pressureSystolic pressure is high when the is high when the heart expels the blood. heart expels the blood.

Diastolic pressureDiastolic pressure occurs when the occurs when the heart ventricles are relaxing. heart ventricles are relaxing.

Both pressures decrease with Both pressures decrease with distance from the left ventricle distance from the left ventricle because blood enters more and more because blood enters more and more arterioles and arteries.arterioles and arteries.

The CapillariesThe Capillaries

CapillariesCapillaries have walls only one cell have walls only one cell thick to allow exchange of gases and thick to allow exchange of gases and nutrients with tissue fluid. nutrients with tissue fluid.

Capillary beds are present in all Capillary beds are present in all regions of the body but not all regions of the body but not all capillary beds are open at the same capillary beds are open at the same time. time.

Anatomy of a capillary bedAnatomy of a capillary bed

Blood Flow in CapillariesBlood Flow in Capillaries

Blood moves slowly in capillaries Blood moves slowly in capillaries because there are more capillaries because there are more capillaries than arterioles. than arterioles.

This allows time for substances to be This allows time for substances to be exchanged between the blood and exchanged between the blood and tissues.tissues.

Bulk Flow in Capillary BedBulk Flow in Capillary Bed

blood tovenule

inward-directedosmotic movement

cells oftissue

outward-directedbulk flowblood

from arteriole

Diffusion ZoneDiffusion Zone

Capillary beds are the site of exchange Capillary beds are the site of exchange between blood and interstitial fluidbetween blood and interstitial fluid

Capillary is a single sheet ofCapillary is a single sheet ofepithelial cellsepithelial cells

Flow is slow; allows gasses to diffuse Flow is slow; allows gasses to diffuse across membranes of blood cells and across membranes of blood cells and across endotheliumacross endothelium

The VeinsThe Veins VenulesVenules drain blood from capillaries, drain blood from capillaries,

then join to form then join to form veinsveins that take blood that take blood to the heart. to the heart.

Veins have much less smooth muscle Veins have much less smooth muscle and connective tissue than arteries. and connective tissue than arteries.

Veins often have Veins often have valvesvalves that prevent that prevent the backward flow of blood when the backward flow of blood when closed.closed.

Veins carry about 70% of the body’s Veins carry about 70% of the body’s blood and act as a blood and act as a reservoirreservoir during during hemorrhage.hemorrhage.

The Venous SystemThe Venous System

Blood flows from capillaries into Blood flows from capillaries into venules, then on to veinsvenules, then on to veins

Veins are large-diameter vessels with Veins are large-diameter vessels with some smooth muscle in wallsome smooth muscle in wall

Valves in some veins prevent blood Valves in some veins prevent blood from flowing backwardfrom flowing backward

Blood Flow in VeinsBlood Flow in Veins

Venous blood flow is dependent Venous blood flow is dependent upon:upon:

1)1) skeletal muscle contraction, skeletal muscle contraction,

2)2) presence of valves in veins, and presence of valves in veins, and

3)3) respiratory movements. respiratory movements. Compression of veins causes blood Compression of veins causes blood

to move forward past a valve that to move forward past a valve that then prevents it from returning then prevents it from returning backward. backward.

Changes in thoracic and abdominal Changes in thoracic and abdominal pressure that occur with breathing pressure that occur with breathing also assist in the return of blood. also assist in the return of blood.

Varicose veinsVaricose veins develop when the develop when the valves of veins become weak. valves of veins become weak.

HemorrhoidsHemorrhoids (piles) are due to (piles) are due to varicose veins in the rectum. varicose veins in the rectum.

PhlebitisPhlebitis is inflammation of a vein is inflammation of a vein and can lead to a blood clot and and can lead to a blood clot and possible death if the clot is dislodged possible death if the clot is dislodged and is carried to a pulmonary vessel.and is carried to a pulmonary vessel.

jugular veins

superior vena cava

pulmonary veins

hepatic portal vein

renal vein

inferior vena cava

iliac veins

femoral vein

carotid arteries

ascending aorta

pulmonary arteries

coronary arteries

renal artery

brachial artery

abdominal aorta

iliac arteries

femoral artery

Major Major VesselsVessels

HemophiliaHemophilia HemophiliaHemophilia is an inherited clotting is an inherited clotting

disorder due to a deficiency in a disorder due to a deficiency in a clotting factor.clotting factor.

Bumps and falls cause bleeding in the Bumps and falls cause bleeding in the joints; cartilage degeneration and joints; cartilage degeneration and resorption of bone can follow.resorption of bone can follow.

The most frequent cause of death is The most frequent cause of death is bleeding into the brain with bleeding into the brain with accompanying neurological damage.accompanying neurological damage.

Cardiovascular DisordersCardiovascular Disorders

Cardiovascular diseaseCardiovascular disease ( (CVDCVD) is the ) is the leading cause of death in Western leading cause of death in Western countries.countries.

Modern research efforts have improved Modern research efforts have improved diagnosis, treatment, and prevention.diagnosis, treatment, and prevention.

Major cardiovascular disorders include Major cardiovascular disorders include atherosclerosis, stroke, heart attack, atherosclerosis, stroke, heart attack, aneurysm, and hypertension.aneurysm, and hypertension.

AtherosclerosisAtherosclerosis

AtherosclerosisAtherosclerosis is due to a build-up of is due to a build-up of fatty material (fatty material (plaqueplaque), mainly ), mainly cholesterol, under the inner lining of cholesterol, under the inner lining of arteries. arteries.

The plaque can cause a The plaque can cause a thrombusthrombus (blood clot) to form.(blood clot) to form.

The thrombus can dislodge as an The thrombus can dislodge as an embolusembolus and lead to and lead to thromboembolismthromboembolism..

Stroke, Heart Attack, and Stroke, Heart Attack, and AneurysmAneurysm

A A cerebrovascular accidentcerebrovascular accident, or , or strokestroke, , results when an embolus lodges in a results when an embolus lodges in a cerebral blood vessel or a cerebral cerebral blood vessel or a cerebral blood vessel bursts; a portion of the blood vessel bursts; a portion of the brain dies due to lack of oxygen. brain dies due to lack of oxygen.

A A myocardial infarctionmyocardial infarction, or , or heart attackheart attack, , occurs when a portion of heart muscle occurs when a portion of heart muscle dies due to lack of oxygen.dies due to lack of oxygen.

Coronary bypass operationCoronary bypass operation

AngioplastyAngioplasty

HypertensionHypertension About 20% of Americans suffer from About 20% of Americans suffer from

hypertensionhypertension ( (high blood pressurehigh blood pressure).).

Hypertension is present when systolic Hypertension is present when systolic pressure is 140 or greater or diastolic pressure pressure is 140 or greater or diastolic pressure is 90 or greater; diastolic pressure is is 90 or greater; diastolic pressure is emphasized when medical treatment is emphasized when medical treatment is considered.considered.

A genetic predisposition for hypertension A genetic predisposition for hypertension occurs in those who have a gene that codes occurs in those who have a gene that codes for for angiotensinogenangiotensinogen, a powerful , a powerful vasoconstrictor.vasoconstrictor.

Blood PressureBlood Pressure

Highest in arteries, lowest in veinsHighest in arteries, lowest in veins Usually measured in the brachial Usually measured in the brachial

arteryartery Systolic pressure is peak pressure Systolic pressure is peak pressure

– Ventricular contraction Ventricular contraction Diastolic pressure is the lowest Diastolic pressure is the lowest

pressurepressure– Ventricular relaxationVentricular relaxation

HemostasisHemostasis

Blood vessel spasm, platelet plug Blood vessel spasm, platelet plug formation, blood coagulationformation, blood coagulation

Clotting mechanismClotting mechanism– Prothrombin is converted to Prothrombin is converted to

thrombinthrombin– Fibrinogen is converted to fibrinFibrinogen is converted to fibrin– Fibrin forms net that entangles Fibrin forms net that entangles

cells and platelets cells and platelets

HypertensionHypertension

Blood pressure above 140/90Blood pressure above 140/90 Tends to be geneticTends to be genetic May also be influenced by dietMay also be influenced by diet Contributes to atherosclerosisContributes to atherosclerosis ““Silent killer”: few outward Silent killer”: few outward

signs signs

AtherosclerosisAtherosclerosis

Arteries thicken, Arteries thicken, lose elasticity, and lose elasticity, and fill up with fill up with cholesterol and cholesterol and lipidslipids

High LDL High LDL increases risk increases risk

Up in SmokeUp in Smoke

The vast majority of smokers picked The vast majority of smokers picked up the habit before age 18up the habit before age 18

Smoking damages the circulatory Smoking damages the circulatory and respiratory systems and respiratory systems

Smokers have increased risk of Smokers have increased risk of respiratory infections, cancers, high respiratory infections, cancers, high blood pressure, stroke, and heart blood pressure, stroke, and heart attackattack