© 2012 Pearson Education, Inc. The Cardiovascular System A closed system of the heart and blood...

© 2012 Pearson Education, Inc.

The Cardiovascular System

•A closed system of the heart and blood vessels

•The functions of the cardiovascular system


The Heart

•Location

•Orientation

•About the size of your fist

© 2012 Pearson Education, Inc. Figure 11.1a

Midsternal line

2nd rib

Diaphragm

(a)

Sternum

Point ofmaximalintensity(PMI)

© 2012 Pearson Education, Inc. Figure 11.1b

Mediastinum

Heart

Left lung

(b)Posterior


The Heart: Coverings•Pericardium—•Fibrous pericardium is loose and superficial•Serous membrane is deep to the fibrous pericardium and composed of two layers

•Serous fluid fills the space between the layers of pericardium

© 2012 Pearson Education, Inc. Figure 11.2

Pericardium

Myocardium

Pulmonarytrunk Fibrous pericardium

Parietal layer of serous pericardiumPericardial cavity

Epicardium (visceral layer of serous pericardium)

Myocardium

Endocardium

Heart chamber

Heart wall


The Heart: Heart Wall•Three layers•Epicardium

•Myocardium

•Endocardium


The Heart: Chambers

•Right and left side act as separate pumps•Four chambers•Atria•Receiving chambers•Right atrium•Left atrium

•Ventricles•Discharging chambers•Right ventricle•Left ventricle


Rightventricle

Muscularinterventricularseptum

Leftventricle


The Heart: Septa

• Interventricular septum

• Interatrial septum


The Heart’s Role in Blood Circulation

•Systemic circulation

•Pulmonary circulation


The Heart: Valves

•Allow blood to flow in only one direction to prevent backflow•Four valves


The Heart: Valves

•AV valves

•Semilunar valves

© 2012 Pearson Education, Inc. Figure 11.6a, step 6

(a) Operation of the AV valves

Blood returningto the atria putspressure againstAV valves; the AVvalves are forcedopen.

As the ventriclesfill, AV valve flapshang limply intoventricles.

Atria contract, forcing additional blood into ventricles.

AV valves open;atrial pressuregreater thanventricular pressure

AV valves closed;atrial pressureless than ventricular pressure

Ventricles

Chordae tendineae tighten, preventing valve flaps from everting into atria.

AV valves close.

Ventricles contract,forcing blood against AV valve flaps.

1

2

3

4

5

6

© 2012 Pearson Education, Inc. Figure 11.6b, step 2

(b) Operation of the semilunar valves

As ventricles contract and intraventricularpressure rises, blood is pushed up against semilunar valves, forcing them open.

As ventricles relax and intraventricularpressure falls, blood flows back from arteries,filling the leaflets of semilunarvalves and forcingthem to close.

Semilunar valves open Semilunar valves closed

Pulmonarytrunk Aorta

1 2


Cardiac Circulation

•Blood in the heart chambers does not nourish the myocardium•The heart has its own nourishing circulatory system consisting of•Coronary

•Cardiac•Coronary

•Blood empties into the right atrium via the coronary sinus


The Heart: Associated Great Vessels

•Arteries•Aorta

•Pulmonary arteries


The Heart: Associated Great Vessels

•Veins


Blood Flow Through the Heart

•Superior and inferior venae cavae dump blood into the right atrium•From right atrium, through the tricuspid valve, blood travels to the right ventricle•From the right ventricle, blood leaves the heart as it passes through the pulmonary semilunar valve into the pulmonary trunk•Pulmonary trunk splits into right and left pulmonary arteries that carry blood to the lungs


Blood Flow Through the Heart

•Oxygen is picked up and carbon dioxide is dropped off by blood in the lungs•Oxygen-rich blood returns to the heart through the four pulmonary veins•Blood enters the left atrium and travels through the bicuspid valve into the left ventricle•From the left ventricle, blood leaves the heart via the aortic semilunar valve and aorta


The Heart: Conduction System

• Intrinsic conduction system (nodal system)


The Heart: Conduction System

•Special tissue sets the pace•Sinoatrial node =

•Atrioventricular node =

•Atrioventricular bundle =

•Bundle branches are in the interventricular septum•Purkinje fibers spread within the ventricle wall muscles


Superior vena cava

Sinoatrial (SA) node (pacemaker)

Atrioventricular(AV) node

Right atrium

Bundle branches

Purkinje fibers

Left atrium

Atrioventricular(AV) bundle(bundle of His)

Purkinje fibers

Interventricularseptum


Heart Contractions

•Contraction is initiated by the sinoatrial node (SA node)

•Force cardiac muscle depolarization in one direction—


Heart Contractions

•Once SA node starts the heartbeat

•At the AV node, the impulse passes through the AV bundle, bundle branches, and Purkinje fibers•Blood is ejected from the ventricles to the aorta and pulmonary trunk as the ventricles contract


Heart Contractions

•Homeostatic imbalance•Heart block—

• Ischemia—

•Fibrillation—


Heart Contractions

•Homeostatic imbalance (continued)•Tachycardia—

•Bradycardia—


The Heart: Cardiac Cycle & Heart Sounds

•Atria contract simultaneously•Atria relax, then ventricles contract



•Cardiac cycle—events of one complete heart beat



•Cardiac cycle—events of one complete heart beat•Ventricular systole

•Atrioventricular valves close causes first heart sound, “lub”•Semilunar valves open as blood pushes against them•Blood travels out of the ventricles through pulmonary trunk and aorta•Atria are relaxed



•Cardiac cycle—events of one complete heart beat•Early diastole

•Second heart sound is heard as semilunar valves close, causing “dup” sound

•Atria finish refilling as pressure in the heart drops•Ventricular pressure is low•Atrioventricular valves open


Left atriumRight atrium

Left ventricleRight ventricle

Ventricularfilling

Atrialcontraction

Isovolumetriccontraction phase

Ventricularejection phase

Isovolumetricrelaxation

Mid-to-late diastole(ventricular filling)

Ventricular systole(atria in diastole)

Early diastole

1 2 3


The Heart: Cardiac Output

•Cardiac output (CO)

•Stroke volume (SV)

•Usually remains relatively constant •About 70 mL of blood is pumped out of the left ventricle with each heartbeat

•Heart rate (HR) •Typically 75 beats per minute


The Heart: Cardiac Output

•CO = HR SV •CO = HR (75 beats/min) SV (70 mL/beat)•CO = 5250 mL/min•Starling’s law of the heart—

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


The Heart: Regulation of Heart Rate

• Increased heart rate

•Hormones

•Exercise•Decreased blood volume


The Heart: Regulation of Heart Rate

•Decreased heart rate



Blood Vessels: The Vascular System

•Transport blood to the tissues and back

•Exchanges between tissues and blood•Capillary beds

•Return blood toward the heart


Artery(a) Vein


Blood Vessels: Microscopic Anatomy

•Three layers (tunics)

•Endothelium

•Smooth muscle•Controlled by sympathetic nervous system

•Mostly fibrous connective tissue


ValveTunica intima

• Loose connective tissue• Endothelium

Internal elasticlamina

Tunica media• Smooth muscle• Elastic fibersExternal elastic laminaTunica externa• Collagen fibers

ArterioleVenule

Capillarynetwork

Basement membrane

Endothelial cells

Capillary(b)

LumenVein

LumenArtery


Structural Differences Among Blood Vessels•Arteries have a thicker tunica media than veins•Capillaries are only one cell layer (tunica intima) to allow for exchanges between blood and tissue•Veins have a thinner tunica media than arteries


Venous Aids for the Return of Blood to the Heart•Veins:

To assist in the movement of blood back to the heart:•Larger veins have valves to prevent backflow•Skeletal muscle “milks” blood in veins toward the heart


Valve (open)

Contractedskeletalmuscle

Valve (closed)

Vein

Direction ofblood flow


Movement of Blood Through Vessels

•Most arterial blood is pumped by the heart•Veins use the milking action of muscles to help move blood


Capillary Beds

•Capillary beds consist of two types of vessels•Vascular shunt—vessel directly connecting an arteriole to a venule•True capillaries—


Truecapillaries

(a) Sphincters open; blood flows through true capillaries.

Vascular shuntPrecapillary sphincters

Terminal arteriole Postcapillary venule



Major Arteries of System Circulation

•Aorta

•Leaves from the left ventricle of the heart•Regions•Ascending aorta—•Aortic arch—•Thoracic

•Abdominal


Major Arteries of System Circulation

•Arterial branches of the ascending aorta•Right and left coronary arteries serve the heart


Major Arteries of Systemic Circulation

•Arterial branches of the aortia arch (BCS)•Brachiocephalic trunk splits into the

•Left common carotid artery splits into the

•Left subclavian artery branches into the•Vertebral artery• In the axilla, the subclavian artery becomes the axillary artery brachial artery radial and ulnar arteries



•Arterial branches of the thoracic aorta• Intercostal arteries supply the muscles of the thorax wall•Other branches of the thoracic aorta supply the



•Arterial branches of the abdominal aorta•Celiac trunk is the first branch of the abdominal aorta. Three branches are

•Superior mesenteric artery supplies most of the small intestine and first half of the large intestine



•Arterial branches of the abdominal aorta•Left and right renal arteries (kidney)•Left and right gonadal arteries

•Lumbar arteries serve muscles of the abdomen and trunk



•Arterial branches of the abdominal aorta• Inferior mesenteric artery serves the second half of the large intestine•Left and right common iliac arteries are the final branches of the aorta• Internal iliac arteries serve the pelvic organs•External iliac arteries enter the thigh femoral artery popliteal artery anterior and posterior tibial arteries


Arteries of the head and trunkInternal carotid arteryExternal carotid arteryCommon carotid arteriesVertebral arterySubclavian arteryBrachiocephalic trunkAortic archAscending aortaCoronary arteryThoracic aorta (above diaphragm)

Celiac trunkAbdominal aorta

Superior mesenteric arteryRenal arteryGonadal artery

Inferior mesenteric artery

Internal iliac artery

Arteries that supply the upper limbSubclavian artery

Axillary artery

Brachial artery

Radial arteryUlnar artery

Deep palmar arch

Superficial palmar arch

Digital arteries

Arteries that supply the lower limbCommon iliac artery

External iliac arteryFemoral artery

Popliteal artery

Anterior tibial arteryPosterior tibial artery

Dorsalis pedis artery

Arcuate artery


Major Veins of Systemic Circulation

•Superior and inferior vena cava enter the right atrium of the heart



•Veins draining into the superior vena cava•Radial and ulnar veins brachial vein axillary vein •These veins drain the arms



•Veins draining into the superior vena cava•Subclavian vein receives



•Veins draining into the superior vena cava•Left and right brachiocephalic veins receive venous blood from the

•Brachiocephalic veins join to form the superior vena cava right atrium of heart•Azygous vein drains the thorax



•Veins draining into the inferior vena cava•Anterior and posterior tibial veins and fibial veins drain the legs•Posterior tibial vein popliteal vein femoral vein external iliac vein•Great saphenous veins (longest veins of the body) receive superficial drainage of the legs



•Veins draining into the inferior vena cava•Right gonadal vein drains the right ovary in females and right testicle in males•Left gonadal vein empties into the left renal vein•Left and right renal veins drain the kidneys



•Veins draining into the inferior vena cava•Left and right hepatic veins drain the liver


Arterial Supply of the Brain

• Internal carotid arteries divide into

•Vertebral arteries join once within the skull to form the basilar artery


Arterial Supply of the Brain

•Posterior cerebral arteries form from the division of the basilar artery


Circle of Willis

•Anterior and posterior blood supplies are united by small communicating arterial branches•Result—


Anterior

Optic chiasma

Middle cerebral artery

Internal carotid artery

Mammillarybody

Temporal lobe

Occipital lobe

Cerebral arterialcircle (circle of Willis) • Anterior communicating artery

• Anterior cerebral artery

• Posterior communicating artery

• Posterior cerebral artery

Basilar artery

Cerebellum

Posterior(a)

PonsVertebral artery

Frontal lobe



Fetal Circulation

•Fetus receives exchanges of gases, nutrients, and wastes through the placenta•Umbilical cord contains three vessels


Superior vena cava

Foramen ovale

Inferior vena cavaHepatic vein

Ductus venosus

Hepatic portal vein

Umbilical veinFetal umbilicus

Umbilical cord

Umbilical arteries

Ductus arteriosus

Pulmonary artery

Pulmonary veins

Inferior vena cava

AortaCommon iliac artery

External iliac arteryInternal iliac artery

Urinary bladder

Placenta

KEY:

High oxygenation Moderate oxygenation Low oxygenation Very low oxygenation


Fetal Circulation

•Blood flow bypasses the liver through the ductus venosus and enters the inferior vena cava right atrium of heart•Blood flow bypasses the lungs


Hepatic Portal Circulation

•Veins of hepatic portal circulation drain

•Hepatic portal vein carries this blood to the liver •Liver helps maintain proper glucose, fat, and protein concentrations in blood


Hepatic Portal Circulation

•Major vessels of hepatic portal circulation


Arterialblood

Stomach and intestineNutrients andtoxins absorbed

Hepaticportal vein

First capillary bed Second capillary bed(liver sinusoids)

Liver cells (hepatocytes)

Nutrientsand toxinsleave

Inferiorvena cava

Venousblood

Hepaticvein

Liver

Hepatic portal system


Inferior vena cava(not part of hepaticportal system)

Gastric veins

Spleen

Stomach

Splenic vein

Inferiormesenteric vein

Superiormesenteric vein

Large intestine

Small intestine

Hepatic portal vein

Liver


Pulse

•Pulse•Pressure wave of blood


Superficial temporal artery

Facial artery

Common carotid artery

Brachial artery

Radial artery

Femoral artery

Popliteal artery

Posterior tibialartery

Dorsalis pedisartery


Blood Pressure

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

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


120

100

80

60

40

20

0

−10

Systolic pressure

Diastolicpressure

Pre

ssu

re (

mm

Hg

)

Ao

rta

Art

erie

s

Art

erio

les

Cap

illa

rie

s

Ve

nu

les

Ve

ins

Ve

nae

ca

vae


Blood pressure120 systolic70 diastolic(to be measured)

Brachialartery

(a) The course of the brachial artery of the arm. Assume a blood pressure of 120/70 in a young, healthy person.


Pressurein cuffabove 120; no soundsaudible

Rubber cuffinflated with air

120 mm Hg

Brachialarteryclosed

(b) The blood pressure cuff is wrapped snugly around the arm just above the elbow and inflated until the cuff pressure exceeds the systolic blood pressure. At this point, blood flow into the arm is stopped, and a brachial pulse cannot be felt or heard.

© 2012 Pearson Education, Inc. Figure 11.21c

Pressurein cuffbelow 120,but above 70

120 mm Hg

70 mm Hg

Soundsaudible instethoscope

(c) The pressure in the cuff is gradually reduced while the examiner listens (auscultates) for sounds in the brachial artery with a stethoscope. The pressure read as the first soft tapping sounds are heard (the first point at which a small amount of blood is spurting through the constricted artery) is recorded as the systolic pressure.

© 2012 Pearson Education, Inc. Figure 11.20d

Pressurein cuffbelow 70;no soundsaudible

70 mm Hg

(d) As the pressure is reduced still further, the sounds become louder and more distinct; when the artery is no longer constricted and blood flows freely, the sounds can no longer be heard. The pressure at which the sounds disappear is recorded as the diastolic pressure.


Blood Pressure: Effects of Factors

•BP is blood pressure

•CO is the amount of blood pumped out of the left ventricle per minute•PR is peripheral resistance, or the amount of friction blood encounters as it flows through vessels•Narrowing of blood vessels and increased blood volume increases PR

•BP = CO PR



•Neural factors

•Renal factors



•Temperature•Heat has a vasodilating effect•Cold has a vasoconstricting effect

•Chemicals•Various substances can cause increases or decreases

•Diet



Variations in Blood Pressure

•Normal human range is variable•Normal•140 to 110 mm Hg systolic•80 to 75 mm Hg diastolic

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

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


Capillary Exchange

•Substances exchanged due to concentration gradients


Capillary Exchange: Mechanisms

•Direct diffusion across plasma membranes•Endocytosis or exocytosis•Some capillaries have gaps (intercellular clefts)

•Fenestrations (pores) of some capillaries


Lumen ofcapillary

Vesicles

Endothelialfenestration(pore)

Intercellularcleft

Transportvia vesicles

Diffusionthrough pore

Diffusion throughintracellular cleft Direct

diffusionthroughmembrane Interstitial fluid

12

3

4


Fluid Movements at Capillary Beds

•Blood pressure forces fluid and solutes out of capillaries•Osmotic pressure draws fluid into capillaries


Tissue cell Interstitial fluid

Net fluidmovement out

Net fluidmovement in

Blood flow Blood flow

Arterialend ofcapillary

Venuleend ofcapillary

At the venule end of the capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary.

At the arterial end of a capillary, blood pressure is more than osmotic pressure, and fluid flows out of the capillary and into the interstitial fluid.

Blood pressure ishigher than osmoticpressure

Osmotic pressure(remains steadyin capillary bed) Blood pressure is

lower than osmoticpressure


Developmental Aspects of the Cardiovascular System•A simple “tube heart” develops in the embryo and pumps by the fourth week

•Few structural changes occur after the seventh week


Developmental Aspects of the Cardiovascular System•Aging problems associated with the cardiovascular system include

•Progressive atherosclerosis•Loss of elasticity of vessels leads to hypertension•Coronary artery disease results from vessels filled with fatty, calcified deposits

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