copyright © 2010 pearson education, inc. the cardiovascular system ch. 11

Copyright © 2010 Pearson Education, Inc.

THE CARDIOVASCULAR SYSTEM

Ch. 11


Heart Anatomy

• Approximately the size of a fist

• Location

• In the mediastinum; superior to diaphragm

• Leans to the left

• Enclosed in pericardium, a double-walled sac

Copyright © 2010 Pearson Education, Inc. Figure 18.1a

Point ofmaximalintensity(PMI)

Diaphragm

(a)

Sternum

2nd rib

Midsternal line

Copyright © 2010 Pearson Education, Inc. Figure 18.1c

(c)

Superiorvena cava

Left lung

AortaParietalpleura (cut)

Pericardium(cut)

Pulmonarytrunk

Diaphragm

Apex ofheart


Pericardium

• Superficial fibrous pericardium

• Protects, anchors, and prevents overfilling

• Deep two-layered serous pericardium

• Parietal layer lines internal surface of fibrous pericardium

• Visceral layer on external surface of heart

• Separated by fluid-filled pericardial cavity (decreases friction)


Fibrous pericardium

Parietal layer ofserous pericardiumPericardial cavity

Epicardium(visceral layerof serouspericardium)Myocardium

Endocardium

Pulmonarytrunk

Heart chamber

Heartwall

Pericardium

Myocardium


Layers of the Heart Wall

1. Epicardium=visceral layer of serous pericardium

2. Myocardium

•Cardiac Muscle Tissue

3. Endocardium

• Is continuous endothelium of blood vessels

3.


Chambers • Four chambers

• Two atria

• Top of heart; receiving chambers

• Separated by the interatrial septum

• Two ventricles

• Bottom of heart; discharging chambers

• Separated by the interventricular septum


Major Blood Vessels of the Heart

• Vessels entering right atrium

• Superior vena cava

• Inferior vena cava

• Coronary sinus

• Vessels entering left atrium

• Right and left pulmonary veins


Ventricles: The Discharging Chambers

• Vessel leaving the right ventricle

• Pulmonary trunk

• Vessel leaving the left ventricle

• Aorta


Pathway of Blood Through the Heart

• The heart is two side-by-side pumps

• Right side is the pump for the pulmonary circuit

• Vessels that carry blood to and from the lungs

• Left side is the pump for the systemic circuit

• Vessels that carry the blood to and from all body tissues

Copyright © 2010 Pearson Education, Inc. Figure 18.5

Oxygen-rich,CO2-poor bloodOxygen-poor,CO2-rich blood

Capillary bedsof lungs wheregas exchangeoccurs

Capillary beds of allbody tissues wheregas exchange occurs

Pulmonary veinsPulmonary arteries

PulmonaryCircuit

SystemicCircuit

Aorta and branches

Left atrium

Heart

Left ventricleRight atrium

Right ventricle

Venae cavae



• Right atrium tricuspid valve right ventricle

• Right ventricle pulmonary semilunar valve pulmonary trunk pulmonary arteries lungs



• Lungs pulmonary veins left atrium

• Left atrium bicuspid valve left ventricle

• Left ventricle aortic semilunar valve aorta

• Aorta systemic circulation


Coronary Circulation

• Blood supply to the heart muscle itself

• Arteries

• Right and left coronary arteries

• Branch from base of aorta

• Veins

• Cardiac veins empty into coronary sinus right atrium


Homeostatic Imbalances

• Angina pectoris

• Thoracic pain caused by a deficiency in blood delivery to the heart

• Myocardial infarction (heart attack)

• Prolonged coronary blockage

• Areas of cell death are repaired with noncontractile scar tissue


Heart Valves

• Ensure unidirectional blood flow through the heart

• Atrioventricular (AV) valves

• Prevent backflow into the atria when ventricles contract

• Tricuspid valve (right)

• Bicuspid valve/Mitral valve (left)

• Chordae tendineae anchor AV valve cusps to papillary muscles


Pulmonaryvalve

AorticvalveArea ofcutawayMitralvalve

Tricuspidvalve

Chordae tendineaeattached to tricuspid valve flap

Papillarymuscle

(c)


Heart Valves

• Semilunar (SL) valves

• Prevent backflow into the ventricles when ventricles relax

• Aortic semilunar valve

• Pulmonary semilunar valve

Copyright © 2010 Pearson Education, Inc. Figure 18.8d

PulmonaryvalveAortic valveArea of cutawayMitral valveTricuspidvalve

Mitral valve

Chordaetendineae

Interventricularseptum

Myocardiumof left ventricle

Opening of inferiorvena cava

Tricuspid valve

Papillarymuscles

Myocardiumof rightventricle

(d)


Microscopic Anatomy of Cardiac Muscle

• Cardiac muscle cells are striated, short, branched

• Endomysium connects to the fibrous skeleton

• T tubules are wide but less numerous; SR is simpler than in skeletal muscle

• Numerous large mitochondria


Nucleus

DesmosomesGap junctions

Intercalated discs Cardiac muscle cell

(a)


Microscopic Anatomy of Cardiac Muscle

• Intercalated discs: junctions between cells anchor cardiac cells

• Desmosomes prevent cells from separating during contraction

• Gap junctions allow ions to pass; electrically couple adjacent cells

• Heart muscle behaves as a functional syncytium

Copyright © 2010 Pearson Education, Inc. Figure 18.11b

Nucleus

Nucleus

I bandA band

Cardiacmuscle cell

Sarcolemma

Z disc

Mitochondrion

Mitochondrion

T tubule

Sarcoplasmicreticulum

I band

Intercalateddisc

(b)


Heart Physiology: Electrical Events

• Intrinsic cardiac conduction system

• Defined: A network of noncontractile (autorhythmic) cells that initiate and distribute impulses to coordinate the depolarization and contraction of the heart


Autorhythmic Cells

• Spontaneously depolarize

• Do not require neural stimulation


Heart Physiology: Sequence of Excitation

1. Sinoatrial (SA) node (pacemaker)

• Generates impulses about 75 times/minute (sinus rhythm)

• Depolarizes faster than any other part of the myocardium



2. Atrioventricular (AV) node

• Delays impulses ~ 0.1 second

• Depolarizes 50 times/min. in absence of SA node input



3. Atrioventricular (AV) bundle (bundle of His)

• Only electrical connection between the atria and ventricles



4. Right and left bundle branches

• Two pathways in the interventricular septum that carry the impulses toward the apex of the heart



5. Purkinje fibers

• Complete the pathway into the apex and ventricular walls

• AV bundle and Purkinje fibers depolarize only 30 times per minute in absence of AV node input


(a) Anatomy of the intrinsic conduction system showing the sequence of electrical excitation

Internodal pathway

Superior vena cavaRight atrium

Left atrium

Purkinje fibers

Inter-ventricularseptum

1 The sinoatrial (SA) node (pacemaker)generates impulses.

2 The impulsespause (0.1 s) at theatrioventricular(AV) node. The atrioventricular(AV) bundleconnects the atriato the ventricles.4 The bundle branches conduct the impulses through the interventricular septum.

3

The Purkinje fibersdepolarize the contractilecells of both ventricles.

5



• Defects in the intrinsic conduction system may result in

1. Arrhythmias: irregular heart rhythms

2. Fibrillation: rapid, irregular contractions; useless for pumping blood



• Defective AV node may result in

• Partial or total heart block

• Few or no impulses from SA node reach the ventricles


Extrinsic Innervation of the Heart

• Heartbeat is modified by the ANS

• Cardiac centers are located in the medulla oblongata

• Cardioacceleratory center innervates: SA and AV nodes, heart muscle, and coronary arteries

• Cardioinhibitory center inhibits: SA and AV nodes


The vagus nerve (parasympathetic) decreases heart rate.

Cardioinhibitory center

Cardio-acceleratorycenter

Sympathetic cardiacnerves increase heart rateand force of contraction.

Medulla oblongata

Sympathetic trunk ganglion

AV node

SA nodeParasympathetic fibersSympathetic fibersInterneurons


Electrocardiography

• Electrocardiogram (ECG or EKG): a composite of all the action potentials generated by nodal and contractile cells at a given time

• Three waves

1. P wave: depolarization of SA node

2. QRS complex: ventricular depolarization

3. T wave: ventricular repolarization


Sinoatrialnode

Atrioventricularnode

Atrialdepolarization

QRS complex

Ventriculardepolarization

Ventricularrepolarization

P-QInterval

S-TSegment

Q-TInterval


Atrial depolarization, initiatedby the SA node, causes theP wave.

P

R

T

QS

SA node

AV node

With atrial depolarizationcomplete, the impulse isdelayed at the AV node.

Ventricular depolarizationbegins at apex, causing theQRS complex. Atrialrepolarization occurs.

P

R

T

QS

P

R

T

QS

Ventricular depolarizationis complete.

Ventricular repolarizationbegins at apex, causing theT wave.

Ventricular repolarizationis complete.

P

R

T

QS

P

R

T

QS

P

R

T

QS

Depolarization Repolarization

1

2

3

4

5

6


(a) Normal sinus rhythm.

(c) Second-degree heart block. Some P waves are not conducted through the AV node; hence more P than QRS waves are seen. In this tracing, the ratio of P waves to QRS waves is mostly 2:1.

(d) Ventricular fibrillation. These chaotic, grossly irregular ECG deflections are seen in acute heart attack and electrical shock.

(b) Junctional rhythm. The SA node is nonfunctional, P waves are absent, and heart is paced by the AV node at 40 - 60 beats/min.


Mechanical Events: The Cardiac Cycle

• Cardiac cycle: all events associated with blood flow through the heart during one complete heartbeat

• Systole—contraction

• Diastole—relaxation


Cardiac Output (CO)

• Volume of blood pumped by each ventricle in one minute

• CO = heart rate (HR) x stroke volume (SV)

• HR = number of beats per minute

• SV = volume of blood pumped out by a ventricle with each beat


Cardiac Output (CO)

• At rest

• CO (ml/min) = HR (75 beats/min) SV (70 ml/beat)

= 5.25 L/min

• Maximal CO is 4–5 times resting CO in nonathletic people

• Maximal CO may reach 35 L/min in trained athletes


Regulation of Stroke Volume

• SV = EDV – ESV

• Three main factors affect SV

• Preload

• Contractility

• Afterload



• Tachycardia: abnormally fast heart rate (>100 bpm)

• If persistent, may lead to fibrillation

• Bradycardia: heart rate slower than 60 bpm

• May result in grossly inadequate blood circulation


Congestive Heart Failure (CHF)

• Progressive condition where the CO is so low that blood circulation is inadequate to meet tissue needs

• Caused by

• Coronary atherosclerosis

• Persistent high blood pressure

• Multiple myocardial infarcts

• Dilated cardiomyopathy (DCM)


Developmental Aspects of the Heart

• Fetal heart structures that bypass pulmonary circulation

• Foramen ovale connects the two atria

• Ductus arteriosus connects the pulmonary trunk and the aorta


BLOOD VESSEL PHYSIOLOGY


Blood Vessels

• Arteries: carry blood away from the heart; oxygenated except for pulmonary arteries

• Capillaries: contact tissue cells and directly serve cellular needs

• Veins: carry blood toward the heart


Large veins(capacitancevessels)

Largelymphaticvessels

Arteriovenousanastomosis

Lymphaticcapillary

Postcapillaryvenule

Sinusoid

MetarterioleTerminal arteriole

Arterioles(resistance vessels)

Muscular arteries(distributingvessels)

Elastic arteries(conductingvessels)

Small veins(capacitancevessels)

Lymphnode

Capillaries(exchange vessels)

Precapillary sphincterThoroughfarechannel

Lymphaticsystem

Venous system Arterial systemHeart


Structure of Blood Vessel Walls• Arteries and veins

• Tunica intima – Endothelium that lines the lumen of all vessels

• Tunica media - Smooth muscle and sheets of elastin

• Sympathetic vasomotor nerve fibers control vasoconstriction and vasodilation of vessels

• Tunica externa - Collagen fibers protect and reinforce

• Lumen

• Central blood-containing space

• Capillaries

• Endothelium with sparse basal lamina; Size allows only a single RBC to pass at a time

• Functions: exchange of gases, nutrients, wastes, hormones, etc.


Tunica media(smooth muscle andelastic fibers)

Tunica externa(collagen fibers)

LumenArtery

LumenVein

Internal elastic lamina

External elastic lamina

Valve

(b)

Endothelial cellsBasement membrane

Capillarynetwork

Capillary

Tunica intima• Endothelium

Copyright © 2010 Pearson Education, Inc. Figure 19.16 (1 of 2)

Red bloodcell in lumenEndothelial cell

Intercellular cleft

Fenestration(pore)Endothelial cell nucleus

Tight junction

Basement membrane

Pinocytotic vesicles


Capillary Exchange of Respiratory Gases and Nutrients

• Diffusion of

• O2 and nutrients from the blood to tissues

• CO2 and metabolic wastes from tissues to the blood

• Lipid-soluble molecules diffuse directly through endothelial membranes

• Water-soluble solutes pass through clefts and fenestrations

• Larger molecules are actively transported in pinocytotic vesicles etc.


Basementmembrane

Endothelialfenestration(pore)

Intercellularcleft

Pinocytoticvesicles

Caveolae

4 Transportvia vesicles orcaveolae (largesubstances)

3 Movementthroughfenestrations (water-soluble substances)

2 Movementthrough intercellular clefts (water-soluble substances)

1 Diffusionthrough membrane (lipid-soluble substances)

Lumen


Hydrostatic Pressures

• Capillary hydrostatic pressure (HPc) (capillary blood pressure)

• Tends to force fluids through (out of) capillary walls

• Is greater at arterial end (35 mm Hg) than venous end (17 mm Hg)


Colloid Osmotic Pressures

• Capillary oncotic pressure (OPc)

• Created by nondiffusible plasma proteins, which draw water toward themselves

• ~26 mm Hg


Net Filtration Pressure (NFP)

• NFP = (HPc—Opc)

• At arterial end = hydrostatic forces dominate

• At venous end =osmotic forces dominate

• Excess fluid is returned to blood (lymphatic system)


HP = hydrostatic pressure• Due to fluid pressing against a wall• “Pushes”• In capillary (HPc) • Pushes fluid out of capillary • 35 mm Hg at arterial end and 17 mm Hg at venous end of capillary in this example

OP = osmotic pressure• Due to presence of nondiffusible solutes (e.g., plasma proteins)• “Sucks”• In capillary (OPc) • Pulls fluid into capillary • 26 mm Hg in this example

Arteriole

Capillary

Interstitial fluid

Net HP—Net OP(35 – 25 = 10

Net HP—Net OP(17 -25 = -8)

Venule

NFP (net filtration pressure)is 10 mm Hg; fluid moves out

NFP is ~8 mm Hg;fluid moves in

NetHP35mm

NetOP25mm

NetHP17mm

NetOP25mm


BLOOD VESSEL PHYSIOLOGY


Common carotid arteries

Subclavian artery

Subclavian artery

Aortic archAscending aorta

Thoracic aorta (abovediaphragm)

Renal artery

Superficial palmar arch

Radial arteryUlnar artery

Internal iliac artery

Deep palmar arch

Brachiocephalic trunk

Axillary artery

Brachial artery

Abdominal aortaSuperior mesenteric artery

Gonadal arteryCommon iliac artery

External iliac artery

Digital arteries

Femoral arteryPopliteal arteryAnterior tibial arteryPosterior tibial artery

(b) Illustration, anterior view

Inferior mesenteric artery

Celiac trunk

Arteries of the head and trunk

Arteries that supply the upper limb

Arteries that supply the lower limb


Middlecerebral artery

Internalcarotid artery

Cerebral arterialcircle (circle of Willis)

• Posterior cerebral arteryBasilar artery

Vertebral artery

• Posterior communicating artery

(d) Major arteries serving the brain (inferior view, right side of cerebellum and part of right temporal lobe removed)

• Anterior cerebral artery

• Anterior communicating artery

Posterior

Anterior


Vertebral artery

Axillary artery

Radial arteryUlnar artery

Brachial artery

Deep palmar archSuperficial palmar archDigital arteries

Common carotidarteries

Right subclavian arteryLeft subclavian artery


Descending aorta

Anterior view


Liver (cut) Diaphragm

Esophagus

Left gastricartery

Superiormesentericmesenteric

LeftgastroepiploicarterySpleen

Stomach

Pancreas(major portion liesposterior to stomach)

Splenic artery

Inferior vena cava

Celiac trunk

Hepatic arteryproper

Common hepaticartery

GastroduodenalarteryRight gastric artery

Gallbladder

Abdominal aorta

Rightgastroepiploicartery

Duodenum

(b) The celiac trunk and its major branches. The left half of the liver has been removed.


(c) Major branches of the abdominal aorta.

Diaphragm

Inferiorphrenic artery

Renal artery

Superiormesenteric artery

Commoniliac artery

Gonadal(testicular or ovarian) artery

Celiac trunk

Adrenal(suprarenal)gland

Kidney

Abdominal aorta

Lumbar arteriesInferiormesenteric artery


Common iliac artery

Femoral artery

Popliteal arteryAnterior tibial arteryPosterior tibial arteryFibular artery

(b) Anterior view

Internal iliac artery

External iliac artery


(c) Posterior view

Popliteal artery

Anterior tibial artery

Fibular artery

Plantar archMedial plantarartery

Lateral plantarartery

Posterior tibialartery


Brachial vein

External jugular vein

Internal jugular vein

Superior vena cava

Right and leftbrachiocephalic veins

Axillary vein

Inferior vena cava

Ulnar vein

Radial vein

Common iliac vein

External iliac vein

Internal iliac vein

Digital veins

Femoral vein

Popliteal vein

Posterior tibial vein

Anterior tibial vein

(b) Illustration, anterior view. The vessels of the pulmonary circulation are not shown.

Subclavian vein

Veins of the head and trunk Veins that drainthe upper limb

Veins that drainthe lower limb


(c) The hepatic portal circulation.

Hepatic veins

Liver

Spleen

Gastric veins

Inferior vena cava

Inferior vena cava(not part of hepaticportal system)

Splenic vein

Inferiormesenteric vein

Superiormesenteric vein

Large intestine

Hepatic portal vein

Small intestine

Rectum


Inferiorvena cavaInferior phrenic veinsHepatic veins

Hepatic portal vein

Superior mesenteric veinSplenic vein

Inferiormesentericvein

L. ascendinglumbar vein

R. ascendinglumbar vein

Gonadal veins

Renal veins

Suprarenalveins

Lumbar veins

Hepaticportalsystem

Cystic vein

External iliac vein

Internal iliac veins

Common iliac veins

(a) Schematic flowchart.


Popliteal vein

Common iliac vein

Fibular veinAnterior tibial vein

Dorsalis pedis veinDorsal venous arch

Dorsal metatarsalveins

(b) Anterior view

Internal iliac veinExternal iliac veinInguinal ligament

Femoral veinGreat saphenousvein (superficial)

Small saphenousvein


(c) Posterior view

Great saphenousvein Popliteal vein

Anterior tibial vein

Fibular vein

Small saphenousvein (superficial)

Posterior tibial vein

Plantar veins

Deep plantar arch

Digital veins


(b) Anterior view


Superior vena cava

Right pulmonaryarteryAscending aortaPulmonary trunk

Right pulmonaryveins

Right atrium

Right coronary artery(in coronary sulcus)Anterior cardiac vein

Right ventricle

Right marginal artery

Small cardiac vein

Inferior vena cava

Left common carotidarteryLeft subclavian artery

Ligamentum arteriosum

Left pulmonary artery

Left pulmonary veins

Circumflex artery

Left coronary artery(in coronary sulcus)

Left ventricle

Great cardiac vein

Anterior interventricularartery (in anteriorinterventricular sulcus)

Apex

Aortic arch

Auricle ofleft atrium

copyright © 2010 pearson education, inc. the cardiovascular system ch. 11

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