ch 21_lecture_presentation

© 2012 Pearson Education, Inc.

21The Cardiovascular System: The Heart

PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska


Introduction

The blood must stay in motion to maintain homeostasis.

The heart keeps blood moving.

The volume of blood pumped by the heart can vary widely, between 5 and 30 liters per minute.


An Overview of the Cardiovascular System

The heart is a small organ; your heart is roughly the size of your clenched fist. Two closed circuits:

Pulmonary circuit carries carbon dioxide—rich blood from the heart to the lungs and back

Systemic circuit transports oxygen-rich blood from the heart to the rest of the body and back

The heart has four muscular chambers: Right and left atria collect blood returning to heart Right and left ventricles discharge blood into vessels to leave

the heart. Left ventricle is considered the strongest chamber of the heart and creates

the highest pressure in the circulation. Right ventricle contains the “Moderator band”.


Figure 21.2a Location of the Heart in the Thoracic Cavity

Anterior view of the open chest cavity showing the positionof the heart and major vessels relative to the lungs. Thesectional plane indicates the orientation of part (c).

Apex of heart

Parietal pericardium(cut)

Base ofheart

Diaphragm

Right lung

TracheaThyroid gland

First rib (cut)

Left lung


An Overview of the Cardiovascular System

Pulmonary circuit Right atrium

Tricuspid valve Right ventricle

Pulmonary valve Pulmonary

trunk/pulmonary arteries.

Systemic circuit Left atrium

Mitral valve

Left ventricle Aortic valve Aorta


CIRCULATIONS


The Pericardium

The pericardium is the serous membrane lining the pericardial cavity, which surrounds the heart

Visceral pericardium (epicardium) covers the heart’s outer surface

Parietal pericardium lines the inner surface of the pericardial sac


Figure 21.2b Location of the Heart in the Thoracic Cavity

Relationships between the heart and the pericardialcavity. The pericardial cavity surrounds the heartlike the balloon surrounds the fist (right).

Pericardialcavity containing

pericardial fluid

Cut edge ofparietal pericardium

Cut edge ofepicardium(visceral pericardium)

Fibrous attachmentto diaphragm

Air space(correspondsto pericardial

cavity)

Balloon


Structure of the Heart Wall

Three distinct layers: Epicardium — covers the outside of the heart Myocardium — cardiac muscle, the thickest

layer of the heart. The muscular ridges in the inner surface of the atria

are called Pectinate muscles. Microscopic appearance of cardiac muscle shows

branched fibers and intercalated discs. Endocardium — lines the inside of the heart


Figure 21.3de Histological Organization of Muscle Tissue in the Heart Wall

Diagrammatic three-dimensionalview of cardiac muscle cells

The structure of an intercalated disc

Cardiac muscle cell

Mitochondria

Intercalateddisc (sectioned)

Nucleus

Cardiac musclecell (sectioned)

Bundles ofmyofibrils

Intercalateddisc

Intercalateddisc

Z lines boundto opposing cell

membranes

Gap junction

Desmosomes


Orientation and Superficial Anatomy of Heart

The heart lies slightly to the left of the midline. The heart sits at an oblique angle to the longitudinal axis of the body. The heart is rotated slightly toward the left. The heart has external sulci that mark internal boundaries.


Figure 21.4 Position and Orientation of the Heart

Base of heart

Ribs

Apex of heart

Inferior border

Superiorborder

Rightborder Left

border

1 1

2 2

3 3

4 4

5 5

6 6

77

88

9 9

10 10


Figure 21.5a Superficial Anatomy of the Heart, Part I

Anterior view of the heart and greatvessels

Fat inanteriorinterventricularsulcus

LEFTVENTRICLE

RIGHTVENTRICLE

RIGHTATRIUM

Fat incoronary

sulcus

Auricleof rightatrium

Superiorvena cava

Ascendingaorta

Brachiocephalic trunk

Left common carotid artery

Auricle ofleft atrium

Pulmonarytrunk

Left pulmonaryartery

Descendingaorta

Ligamentumarteriosum

Arch of aorta

Left subclavian artery


Figure 21.5b Superficial Anatomy of the Heart, Part I

Posterior view of the heart and greatvessels

LEFTVENTRICLE

Fat incoronary

sulcus

Coronarysinus

Left pulmonary artery

Left pulmonary veins

RIGHTVENTRICLE

LEFTATRIUM

RIGHTATRIUM

Arch of aorta

Right pulmonaryartery

Superiorvena cava

Right pulmonaryveins (superiorand inferior)

Inferiorvena cava

Fat in posteriorinterventricular sulcus


Orientation and Superficial Anatomy of Heart

• The left and right atria• Positioned superior to the coronary sulcus• Both have thin walls• Both consist of expandable extensions called

auricles

• The left and right ventricles• Positioned inferior to the coronary sulcus• Much of the right ventricle forms the

diaphragmatic surface


Figure 21.6a Superficial Anatomy of the Heart, Part II

In this photo, the pericardial sac has beencut and reflected to expose the heart andgreat vessels.

Parietal pericardium fused to diaphragm

RIGHTVENTRICLE

RIGHTATRIUM

LEFTVENTRICLE

Marginal branchof right

coronary artery

Coronary sulcus

Right coronaryartery

Auricle ofright atrium

Superiorvena cava

Parietalpericardium

Ascendingaorta

Fibrouspericardium

Pulmonary trunk

Auricle ofleft atrium

Anteriorinterventricularsulcus


Diagrammatic frontal section through the relaxed heart shows the majorlandmarks and the path of blood flow through the atria and ventricles (arrows).

Inferior vena cava

RIGHT VENTRICLE

Papillary muscle

Chordae tendineae

Cusp of right AV(tricuspid) valve

Conus arteriosus

Pectinate muscles

RIGHT ATRIUM

Opening ofcoronary sinus

Ascendingaorta

Rightpulmonary

arteries

Fossa ovalis

Superiorvena cava

Brachiocephalictrunk

Aortic arch

LEFTATRIUM

Left common carotid artery


Ligamentum arteriosum

Pulmonary trunk

Pulmonary valve

Left pulmonaryarteries

Left pulmonaryveins

Interatrial septumAortic valve

Cusp of left AV(mitral) valve

LEFT VENTRICLE

Interventricularseptum

Trabeculaecarneae

Moderatorband

Descendingaorta

Figure 21.7b Sectional Anatomy of the Heart, Part I


Cardiac cycle

All of the electrical and mechanical events that take place during one heart beat are referred to as one cardiac cycle.

Systole — contraction Atrial systole Ventricular systole

Blood is pushed out of the heart. AV valves are closed

Diastole — relaxation, when the chambers of the heart fill. Atrial diastole

RA receives blood from SVC and IVC. LA receives blood from pulmonary veins.


Figure 21.9a Valves of the Heart

Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle

POSTERIOR

ANTERIOR

RIGHTVENTRICLE

LEFTVENTRICLE

Fibrousskeleton

Left AV (bicuspid)valve (open)

Aortic valve(closed)

Pulmonaryvalve (closed)

Right AV(tricuspid)

valve (open)Ve

ntr

icu

lar

Dia

sto

le

When the ventricles are relaxed, the AV valves are open andthe semilunar valves are closed. The chordae tendineae areloose, and the papillary muscles are relaxed.

Aortic valve(closed)

Pulmonaryveins

LEFTATRIUM

Left AV(bicuspid)valve (open)

Chordaetendineae(loose)

Papillarymuscles(relaxed)

LEFT VENTRICLE(dilated)

Aortic valve closed


Figure 21.9b Valves of the Heart

Ve

ntr

icu

lar

Sy

sto

le

When the ventricles are contracting, the AV valvesare closed and the semilunar valves are open. Inthe frontal section notice the attachment of the leftAV valve to the chordae tendineae and papillarymuscles.

RIGHTVENTRICLE

Right AV(tricuspid) valve

(closed)

Fibrousskeleton

Left AV(bicuspid) valve

(closed)LEFTVENTRICLE

Aortic valve(open)

Pulmonaryvalve (open)

Aortic valve open

Transverse Sections, Superior View, Atria and Vessels Removed Frontal Sections Through Left Atrium and Ventricle

LEFTATRIUM

Aorta

Aortic sinus

Aortic valve(open)

Left AV(bicuspid)valve (closed)

Chordaetendineae(tense)

Papillarymuscles(contracted)

Left ventricle(contracted)


Blood supply to the heart

• The heart muscle is receiving its own blood from right and left coronary arteries.

• Coronary arteries are originating from the base of the ascending aorta.


Figure 21.10a Coronary Circulation

Coronary vessels supplying theanterior surface of the heart

Marginal branchof RCA

Anterior cardiacveins

Small cardiacvein

Atrialbranches

of RCA

LEFTVENTRICLERIGHT

VENTRICLE

RIGHTATRIUM

Aorticarch

Rightcoronary

artery(RCA)

Pulmonarytrunk

Brachiocephalictrunk

Left common carotidartery


LEFT ATRIUM

Left coronaryartery (LCA)

Circumflexbranch of LCA

Diagonal branchof LCA

Anteriorinterventricularbranch of LCA

Great cardiacvein


Figure 21.10b Coronary Circulation

Coronary vessels supplying theposterior surface of the heart

Marginalbranch of LCAPosterior vein

of left ventricle

Posteriorleft ventricularbranch of LCA

Circumflexbranch of LCA

Atrial branchof LCA

LEFTVENTRICLE

RIGHTVENTRICLE

LEFTATRIUM

RIGHTATRIUM

Coronarysinus

Small cardiacvein

Rightcoronaryartery (RCA)

Right marginalbranch of RCA

Middle cardiacvein

Posterior interventricularbranch of RCA

Great cardiac vein


The Cardiac Cycle

• The cardiac cycle consists of alternate periods of contraction and relaxation• Contraction is systole

• Blood is ejected into the ventricles• Blood is ejected into the pulmonary trunk and the

ascending aorta

• Relaxation is diastole• Chambers are filling with blood


Figure 21.11 The Cardiac Cycle

Cardiaccycle

370msec

100msec

0msec800

msec

Ventricular diastole—early:As ventricles relax, pressure in ventriclesdrops; blood flows back against cusps ofsemilunar valves and forces them closed.Blood flows into the relaxed atria.

Ventricular systole—second phase: As ventricular pressure risesand exceeds pressurein the arteries, thesemilunar valvesopen and bloodis ejected.

Ventricular diastole—late:All chambers are relaxed.Ventricles fill passively.

Ventricular systole—first phase:Ventricular contractionpushes AV valvesclosed but does notcreate enoughpressure to opensemilunar valves.

Atrial systole ends,atrial diastolebegins

Atrial systole begins:Atrial contraction forces a small amountof additional blood into relaxed ventricles.

Start

Atrial systole

Atrial diasto le

Ven

tric

ula

rdi

asto

le

Ven

tri c

ul a

rsy

sto

le


Figure 21.12a The Conducting System of the Heart

The stimulus for contraction is generated by pacemaker cells atthe SA node. From there, impulses follow three different pathsthrough the atrial walls to reach the AV node. After a brief delay,the impulses are conducted to the bundle of His (AV bundle), andthen on to the bundle branches, the Purkinje fibers, and theventricular myocardial cells.

Purkinje fibersModerator band

Right bundle branch

Left bundle branch

AV bundle

Atrioventricular(AV) node

Internodalpathways

Sinoatrial(SA) node


Figure 21.12b The Conducting System of the Heart

The movement of the contractile stimulus through theheart is shown in STEPS 1–5.

SA node activity andatrial activation begin.

SA node

Time 0

Stimulus spreads acrossthe atrial surfaces andreaches the AV node. AV node

Elapsed time 50 msec


AVbundle

Bundlebranches

There is a 100 msec delayat the AV node. Atrialcontraction begins.

The impulse travels along theinterventricular septum withinthe AV bundle and the bundlebranches to the Purkinje fibersand, via the moderator band,to the papillary muscles of theright ventricle.

ModeratorbandElapsed time 175 msec


The impulse is distributed byPurkinje fibers and relayedthroughout the ventricularmyocardium. Atrial contractionis completed, and ventricularcontraction begins.

Purkinjefibers


The Cardiac Cycle

The ECG is a recording of the electrical events in the heart and reveals the condition of cunducting system of the heart.

P wave — atrial depolarization QRS complex — ventricular depolarization T wave — ventricular repolarization


ECG


Figure 21.13 The Autonomic Innervation of the Heart

Sympathetic Parasympathetic

Parasympatheticpreganglionicfiber

Synapses incardiac plexus

Parasympatheticpostganglionicfibers

Sympatheticpostganglionic fiber

Cardiac nerve

Sympatheticpreganglionic

fiber

Sympathetic ganglia(cervical ganglia and

superior thoracicganglia [T1–T4])

Spinal cord

Vagus (N X)

Medullaoblongata

Vagal nucleus

Cardioacceleratorycenter

Cardioinhibitorycenter

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