chapter 22 - heart

8/7/2019 Chapter 22 - Heart

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13-1Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 22Heart


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Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

In thoracic cavity mediastinum Between the lungs

Between the sternum and vertebral column

Majority of heart is left of the bodys midline

Heart Location


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Heart Orientation

Cone-shaped; size of clenched fist Apex - directed anteriorly, inferiorly and to left

Base - directed posteriorly, superiorly and to right


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Heart Orientation

Rotated such that the right side is located

more anteriorly

the left side is located

more posteriorly.

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Pericardium

Fibrous pericardium tough, dense CT

protects

anchors heart to diaphragm

and major blood vessels restricts movement

prevents over-filling

Serous pericardium

thin delicate membrane contains

parietal layer-outer layer

pericardial cavity withpericardial fluid

visceral layer (epicardium)


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Fibrous

pericardium


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Layers of Heart Wall

Epicardium

visceral layer of serous

pericardium Myocardium

cardiac muscle layer isthe bulk of the heart

Endocardium

internal lining of heart

chambers


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Intercalated Disks-Junctions for cardiac

muscle cells


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Layers Associated with the Heart

Superficial

Deep


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Functions of the Heart

Center of the cardiovascular system Connects to blood vessels that transport blood

(oxygen, nutrients) to other body tissues

arteries carry blood away from the heart

veins carry blood back to the heart

Arteries carry blood high in oxygen.

(except for the pulmonary arteries)

Veins carry blood low in oxygen.

(except for the pulmonary veins)

Arteries and veins entering and leaving the heartare called the great vessels due to their relativelylarge diameter


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Functions of the Heart

Ensures the unidirectional flow of blood through boththe heart and the blood vessels. Valves prevent backflow of blood

Acts like two independent, side-by-side pumps that

work independently but at the same rate. one directs blood to the lungs for gas exchange the other directs blood to body tissues for nutrient delivery

Heart develops blood pressure through alternate cyclesof heart wall contraction and relaxation.

Minimum blood pressure is essential to push bloodthrough blood vessels to the body tissues for nutrientand waste exchange.


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Heart Structures

4 Heart Chambers Right ventricle, left ventricle, right atrium, left atrium

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Heart Structures Right & Left Atrium

Superior to the ventricles

Atrium chambers are covered by small flaps of tissuecalled auricles (little ear)

Right atrium Receives de-oxygenatedsystemic blood by way of the superior

vena cava and inferior vena cava.

Receives de-oxygenatedblood from the heart itself

(myocardium) by way of the coronary sinus Left atrium

Receives oxygenatedblood from the lungs by way of thepulmonary veins

Internally the 2 atria are separated by thin wall calledthe interatrial septum

Atria separated from ventricles by coronary sulcus13-17


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Heart Structures

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Heart Structures


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Heart Structures Right & Left Ventricles

Located inferior to the atrium

Internally the 2 ventricles are separated by theinterventricular septum

Externally the 2 ventricles are separated by the

anterior & posterior interventricular sulci

R ventricle receives blood from the R atrium Sends blood to lungs by way of pulmonary trunk and

pulmonary arteries

L ventricle receives blood from L atrium

Sends blood out to the rest of the body by way of the aorta


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Heart Structures

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Heart Structures


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Heart Structures Valves

Purpose is to help control blood flow

Atrio-ventricular valves (AV valves)

Right AV valve (Tricuspid valve)

Left AV valve (Bicuspid valve, mitral valve)

Semilunar valves Pulmonary semilunar valve

Aortic semilunar valves

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Heart Structures Atrio-ventricular Valves (AV valves)

Right AV valve

Located between R Atrium & R Ventricle

Left AV valve

Located between L Atrium & L Ventricle

Valves remain open as ventricles fill w/blood Valves close when ventricles contract to

prevent backflow into Atrium

Action of AV valves controlled by the papillary

muscles and chordae tendinae


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Heart Structures


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Heart Structures Semilunar Valves

Pulmonary semilunar valve

Located between Right Ventricle and Pulmonary

Trunk/Artery

Aortic semilunar valve

Located between Left Ventricle and Aorta

Valves remain open as ventricles contract

Valves close when ventricles relax

Prevents backflow into the Ventricles

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Figure 22.5


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Table 22.03


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Fig. 20.10(TE Art)


3

4

8

7

75

66

2

1

10

11

12

13

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Aorta

Right

pulmonaryveins

Inferior

vena cava

Right AV

(tricuspid)valveRightventricle

Rightatrium

Superiorvena cava

Pulmonarytrunk

Leftpulmonary

artery

Left

pulmonaryveins

Aortic valve

Left AV(bicuspid)

valve

Left atrium

Leftventricle

9

14


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Practice at Home 1. Put each heart term (chamber, valve,

artery, vein) on a notecard

2. Rearrange notecards in the order which

blood flows through the heart

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Question Does the heart muscle tissue itself

(myocardium) ever receive any blood?

YES!!

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Blood Supply of Heart Left coronary artery (oxygenated blood)

Anterior interventicular artery Supplies anterior wall of both ventricles

Circumflex artery Supplies left atrium and left ventricle

Right coronary artery (oxygenated blood)Posterior interventricular artery

Supplies posterior walls of both ventricles

Right marginal artery Supplies right border of right ventricles

Coronary sinus Returns de-oxygenated blood to right atrium

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Fig. 20.11a(TE Art)


Rightcoronary

artery

Aortic arch

Left coronary

artery

*Coronary arteries

branch from the aorta


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Fig. 20.11b(TE Art)


Coronarysinus


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*Blood going to R. Atrium


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Heart itself is responsible for initiating heart beat Nervous system alters heart rate not start of heart beat

1. Intrinsic conduction system Autorhythmic cells

Non-contractile cells that initiate and distribute impulses Act as pacemaker for heart

2. Gap junctions

SA node

cluster of autorhythmic cells in wall of right atrium generates impulse which begins heart activity

75 beats/min spreads to atria and triggers atria contraction excitation spreads to AV node

Conduction System of Heart


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Conduction System of Heart

AV node Located on the floor of the right atrium

Causes 0.1s delay in the impulse from atria toventricle

Allows atria and ventricles to contract separately Acts as a backup pacemaker (40-60bpm)

Sends impulse to AV bundle

AV bundle (Bundle of His)

The connection between atria and ventricles Brings signal from atria to ventricles Divides into bundle branches & Purkinje fibers

triggers ventricles to contract Purkinje fibers in left ventricle due to larger size

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Rhythm of Conduction System

SA node fires spontaneously 60-100 (~75) times

per minute

AV node fires at 40-60 times per minute

If both nodes are suppressed, fibers in ventricles

themselves fire 20-40 times per minute

Artificial pacemaker needed if pace is too slow


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Timing of Atrial &

Ventricular Excitation

SA node setting pace since it is the fastest

In 50 msec excitation spreads through both atria

and down to AV node

100 msec delay at AV node - allows atria to fully

contract filling ventricles before ventricles contract


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Electrocardiogram (ECG or EKG) Terminology

ECG/EKG: recording of electrical activity of heart

Cardiac cycle: all heart processes which occur from thestart of one heartbeat to the start of the next heartbeat

Systole: contraction of a heart chamber

Diastole: relaxation of a heart chamber

Depolarization: cell membrane potential becomesmore positive (less negative)

Repolarization: cell membrane potential returns toresting potential

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Electrocardiogram (ECG or EKG)

P wave

atrial depolarization (wavefrom SA node through atria)

P to Q interval

atrial systole

QRS complex

ventricular depolarization

atrial repolarization (hidden)

S - T segment

ventricular systole

T wave

ventricular repolarization


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Auscultation

Stethoscope

Sounds of heartbeat are from turbulence in

blood flow caused by valve closure

first heart sound (lubb) is created with the closing

of the atrioventricular valves

second heart sound (dupp) is created with the

closing of semilunar valves


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Heart Sounds

Where to listen on chest wall for heart sounds.

chapter 22 - heart

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