1Rob SwatskiAssistant Professor of Biology

HACC York Campus

Chapter 20

Cardiovascular System: The Heart

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6Heart Location: Mediastinum

7Heart OrientationApex: anteriorly, inferiorly, left-sideBase: posteriorly, superiorly, right-side

Anterior surface: deep to sternum & ribs

Inferior surface: on diaphragm

Right border: faces right lung

Left border (Pulmonary border): faces left lung

8Heart Surface Projection

Superior right point: sup border - 3rd right costal cartilage

Superior left point: inf border - 2nd left costal cartilage, 3 cm left of midline

Inferior left point: 5th intercostal space, 9 cm left of midline

Inferior right point: sup border - 6th right costal cartilage, 3 cm right of midline

9Pericardium Pericardium

Fibrous pericardium (outer)- dense irregular CT- protects & anchors heart- prevents overstretching

Serous pericardium (epicardium):- thin, delicate membrane- parietal & visceral layers- pericardial cavity - pericardial fluid

Pericarditis

Cardiac tamponade

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Layers of the Heart WallEpicardium: mesothelium & CT (visceral layer of serous

pericardium)

Myocardium: cardiac muscle

Endocardium: endothelium & CT (lines chambers & valves)

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Myocarditis & Endocarditis

endocarditis

myocarditis

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Muscle Bundles of the Myocardium

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Chambers & Sulci of the Heart

4 Chambers: - 2 superior atria

- 2 inferior ventricles

Sulci: grooves on heart surface- contain coronary BVs & adipose

Coronary sulcus- encircles heart b/w atria & ventricles

Anterior interventricular sulcus- ant. boundary b/w ventricles

Posterior interventricular sulcus- post. boundary b/w ventricles

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Right Atrium

Receives blood from 3 sources:superior vena cava, inferior vena cava, & coronary sinus

Interatrial septum

Fossa ovalis: remnant of fetal foramen ovale

Tricuspid valve

- blood flows through into right ventricle

- 3 cusps of dense CT

- RAT on the Right (Right Atrioventricular, Tricuspid)

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Right Ventricle

Forms most of ant. surface of heart

Interventricular septum

Trabeculae carneae

Papillary muscles

Chordae tendineae

Pulmonary semilunar valve

- allows blood into pulmonary trunk

Papillary Muscles & Chordae Tendineae

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Left Atrium

Forms most of base of heart

Receives blood from lungs through 4 pulmonary veins- 2 right & 2 left

Bicuspid valve: blood flows through into left ventricle- 2 cusps- LAMB on the Left: Left Atrioventricular, Mitral, or Bicuspid

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Left Ventricle

Forms apex of heart

Chordae tendineae, papillary muscles, & trabeculaecarneae

Aortic semilunar valve- allows blood into ascending aorta- openings to the coronary arteries directly above valve

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Myocardial Thickness & FunctionThickness varies based on each chambers function:

- Atria walls are thin; Ventricle walls are thick- Right ventricle walls are thin; Left ventricle walls are

thick

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Fibrous Skeleton of Heart

Dense CT rings surround heart valves- fuse together & merge with interventricular

septum

Functions of fibrous skeleton: - valve support structure

- insertion point for cardiac muscle bundles- electrical insulator b/w atria & ventricles

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AV Valves OPEN

Allow blood flow from atria into ventricles when ventricular pressure is lower than

atrial pressure

Occurs during ventricular relaxation:- papillary muscles are relaxed- chordae tendineae are slack

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AV Valves CLOSED

Prevents backflow of blood into atria

Occurs during ventricular contraction:- papillary muscles contract

- chordae tendineae pulled taut- valve cusps pushed closed

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SL Valves

SL valves OPEN during ventricular contraction- allow blood flow into pulmonary trunk & aorta

SL valves CLOSE during ventricular relaxation- blood fills cusps & valves close

- prevents blood from flowing backwards into ventricles

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Heart Valve DisordersStenosis: narrowing of valve that restricts blood flow- repaired by balloon valvuloplasty, surgery, or valve

replacement

Insufficiency or incompetence: valve cannot close completely

Balloon valvuloplasty

Mitral Valve Stenosis 34

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Systemic Circulation

LEFT side of heart pumps oxygenated blood to body

Left ventricle Aorta Arteries Capillaries Organs Venules Veins Superior/Inferior vena

cava/Coronary sinus Right atrium

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Pulmonary Circulation

RIGHT side of heart pumps deoxygenated blood to lungs

Right atrium Right ventricle Pulmonary trunk Pulmonary arteries Lungs Pulmonary Veins

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Coronary Circulation

Blood flow through

myocardium

The heart feeds itself

first

Many anastomoses

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Coronary Arteries

Right coronary artery

Marginal branch

Posterior interventricular

branch

Left coronary artery

Anterior interventricular

branch (LAD)

Circumflex branch

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Coronary Veins

Collect wastes from myocardium

Great cardiac vein, middle cardiac vein

Drain into coronary

sinus

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Cardiac Muscle Tissue

Striated, branching,

shorter fibers of heart

Intercalated discs with gap

junctions

One central nucleus per fiber

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Cardiac Muscle Histology

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Cardiac Muscle Tissue

Same actin & myosin

arrangement as skeletal muscle

Autorhythmic

Longer contractions (longer Ca+2

delivery)

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Cardiac Myofibril

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Conduction System

Autorhythmicfibers

spontaneous APs

Propagate APs through

myocardium

Sinatrial (SA) node =

pacemaker

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SA node

AV node

AV bundle (of His)

Right & left bundle branches

Purkinje fibers

Conduction System

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Regulation of the Conduction

System

Autonomic Nervous System

(ANS)

Hormones(epinephrine)

Modify heart rate & strength of contraction

They do NOT establish the fundamental

rhythm

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Action Potential

Depolarization

Plateau

Repolarization

Refractory period

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Physiology of Contraction

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Role of Ions in the Action Potential

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Electro-cardiogram

(EKG)

Visual record of allAPs during each

cardiac cycle (heartbeat)

Detected at bodys surface

Diagnostic value

Detects abnormal conduction,

enlargement, & muscle damage

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EKG

P wave

P-Q interval

QRS complex

T wave

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Cardiac Cycle

At 75 beats/min, 1 cycle = 0.85

sec

Pressure & volume changes

during cycle

Blood pumped from high to lowpressure areas

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Atrial systole (contraction)

Atrial diastole (relaxation)

Ventricular systole

Ventricular diastole

Cardiac Cycle

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Blood Volumes

End Diastolic Volume (EDV)

= 130 ml

End Systolic Volume (ESV)

= 60 ml

Stroke Volume (SV) =

70 ml

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SV = EDV - ESV

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Phases of the Cardiac Cycle

IsovolumetricRelaxation

(all valves close)

Ventricular Filling

(AV valves open)

IsovolumetricContraction

(AV valves close)

Ventricular Ejection

(SL valves open)

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Ventricular Pressures

Aortic BP = 120 mmHg

Pulmonary trunk BP = 30

mmHg

Why? How?

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Heart Sounds

Produced when valves

close

lubb = AV valves close

DUPP = SL valves close

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Heart Sounds

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Heart Murmurs

Abnormal sounds before, b/w, or after

normal sounds

May also mask normal sounds

Caused by valve disorders,

increased blood flow/volume

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Cardiac Output

Volume of blood ejected each minute from either

ventricle

CO = Stroke Volume (SV) x

Heart Rate (HR)

70 ml SV x 75 beats/min = 5.25 L/min

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Influences on Stroke Volume

Preload (Frank-Starling

Law of the Heart)

Contractility

Afterload

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Preload

The greater the stretch, the

greater the force of contraction

The greater the blood volume, the greater the force

of contraction

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Contractility

Autonomic Nervous

System (ANS)

Hormones

Ca+2 or K+

levels

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Afterload

The back pressure that must be overcome

before the semilunar valve

can open

The greater the BP = the greater

the afterload

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Congestive Heart Failure

If afterload is high, more blood remains

in the ventricles

which increasesthe preload

Left ventricular failure = pulmonary

edema

Right ventricular failure = peripheral

edema

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Neural Regulation of

Heart Rate

Cardiovascular center in medulla

oblongata

Sympatheticimpulses increase

HR & force of contraction

Parasympathetic impulses decrease

HR & force of contraction

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Nervous System

Receptors

Baroreceptors: monitor BP

Proprioceptors: monitor

movements

Chemoreceptors: monitor blood

chemistry

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Biochemical Regulation of

Heart Rate

Epinephrine, norepinephrine,

thyroid hormones

Na+, K+, Ca+2

Age, gender, physical fitness,

temperature

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High blood cholesterol

High BP Smoking

ObesityLack of regular exercise

Family history

Male gender DiabetesLeft

ventricular hypertrophy

Risk Factors for Heart Disease

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Plasma Lipids & Heart Disease

High blood cholesterol:

promotes plaques

High-Density Lipoproteins

(HDLs)

Low-Density Lipoproteins

(LDLs)

Very Low-Density Lipoproteins

(VLDLs)

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Coronary Artery Disease (CAD)

Ischemia

Reduced blood flow through

coronary arteries

Causes hypoxia & weakens

cardiac muscle

Angina Pectoris

Narrowing of coronary arteries

Leads to reduced blood flow, chest

pain, pressure, discomfort

Myocardial Infarction

Complete obstruction of coronary blood

flow causing heart attack

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Coronary Artery Disease Obstructions

Atherosclerosis

Coronary artery spasm

Coronary artery thrombosis

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Atherosclerosis & Plaque Development

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Coronary Artery Bypass Grafting (CABG)

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Congenital Heart Defects

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Congenital Heart Defects, cont.

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Arrhythmia

Irregularity in heart rhythm due to

conduction system defect

Bradycardia

Tachycardia

Fibrillation

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