Download - Ch. 20 Heart
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Thoracic cavities:
1. R. & L. pleural cavities.2. Pericardial cavity.
3. Mediastinum
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Pericardium: (serous membranes that cover the heart):
1. Parietal pericardium: close to chest wall.
** Pericardial cavity: space between 2 pericardiums.
a. Containing pericardial fluid.
b. Acts as a lubricant to reduce friction between heart &
chest wall.
2. Visceral pericardium (= Epicardium): Surface membrane of the heart
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2. Four valves:
A. Tricuspid valve: R.A. R.V.
B. Pulmonary valve: R.V. pulmonary trunkC. Bicuspid (=mitral) valve: L.A. L.V.
D. Aortic valve: L.V. Aorta
Chordae tendineae:
connective tissues connected tricuspid valve& bicuspid valve to heart wall through papillary muscles.
* Papillary muscles:
* A-V valves: including tricuspid valve and bicuspid valve.
* Semilunar valves: including pulmonary valve and aortic valve
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Superficial Anatomy of the Heart
Sulci
Coronary sulcusdivides atria and ventricles
Anterior interventricular sulcusand
posterior interventricular sulcus
Separate left and right ventricles
Contain blood vessels of cardiac muscle
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3. Three layers of heart wall:
A. Epicardium: ( or visceral pericardium): outer layer
B. Myocardium: muscular wall , thickest layer
C. Endocardium: inner surfaces (including valves)
4. Base & Apex of heart:
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Right atrium:
1. Also called R. auricle(ear shape)
2. Receiving blood from:
a. Superior vena cava
b. Inferior vena cava
c. Coronary sinus
3. Fossa ovalis: a remnant site of foramen ovale in fetus
(a hole between RA & LA)
4. Containing SA node & AV node.
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Right ventricle:
1. Tricuspid valve (= right A-V valve): gate between RA & RV
2. Chordae tendineae and papillary muscles:
3. Moderator band: muscle ridge containing nerve fibers
for conducting system
4. Conus arteriosus: superior end of RV, leading to pulmonary valve
5. Pulmonary valve (= pulmonary semilunar valve)
6. Pulmonary trunk: branches into 2 R. & 2 L. pulmonary arteries.
7. Ligamentum arteriosum: remnant of ductus arteriosus in fetus.
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Trabeculae carneae
Muscular ridges on internal surface of right
and left ventricles
moderator band: (in RV only)
Ridge contains part of condu ct ing system
Coordinates contractions of cardiac muscle
cells
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Left atrium:
1. auricle
2. Collecting blood from: 2 R & 2 L pulmonary veins
3. Bicuspid valve (=mitral valve: bishops hat): LA --> LV
Left ventricle:
1. Wall is thicker than that of RV. (Larger pressure, 4-6 times, is needed
for systemic circulation.)
2. Only 1 pair of papillary muscle. Chordae tendineae are less than that of RV.
3. No moderator band on ventricular muscles
4. Aortic valve (= aortic semilunar v.): between LV and aorta.
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*** R. & L. A-V valves Semilunar valves
1. Pieces of cuspids: R=3, L=2 All 3
2. Chodae tendineae: yes no
3. Papillary muscles: yes no
4. Fibrous skeleton: yes yes
(=Cardiac skeleton)
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Valvular heart disease (VHD):
1.Reasons:a. Valves can not be closed completely due to damages of
papillary muscles, chordae tendineae or valves.
b. Inflammation of heart (carditis) is one of the major
factor (ex. rheumatic fever).
2.Symptoms:
a. Backflow (regurgitation) of blood from ventricle to
atrium, or aorta to L. ventricle, or pulmonary trunk to
R. ventricle. (Bicuspid valve damage is most common.)
b. Abnormal heart sound (murmur).
c. Short of breath (due to the lack of oxygen).
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Intercalated disc of cardiac muscles:
1. These discs interlock adjacent cells by desmosomes & gap junctions.
2. Function: propagate action potentials (AP).
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Cardiac muscles differ from skeletal muscles in:
1. Cardiac have smaller-size cells.
2. Only a single nucleus in one cardiac muscle cell.
3. Presence of intercalated discs.
4. Having branching interconnections
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Direction of blood flow in heart:
Superior vena cava
RA RV pulmonary trunkInferior vena cava
Lungs
2R & 2L Pulmonary veins
LA
LV
Aorta
Systemic Circulation
Coron ary arter ies
Coronary s inus
2R & 2L Pulmonary arteries
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Coronary circulation:
1.Coronary arteries:
A. Right coronary art.
a. Marginal art.
b. Posterior interventricular art.
(= posterior descending art. = PAD)
B. Left coronary art.
a. Circumflex art. Marginal art.
b. Anterior interventricular art.
(= Left anterior descending art. = LAD)
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Right Coronary Artery
Supplies blood to the following areas:
Right atrium
Portions of both ventricles
Cells of sinoatrial (SA) and atrioventricular
nodes
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Left Coronary Artery
Supplies blood to the following areas:
Left ventricle
Left atrium
Interventricular septum
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2. Cardiac veins:
A. Coronary sinus: collecting blood from the followings:
a. Great cardiac Vein:
b. Posterior cardiac V.
c. Middle cardiac V.
d. Small cardiac V.
B. Anterior cardiac veins (very small):
empty blood into R. atrium directly.
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Coronary circulation:
1. Originates at the base of the ascending aorta (= aortic sinuses)
R. coronary artery L. coronary artery
Circumflex artery
RA Anteriorinterventricular art.
RV
LA
Posterior interventricular art. LV
Small cardiac v. Middlecard. v. Posterior card. v. Greater card. v.
Coronary sinus
RA (chamber)
2. Arterial anastomoses: Multiple arteries supply one tissue area (ex. LV).
ex. Connection between anterior& posteriorinterventricular arteries.
wall
wall
wall
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Two types of cardiac muscles:1. Conducting system (1 % )
2. Contractile cells (99 %)
Conducting system:
1. Sinoatrial (SA) node: 1st. pacemaker (80-100 pulses/min)
2. Internodal pathways:
3. Atrioventricular (AV) node: 2nd pacemaker (40-60 pulses/min)
4. AV bundle (=Bundle of His)
5. Bundle branches:
a. L: to LV (Larger size)
b. R: to moderator band papillary muscle tricuspid valve
6. Purkinje fibers: to L & R ventricles.
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EKG, ECG (electrocardiogram):
1. P wave: depolarization of the atria (R & L)
2. QRS complex: depolarization of the ventricles
3. T wave: repolarization of ventricles
4. Two important factors of ECG:a. voltage (mV)
b. duration (m sec): interval:[including wave(s)]
and segment: [between waves]
5. Depolarization: causing muscle contraction (= systole).
6. Repolarization: causing muscle relaxation (= diastole).
Figure 20-13b An Electrocardiogram
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g g
800 msec
SQ
QRS interval
(ventricles depolarize)
Millivolts
R
PR segmentT wave
(ventricles repolarize)
R
P wave
(atria
depolarize)
ST
segment
ST
interval
QT
interval
PR
interval
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Cardiac cycle:
1. Two phases:
a. systole (contraction of atria & ventricles)
b. diastole (relaxation of atria & ventricles)
2. period between each heart beat (800 mSec/cycle = mSec/beat)
3. 1 min= 60 Sec = 60,000 mSec;
60000 mSec/min
= 75 beats/min.
800 mSec/beat
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Action potential (AP) in cardiac muscles:
1. Rapid depolarization: sodium entry by fast sodium channels
2. Plateau: calcium entry by slow calcium channels
3. Repolarization: potassium loss (move out of cells)
AP in skeletal muscles:
1. No plateau stage
2. AP: shorter duration
3. Muscle contraction: shorter duration.
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Blood pressure (BP):
1. Measuring by Sphygmomanometer.
2. Listen to the sound (Korotkoff Sound) by stethoscope
** The sound is due to the turbulence of blood flow.
3. It is written as: systolic P./ diastolic P.
(ex. 120 mmHg/80 mmHg = 120/80)
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Blood volumes in L. ventricle during cardiac cycle:
1. EDV: (end-diastolic volume)--- 130 ml
2. ESV: (end-systolic volume) ----- 50 ml
3. SV: (stroke volume = pump-out volume),
SV = EDV- ESV (ex. 130-50= 80 ml)
Cardiac output (CO):
CO = HR x SV = (heart rate) x (stroke volume)
= HR x (EDV-ESV)
(ml/min) = (beats/min) x (ml/beat)
Ex. CO= 75 (b/min) x 80 (ml/b)= 6000 (ml/min)
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Heart sounds:
1. Using instrument: stethoscope
2. First heart sound (S1): lubb, AV valves close (last longer)
3. Second HS (S2): dupp, semilunar valves close
4. S3 (blood flows to ventricles), S4 (atrial contraction): both are weak
5. Places to listen (fig. 20-18a)
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Factors affects cardiac output:
1. Cardiac reflexes:
a. By baroreceptors and chemoreceptors
b. Cardiac center: medulla oblongata(-) BP, (-) O2, (+) CO2 (+) HR
2. Autonomic tone:
a. Sympathetic N.: ---------- NE (+) HR
b. Parasympathetic N.: ---- Ach (-) HR (Nerves IX & X)
3. Hormones:
a. Epi, NE (norepinephrine): (+) HR
b. Thyroid hormones (T4, T3): (+) HR
c. Glucagon: (+) SV (+) CO
4. EDV:
5. ESV:
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4. EDV:
* Frank-Starling Principle = Starling Law
(+) EDV (+)SV (+) CO , (More blood in = More blood out)(More EDV More CO)
(More preload More CO)
5. ESV: (-) Afterload (-) ESV (+) SV (+) CO
(+) Afterload (+) ESV, (-) SV (-) CO
(Less afterload less ESV More CO)
** (ps) Afterload:
the amount of tension (or pressure) that ventricles
must produce to force open semilunar valves.
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Baroreceptors (for blood pressure):
1. R. & L. internal carotid sinuses
2. Aortic sinus: near the base of aortic arch
** When blood pressure is high at carotid & aortic sinuses:
increasing stretch of baroreceptors CNS
activating parasympathetic N.releasing Ach
(-) HR, (+) vasodilation
(-) blood pressure
3. Right atrial baroreceptors (atrium wall)
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Influences on Stroke Volume Preload(affect of stretching)
Frank-Starling Law of Heart
more muscle is stretched ( EDV),
greater force of contraction
more blood in, more force of contraction results
Contractility
autonomic nerves, hormones, Ca+2or K+levels
Afterload
amount of pressure (tension) created by
semilunar valves & arteries
high blood pressure creates high afterload
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Clinic terms:
1. CAD: coronary artery disease
2. Heart attack: blockage of coronary circulation &
death of some cardiac muscles.
3. Stroke: bleeding in brain due to clotted andbroken blood vessels
4. Bradycardia: slow HR
5. Tachycardia: fast HR
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Clinical Problems
MI = myocardial infarction = (heart attack)
death of area of heart muscles due to lack of O2
replaced with scar tissue
results depend on size & location of damage
Blood clot
use clot dissolving drugs streptokinase or t-PA
& heparin
balloon angioplasty
Angina pectoris----heart pain due to ischemia of
cardiac vessels & short of O2 in cardiac muscles.
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Myocardial infarction (MI), or heart attack
Pain does not always accompany a heartattack, therefore, the condition may goundiagnosed and may not be treatedbefore a fatal MI occurs
Damaged myocardial cells releaseenzymes into the blood circulation.
The enzymes include:
Cardiac troponin T,
Cardiac troponin I,
Creatinine phosphokinase, CK-MB
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Congestive Heart Failure
Causes of CHF coronary artery disease, hypertension, MI, valve
disorders, congenital defects
Left side heart failure
less effective pump so more blood remains inventricle
heart is overstretched & even more blood remains
blood backs up into lungs as pulmonary edema suffocation & lack of oxygen to the tissues
Right side failure
fluid builds up in tissues as peripheral edema
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Risk Factors for Heart Disease
Risk factors in heart disease: high blood cholesterol level
high blood pressure
cigarette smoking
obesity & lack of regular exercise.
Other factors include:
diabetes mellitus
genetic predisposition
male gender
high blood levels of fibrinogen
left ventricular hypertrophy
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Plasma Lipids and Heart Disease
Risk factor for developing heart disease ishigh blood cholesterol level.
Most lipids are transported as lipoproteins HDLs remove excess cholesterol from circulation
LDLs are associated with the formation of fattyplaques
VLDLs contribute to increased fatty plaqueformation
There are two sources of cholesterol in thebody: in foods we ingest
formed by liver
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Desirable Levels of Blood
Cholesterol for Adults
TC (total cholesterol) under 180 mg/dl
LDL under 100 mg/dl
HDL over 40 mg/dl
Triglycerides: 10-190 mg/dl.
Among the therapies used to reduce blood
cholesterol level are exercise, diet, and drugs.
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Total cholesterol
= LDL + HDL + (Triglyceride x 0.2)
Ex. 100 + 50 + (150 x 0.2)
= 100 + 50 + 30
= 180 (mg/dL)
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Exercise and the Heart
Sustained exercise increases oxygen demandin muscles.
Benefits of aerobic exercise (any activity that
works large body muscles for at least 20minutes, preferably 3-5 times per week) are;
increased cardiac output
increased HDL and decreased triglycerides
improved lung function
decreased blood pressure
weight control.