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A. Includes a powerful pump (heart) and extensive system of
tubes (blood vessels)
B. Functions to transport oxygen, nutrients, and wastes.
A. Size
1. Varies with body size average adult 9 cm x 14 cm
B. Location
1. Nearly centered in the
thoracic cavity, with the distal
end toward the left side.
C. Coverings of the heart
Superior vena cava
aorta
Heart covered by
visceral pericardium
Right ventricle
Left ventricle
1. Pericardium outer layer
2. Visceral pericardium (inner layer)
3. Parietal pericardium (middle layer)
Pericardial cavity - serous fluid
1. Pericardium outer layer
2. Visceral pericardium (inner layer)
3. Parietal pericardium (middle layer)
D. Wall of the Heart
1. endocardium
a. serous membrane
2. myocardium
a. thick cardiac
muscle layer
3. epicardium
a. epithelial and
connective tissue
b. specialized muscle
fibers - Purkinje
fibers
E. Heart Chambers and Valves
1. chambers
a. right atrium - receives returning blood from body
b. right ventricle - pumps blood to lungs
c. left atrium - receives blood from lungs
d. left ventricle - pumps blood throughout body
C
C
A
A
D
D
B
B
Interventricular septum
2. Valves
= three cusps to valve
= two cusps to valve
a. tricuspid valve* - allows blood from right atrium to right ventricle
b. pulmonary valve# - allows blood to leave right ventricle
c. bicuspid (mitral) valve* - allows blood from left atrium to ventricle
d. aortic valve# - prevents blood from flowing back into the left
ventricle after contraction - located at base of aorta.
*=AV valve
#= semi lunar valve
3. Skeleton of heart
a. connective tissue
provide firm attachment
points for valves, muscles Prevent atria & ventricles from dialating
a. aorta & branches
4. Path of Blood Through the Heart e.
b. capillary beds of all
body tissues where gas
exchange occurs
d.
f.
c.
a.
c. superior and inferior
vena cavae
d. pulmonary
arteries
b.
e. capillary beds of
the lungs where gas
exchange occurs
f. pulmonary veins
5. Blood Supply to Heart
a. coronary arteries i. Supply blood to heart
tissue
ii. Feed into many
capillaries of myocardium
iii. Small alternative
branches (anastomoses)
b. cardiac veins i. Drains blood to
coronary sinus on hearts
posterior surface - empties
into right atrium
A. Cardiac Cycle - (the coordinated contractions / relaxation of heart)
1. Atria - relaxed (atrial diastole)
a. blood flows in
b. pressure increases - A-V valves open blood flows into ventricle
2. Atria - contracted (atrial systole)
a. atrial pressure rises - forcing remaining blood into ventricle
3. Ventricles contract (ventricular systole)
a. A-V valve closes - partially extends into atrium
b. papillary muscles contract pulling on chordae tendineae reducing
valve extension back into atria.
c. A-V valve remains closed as atria refills - pressure increases
d. ventricle pressure increases opening semi-lunar valves
e. Blood leaves ventricles
4. Ventricles relax (ventricular diastole)
a. A-V valve opens blood flows into ventricle - atria pressure drops
b. ventricle pressure low while filling - increases slightly with atria
contraction
c. semi-lunar valves close
B. Heart Sounds
1. Lubb - first part - when ventricles contract A-V valves are closing
2. Dubb - second sound - when ventricles relax - semi-lunar valves
close
C. Cardiac muscle Fibers
1. Cardiac muscle fibers in branching networks
a. stimulation to part - impulses to all - contracts as a unit
i. unit is functional syncytium
Atrial syncytium and ventricular syncytium
Separated by fibrous skeleton
D. Cardiac Conduction System
1. Sinoatrial node (S-A node)
a. self initiating impulses travel to atrial syncytium
b. right and left atria contract simultaneously
c. impulse passes to atrioventricular node (A-V node) via
junctional fibers (JF)
2. A-V node
a. JF fibers small diameter conduct impulses slowly - delays impulse
b. A-V node further slows impulse - allows for atrium to empty
before ventricle contracts
3. A-V bundle - (bundle of His)
a. from A-V node impulse travels along A-V bundle - through
interventricular septum
4. Purkinje Fibers (PF)
a. PF arise from A-V bundle
b. spread into papillary muscles
c. branch into small fibers contacting cardiac muscle fibers
5. Whorls of muscle fibers in ventricles contract in a twisting motion
squeezing blood from ventricle
E. Regualation of the Cardiac Cycle
1. Parasympathetic fibers contacting S-A, A-V node - continuous
a. acetylcholine release decreases S-A and A-V node activity
2. Sympathetic fibers contact S-A, A-V nodes and other areas
a. norepinephrine released - increases rate and force of contraction
3. Monitored by medulla oblongata (MO)
a. Baroreceptors - monitor blood pressure
i. Increase pressure - slows down heart rate (HR)
b. Cerebrum and hypothalmus - influence MO
c. Temperature
i. Decrease - decrease HR
d. Ions
i. K+ - decrease HR
ii. Ca+2 - increase HR
S-A node
Atrial syncytium
Junctional fibers
A-V node
A-V bundle
bundle branches
Purkinje fibers
Ventricular syncytium
F. Electrocardiogram (ECG) or (EKG)
1. A recording of electrical changes in the myocardium during a
cardiac cycle - (waves or deflections)
2. S-A node triggers - atrial fibers depolarize - P wave recorded
3. When ventricular fibers depolarize - QRS complex recorded
a. Q wave
Depolarization of ventricular fibers just prior to
b. R wave
contraction
c. S wave
4. Ventricular fibers repolarizing produce T wave
5. repolarizing of atria mask by ventricle depolarizing
A. Arteries
1. Elastic vessels - carry blood away from heart
2. Branch into smaller arterioles - capillaries
3. Structure a. three layers
i. Tunica interna
Endothelium cells
smooth surface,
ii. Tunica media
Smooth muscle
encircle tube.
Elastic connective
tissue
iii. Tunica externa
Connective tissue with elastic and collagenous fibers
B. Capillaries
1. Smallest diameter BV
2. Connect arterioles with venules
3. Thin walls for O2, CO2, nutrient and waste exchange with blood
4. Density varies with need - muscles, endocrine glands, SI,
increased numbers
5. Precapillary sphincters - open and close off capillaries as needed
6. Exchanges of substances
a. diffusion - high to low
concentration.
b. filtration - high pressure in
arteriole end of capillary
forces out molecules
c. osmosis - water tends to
enter toward venous end of
capillary.
C. Veins
1. Return blood to heart
2. Smaller branches - venules
3. Three layer walls similar to arteries
4. Valves prevent back flow
5. Collapse when empty
A. A measure of force exerted on inner walls of blood vessels.
1. Systolic pressure - high end of the measured pressures
2. Diastolic pressure - low end of measured pressures
B. Factors influencing blood pressure (BP)
1. Heart action - (cardiac output) - determines how much blood
enters arterial system.
a. Cardiac output = stroke volume x heart rate.
2. Blood volume 3. Peripheral resistance - friction between blood and walls of
blood vessels
4. Blood viscosity - ease at which fluid molecules move past one
another
C. BP control
1. Regulation of cardiac output and peripheral resistance