Download fibrous skeleton insulates atria from ventricles


Circulatory system


Cardiovascular system


carries blood to lungs for gas exchange
Systemic circuit - left side of heart

19-2
heart, arteries, veins and capillaries
Two major divisions:
Pulmonary circuit - right side of heart


heart, blood vessels and blood
supplies blood to all organs of the body

One side pumps to the
lungs


One side pumps to the
lungs
One side pumps to the
rest of the body




19-6
Located in mediastinum,
between lungs
Base - broad superior
portion of heart
Apex - inferior end, tilts to
the left, tapers to point
3.5 in. wide at base,
5 in. from base to apex and
2.5 in. anterior to
posterior; weighs 10 oz
Pericardial cavity contains 5
to 30 ml of pericardial fluid


Allows heart to beat
without friction, room to
expand and resists
excessive expansion
Parietal pericardium


Pericardial cavity


outer, tough, fibrous layer
of CT
filled with pericardial fluid
Visceral pericardium
(a.k.a. epicardium of
heart wall)
19-7
Pericardial cavity contains 5
to 30 ml of pericardial fluid

Epicardium (a.k.a.
visceral pericardium)


Myocardium



serous membrane
covers heart
thick muscular layer
fibrous skeleton network of collagenous
and elastic fibers
Endocardium - smooth
inner lining
19-8

Right and left atria



two superior, posterior
chambers
receive blood returning to
heart
Right and left ventricles


two inferior chambers
pump blood into arteries
19-9

Interatrial septum


Interventricular septum


wall that separates
ventricles
Pectinate muscles


wall that separates atria
internal ridges of
myocardium in right
atrium and both auricles
Trabeculae carneae

internal ridges in both
ventricles
19-10

Atrioventricular (AV)
valves




right AV valve has 3 cusps
(tricuspid valve)
left AV valve has 2 cusps
(mitral, bicuspid valve)
chordae tendineae - cords
connect AV valves to
papillary muscles (on floor
of ventricles)
Semilunar valves - control
flow into great arteries


pulmonary: right ventricle
into pulmonary trunk
aortic: from left ventricle
into aorta
19-11
Where are the
semi-lunar valves?
Pulmonary and
aortic valves are
semilunar valves?

Ventricles relax




pressure drops
semilunar valves close
AV valves open
blood flows from atria to ventricles

Ventricles contract




AV valves close
pressure rises
semilunar valves open
blood flows into great vessels

Ventricles relax




pressure drops
semilunar valves close
AV valves open
blood flows from atria to ventricles
19-14

Ventricles contract




AV valves close
pressure rises
semilunar valves open
blood flows into great vessels

Sympathetic nerves from




upper thoracic spinal cord, through sympathetic
chain to cardiac nerves
directly to ventricular myocardium
can raise heart rate to 230 bpm
Parasympathetic nerves
right vagal nerve to SA node
 left vagal nerve to AV node
 vagal tone – normally slows heart rate to
70 - 80 bpm

19-15

Properties
myogenic - heartbeat
originates within heart
 autorhythmic – regular,
spontaneous depolarization

19-16


SA node: pacemaker,
initiates heartbeat, sets
heart rate
fibrous skeleton insulates
atria from ventricles
19-17


AV node: electrical gateway
to ventricles
AV bundle: pathway of
signals from AV node
19-18


Right and left bundle branches:
divisions of AV bundle that
enter interventricular septum
Purkinje fibers: upward from
apex spread throughout
ventricular myocardium
19-19



Short, branched cells, one central nucleus
 Sarcoplasmic reticulum, large T-tubules
Intercalated discs join myocytes end to end



19-20
interdigitating folds -  surface area
mechanical junctions tightly join myocytes
electrical junctions - gap junctions allow ions to flow





19-21
Aerobic respiration
Rich in myoglobin and glycogen
Large mitochondria
Organic fuels: fatty acids, glucose, ketones
Fatigue resistant




Auscultation - listening to sounds made by body
First heart sound (S1), louder and longer “lubb”, occurs
with closure of AV valves
Second heart sound (S2), softer and sharper “dupp”
occurs with closure of semilunar valves
S3 - rarely heard in people > 30
19-23

Pressure causes a fluid to flow

pressure gradient - pressure
difference between two
points
• Resistance opposes flow
– great vessels have positive
blood pressure
– ventricular pressure must rise
above this resistance for blood
to flow into great vessels
19-24




One complete contraction and relaxation of all
4 chambers of the heart
Atrial systole, Ventricle diastole
Atrial diastole, Ventricle systole
Quiescent period
Systole is the contraction of a chamber of the heart
Diastole is the relaxation of a chamber of the heart
19-25
19-26

Quiescent
period

Ventricular
filling

Isovolumetric
contraction

Ventricular
ejection

Isovolumetric
relaxation

Quiescent period



all chambers relaxed
AV valves open and blood flowing into ventricles
Atrial systole
SA node fires, atria depolarize
 P wave appears on ECG
 atria contract, force additional blood into ventricles
 ventricles now contain end-diastolic volume (EDV) of about
130 ml of blood

19-27
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




19-28
Atria repolarize and relax
Ventricles depolarize
QRS complex appears in ECG
Ventricles contract
Rising pressure closes AV valves - heart sound S1
occurs
No ejection of blood yet (no change in volume)






19-29
Rising pressure opens semilunar valves
Rapid ejection of blood
Reduced ejection of blood (less pressure)
Stroke volume: amount ejected, 70 ml at rest
SV/EDV= ejection fraction, at rest ~ 54%, during
vigorous exercise as high as 90%, diseased heart <
50%
End-systolic volume: amount left in heart





T wave appears in ECG
Ventricles repolarize and relax (begin to expand)
Semilunar valves close - heart sound S2 occurs
AV valves remain closed
Ventricles relax but do not fill (no change in volume)
19-30
Rapid ventricular filling
1.
•
Diastasis
2.
•
sustained lower pressure, venous return
Atrial systole
3.
•
19-31
AV valves first open
filling completed



Atrial systole, 0.1 sec
Ventricular systole, 0.3 sec
Quiescent period, 0.4 sec
Total 0.8 sec, heart rate 75 bpm
19-32
Both ventricles
must eject
same amount
of blood.
They should
have the same
stroke volume.
19-33
Both ventricles
must eject
same amount
of blood.
They should
have the same
stroke volume.
19-34