Transcript Cardovascular System The Heart Chap. 12

Cardiovascular System
The Heart
Chap. 12
The Cardiovascular system is comprised
of the heart, blood vessels, & blood
 The heart acts as a “pump”, creating
pressure which causes blood to move
through the blood vessels of the body,
allowing O2 & nutrients to be distributed to,
& wastes removed from, body tissues

Heart Anatomy Overview
Play Heart Anatomy video
Anatomical Features of the Heart
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The heart lies within the
mediastinum of the thoracic cavity
Hollow muscular organ with four
internal chambers
 (2) atria (lt. atrium & rt. atrium)receive blood from veins
 (2) ventricles (lt. ventricle & rt.
ventricle)- pump blood into
arteries
Superior aspect of heart is the “base”, where the
blood vessels attach; Inferior is the “apex”, which
rests on the relaxed diaphragm

Pericardium

The heart lies enclosed within pericardial
membranes
pericardium (pericardial sac) – outer layer of
dense CT that protects & anchors
 Serous pericardium – double layered membrane with
“pericardial fluid” between
 Fibrous


Parietal pericardium – lines the pericardial sac
Visceral pericardium – covers the heart; also known as the
“epicardium”
etal
cardium
Figure 12.2
Layers of Heart Wall
 Epicardium (a.k.a. visceral pericardium)
 Myocardium
 Endocardium
Figure 12.4
Cardiac Muscle Tissue
Because of the characteristics of cardiac
muscle tissue & the arrangement of connective
tissue (fibrous skeleton) within the heart, the
heart basically has two functional units:
 the myocardium of the atria (upper chambers)
act as one functional unit
 the myocardium of the ventricles (lower
chambers) act as the other
This allows the atria to contract simultaneously
while the ventricles are relaxed; then the
ventricles contract simultaneously while the atria
relax
External Features
 Auricles
 Coronary sulcus – contains the
coronary sinus
 Anterior interventricular sulcus –
contains coronary vessels
 Posterior interventricular sulcus –
contains coronary vessels
SVC
Interatrial septum
Pulmonary
veins
Lt Atrium
Rt Atrium
Pectinate
muscles
Bicuspid (mitral)
valve
Coronary sinus
(opening)
Chordae tendineae
Tricuspid valve
Papillary muscle
Chordae tendineae
Papillary muscle
IVC
Deoxygenated
blood
Oxygenated
blood
Atrioventricular
(AV) valves
 Tricuspid
 Bicuspid
Lt. common carotid artery
Brachiocephalic
trunk
Lt. subclavian artery
Aorta
Ligamentum
arteriosum
Pulmonary artery
Pulmonary trunk
Pulmonary semilunar
valve
Aortic semilunar valve
Trabeculae
carneae
Lt ventricle
Rt ventricle
Interventricular
septum
Anatomy
Coronary Circulation
 Myocardium receives oxygenated
blood from the left & right Coronary
arteries – branches off the ascending
aorta
 Deoxygenated blood is drained
through Cardiac veins, which all
eventually merge into the coronary
sinus
Fig. 12.7
Conducting System
 Intrinsic regulating system that
generates “heartbeat”
 comprised of functionally
specialized “autorhythmic
(conducting) cells” – which can
spontaneously generate action
potentials
Fig. 12.9
The electrical
events that occur in
the heart can be
detected on the
surface of the body
The resulting
pattern of activity is
known as an ECG
(or EKG) Electrocardiogram
(ventricular repolarization)
Electrocardiogram
(ECG)
(atrial depolarization)
(ventricular depolarization)
 The activity of the conduction system results in the
contraction (systole) & relaxation (diastole) of the heart
chambers
 The change in volume (size) of the chambers results in
changes in pressure within the heart – decreased volume 
increased pressure & vice-versa.
 Blood will flow through the chambers (and throughout the
cardiovascular system) due to the differences in pressure
(blood moves from high  low pressure)
Cardiac Cycle
 One
complete “heartbeat” is referred to as a “Cardiac
Cycle”
 Average 75 cycles/minute
 Each cycle lasts approx. 0.8 seconds
 Continuous, repetitive cycle that can be “divided” into 3
phases for ease of understanding:
 atrial diastole/ventricular diastole (0.4 sec.)
 atrial systole/ventricular diastole (0.1 sec.)
 atrial diastole/ventricular systole (0.3 sec.)
Cardiac Cycle
atrial systole/ventricular
diastole
atrial diastole/
ventricular diastole
“Lub”
“dupp”
atrial diastole/ventricular
systole
Cardiac Output
 Important physiological measurement of cardiac function
 Refers to the amount of blood ejected by the left ventricle
each minute
 C.O. = stroke volume X heart rate
 stroke volume – amount of blood ejected from
ventricle each contraction (80 ml average)
 heart rate – beats (cardiac cycles) per minute
(75 bpm average)
 average C.O. = 6000 ml/min (6 L/min)
Cardiac Output
Cardiac output is primarily regulated by:
1. Blood volume reflexes – there is a direct relationship
between blood entering the heart & amount ejected
 increased venous return  atrial reflex (aka
Bainbridge reflex)  increased heart rate (through
increase in sympathetic activity)
 increased venous return  ventricular reflex (aka
Frank-Starling principle)  increased stroke volume
Cardiac Output
2. Cardiac center of M.O. – ANS input to SA node to
increase/decrease heart rate & stroke volume
Cardiac center influenced by:
 baroreceptors – detect blood pressure changes
 chemoreceptors – detect oxygen/carbon dioxide
concentrations
 higher brain centers – ie. hypothalamus
3. Hormones – epinephrine/norepinephrine, thyroid
hormones, glucagon, etc can increase heart rate & force of
contraction