Review of Cardiac
Anatomy and Physiology
Heart and heart wall layers

The heart is in the left side of the
mediastinum.

Heart layers

epicardium (outermost)

myocardium (middle layer)

endocardium (innermost layer
and lines the inner chambers
and heart valves)
Pericardial sac
Encases and protects the heart from
trauma and infection

Layers:

parietal pericardium: tough,
fibrous`outer membrane that
attaches anteriorly to the lower
half of the sternum, posteriorly
to the thoracic vertebrae, and
inferiorly to the diaphragm

visceral pericardium: thin, inner
layer that closely adheres to the
heart

pericardial space : holds 5 to 20 mL of
pericardial fluid, which lubricates the
pericardial surfaces, and cushions the
heart

Heart chambers
RA receives deoxygenated blood from
the body via the SVC and IVC

RV receives blood from the RA and
pumps it to the lungs via the PA

LA receives oxygenated blood from
the lungs via four pulmonary veins

LV receives oxygenated blood from
the lungs via the LA and pumps blood
into the systemic circulation via the
aorta



Heart valves (AV)
The atrioventricular valves close at
the beginning of ventricular
contraction and prevent blood from
flowing back into the atria from the
ventricles; these valves open when
the ventricle relaxes.
Heart valves (SL)
The semilunar valves prevent blood
from flowing back into the ventricles
during relaxation; they open during
ventricular contraction and close
when the ventricles begin to relax.
Pacemaker cells
Coronary arteries




RCA supplies the RA and RV, the
inferior portion of the LV, the
posterior septal wall, and the SA and
AV nodes.
The LCA consists of two major
branches, the left anterior descending
(LADA) and the circumflex arteries.
The LADA supplies blood to the
anterior wall of the LV, the anterior
ventricular septum, and the apex of
the LV.
The circumflex artery supplies blood
to the LA and the lateral and posterior
surfaces of the LV.
Heart sounds
(S1) : heard as the AV close and is
heard loudest at the apex
 (S2) : heard when the SL close and is
heard loudest at the base
 (S3) : heard if ventricular wall
compliance is decreased and structures
in the ventricular wall vibrate (e.g. CHF
or valvular regurgitation)
 (S4) : heard on atrial systole if
resistance to ventricular filling is
present

Heart rate
The faster the heart rate, the less time
the heart has for filling, and the cardiac
output decreases.
 An increase in heart rate increases
oxygen consumption.
 Bradycardia
 Tachycardia

Autonomic nervous system
 (sympathetic) NOREPINEPHRINE: DUE
TO HYPOTENSION
• Tachycardia
• increased conduction rate
• increased contractility
• peripheral vasoconstriction
 (parasympathetic) ACETYLCHOLINE:
DUE TO HYPERTENSION
• Actions opposite to NE
BP CONTROL
•Baroreceptors
•Stretch receptors
•Antidiuretic hormone
•RAAS
___________________________________
 Baroreceptors, also called
pressoreceptors, are located in the
walls of the aortic arch and carotid
sinuses.
 Increases in arterial pressure stimulate
baroreceptors, and the heart rate and
arterial pressure decrease.
 Decreases in arterial pressure reduce
stimulation of the baroreceptors and
vasoconstriction occurs, as does an
increase in heart rate.
_________________________________
 Stretch receptors, located in the vena
cava and the right atrium, respond to
pressure changes that affect
circulatory blood volume.
 When the BP decreases as a result of
hypovolemia, a sympathetic response
occurs, causing an increased heart rate
and blood vessel constriction; when
the BP increases as a result of
hypervolemia, an opposite effect
occurs.
________________________________
 Antidiuretic hormone (vasopressin)
influences BP indirectly by regulating
vascular volume.
 Hypervolemia result in decreased ADH
release, increasing diuresis, decreasing
BV, and thus decreasing BP.
 Hypovolemia result in increased ADH
release; this promotes an increase in
BV and therefore BP.
___________________________________
 Renin, a potent vasoconstrictor, causes
the BP to increase.
 Renin converts angiotensinogen to
angiotensin I; angiotensin I is then
converted to angiotensin II in the lungs
___________________________________
 Angiotensin II stimulates the release of
aldosterone, which promotes water
and sodium retention by the kidneys;
this action increases blood volume and
BP.
Vascular system
•Arteries
•Arterioles
•Capillaries
•Venules
•Veins