Transcript 14 Heart anatomy and fetal changes

The Heart
(See an anatomy book
and chapter 9 of G&H)
The Cardiovascular System
What are the components?
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Functions of
the Heart
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Blood vessels
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Arteries- away from
heart
Veins- toward heart
Pulmonary circuitblood to lungs
Systemic – blood to
organs of the body
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Includes heart and
lung wall tissues
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Location
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Base- inferior
border of second
rib
Apex- rests on
diaphragm and in
between 5th and
6th rib
Tilts to the left
and anteriorly
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Pericardial Membranes (3
total) and Heart wall
Fibrous skeleton- anchoring, structural support, and electrical insulation
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5
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Atria
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Right:
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Auricle
Smooth wall
(posterior)
Pectinate muscles
Crista terminalis
Fossa ovalis
Coronary sinus, IVC,
SVC openings
Right AV valve
Left:
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Mostly smooth with
pectinate muscle
Left AV valve
What vessels lead into each atria?
Describe the blood these vessels are carrying
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ventricles
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Trabeculae Carneae
Papillary muscles
Chordae tendineae
Valves
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Valves
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Sulci and
Vessels
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Coronary sulcus
Interventricular
sulci (anterior and
posterior)
Cardiac vessels
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Arteries
veins
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Blood Flow
Pulmonary vs systemic circuit
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“Lub-Dub” Sounds
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Conductive System of the
Heart-Myogenic (72bpm)
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Muscle, not Nerves that
are autorhythmic!
 Sinoatrial nodepacemaker
 Internodal bundles
 Atrioventricular node
 Atrioventricular
bundles (bundle of
His)
 Bundle branches
 Purkinje fibers
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Innervation by Autonomic
Nervous System
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Alter rate and Force only!
Visceral sensory
Parasympathetic- (Vagus)slow down (20bpm or even
stop)- SA would normally beat
at 100bpm- but vagal tone
slows down.
Sympathetic – speed up
(230bpm)
Hypothalamus and Amygdala
and Medulla Oblongata
Most dense at SA and AV
node
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Review of Heart Muscle
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Cardiocytes
Branch
Intercalated discsinterdigitating folds,
mechanical junctions
(desmosomes) and
electrical junctions
(gap junctions).
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Fetal Circulation
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Foramen ovale- right
to left shunt. Most
of the blood goes
through here.
Ductus arteriosusright to left shunt.
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Blood Flow within the Fetal Heart
Right atrium
Foramen ovale
Left atrium
(Most of the blood)
Right ventricle
Pulmonary trunk
Pulmonary
circuit
Left ventricle
Ductus arteriosus
Aorta
Systemic circuit
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Birth
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Prostaglandin levels drop
Baby breathes- lowers
pressure in pulmonary circuit
Umbilical cord is clamped and
cut and increases systemic
pressure
Foramen ovale closes and
becomes fossa ovalis
Ductus arteriosus closes and
becomes ligamentum
arteriosum (oxygen content is
signal for vessel to close)
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Foramen Ovale
Fossa Ovalis
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Ductus Arteriosus
Ligamentum Arteriosum
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PDA- patent ductus arteriosus
Left to right shunt
 Blood flows back to
lungs repeatedly- why?
• Net CO decreases so
blood vol. increase and
CO goes back toward
normal
 Left and right
ventricular hypertrophy
 Characteristic cyanosis
of baby
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Pulmonary
veins
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Tetralogy of Fallot
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“Blue Babies”
Right to left shunt
Tetralogy of Fallot
is made up of 4
heart defects
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Physiologic considerations
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Electrical features to know
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Cardiac muscle fibers: branched, with intercalated
disks. Gap junctions. Low resistance (1/400) pathway
for electrical spread from cell to cell.
“functional syncitium”
Two types of fibers in the heart: “specialized” (or
leading cells and “contractile” (or following cells.)
Autorhythmicity; intrinsic to the specialized cells. AP is
generated within these cells (membrane feature) not
from nerves or hormones. “intrinsic rhythm” Nerves,
hormones can modify rate or force.
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Physiologic considerations
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Mechanical (contraction) features to know:
 4 chambers, septa, valves
 Non-conductive connective tissue skeleton, wringing action. In
ventricles direction is propelling blood from apex toward base.
 Systole = period of contraction and emptying
 Diastole = period of relaxation and filling
 Specify which chamber, as atrial and ventricular events are not the
same. Show this!
 Ohm’s law: Pressure difference = flow x resistance
 Pressures generated in rt and left sides are different (more later.)
 Valves: damage can lead to stenosis and/or regurgitation
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Physiologic
considerations
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Vasculature:
 Normal circuit is A,a,c,v,V
 Arteries: thick wall, narrower
lumen than veins of same outer
diameter. Muscular and elastic.
Stretch and recoil, give back
potential for kinetic energy.
 Arterioles: resistance vessels;
precapillary sphincters.
 Capillaries: exchange vessels,
thin wall, simple squamous
endothelium, diffusion.
 Venules: thin walled, more elastic
 Veins: Capacitance vessels, hold
large volume of blood supply
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Physiologic considerations
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Right/left side differences:
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In series circuit, R to L and around again.
Same amt of blood pushed by each side, “cardiac
output.” CO=6L/min at rest.
R side (pulmonary circuit) pushes blood to lungs; low
resistance circuit
L side (systemic circuit) pushes blood to all organs in
head, torso and limbs, ie. The system; high resistance
circuit.
In summary, same amt of blood, but with different
resistance, require different pressures.
MAP on L side = 100 mm Hg; MAP on R side =10 mm Hg
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Series Circuit
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