Download Heart

Heart
Cardiac= heart.
• delivery of
nutrients to and
the removal of
wastes from the
body tissues.
Myocardium: the muscular wall of the
heart/cardiac muscle
Cardiac Chambers
Four chambers.
• Two chambers at superior aspect
• two at inferior aspect.
• Interventricular septum thick, muscular wall
that separate the inferior chambers
Interatrial septum separates the two upper
chambers.
• Atria (singular atrium) the superior thinwalled collecting chambers.
– All blood returning to the heart from elsewhere in
the body must enter one of these two chambers.
• right atrium Blood returning to the heart from
the body organs
• left atrium: blood returning to the heart from
the lungs
• ventricles. Inferior, thick-walled pumping
chambers.
– right ventricle pumps blood to the lungs.
– left ventricle pumps blood to the body. nearly
twice as thick /pumps with significantly greater
force.
Cardiac Valves
valves ensure blood always
flows proper direction.
atrioventricular (A-V) style
valves: separate the atrium
from the ventricle on the
same side of the heart.
Cardiac Valves
• have a flap and string-like design.
• Pressures on these valves are quite high.
• string-like structures help to anchor the valve
flap when the ventricle is contracting.
Tricuspid valve valve on the right side of the
heart
Bicuspid or mitral valve valve on the left side
– under very high pressures
– more likely to weaken and fail as an individual
ages.
semilunar style valves separate the ventricle
from its major artery.
– pocket-type design.
– Pressures not quite as strong as those on the A-V
valves.
• pulmonic valve: semilunar valve / right side
heart/ separating the right ventricle from the
pulmonary artery.
• aortic valve: semilunar valve /left side heart/
separating the left ventricle from the aorta
Cardiac Vessels
• arteries blood vessels that
transport blood AWAY
from the heart.
– typically transport highly
oxygenated blood the body.
Cardiac Vessels
• Veins: blood vessels that
transport blood TOWARDS
the heart.
– typically transport very low
oxygen blood, returning
from the body.
Aorta emerges from the superior part of the left
ventricle.
– very large diameter tube/ curves around above
the heart and then travels behind the heart
towards the lower portions of the body. Branches
of the aorta deliver blood to the body
Pulmonary artery emerges from the superior
portion of the right ventricle, at the very front
of the heart.
– transporting blood with a very low oxygen
content. traveling to the lungs to pick up a new
supply of oxygen.
Superior vena cava: merge from veins of the
head, arms, and torso that lie superior to the
heart. Goes to right atrium
Inferior vena cava : merge from veins legs and
torso areas that lie inferior to the heart. Goes
to right atrium
• pulmonary veins: left atrium. are returning
blood to the heart from the lungs.
Divisions of the Circulation
• Pulmonic
• Systemic
• Coronary
– It takes the entire blood volume of your body only
about one minute to make the complete circuit.
Pulmonary (pulmonic) Circulation
• Transports blood from the heart to the
lungs and back.
Systemic Circulation
• From the heart to the body and back.
Coronary Circulation
• Small branch of the systemic
circulation
• Coronary arteries first tiny
branches off of the aorta.
These vessels supply
nutrients and remove wastes
from the myocardial muscle
layer of the heart
• Blood recollects into
the cardiac veins that join to
form the coronary sinus, a
large vein, and then returns
to the right atrium.
• Obstruction of these vessels
can result in a heart attack.
Cardiac Muscle
• cardiac muscle cells of the atria are
interconnected with one another and function
as a unit.
• cardiac muscle cells of the ventricles are also
interconnected with one another and function
as a unit.
Intercalated discs between adjacent cardiac
cells/ allow rapid signal transmission.
• no direct interconnection between the atrial
and ventricular muscle groups.
• intricate communication pathway to
communicate between the two areas
Autorhythmic : cells capable of selfstimulation. They can contract on their own
without being told to do so by the nervous
system. All cardiac muscle cells
Cardiac Conduction Sequence
Sinoatrial (SA) node beginning of all normal
contractions of the heart This is pacemaker of
the heart.
Cardiac Conduction Sequence
Special group of cardiac muscle cells that are
autorhythmic at about 70 times per minute.
– located in the right atrium where the superior
vena cava attaches to that chamber.
• The signal spreads from the SA node through
the right atria and on to the left atrium, being
passed cell-to-cell via the intercalated discs.
• The atria then contract and push some blood
into the ventricles (most blood enters strictly
by gravity prior to that, however).
• The atrial cells then signal the atrioventricular
(AV) node, a second group of special cardiac
muscle cells that are also autorhythmic, but at
a slower rate, about 40 times per minute.
• located near the septum in the lower portion
of the right atrium.
• The AV node is the only electrical connection
between the atrial and ventricular muscle
masses.
– The only way in which the atrial and ventricular
muscle masses can communicate.
A-V Node
Conducts the message that it is time to
contract from the sinoatrial node to the
ventricles.
A-V Node
• As long as the AV node receives a message from
the SA node, it does not contract on its own. If
there is a communication problem and the
message is not received, the atrioventricular
node may assume the role of pacemaker. The
heart rate is often about half of the normal heart
rate
– person will generally have difficulty doing anything
which requires more blood to be pumped by the
heart,
A-V Node
• Screens out excessive
contractions of the heart
muscle.
• The message is then sent
via special conduction
tissue, the AV Bundle and
its branches to the
ventricular cells,
stimulating the ventricles
to contract. The ventricles
then relax.
A-V Node
• Screens out excessive contractions of the
heart muscle.
– Heart rates over 180 beats/minute are lifethreatening. Because the heart is contracting so
rapidly, there is too little time for the ventricles to
fill; therefore no blood is being pumped from the
heart. The AV node will eliminate some of the
beats and only pass on a reasonable number to
the ventricles if an excessive number are coming
from the atria.